List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Abbreviations and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Standards and Organizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Chapter 1—Housing History and Purpose

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Preurban Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Ephemeral Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Episodic Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Periodic Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Seasonal Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Semipermanent Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Permanent Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Urbanization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Trends in Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7

Chapter 2—Basic Principles of Healthy Housing 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

Fundamental Physiologic Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

Fundamental Psychologic Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

Protection Against Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

Protection Against Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

Protection Against Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

Fire Extinguishers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

Protection Against Toxic Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-11

Chapter 3—Housing Regulations

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

Zoning, Housing Codes, and Building Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

Zoning and Zoning Ordinances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

Exceptions to the Zoning Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Housing Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6

Building Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-13

Healthy Housing Reference Manual 1

Contents
Chapter 4—Disease Vectors and Pests

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Disease Vectors and Pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Rodents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Cockroaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Fleas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

Flies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7

Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8

Fire Ants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-13

Mosquitoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-15

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-17

Chapter 5—Indoor Air Pollutants and Toxic Materials

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Indoor Air Pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Biologic Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Chemical Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

Toxic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-13

Asbestos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-13

Lead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-15

Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-19

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-20

Chapter 6—Housing Structure

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

New Housing Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Old Housing Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-8

Vapor Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Crawl Space Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Vapor Barriers for Concrete Slab Homes . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Wall and Ceiling Vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

House Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Foundation Sills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Flooring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Studs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Interior Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Stairways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Roof Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Rafters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Collar Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Purlin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Ridge Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Hip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Roof Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Dormer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

2 Contents
Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Asphalt Shingle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

EPDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Asphalt Built-up Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Coal Tar Pitch Built-up Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Slate Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Tile Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Copper Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Galvanized Iron Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Wood Shingle Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Roof Flashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Gutters and Leaders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Exterior Walls and Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-21

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-22

Chapter 7—Environmental Barriers

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1

Roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2

Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Siding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Fiber Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Brick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Stucco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Vinyl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

Asbestos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-6

Chapter 8—Rural Water Supplies and Water-quality Issues

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Water Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Source Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2

Well Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Sanitary Design and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Pump Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Dug and Drilled Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Cisterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Disinfection of Water Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7

Chlorine Carrier Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Routine Water Chlorination (Simple) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Well Water Shock Chlorination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Backflow, Back-siphonage, and Other Water Quality Problems . . . . . . . . . . . . . . .8-9

Backflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Back-siphonage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

Other Water Quality Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

Healthy Housing Reference Manual 3
Protecting the Groundwater Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-12

Chapter 9—Plumbing

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Elements of a Plumbing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Water Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Hot and Cold Water Main Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-3

Water Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

Drainage System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

Corrosion Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Water Conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-14

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-15

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-16

Chapter 10—On-site Wastewater Treatment

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

Treatment of Human Waste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

On-site Wastewater Treatment Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Septic Tank Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Alternative Septic Tank Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-6

Maintaining the On-site Wastewater Treatment Systems . . . . . . . . . . . . . . . . . . .10-8

Symptoms of Septic System Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-9

Septic Tank Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-9

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-12

Chapter 11—Electricity

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-1

Flow of Electric Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-2

Electric Service Entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Service Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Underground Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Electric Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Two- or Three-wire Electric Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Residential Wiring Adequacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Wire Sizes and Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Reducing Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Wire Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Wire Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Types of Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Flexible Cords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

The Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

The Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

4 Contents
Safety Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Open Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Concealed Knob and Tube Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Electric Service Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Over-Current Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Circuit Breakers (Fuseless Service Panels) . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Ground Fault Circuit Interrupters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Arc-fault Circuit Interrupters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Fused Ampere Service Panel (Fuse Box) . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Electric Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Outlet Switches and Junction Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Grounding Outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Polarized Plugs and Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-14

Common Electrical Violations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-14

Excessive or Faulty Fusing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-15

Cords Run Through Walls or Doorways and Hanging Cords or Wires . . . . .11-15

Temporary Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Excessively Long Extension Cords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Dead or Dummy Outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Aluminum Wiring Inside the Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Inspection Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-17

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-17

Chapter 12—Heating, Air Conditioning, and Ventilating

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-1

Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-4

Standard Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-4

Central Heating Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-7

Space Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-12

Hydronic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Direct Vent Wall Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-15

Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-15

Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-15

Circulation Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Evaporation Coolers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-17

Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-17

Fireplaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-18

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-19

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-19

Chapter 13—Energy Efficiency

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

Energy Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

R-values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

Healthy Housing Reference Manual 5
Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-2

Ridge Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Fan-powered Attic Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

White Roof Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Wall Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Floor Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Hot Water Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Caulking and Weather-stripping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Replacing Window Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Tinted Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Reducing Heat Loss and Condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Layering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Other Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Active Solar Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Passive Solar Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-10

Conducting an Energy Audit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-11

Chapter 14—Residential Swimming Pools and Spas

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-1

Child-proofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-1

Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-2

Public Health Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-2

Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-3

Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-3

Water Testing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-3

Disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-4

Content Turnover Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-4

Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

High-rate Sand Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Cartridge Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Diatomaceous Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Filter Loading Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Disinfectants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Effect of pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-6

Chlorine Disinfectants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-6

Pool Water Hardness and Alkalinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-8

Liquid Chemical Feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-9

Positive Displacement Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-9

Erosion and Flow-through Disinfectant Feeders . . . . . . . . . . . . . . . . . . . . .14-10

Spas and Hot Tubs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-11

6 Contents
Chapter 1—Housing History and Purpose

Figure 1.1. Conditions in the Tenements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

Figure 1.2. Levittown, New York . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6

Chapter 2—Basic Principles of Healthy Housing 

Figure 2.1. Circa 1890 Icebox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

Figure 2.2. Smoke Alarm Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Chapter 3—Housing Regulations

Figure 3.1. Example of a Floor Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Figure 3.2. Example of an Angle of Light Obstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Chapter 4—Disease Vectors and Pests

Figure 4.1. Field Identification of Domestic Rodents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Figure 4.2. Norway Rat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Figure 4.3. Roof Rat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Figure 4.4. Signs of Rodent Infestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

Figure 4.5. Rodent Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Figure 4.6. Live Trap for Rats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Figure 4.7. Kill Traps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Figure 4.8. American, Oriental, German, and Brown-banded Cockroaches . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.9. American Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.10. Oriental Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.11. German Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.12. Brown-banded Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.13. Wood Cockroach, Adult Male . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.14. Reported Human Plague Cases (1970–1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

Figure 4.15. Flea Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

Figure 4.16. Housefly (Musca domestica) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7

Figure 4.17. Life Cycle of the Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8

Figure 4.18. Termite Tube Extending From Ground to Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9

Figure 4.19. Termite Mud Shelter Tube Constructed Over A Brick Foundation . . . . . . . . . . . . . . . . . . .4-9

Figure 4.20. Differences Between Ants and Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9

Figure 4.21. Life Cycle of the Subterranean Termite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-10

Figure 4.22. Subterranean Termite Risk in the United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-11

Figure 4.23. Typical Points of Attack by Termites in the Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-12

Figure 4.24. Construction Techniques That Discourage Termite Attacks . . . . . . . . . . . . . . . . . . . . . . . . .4-14

Figure 4.25. Fire Ants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-14

Figure 4.26. Range Expansion of Red Imported Fire Ants (RIFA) in the United States, 1918–1998 . . . .4-15

Figure 4.27. Fire Ant Mound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-15

Chapter 5—Indoor Air Pollutants and Toxic Materials

Figure 5.1. Mold Growth in the Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7

Figure 5.2. Home Carbon Monoxide Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7

Figure 5.3. Environmental Tobacco Smoke and Children’s Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8

Figure 5.4. Wood Products Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-10

Figure 5.5. EPA Map of Radon Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-10

Figure 5.6. Radon Entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-11

Figure 5.7. Home Radon Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12

List of Figures

Healthy Housing Reference Manual 7
Figure 5.9. Radon-resistant Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12

Figure 5.10. Arsenic Label. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-19

Chapter 6—Housing Structure

Figure 6.1. Housing Structure Terminology, Typical House Built Today . . . . . . . . . . . . . . . . .6-1

Figure 6.2. Housing Structure Terminology, Typical House Built Between 1950 and 1980 . . . .6-6

Figure 6.3. Foundation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Figure 6.4. Foundation Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Figure 6.5. Interior Stairway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Figure 6.6. Classifications of Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Figure 6.7. Three-dimensional View of a Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Figure 6.8. Window Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Figure 6.9. Wall Framing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

Chapter 7—Environmental Barriers

Figure 7.1. Sources of Moisture and Air Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1

Figure 7.2. Blown Attic Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Figure 7.3. Depth of Attic Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Figure 7.4. Attic Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Figure 7.5. Brick Structural Defect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Figure 7.6. Corrosion in Piping Resulting From Galvanic Response . . . . . . . . . . . . . . . . . . . .7-5

Chapter 8—Rural Water Supplies

Figure 8.1. U.S. Water Supply by Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Figure 8.2. Cross Section of a Driven Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Figure 8.3. Well Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Figure 8.4. Converted Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Figure 8.5. Recapped and Sealed Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.6. Drilled Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.7. Typical Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.8. Sewage in Drainage Ditch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Figure 8.9. Drilled Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Figure 8.10. Spring Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Chapter 9—Plumbing

Figure 9.1. Typical Home Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Figure 9.2. House Service Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2

Figure 9.3. Gas Water Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

Figure 9.4. Temperature-pressure Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

Figure 9.5. Branch Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-10

Figure 9.6. P-trap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-10

Figure 9.7. Types of S-traps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-10

Figure 9.8. Trap Seal: (a) Seal Intact; (b) Fixture Draining; (c) Loss of Gas Seal . . . . . . . . . . . .9-10

Figure 9.9. Loss of Trap Seal in Lavatory Sink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

Figure 9.10. Back-to-back Venting (Toilet). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

Figure 9.11. Back-to-back Venting (Sink). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

Figure 9.12. Wall-hung Fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Figure 9.13. Unit Vent Used in Bathtub Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Figure 9.14. Toilet Venting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Figure 9.15. Janitor’s Sink. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Figure 9.16. Common Y-trap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Figure 9.17. Hose Bib With Vacuum Breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

8 List of Figures
Chapter 10—On-site Wastewater Treatment

Figure 10.1. Conventional On-site Septic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

Figure 10.2. Straight Pipe Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-2

Figure 10.3. Clear Creek Water Contaminated With Sewage. . . . . . . . . . . . . . . . . . . . . . . . . .10-2

Figure 10.4. Septic Tank System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Figure 10.5. Septic Tank. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-4

Figure 10.6. On-site Sewage Disposal System Site Evaluation Form . . . . . . . . . . . . . . . . . . . .10-5

Figure 10.7. Cross-section of an Absorption Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-5

Figure 10.8. Mound System Cutaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-7

Figure 10.9. Low Pressure On-site System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-7

Figure 10.10. Plant-rock Filter System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-8

Figure 10.11. Sludge and Scum in Multicompartment Septic Tank . . . . . . . . . . . . . . . . . . . . . .10-10

Chapter 11—Electricity

Figure 11.1. Utility Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Figure 11.2. Entrance Head. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Figure 11.3. Armored Cable Service Entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Figure 11.4. Breakers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Figure 11.5. Thin-wall Conduit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Figure 11.6. Electric Meter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-5

Figure 11.7. Typical Service Entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-5

Figure 11.8. Grounding Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Figure 11.9. Grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Figure 11.10. Three-wire Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Figure 11.11. Two-wire Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Figure 11.12. Wire Markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Figure 11.13. Armored Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

Figure 11.14. 200-Amp Service Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Figure 11.15. External Power Shutoff and Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Figure 11.16. Ground Fault Circuit Interruptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Figure 11.17. Arc Interrupter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Figure 11.18. Types of Fuses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Figure 11.19. Appliance Ground and Grounded Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-14

Chapter 12—Heating, Air Conditioning, and Ventilating

Figure 12.1. Heat Pump in Cooling Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-5

Figure 12.2. Piping Hookup for Inside Tank Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-6

Figure 12.3. Piping Hookup for Buried Outside Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-6

Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm Air Furnace . . . . . .12-7

Figure 12.5. Minimum Clearance for Steam or Hot Water Boiler and Mechanical Warm-air Furnace .12-7

Figure 12.6. Heating Ducts Covered With Asbestos Insulation . . . . . . . . . . . . . . . . . . . . . . . .12-7

Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers . . . . . . . . . . . . . . . . .12-8

Figure 12.8. Cutaway View of Typical High-pressure Gun Burner . . . . . . . . . . . . . . . . . . . . . .12-9

Figure 12.9. Gas-fired Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-9

Figure 12.10. Typical Gravity One-pipe Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-10

Figure 12.11. One-pipe Gravity Water Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-11

Figure 12.12. Two-pipe Gravity Water Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-11

Figure 12.13. Warm-air Convection Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-11

Figure 12.14. Cross-sectional View of Building Showing Forced-warm-air Heating System . . . .12-12

Figure 12.15. Perforated-sleeve Burner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-13

Figure 12.16. Condition of Burner Flame With Different Rates of Fuel Flow . . . . . . . . . . . . . .12-13

Figure 12.17. Wall and Ceiling Clearance Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Healthy Housing Reference Manual 9
Figure 12.18. Draft in Relation to Height of Chimney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Figure 12.19. Location and Operation of Typical Backdraft Diverter . . . . . . . . . . . . . . . . . . . .12-15

Figure 12.20. Split-system Air Conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Figure 12.21. External Air-conditioning Condenser Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Figure 12.22. Chimney Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-17

Figure 12.23. Fireplace Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-18

Chapter 13—Energy Efficiency

Figure 13.1. Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Figure 13.2. Potential Effects of Radiant Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Figure 13.3. Common Floor Insulation Flaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Figure 13.4. Insulation Cavity Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-6

Figure 13.5. Solar Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Chapter 14—Residential Swimming Pools and Spas

Figure 14.1. Pool Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-2

Figure 14.2. Typical Home Pool Equipment System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

10 List of Figures
Healthy Housing Reference Manual 11

Chapter 8—Rural Water Supplies and Water-quality Issues

Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources . . . . . . . .8-2

Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters . . . . . . . .8-3

Table 8.3. Disinfection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7

Table 8.4. Chlorination Guide for Specific Water Conditions . . . . . . . . . . . . . . . . . . . . . . . .8-8

Table 8.5. Preparing a 200-ppm Chlorine Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Table 8.6. Analyzing and Correcting Water Quality Problems . . . . . . . . . . . . . . . . . . . . . . . .8-11

Chapter 9—Plumbing

Table 9.1. Fixture Unit Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-9

Table 9.2. Sanitary House Drain Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-9

Table 9.3. Minimum Fixture Service Pipe Diameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Chapter 10—On-site Wastewater Treatment

Table 10.1. Mound System Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . .10-6

Table 10.2. Low-pressure Pipe Systems Advantages and Disadvantages . . . . . . . . . . . . . . . . . .10-7

Table 10.3. Plant Rock Filter System Advantages and Disadvantages . . . . . . . . . . . . . . . . . . .10-8

Table 10.4. Septic Tank System Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-10

Chapter 13—Energy Efficiency

Table 13.1. Cost-effective Insulation R-values for Existing Homes . . . . . . . . . . . . . . . . . . . . .13-2

Table 13.2. R-values of Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Table 13.3. Floor Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Chapter 14—Residential Swimming Pools and Spas

Table 14.1. Pool Water Quality Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-7

Table 14.2. pH Effect on Chlorine Disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-8

Table 14.3. Chlorine Use in Swimming Pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-8

Table 14.4. Swimming Pool Operating Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-9

Table 14.5. Spa and Hot Tub Operating Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-11

List of Tables
12 List of Tables
Healthy Housing Reference Manual 13

Housing quality is key to the public’s health. Translating that simple axiom into action is the topic of this book.

In the 30 years since the first edition was published, the nation’s understanding of how specific housing conditions are related to disease and injury has matured and deepened. This new edition will enable public health

and housing professionals to grasp our shared responsibility to ensure that our housing stock is safe, decent, affordable, and healthy for our citizens, especially those who are particularly vulnerable and who spend more time in the

home, such as children and the elderly.

The Centers for Disease Control and Prevention and the U.S. Department of Housing and Urban Development

(HUD) have worked together with many others to discover the ways to eliminate substandard housing conditions that

harm health. For example, the advances in combating water borne diseases was possible, in part, through standardization of indoor plumbing and sewage, and the institution of federal, state and local regulations and codes. Childhood

lead poisoning has been dramatically reduced, in part, through the elimination of residential lead-based paint hazards.

Other advances have been made to protect people from carbon monoxide poisoning, falls, safety hazards, electrocution, and many other risks. 

However, more must be done to control existing conditions and to understand emerging threats that remain poorly

understood. For example, nearly 18 million Americans live with the health threat of contaminated drinking water

supplies, especially in rural areas where on-site wastewater systems are prevalent. Despite progress, thousands of children still face the threat of lead poisoning from residential lead paint hazards. The increase in asthma in recent

decades and its relationship to housing conditions such as excess moisture, mold, settled dust allergens and ventilation

remains the subject of intense research. The impact of energy conservation measures on the home environment is still

unfolding. Simple affordable construction techniques and materials that minimize moisture problems and indoor air

pollution, improve ventilation, and promote durability and efficiency continue to be uncovered.

A properly constructed and maintained home is nearly timeless in its usefulness. A home is often the biggest single

investment people make. This manual will help to ensure that the investment is a sound one that promotes healthy

and safe living.

Home rehabilitation has increased significantly in the last few years and HUD has prepared a nine-part series, The

Rehab Guide, that can assist both residents and contractors in the rehabilitation process. For additional information,

go to http://www.huduser.org/publications/destech/rehabgui.html. 

Preface
14 Preface
We acknowledge the suggestions, assistance, and review of numerous individuals and organizations that went

into the original and current versions of this manual. The revisions to this manual were made by a team of

environmental health, housing, and public health professionals led by Professor Joe Beck, Dr. Darryl

Barnett, Dr. Gary Brown, Dr. Carolyn Harvey, Professor Worley Johnson, Dr. Steve Konkel, and Professor Charles

Treser.

Individuals from the following organizations were involved in the various drafts of this manual:

• Department of Housing and Urban Development (HUD), Office of Healthy Homes and Lead Hazard

Control;

• U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC),

National Center for Environmental Health (NCEH); 

• National Healthy Homes Training Center and Network; 

• National Association of Housing and Redevelopment Officials;

• Department of Building, Housing and Zoning (Allentown, Pennsylvania); 

• Code Enforcement Associates (East Orange, New Jersey); 

• Eastern Kentucky University (Richmond, Kentucky); 

• University of Washington; Seattle (Washington); and

• Battelle Memorial Institute (Columbus, Ohio). 

Specifically, our gratitude goes to the following reviewers:

• Dr. David Jacobs, Martin Nee, and Dr. Peter Ashley, HUD; 

• Pat Bohan, East Central University; 

• James Larue, The House Mender Inc.; 

• Ellen Tohn, ERT Associates; 

• Dr. Stephen Margolis, Emory University; and 

• Joseph Ponessa and Rebecca Morley, Healthy Homes Training Center. 

A special thank-you for assistance from Carolyn Case-Compton, Habitat for Humanity, 123 East Main Street,

Morehead, Kentucky. Pictures of a home under construction are courtesy of Habitat for Humanity and John King,

home builder and instructor, Rowan County Technical College, Morehead, Kentucky; and Don W. Johnson, building

photographer of Habitat for Humanity.

In addition, a special thank you to CAPT Craig Shepherd and CAPT Michael Herring, Commissioned Corps, U.S.

Public Health Service, CDC/NCEH/Environmental Health Services Branch for their research and review during the

editing of this manual. Special thanks to Pamela S. Wigington and Joey L. Johnson for their hard work preparing this

manual for publication and to Teresa M. Sims for Web publication.

Acknowledgments

Healthy Housing Reference Manual 15
16 Acknowledgments
Healthy Housing Reference Manual 17

ABS acrylonitrile-butadiene-styrene

ADA Americans with Disabilities Act

AGA American Gas Association

ALA American Lung Association

ANSI American National Standards Institute

APHA American Public Health Association

ASME American Society of Mechanical Engineers

ASSE American Society of Structural Engineers

ASTM American Society for Testing Materials

ATSDR Agency for Toxic Substances and Disease Registry

AWG American Wire Gauge

AWWA American Waters Works Association

BTU British thermal unit

CDC Centers for Disease Control and Prevention

CFR Code of Federal Regulations

CGA Canadian Gas Association

CO carbon monoxide

CPR cardiopulmonary resuscitation

CPSC Consumer Product Safety Commission

CSIA Chimney Safety Institute of America

DDT dichlorodiphenyltrichlorethane

DE diatomaceous earth

DPD N,N-diethyl-p-phenylene diamine

DWV drain, waste, and vent

EIFS exterior insulation and finish system

EPA U.S. Environmental Protection Agency

EPDM ethylene propylene dieneterpolymer

ETS environmental tobacco smoke

FHA Federal Housing Administration

FM Factory Mutual

GFCI ground fault circuit interrupter

HEPA high-efficiency particulate air

HHS Health and Human Services, U.S. Department of

HSC Home Safety Council

HUD Housing and Urban Development, U.S. Department of

HVAC heating, ventilating and air conditioning

IAPMO International Association of Plumbing and Mechanical Officials

ICC International Code Council

IPM integrated pest management

ISO International Standard Organization

kg kilogram

LPP low-pressure pipe

MPMH Military Pest Management Handbook

MSS Mechanical Standardization Society of the Valve and Fitting Industry

NCEH National Center for Environmental Health

NCI National Cancer Institute

NIA National Institute on Aging

NSF National Science Foundation

NTU nephelometric turbidity unit

Abbreviations and Acronyms
18 Abbreviations and Acronyms

ODTS organic dust toxic syndrome

OSHA Occupational Safety and Health Administration

PEX cross-formulated polyethylene

POTW publicly owned treatment works

ppm parts per million

psi pound per square inch

PVC polyvinyl chloride

PW potable water

RIFA red imported fire ant

SDWA Safe Drinking Water Act

SEER seasonal energy efficiency ratio

T&P temperature-pressure

TSP trisodium phosphate

UF urea-formaldehyde

UL Underwriters Laboratories

USCB U.S. Census Bureau 

USDA U.S. Department of Agriculture

USFA U.S. Fire Administration

USGS U.S. Geological Survey

USHA United States Housing Authority

VA Veteran’s Administration

VOC volatile organic compound

XRF X-ray fluorescence
Healthy Housing Reference Manual 19

Accessory building or structure: a detached building or structure in a secondary or subordinate capacity from the

main or principal building or structure on the same premises.

Appropriate authority/Authority having jurisdiction (AHJ): a person within the governmental structure of the

corporate unit who is charged with the administration of the appropriate code.

Ashes: the residue from burning combustible materials.

Attic: any story or floor of a building situated wholly or partly within the roof, and so designed, arranged, or built to

be used for business, storage, or habitation.

Basement: the lowest story of a building, below the main floor and wholly or partially lower than the surface of the ground.

Building: a fixed construction with walls, foundation, and roof, such as a house, factory, or garage.

Bulk container: any metal garbage, rubbish, or refuse container having a capacity of 2 cubic yards or greater and which is

equipped with fittings for hydraulic or mechanical emptying, unloading, or removal.

Central heating system: a single system supplying heat to one or more dwelling unit(s) or more than one rooming unit.

Chimney: a vertical masonry shaft of reinforced concrete, or other approved noncombustible, heat-resisting material

enclosing one or more flues, for the purpose of removing products of combustion from solid, liquid, or gaseous fuel.

Dilapidated: in a state of disrepair or ruin and no longer adequate for the purpose or use for which it was originally intended.

Dormitory: a building or a group of rooms in a building used for institutional living and sleeping purposes by four or

more persons.

Dwelling: any enclosed space wholly or partly used or intended to be used for living, sleeping, cooking, and eating.

(Temporary housing, as hereinafter defined, shall not be classified as a dwelling.) Industrialized housing and modular

construction that conform to nationally accepted industry standards and are used or intended for use for living,

sleeping, cooking, and eating purposes shall be classified as dwellings.

Dwelling unit: a room or group of rooms located within a dwelling forming a single habitable unit with facilities used

or intended to be used by a single family for living, sleeping, cooking, and eating.

Egress: arrangements and openings to assure a safe means of exit from buildings.

Extermination: the control and elimination of insects, rodents, or other pests by eliminating their harborage places;

by removing or making inaccessible materials that may serve as their food; by poisoning, spraying, fumigating,

trapping, or any other recognized and legal pest elimination methods approved by the local or state authority having

such administrative authority. Extermination is one of the components of integrated pest management.

Fair market value: a price at which both buyers and sellers will do business.

Family: one or more individuals living together and sharing common living, sleeping, cooking, and eating facilities

(See also Household).

Definitions
Flush toilet: a toilet bowl that can be flushed with water supplied under pressure and that is equipped with a watersealed trap above the floor level.

Garbage: animal and vegetable waste resulting from handling, preparation, cooking, serving, and nonconsumption of food.

Grade: the finished ground level adjacent to a required window.

Guest: an individual who shares a dwelling unit in a nonpermanent status for not more than 30 days.

Habitable room: a room or enclosed floor space used or intended to be used for living, sleeping, cooking or eating

purposes, excluding bathrooms, laundries, furnace rooms, pantries, kitchenettes and utility rooms of less than

50 square feet of floor space, foyers, or communicating corridors, stairways, closets, storage spaces, workshops, and hobby

and recreation areas.

Health officer: the legally designated health authority of the jurisdiction or that person’s authorized representative.

Heated water: water heated to a temperature of not less than 120°F–130°F (49°C–54°C) at the outlet.

Heating device: all furnaces, unit heaters, domestic incinerators, cooking and heating stoves and ranges, and other similar devices.

Household: one or more individuals living together in a single dwelling unit and sharing common living, sleeping,

cooking, and eating facilities (see also Family).

Infestation: the presence within or around a dwelling of any insects, rodents, or other pests.

Integrated pest management: a coordinated approach to managing roaches, rodents, mosquitoes, and other pests that

combines inspection, monitoring, treatment, and evaluation, with special emphasis on the decreased use of toxic agents. 

Kitchen: any room used for the storage and preparation of foods and containing the following equipment: sink or

other device for dishwashing, stove or other device for cooking, refrigerator or other device for cold storage of food,

cabinets or shelves for storage of equipment and utensils, and counter or table for food preparation.

Kitchenette: a small kitchen or an alcove containing cooking facilities.

Lead-based paint: any paint or coating with lead content equal to or greater than 1 milligram per square centimeter,

or 0.5% by weight. 

Multiple dwelling: any dwelling containing more than two dwelling units.

Occupant: any individual, over 1 year of age, living, sleeping, cooking, or eating in or having possession of a dwelling

unit or a rooming unit; except that in dwelling units a guest shall not be considered an occupant.

Operator: any person who has charge, care, control or management of a building, or part thereof, in which dwelling

units or rooming units are let.

Ordinary summer conditions: a temperature 10°F (-12°C) below the highest recorded temperature in the locality for

the prior 10-year period.

Ordinary winter conditions: mean a temperature 15°F (-9.4°C) above the lowest recorded temperature in the locality

for the prior 10-year period.

20 Definitions
Owner: any person who alone, jointly, or severally with others (a) shall have legal title to any premises, dwelling, or

dwelling unit, with or without accompanying actual possession thereof, or (b) shall have charge, care or control of any

premises, dwelling, or dwelling unit, as owner or agent of the owner, or as executor, administrator, trustee, or guardian

of the estate of the owner.

Permissible occupancy: the maximum number of individuals permitted to reside in a dwelling unit, rooming unit, or dormitory.

Person: any individual, firm, corporation, association, partnership, cooperative, or government agency.

Plumbing: all of the following supplied facilities and equipment: gas pipes, gas burning equipment, water pipes,

garbage disposal units, waste pipes, toilets, sinks, installed dishwashers, bathtubs, shower baths, installed clothes

washing machines, catch basins, drains, vents, and similarly supplied fixtures, and the installation thereof, together with all

connections to water, sewer, or gas lines.

Privacy: the existence of conditions which will permit an individual or individuals to carry out an activity commenced

without interruption or interference, either by sight or sound by unwanted individuals.

Rat harborage: any conditions or place where rats can live, nest or seek shelter.

Ratproofing: a form of construction that will prevent the entry or exit of rats to or from a given space or building, or

from gaining access to food, water, or harborage. It consists of the closing and keeping closed of every opening in

foundations, basements, cellars, exterior and interior walls, ground or first floors, roofs, sidewalk gratings, sidewalk

openings, and other places that may be reached and entered by rats by climbing, burrowing, or other methods, by the

use of materials impervious to rat gnawing and other methods approved by the appropriate authority.

Refuse: leftover and discarded organic and nonorganic solids (except body wastes), including garbage, rubbish, ashes, and dead animals.

Refuse container: a watertight container that is constructed of metal, or other durable material impervious to rodents,

that is capable of being serviced without creating unsanitary conditions, or such other containers as have been

approved by the appropriate authority (see also Appropriate Authority). Openings into the container, such as covers and

doors, shall be tight fitting.

Rooming house: any dwelling other than a hotel or motel or that part of any dwelling containing one or more

rooming units, or one or more dormitory rooms, and in which persons either individually or as families are housed with or

without meals being provided.

Rooming unit: any room or group of rooms forming a single habitable unit used or intended to be used for living

and sleeping, but not for cooking purposes.

Rubbish: nonputrescible solid wastes (excluding ashes) consisting of either: (a) combustible wastes such as paper,

cardboard, plastic containers, yard clippings and wood; or (b) noncombustible wastes such as cans, glass, and crockery. 

Safety: the condition of being reasonably free from danger and hazards that may cause accidents or disease.

Space heater: a self-contained heating appliance of either the convection type or the radiant type and intended

primarily to heat only a limited space or area such as one room or two adjoining rooms. 

Supplied: paid for, furnished by, provided by, or under the control of the owner, operator or agent.

System: the dynamic interrelationship of components designed to enact a vision.

Healthy Housing Reference Manual 21
Systems theory: The concept proposed to promote the dynamic interrelationship of activities designed to accomplish

a unified system.

Temporary housing: any tent, trailer, mobile home, or other structure used for human shelter that is designed to be

transportable and which is not attached to the ground, to another structure, or to any utility system on the same premises for

more than 30 consecutive days.

Toxic substance: any chemical product applied on the surface of or incorporated into any structural or decorative

material, or any other chemical, biologic, or physical agent in the home environment or its immediate surroundings,

which constitutes a potential hazard to human health at acute or chronic exposure levels.

Variance: a difference between that which is required or specified and that which is permitted. 

22 Definitions
Healthy Housing Reference Manual 23

In addition to the standards and organizations listed in this section, the U.S. Justice Department enforces the

requirements of the Americans with Disabilities Act (ADA) (http://www.ada.gov) and assures that products fully

comply with the provisions of the act to ensure equal access for physically challenged users.

ABPA The American Backflow Prevention Association, http://abpa.org

Develops cross-connections; ABPA is an organization whose members have a common interest in 

protecting drinking water from contamination. 

ACI American Concrete Institute, http://www.concrete.org/general/home.asp

Has produced more than 400 technical documents, reports, guides, specifications, and codes for the best use of 

concrete. ACI conducts more than 125 educational seminars each year and has 13 certification programs 

for concrete practitioners, as well as a scholarship program to promote careers in the industry.

AGA American Gas Association, http://www.aga.org

Develops standards, tests, and qualifies products used in gas lines and gas appliance installations.

AGC Associated General Contractors of America, http://www.agc.org

Is dedicated to improving the construction industry by educating the industry to employ the finest skills, 

promoting use of the latest technology and advocating building the best quality projects for owners—

public and private. 

AMSA Association of Metropolitan Sewerage Agencies, http://www.amsa-cleanwater.org

Represents the interests of the country’s wastewater treatment agencies. 

ANSI American National Standards Institute, http://www.ansi.org

Coordinates work among U.S. standards writing groups. Works in conjunction with other groups such as 

ISO, ASME, and ASTM.

ARI Air-Conditioning and Refrigeration Institute, http://www.ari.org

Provides information about the 21st Century Research (21-CR) initiative, a private-public sector research

collaboration of the heating, ventilation, air-conditioning, and refrigeration industry, with a focus on 

energy conservation, indoor environmental quality, and environmental protection. 

ASCE American Society of Civil Engineers, http://www.asce.org

Provides essential value to its members, careers, partners, and the public by developing leadership, 

advancing technology, advocating lifelong learning, and promoting the profession.

ASHI The American Society of Home Inspectors, http://www.ashi.org

Is a source of information about the home inspection profession. 

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, http://www.ashrae.org

Writes standards and guidelines that include uniform methods of testing for rating purposes, describe 

recommended practices in designing and installing equipment and provide other information to guide the 

industry. ASHRAE has more than 80 active standards and guideline project committees, addressing such

broad areas as indoor air quality, thermal comfort, energy conservation in buildings, reducing refrigerant 

emissions, and the designation and safety classification of refrigerants.

Standards and Organizations
24 Standards and Organizations

ASME The American Society of Mechanical Engineers, http://www.asme.org

Develops standards for materials and testing as well as finished products. 

ASSE American Society of Sanitary Engineering, http://www.asse.org

Develops standards and qualifies products for plumbing and sanitary installations.

ASTM American Society for Testing and Materials, http://www.astm.org

Is one of the largest voluntary standards development organizations in the world-a trusted source for 

technical standards for materials, products, systems, and services. 

AWWA American Water Works Association, http://www.awwa.org

Promotes public health through improvement of the quality of water and develops standards for valves, fittings, and other 

equipment.

CGA Canadian Gas Association, http://www.cga.ca

Develops standards, tests, and qualifies products used in gas lines and gas appliance installations.

CPSC U.S Consumer Product Safety Commission, http://www.cpsc.gov

Protects the public from unreasonable risks for serious injury or death from more than 15,000 types of 

consumer products. CPSC is committed to protecting consumers and families from products that pose a 

fire, electrical, chemical, or mechanical hazard or can injure children. 

CRBT Center for Resourceful Building Technology, http://www.crbt.org

Contains the online Guide to Resource-Efficient Building Elements, which provides information about 

environmentally efficient construction materials, including foundations, wall systems, panels, insulation, 

siding, roofing, doors, windows, interior finishing, and floor coverings. 

EPA U.S. Environmental Protection Agency, http://www.epa.gov

Protects human health and the environment. 

FM Factory Mutual, http://fmglobal.com

Develops standards and qualifies products for use by the general public and develops standards for materials, 

products, systems, and services.

HFHI Habitat for Humanity International, http://www.habitat.org

Is a nonprofit, ecumenical Christian housing ministry. HFHI seeks to eliminate poverty housing and 

homelessness from the world, and to make decent shelter a matter of conscience and action.

HUD U.S. Department of Housing and Urban Development, http://www.hud.gov

As part of the HUD efforts toward eliminating childhood lead poisoning, the Office of Healthy Homes 

and Lead Hazard Control is sharing local lead ordinances and regulations that have proven effective in 

helping communities deal with lead-based paint hazards. Also, the design and construction of 

manufactured housing are regulated by the federal government and must comply with HUD’s 

Manufactured Home Construction and Safety Standards. Modular and panelized construction must 

comply with model or local building codes.

IAPMO International Association of Plumbing and Mechanical Officials, http://www.iapmo.org

Developed and maintains the Uniform Plumbing Code and the Uniform Mechanical Code. 
ICBO The Uniform Building Code (UBC)/International Conference of Building Officials, 

http://www.iccsafe.org

Is the most widely adopted model building code in the world and is a proven document meeting the 

needs of government units charged with enforcement of building regulation. Published triennially, the 

UBC provides complete regulations covering all major aspects of building design and construction relating 

to fire and life safety and structural safety. The requirements reflect the latest technologic advances available 

in the building and fire- and life-safety industry.

ICC International Code Council, http://www.iccsafe.org

Produces the most widely adopted and enforced building safety codes in the United States (I-Codes). 

International Residential Code (IRC) 2003 has been adopted by many states, jurisdictions, and localities. 

IRC also references several industry standards such as ACI 318, ASCE 7, ASTM, and ANSI standards that 

cover specific load, load combinations, design methods, and material specifications.

ISO International Standard Organization, http://www.iso.org

Provides internationally recognized certification for manufacturers that comply with high standards of 

quality control, developed standards ISO-9000 through ISO-9004, and qualifies and lists products suitable for 

use in plumbing installations.

MSS Manufacturers Standardization Society of the Valve and Fittings Industry, Inc., http://www.mss-hq.com

Develops technical codes and standards for the valve and fitting industry.

NACHI The National Association of Certified Home Inspectors, http://www.nachi.org/index.htm

Is the world’s largest, most elite nonprofit inspection association. 

NAHB National Association of Home Builders, http://www.nahb.org

Is a trade association representing more than 220,000 residential home building and remodeling industry 

members. NAHB is affiliated with more than 800 state and local home builders associations around the 

country. NAHB urges codes and standards development and application that protects public health and 

safety without cost impacts that decrease affordability and consequently prevent people from moving into

new, healthier, safer homes.

NEC National Electrical Code, http://www.nfpa.org

Protects public safety by establishing requirements for electrical wiring and equipment in virtually all 

buildings. 

NESC National Environmental Services Center, http://www.nesc.wvu.edu/nesc/nesc_about.htm

Is a repository for water, wastewater, solid waste, and environmental training research. 

NFPA National Fire Protection Association, http://www.nfpa.org/index.asp

Develops, publishes, and disseminates more than 300 consensus codes and standards intended to 

minimize the possibility and effects of fire and other risks. 

NOWRA National Onsite Wastewater Recycling Association, http://www.nowra.org

Provides leadership and promotes the onsite wastewater treatment and recycling industry through 

education, training, communication, and quality tools to support excellence in performance. 

NSF National Sanitation Foundation, http://www.nsf.org

Develops standards for equipment, products and services; a nonprofit organization now known as NSF 

International. 

Healthy Housing Reference Manual 25
UL Underwriters Laboratory, http://www.ul.com

Has developed more than 800 Standards for Safety. Millions of products and their components are tested 

to UL’s rigorous safety standards. 

WEF Water Environment Federation, http://www.wef.org

Is a not-for-profit technical and educational organization with members from varied disciplines who work 

toward the WEF vision of preservation and enhancement of the global water environment. The WEF 

network includes water quality professionals from 76 member associations in 30 countries.

26 Standards and Organizations
Healthy Housing Reference Manual 27

The original Basic Housing Inspection manual was published in 1976 by the Center for Disease Control (now

known as the Centers for Disease Control and Prevention). Its Foreword stated: 

The original Basic Housing Inspection manual has been successfully used for several decades by public health and

housing personnel across the United States. Although much has changed in the field of housing construction and

maintenance, and health and safety issues have expanded, the manual continues to have value, especially as it relates to

older housing. 

Many housing deficiencies impact on health and safety. For example, lead-based paint and dust may contribute to

lead poisoning in children; water leakage and mold may contribute to asthma episodes; improper use and storage of

pesticides may result in unintentional poisoning; and lack of working smoke, ionization, and carbon monoxide alarms may

cause serious injury and death.

Government agencies have been very responsive to “healthy homes” issues. The U.S. Department of Housing and

Urban Development (HUD) created an office with an exclusive focus on healthy homes. In 2003, CDC joined HUD

in the effort to improve housing conditions through the training of environmental health practitioners, public health

nurses, housing specialists, and others who have interest and responsibility for creating healthy homes.

The revised Basic Housing Inspection manual, renamed the Healthy Housing Reference Manual, responds to the

enormous changes that have occurred in housing construction methods and materials and to new knowledge related

to the impact of housing on health and safety. New chapters have been added, making the manual more

comprehensive. For example, an entire chapter is devoted to rural water supplies and on-site wastewater treatment. A

new chapter was added that discusses issues related to residential swimming pools and spas. At over 230 pages, the

comprehensive revised manual is designed primarily as a reference document for public health and housing

professionals who work in government and industry. 

The Healthy Housing Reference Manual contains 14 chapters, each with a specific focus. All chapters contain annotated

references and a listing of sources for additional topic information. A summary of the content of each chapter follows:

Chapter One, Housing History and Purpose, describes the history of dwellings and urbanization and housing

trends during the last century. 

Chapter Two, Basic Principles of Healthy Housing, describes the basic principles of healthy housing and

safety—physiologic needs, psychologic needs, protection against injury and disease—and lays the groundwork

for following chapters. 

Executive Summary

“The growing numbers of new families and the increasing population in the United States have

created a pressing demand for additional housing that is conducive to healthful living. These

demands are increased by the continuing loss of existing housing through deterioration resulting

from age and poor maintenance. Large numbers of communities in the past few years have adopted

housing codes and initiated code enforcement programs to prevent further deterioration of existing

housing units. This growth in housing activities has caused a serious problem for communities in

obtaining qualified personnel to provide the array of housing service needed, such as information,

counseling, technical advice, inspections, and enforcement. As a result many agencies throughout the

country are conducting comprehensive housing inspection training courses. This publication has

been designed to be an integral part of these training sessions.”
28 Executive Summary

Chapter Three, Housing Regulations, reviews the history of housing regulations, followed by a discussion of

zoning, housing, and building codes.

Chapter Four, Disease Vectors and Pests, provides a detailed analysis of disease vectors that have an impact on

residences. It includes information on the management of mice, rats, cockroaches, fleas, flies, termites, and fire ants. 

Chapter Five, Indoor Air Pollution and Toxic Materials, provides information on indoor air pollution, both

biologic and chemical, and to toxic materials in the home, including methods for controlling these hazards. The

impact of cockroaches, dust mites, pets, and mold are discussed. Also included is information about the impact

of carbon monoxide, ozone, tobacco smoke, volatile organic compounds, radon, and pesticides.

Chapter Six, Housing Structure, contains information about “older” housing construction and new construction

materials and methods. The chapter also introduces new terminologies and includes information about

foundations, vapor barriers, house framing, roof framing, exterior walls, and roofs. 

Chapter Seven, Environmental Barriers, provides information on roofing, insulation, and siding materials.

Chapter Eight, Rural Water Supplies and Water-quality Issues, covers issues related to the drilling and proper

maintenance of wells. Research information is provided that indicates that many wells are not properly sealed,

allowing for the leakage of contaminated water into wells during hurricanes and periods of significant flooding.

Chapter Nine, Plumbing, provides information on plumbing standards and how they can be accessed, followed

by a review of the elements of a residential water delivery system, the types of available hot-water heaters,

drainage systems, and methods for water conservation. It also includes a visual synthesis of water system

components during new residential construction.

Chapter Ten, On-site Wastewater Treatment, complements chapter seven by providing information on proper

on-site methods for the treatment of human waste. 

Chapter Eleven, Electricity, expands on information contained in the original manual covering such topics as

breaker systems and polarized plugs and connectors. It also provides a format for the inspection of residential

electrical systems.

Chapter Twelve, Heating, Air Conditioning, and Ventilation, provides information about types of residential

fuels and heating systems, including solar heating and minor sources of heating (e.g., coal-fired, oil-fired, gasfired, and electrical space heaters). Chimney and fireplace safety and the variety of cooling systems are also

discussed.

Chapter Thirteen, Energy Efficiency, discusses energy efficiency, including R-values and their interpretation, roof

ventilation, wall and floor insulation, and door and window energy efficiency systems. It also discusses active and

passive solar systems and provides a methodology for conducting a residential energy audit.

Chapter Fourteen, Residential Swimming Pools and Spas, provides information about child safety, pool and spa

hazards, and diseases. It also provides information on methods for testing and ensuring a safe water system and

on methods for spa and pool disinfection. Further, it covers concerns related to unregulated individual

residential pools and spas.
The quality of housing plays a decisive role in the health status of its occupants. Substandard housing conditions have

been linked to adverse health effects such as childhood lead poisoning, asthma and other respiratory conditions, and

unintentional injuries. This new and revised Healthy Housing Reference Manual is an important reference for anyone

with responsibility and interest in creating and maintaining healthy housing. 

The housing design and construction industry has made great progress in recent years through the development of

new innovative techniques, materials technologies, and products. The HUD Rehab Guide series was developed to

inform the design and construction industry about state-of-the-art materials and innovative practices in housing

rehabilitation. The series focuses on building technologies, materials, components, and techniques rather than on

projects such as adding a new room. The nine volumes each cover a distinct element of housing rehabilitation and

feature breakthrough materials, labor-saving tools, and cost-cutting practices. The nine volumes address foundations;

exterior walls; roofs; windows and doors; partitions, ceilings, floors, and stairs; kitchen and baths; electrical/

electronics; heating, air conditioning, and ventilation; plumbing; and site work. 

Additional information about the series can be found at http://www.huduser.org/publications/destech/rehabgui.html

and http://www.pathnet.org/sp.asp?id=997. This series is an excellent adjunct to the Healthy Housing Reference Manual.

Healthy Housing Reference Manual 29
30 Executive Summary
Chapter 1—Housing History and Purpose

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Preurban Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Ephemeral Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Episodic Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Periodic Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Seasonal Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Semipermanent Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Permanent Dwellings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Urbanization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Trends in Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7

Figure 1.1. Conditions in the Tenements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

Figure 1.2. Levittown, New York . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6

Chapter 2—Basic Principles of Healthy Housing 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

Fundamental Physiologic Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

Fundamental Psychologic Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

Protection Against Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

Protection Against Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

Protection Against Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

Fire Extinguishers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

Protection Against Toxic Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-11

Figure 2.1. Circa 1890 Icebox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5

Figure 2.2. Smoke Alarm Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Chapter 3—Housing Regulations

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

Zoning, Housing Codes, and Building Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

Zoning and Zoning Ordinances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

Exceptions to the Zoning Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Housing Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6

Building Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-13

Figure 3.1. Example of a Floor Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Figure 3.2. Example of an Angle of Light Obstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Healthy Housing Reference Manual 1

Contents
“Safe, affordable housing is a basic necessity for every family.

Without a decent place to live, people cannot be productive

members of society, children cannot learn and families

cannot thrive.” 

Tracy Kaufman, Research Associate

National Low Income Housing Coalition/

Low Income Housing Information Service

http://www.habitat.org/how/poverty.html; 2003

Introduction

The term “shelter,” which is often used to define housing,

has a strong connection to the ultimate purpose of

housing throughout the world. The mental image of a

shelter is of a safe, secure place that provides both privacy

and protection from the elements and the temperature

extremes of the outside world. 

This vision of shelter, however, is complex. The

earthquake in Bam, Iran, before dawn on December 26,

2003, killed in excess of 30,000 people, most of whom

were sleeping in their homes. Although the homes were

made of the most simple construction materials, many

were well over a thousand years old. Living in a home

where generation after generation had been raised should

provide an enormous sense of security. Nevertheless, the

world press has repeatedly implied that the construction

of these homes destined this disaster. The homes in Iran

were constructed of sun-dried mud-brick and mud. 

We should think of our homes as a legacy to future

generations and consider the negative environmental

effects of building them to serve only one or two

generations before razing or reconstructing them. Homes

should be built for sustainability and for ease in future

modification. We need to learn the lessons of the

earthquake in Iran, as well as the 2003 heat wave in

France that killed in excess of 15,000 people because of

the lack of climate control systems in their homes. We

must use our experience, history, and knowledge of both

engineering and human health needs to construct

housing that meets the need for privacy, comfort,

recreation, and health maintenance.

Health, home construction, and home maintenance are

inseparable because of their overlapping goals. Many

highly trained individuals must work together to achieve

quality, safe, and healthy housing. Contractors, builders,

code inspectors, housing inspectors, environmental health

officers, injury control specialists, and epidemiologists all

are indispensable to achieving the goal of the best

housing in the world for U.S. citizens. This goal is the

basis for the collaboration of the U.S. Department of

Housing and Urban Development (HUD) and the

Centers for Disease and Control and Prevention (CDC). 

Preurban Housing

Early dwelling designs were probably the result of cultural,

socioeconomic, and physical forces intrinsic to the

environment of their inhabitants. The housing similarities

among civilizations separated by vast distances may have

been a result of a shared heritage, common influences,

or chance. 

Caves were accepted as dwellings, perhaps because they

were ready made and required little or no construction.

However, in areas with no caves, simple shelters were

constructed and adapted to the availability of resources

and the needs of the population. Classification systems

have been developed to demonstrate how dwelling types

evolved in preurban indigenous settings [1].

Ephemeral Dwellings

Ephemeral dwellings, also known as transient dwellings,

were typical of nomadic peoples. The African bushmen

and Australia’s aborigines are examples of societies whose

existence depends on an economy of hunting and food

gathering in its simple form. Habitation of an ephemeral

dwelling is generally a matter of days. 

Episodic Dwellings

Episodic housing is exemplified by the Inuit igloo, the

tents of the Tungus of eastern Siberia, and the very

similar tents of the Lapps of northern Europe. These

groups are more sophisticated than those living in

ephemeral dwellings, tend to be more skilled in hunting

or fishing, inhabit a dwelling for a period of weeks, and

have a greater effect on the environment. These groups

also construct communal housing and often practice

slash-and-burn cultivation, which is the least productive

use of cropland and has a greater environmental impact

than the hunting and gathering of ephemeral dwellers. 

Periodic Dwellings

Periodic dwellings are also defined as regular temporary

dwellings used by nomadic tribal societies living in a

Chapter 1: Housing History and Purpose

Healthy Housing Reference Manual 1-1
pastoral economy. This type of housing is reflected in the

yurt used by the Mongolian and Kirgizian groups and the

Bedouins of North Africa and western Asia. These groups’

dwellings essentially demonstrate the next step in the

evolution of housing, which is linked to societal

development. Pastoral nomads are distinguished from

people living in episodic dwellings by their homogenous

cultures and the beginnings of political organization.

Their environmental impact increases with their increased

dependence on agriculture rather than livestock.

Seasonal Dwellings

Schoenauer [1] describes seasonal dwellings as reflective of

societies that are tribal in nature, seminomadic, and based

on agricultural pursuits that are both pastoral and

marginal. Housing used by seminomads for several

months or for a season can be considered semisedentary

and reflective of the advancement of the concept of

property, which is lacking in the preceding societies. This

concept of property is primarily of communal property, as

opposed to individual or personal property. This type of

housing is found in diverse environmental conditions and is

demonstrated in North America by the hogans and armadas

of the Navajo Indians. Similar housing can be found in

Tanzania (Barabaig) and in Kenya and Tanzania (Masai).

Semipermanent Dwellings

According to Schoenauer [1], sedentary folk societies or

hoe peasants practicing subsistence agriculture by

cultivating staple crops use semipermanent dwellings.

These groups tend to live in their dwellings various amounts

of time, usually years, as defined by their crop yields. When

land needs to lie fallow, they move to more fertile areas.

Groups in the Americas that used semipermanent

dwellings included the Mayans with their oval houses and

the Hopi, Zuni, and Acoma Indians in the southwestern

United States with their pueblos.

Permanent Dwellings

The homes of sedentary agricultural societies, whose

political and social organizations are defined as nations

and who possess surplus agricultural products, exemplify

this type of dwelling. Surplus agricultural products

allowed the division of labor and the introduction of

other pursuits aside from food production; however,

agriculture is still the primary occupation for a significant

portion of the population. Although they occurred at

different points in time, examples of early sedentary

agricultural housing can be found in English cottages,

such as the Suffolk, Cornwall, and Kent cottages [1].

Urbanization

Permanent dwellings went beyond simply providing

shelter and protection and moved to the consideration of

comfort. These structures began to find their way into what is

now known as the urban setting. The earliest available

evidence suggests that towns came into existence around

4000 BC. Thus began the social and public health problems

that would increase as the population of cities increased

in number and in sophistication. In preurban housing,

the sparse concentration of people allowed for movement

away from human pollution or allowed the dilution of

pollution at its location. The movement of populations

into urban settings placed individuals in close proximity,

without the benefit of previous linkages and without the

ability to relocate away from pollution or other people. 

Urbanization was relatively slow to begin, but once

started, it accelerated rapidly. In the 1800s, only about

3% of the population of the world could be found in

urban settings in excess of 5,000 people. This was soon to

change. The year 1900 saw the percentage increase to

13.6% and subsequently to 29.8% in 1950. The world’s

urban population has grown since that time. By 1975,

more than one in three of the world’s population lived in

an urban setting, with almost one out of every two living

in urban areas by 1997. Industrialized countries currently

find approximately 75% of their population in an urban

setting. The United Nations projects that in 2015 the

world’s urban population will rise to approximately 55%

and that in industrialized nations it will rise to just over 80%.

In the Western world, one of the primary forces driving

urbanization was the Industrial Revolution. The basic

source of energy in the earliest phase of the Industrial

Revolution was water provided by flowing rivers. Therefore,

towns and cities grew next to the great waterways. Factory

buildings were of wood and stone and matched the houses

in which the workers lived, both in construction and in

location. Workers’ homes were little different in the urban

setting than the agricultural homes from whence they

came. However, living close to the workplace was a

definite advantage for the worker of the time. When the

power source for factories changed from water to coal,

steam became the driver and the construction materials

became brick and cast iron, which later evolved into

steel. Increasing populations in cities and towns increased

social problems in overcrowded slums. The lack of

inexpensive, rapid public transportation forced many

workers to live close to their work. These factory areas

were not the pastoral areas with which many were

familiar, but were bleak with smoke and other pollutants.

The inhabitants of rural areas migrated to ever-expanding

1-2 Housing History and Purpose
cities looking for work. Between 1861 and 1911 the

population of England grew by 80%. The cities and

towns of England were woefully unprepared to cope with

the resulting environmental problems, such as the lack of

potable water and insufficient sewerage. 

In this atmosphere, cholera was rampant; and death rates

resembled those of Third World countries today. Children

had a one in six chance of dying before the age of 1 year.

Because of urban housing problems, social reformers such

as Edwin Chadwick began to appear. Chadwick’s Report

on an Enquiry into the Sanitary Condition of the Labouring

Population of Great Britain and on the Means of its

Improvement [2] sought many reforms, some of which

concerned building ventilation and open spaces around

the buildings. However, Chadwick’s primary contention

was that the health of the working classes could be improved

by proper street cleaning, drainage, sewage, ventilation,

and water supplies. In the United States, Shattuck et al.

[3] wrote the Report of the Sanitary Commission of

Massachusetts, which was printed in 1850. In the report,

50 recommendations were made. Among those related to

housing and building issues were recommendations for

protecting school children by ventilation and sanitation of

school buildings, emphasizing town planning and controlling

overcrowded tenements and cellar dwellings. Figure 1.1

demonstrates the conditions common in the tenements. 

In 1845, Dr. John H. Griscom, the City Inspector of

New York, published The Sanitary Condition of the

Laboring Population of New York [4]. His document

expressed once again the argument for housing reform

and sanitation. Griscom is credited with being the first to

use the phrase “how the other half lives.” During this

time, the poor were not only subjected to the physical

problems of poor housing, but also were victimized by

corrupt landlords and builders.

Trends in Housing

The term “tenement house” was first used in America and

dates from the mid-nineteenth century. It was often

intertwined with the term “slum.” Wright [5] notes that

in English, tenement meant “an abode for a person or for

the soul, when someone else owned the property.” Slum,

on the other hand, initially was used at the beginning of

the 19th century as a slang term for a room. By the

middle of the century, slum had evolved into a term for a

back dwelling occupied by the lowest members of society.

Von Hoffman [6] states that this term had, by the end of

the century, begun to be used interchangeably with

tenement. The author noted that in the larger cities of

the United States, the apartment house emerged in the

1830s as a housing unit of two to five stories, with each

story containing apartments of two to four rooms. It was

originally built for the upper group of the working class.

The tenement house emerged in the 1830s when

landlords converted warehouses into inexpensive housing

designed to accommodate Irish and black workers.

Additionally, existing large homes were subdivided and

new structures were added, creating rear houses and, in

the process, eliminating the traditional gardens and yards

behind them. These rear houses, although new, were

no healthier than the front house, often housing up to

10 families. When this strategy became inadequate to

satisfy demand, the epoch period of the tenements began.

Although unpopular, the tenement house grew in

numbers, and, by 1850 in New York and Boston, each

tenement housed an average of 65 people. During the

1850s, the railroad house or railroad tenement was

introduced. This structure was a solid, rectangular block

with a narrow alley in the back. The structure was

typically 90 feet long and had 12 to 16 rooms, each about

6 feet by 6 feet and holding around four people. The

facility allowed no direct light or air into rooms except

those facing the street or alley. Further complicating this

structure was the lack of privacy for the tenants. A lack of

hallways eliminated any semblance of privacy. Open sewers,

a single privy in the back of the building, and uncollected

Healthy Housing Reference Manual 1-3

Figure 1.1. Conditions in the Tenements
garbage resulted in an objectionable and unhygienic place to

live. Additionally, the wood construction common at the

time, coupled with coal and wood heating, made fire an

ever-present danger. As a result of a series of tenement

fires in 1860 in New York, such terms as death-trap and

fire-trap were coined to describe the poorly constructed

living facilities [6]. 

The two last decades of the 19th century saw the

introduction and development of dumbbell tenements, a

front and rear tenement connected by a long hall. These

tenements were typically five stories, with a basement and

no elevator (elevators were not required for any building

of less than six stories). Dumbbell tenements, like other

tenements, resulted in unaesthetic and unhealthy places to

live. Garbage was often thrown down the airshafts, natural

light was confined to the first floor hallway, and the public

hallways only contained one or two toilets and a sink.

This apparent lack of sanitary facilities was compounded

by the fact that many families took in boarders to help with

expenses. In fact, 44,000 families rented space to boarders

in New York in 1890, with this increasing to 164,000

families in 1910. In the early 1890s, New York had a

population of more than 1 million, of which 70% were

residents of multifamily dwellings. Of this group, 80%

lived in tenements consisting mostly of dumbbell tenements.

The passage of the New York Tenement House Act of

1901 spelled the end of the dumbbells and acceptance of

a new tenement type developed in the 1890s—the park

or central court tenement, which was distinguished by a

park or open space in the middle of a group of buildings.

This design was implemented to reduce the activity on

the front street and to enhance the opportunity for fresh

air and recreation in the courtyard. The design often

included roof playgrounds, kindergartens, communal

laundries, and stairways on the courtyard side. 

Although the tenements did not go away, reform groups

supported ideas such as suburban cottages to be

developed for the working class. These cottages were twostory brick and timber, with a porch and a gabled roof.

According to Wright [5], a Brooklyn project called

Homewood consisted of 53 acres of homes in a planned

neighborhood from which multifamily dwellings, saloons,

and factories were banned.

Although there were many large homes for the well-to-do,

single homes for the not-so-wealthy were not abundant.

The first small house designed for the individual of

modest means was the bungalow. According to

Schoenauer [1], bungalows originated in India. The

bungalow was introduced into the United States in 1880

with the construction of a home in Cape Cod. The bungalow,

derived for use in tropical climates, was especially popular

in California. 

Company towns were another trend in housing in the

19th century. George Pullman, who built railway cars in the

1880s, and John H. Patterson, of the National Cash

Register Company, developed notable company towns.

Wright [5] notes that in 1917 the U.S. Bureau of Labor

Standards estimated that at least 1,000 industrial firms were

providing housing for their employees. The provision of

housing was not necessarily altruistic. The motivation

for providing housing varied from company to company.

Such motivations included the use of housing as a

recruitment incentive for skilled workers, a method of

linking the individual to the company, and a belief that a

better home life would make the employees happier and

more productive in their jobs. Some companies, such as

Firestone and Goodyear, went beyond the company town

and allowed their employees to obtain loans for homes

from company-established banks. A prime motivator of

company town planning was sanitation, because

maintaining the worker’s health could potentially lead to

fewer workdays lost due to illness. Thus, in the

development of the town, significant consideration was

given to sanitary issues such as window screens, sewage

treatment, drainage, and water supplies. 

Before World War I there was a shortage of adequate

dwellings. Even after World War I, insufficient funding, a

shortage of skilled labor, and a dearth of building materials

compounded the problem. However, the design of homes

after the war was driven in part by health considerations,

such as providing good ventilation, sun orientation and

exposure, potable pressurized water, and at least one

private toilet. Schoenauer [1] notes that, during the

postwar years, the improved mobility of the public led to

an increase in the growth of suburban areas, exemplified

by the detached and sumptuous communities outside

New York, such as Oyster Bay. In the meantime, the

conditions of working populations consisting of many

immigrants began to improve with the improving

economy of the 1920s. The garden apartment became

popular. These units were well lighted and ventilated and

had a courtyard, which was open to all and well maintained. 

Immediately after World War I and during the 1920s, city

population growth was outpaced by population growth in

the suburbs by a factor of two. The focus at the time was

on the single-family suburban dwelling. The 1920s were a

time of growth, but the decade following the Great

1-4 Housing History and Purpose
Depression, beginning in 1929, was one of deflation,

cessation of building, loss of mortgage financing, and the

plunge into unemployment of large numbers of building

trade workers. Additionally, 1.5 million home loans were

foreclosed during this period. In 1936, the housing market

began to make a comeback; however, the 1930s would

come to be known as the beginning of public housing,

with increased public involvement in housing

construction, as demonstrated by the many laws passed

during the era [5]. The National Housing Act was

passed by Congress in 1934 and set up the Federal Housing

Administration. This agency encouraged banks, building 

and loan associations, and others to make loans for

building homes, small business establishments, and farm

buildings. If the Federal Housing Administration

approved the plans, it would insure the loan. In 1937,

Congress passed another National Housing Act that

enabled the Federal Housing Administration to take

control of slum clearance. It made 60-year loans at low

interest to local governments to help them build

apartment blocks. Rents in these homes were fixed and

were only available to low-income families. By 1941, the

agency had assisted in the construction of more than

120,000 family units. 

Healthy Housing Reference Manual 1-5

1934 Housing Act establishes Federal Housing Administration to insure mortgages and make loans to 

low-income families; Fannie Mae created.

1937 Housing Act establishes public housing.

1944 Serviceman’s Readjustment Act creates Veteran Administration mortgages; trend toward 

suburbia begins.

Late 1950s Urban renewal begins; slum clearance developed to promote construction of affordable housing.

1965 Department of Housing and Urban Development created.

1968 Model Cities program launched; fair housing launched through the Civil Rights Act.

1971 Lead-Based Paint Poisoning Prevention Act passed. 

1974 Section 8 rental subsidy program begins; Community Development Block Grant program begins.

1977 Urban Development Action Grants begin.

1986 Low-income housing tax credit created.

1987 McKinney Homeless Assistance Act passed; creation of low-income housing tax credit.

1991–1994 Public housing inspection for lead paint.

1992 Residential Lead Hazard Reduction Act passed (Title X of the 1992 Housing and Community 

Development Act).

1993 Hope VI program begins to redevelop old public housing.

1996 Lead-based paint disclosure becomes law.

1999 HUD and CDC launch the Healthy Homes Initiative.

2000 HUD publishes new lead paint regulations for federally funded assisted housing; President’s Task 

Force releases federal interagency plan to eliminate childhood lead paint poisoning by 2010.

2001 EPA publishes final standards for lead in paint, dust, and soil in housing.

History of the Department of Housing and Urban Development
During World War II, the focus of home building was on

housing for workers who were involved in the war effort.

Homes were being built through federal agencies such as

the newly formed Federal Housing Administration, formed

in 1934 and transferred to HUD in 1965. According to

the U.S. Census Bureau (USCB) [7], in the years since

World War II, the types of homes Americans live in have

changed dramatically. In 1940, most homes were considered

attached houses (row houses, townhouses, and duplexes).

Small apartment houses with two to four apartments had

their zenith in the 1950s. In the 1960 census, two-thirds

of the housing inventory was made up of one-family detached

houses, which declined to less than 60% in the 1990 census.

The postwar years saw the expansion of suburban housing

led by William J. Levitt’s Levittown, on Long Island,

which had a strong influence on postwar building and

initiated the subdivisions and tract houses of the

following decades (Figure 1.2). The 1950s and 1960s saw

continued suburban development, with the growing ease of

transportation marked by the expansion of the interstate

highway system. As the cost of housing began to increase

as a result of increased demand, a grassroots movement to

provide adequate housing for the poor began to emerge.

According to Wright [5], in the 1970s only about 25% of the

population could afford a $35,000 home. According to

Gaillard [8], Koinonia Partners, a religious organization

founded in 1942 by Clarence Jordan near Albany,

Georgia, was the seed for Habitat for Humanity. Habitat

for Humanity, founded in 1976 by Millard Fuller, is

known for its international efforts and has constructed

more than 150,000 houses in 80 countries; 50,000 of these

houses are in the United States. The homes are energyefficient and environmentally friendly to conserve resources

and reduce long-term costs to the homeowners. 

Builders also began promoting one-floor minihomes and

no-frills homes of approximately 900 to 1,200 square feet.

Manufactured housing began to increase in popularity,

with mobile home manufacturers becoming some of the

most profitable corporations in the United States in the

early 1970s. In the 1940 census, manufactured housing

were lumped into the “other” category with boats and tourist

cabins: by the 1990 census, manufactured housing made up

7% of the total housing inventory. Many communities

ban manufactured housing from residential

neighborhoods. 

According to Hart et al. [9], nearly 30% of all home sales

nationwide are of manufactured housing, and more than

90% of those homes are never moved once they are

anchored. According to a 2001 industry report, the

demand for prefabricated housing is expected to increase

in excess of 3% annually to $20 billion in 2005, with

most units being manufactured homes. The largest

market is expected to continue in the southern part of the

United States, with the most rapid growth occurring in

the western part of the country. As of 2000, five

manufactured-home producers, representing 35% of the

market, dominated the industry. This industry, over the

past 20 to 25 years, has been affected by two pieces of

federal legislation. The first, the Mobile Home

Construction and Safety Standards Act, adopted by HUD

in 1974, was passed to aid consumers through regulation

and enforcement of HUD design and construction

standards for manufactured homes. The second, the 1980

Housing Act, required the federal government to change

the term “mobile home” to “manufactured housing” in all

federal laws and literature. One of the prime reasons for

this change was that these homes were in reality no longer

mobile in the true sense. 

The energy crisis in the United States between 1973 and

1974 had a major effect on the way Americans lived,

drove, and built their homes. The high cost of both

heating and cooling homes required action, and some of

the action taken was ill advised or failed to consider

healthy housin concerns. Sealing homes and using untried

insulation materials and other energy conservation actions

often resulted in major and sometimes dangerous

buildups of indoor air pollutants. These buildups of

toxins occurred both in homes and offices. Sealing

buildings for energy efficiency and using off-gassing

building materials containing urea-formaldehyde, vinyl,

and other new plastic surfaces, new glues, and even

wallpapers created toxic environments. These newly sealed

environments were not refreshed with makeup air and

resulted in the accumulation of both chemical and

1-6 Housing History and Purpose

Figure 1.2. Levittown, New York
biologic pollutants and moisture leading to mold growth,

representing new threats to both short-term and longterm health. The results of these actions are still being

dealt with today. 

References

1. Schoenauer N. 6,000 years of housing. New York/

London: W.W. Norton & Company, Inc.; 2000.

2. Chadwick E. Report on an enquiry into the

sanitary condition of the labouring population of

Great Britain and on the means of its

improvements. London: Clowes and Sons; 1842.

3. Shattuck L, Banks N Jr, Abbot J. Report of the

Sanitary Commission of Massachusetts, 1850.

Boston: Dutton and Wentworth; 1850. Available

from URL: http://www.deltaomega.org/shattuck.pdf.

4. Griscom JH. The sanitary condition of the

labouring population of New York. New York:

Harper; 1845. 

5. Wright G. Building the dream—a social history

of housing in America. Cambridge, MA/London:

The MIT Press; 1998. 

6. Von Hoffman A. The origins of American

housing reform. Cambridge, MA: Joint Center

for Housing Studies—Harvard University; August

1998. p. W98-2.

7. US Census Bureau. Historical census of housing

tables—units in structure; 2002. Washington, DC:

US Census Bureau; 2002. Available from URL: 

http://www.census.gov/hhes/www/housing/census/

historic/units.html.

8. Gaillard F. If I were a carpenter, twenty years of

Habitat for Humanity. Winston-Salem, NC:

John E. Blair; 1996.

9. Hart JF, Rhodes MJ, Morgan JT, Lindberg MB.

The unknown world of the mobile home.

Baltimore, MD: Johns Hopkins University

Press; 2002.

Additional Sources of Information 

Dolkart A. The 1901 Tenement House Act: chapter 6,

cleaning up the toilets. New York: Lower East Side

Tenement Museum; no date. Available from URL:

http://www.tenement.org/ features_dolkart7.html.

Hale EE. Workingmen’s homes, essays and stories, on the

homes of men who work in large towns. Boston: James

R. Osgood and Company; 1874.

History of plumbing in America. Plumbing and

Mechanical Magazine. 1987 Jul. Available from URL:

http://www.plumbingsupply.com/pmamerica.html.

Housing Act of 1949, The US Committee on

Agriculture Glossary.

Lang RE, Sohmer RR. Editors’ introduction, legacy of

the Housing Act of 1949: the past, present, and future of

federal housing and urban policy. Housing Policy Debate

2000; 11(2) 291–8. Available from URL:

http://www.fanniemaefoundation.org/ programs/hpd/v11i2-

edintro.shtml.

Mason JB. History of housing in the US. 1930–1980.

Houston, TX: Gulf Publishing Company; 1982. 

Passic F. Urban renewal. Morning Star [Albion,

Michigan]. 1997 Feb 13; 6. Available from URL:

http://www.albionmich.com/ history/

histor_notebook/940213.shtml. 

Red-lining [definition of], 535A.1 Definitions, Iowa

Code 2001: Section 535A.1. Des Moines, IA: The Iowa

Legislature. Available from URL:

http://www.legis.state.ia.us/IACODE/

2001/535A/1.html.

Rental Housing On Line. Federal housing acts. Port

Huron, MI: Rental Housing On Line; no date. Available

from URL: http://www.rhol.org/rental/fedact.htm.

Rental Housing On Line. Government’s role in low

income housing. Port Huron, MI: Rental Housing

On Line; no date. Available from URL:

http://www.rhol.org/rental/housing.htm.

Texas Low Income Housing Information Service. The

past: special interests, race, and local control; Housing

Act of 1949: bipartisan support for public housing.

Austin, TX: Texas Low Income Housing Information

Service; no date. Available from URL:

http://www.texashousing.org/txlihis/ phdebate/past12.html.

US Department of Housing and Urban Development.

Fair housing laws and presidential Executive Orders.

Washington, DC: US Department of Housing and 

Healthy Housing Reference Manual 1-7
Urban Development; no date. Available from URL:

http://www.hud.gov/ offices/ fheo/ FHLaws/index.cfm.

US Department of Housing and Urban Development.

Homes and communities. Washington, DC: US

Department of Housing and Urban Development; no

date. Available from URL: http://www.hud.gov.

Warth G. Research project looking at red-lining. North

County [California] Times 2002 May 5. Available from

URL: http://www.nctimes.com/ articles/2002/05/

05/export8963.txt.

1-8 Housing History and Purpose
“The connection between health and dwelling is one of the

most important that exists.” 

Florence Nightingale

Introduction

It seems obvious that health is related to where people

live. People spend 50% or more of every day inside their

homes. Consequently, it makes sense that the housing

environment constitutes one of the major influences on

health and well-being. Many of the basic principles of the

link between housing and health were elucidated more

than 60 years ago by the American Public Health

Association (APHA) Committee on the Hygiene of

Housing. After World War II, political scientists,

sociologists, and others became interested in the relation

between housing and health, mostly as an outgrowth of a

concern over poor housing conditions resulting from the

massive influx into American cities of veterans looking

for jobs. Now, at the beginning of the 21st century, there is

a growing awareness that health is linked not only to the

physical structure of a housing unit, but also to the

neighborhood and community in which the house is located.

According to Ehlers and Steel [1], in 1938, a Committee

on the Hygiene of Housing, appointed by APHA,

created the Basic Principles of Healthful Housing, which

provided guidance regarding the fundamental needs of

humans as they relate to housing. These fundamental

needs include physiologic and psychologic needs,

protection against disease, protection against injury,

protection against fire and electrical shock, and

protection against toxic and explosive gases. 

Fundamental Physiologic Needs 

Housing should provide for the following physiologic needs:

1. protection from the elements,

2. a thermal environment that will avoid undue heat loss,

3. a thermal environment that will permit adequate

heat loss from the body,

4. an atmosphere of reasonable chemical purity,

5. adequate daylight illumination and avoidance

of undue daylight glare,

6. direct sunlight,

7. adequate artificial illumination and avoidance of glare,

8. protection from excessive noise, and

9. adequate space for exercise and for children to play.

The first three physiologic needs reflect the requirement

for adequate protection from the elements. The lack of

adequate heating and cooling systems in homes can

contribute to respiratory illnesses or even lead to death

from extreme temperatures. According to the National

Weather Service, 98 people died from extreme

temperatures in 1996; 62 of these were due to extreme

cold. Hypothermia occurs when the body temperature

drops below 96°F (46°C). It can occur in any person

exposed to severe cold without enough protection. Older

people are particularly susceptible because they may not

notice the cold as easily and can develop hypothermia

even after exposure to mild cold. Susceptibility to the

cold can be exacerbated by certain medications, medical

conditions, or the consumption of alcohol. Hyperthermia is

the name given to a variety of heat-related illnesses. The two

most common forms of hyperthermia are heat

exhaustion and heat stroke. Of the two, heat stroke is

especially dangerous and requires immediate medical attention. 

According to the National Institute on Aging (NIA) [2],

lifestyle factors can increase the risk for hyperthermia:

Unbearably hot living quarters. This would include

people who live in homes without fans or air

conditioners. To help avert the problem, residents should

open windows at night; create cross-ventilation by opening

windows on two sides of the building; cover windows

when they are exposed to direct sunlight and keep curtains,

shades, or blinds drawn during the hottest part of the day.

Lack of transportation. People without fans or air conditioners

often are unable to go to shopping malls, movie theaters, and

libraries to cool off because of illness or the lack of

transportation.

Inadequate or inoperable windows. Society has become

so reliant on climate control systems that when they fail,

windows cannot be opened. As was the case in the 2003

heat wave in France, many homes worldwide do not even

have fans for cooling.

Chapter 2: Basic Principles of Healthy Housing

Healthy Housing Reference Manual 2-1
Overdressing. Older people, because they may not feel

the heat, may not dress appropriately in hot weather. 

Visiting overcrowded places. Trips should be scheduled

during nonrush-hour times and participation in special events

should be carefully planned to avoid disease transmission.

Not checking weather conditions. Older people,

particularly those at special risk, should stay indoors on

especially hot and humid days, particularly when an air

pollution alert is in effect.

USCB [3] reported that about 75% of homes in the

United States used either utility gas or electricity for

heating purposes, with utility gas accounting for about

50%. This, of course, varies with the region of the

country, depending on the availability of hydroelectric

power. This compares with the 1940 census, which found

that three-quarters of all households heated with coal or

wood. Electric heat was so rare that it was not even an

option on the census form of 1940. Today, coal has

virtually disappeared as a household fuel. Wood all but

disappeared as a heating fuel in 1970, but made a modest

comeback at 4% nationally by 1990. This move over time

to more flexible fuels allows a majority of today’s homes

to maintain healthy temperatures, although many houses

still lack adequate insulation.

The fifth through the seventh physiologic concerns

address adequate illumination, both natural and artificial.

Research has revealed a strong relationship between light

and human physiology. The effects of light on both the

human eye and human skin are notable. According to

Zilber [4], one of the physiologic responses of the skin to

sunlight is the production of vitamin D. Light allows us

to see. It also affects body rhythms and psychologic

health. Average individuals are affected daily by both

natural and artificial lighting levels in their homes.

Adequate lighting is important in allowing people to see

unsanitary conditions and to prevent injury, thus

contributing to a healthier and safer environment.

Improper indoor lighting can also contribute to eyestrain

from inadequate illumination, glare, and flicker. 

Avoiding excessive noise (eighth physiologic concern) is

important in the 21st century. However, the concept of

noise pollution is not new. Two thousand years ago, Julius

Caesar banned chariots from traveling the streets of Rome

late at night. In the 19th century, numerous towns and

cities prohibited ringing church bells. In the early 20th

century, London prohibited church bells from ringing

between 9:00 PM and 9:00 AM. In 1929, New York City

formed a Noise Abatement Commission that was charged

with evaluating noise issues and suggesting solutions. At

that time, it was concluded that loud noise affected health

and productivity. In 1930, this same commission

determined that constant exposure to loud noises could

affect worker efficiency and long-term hearing levels. In

1974, the U.S. Environmental Protection Agency (EPA)

produced a document titled Information on Levels of

Environmental Noise Requisite to Protect Public Health and

Welfare With an Adequate Margin of Safety [5]. This

document identified maximum levels of 55 decibels outdoors

and 45 decibels indoors to prevent interference with

activities and 70 decibels for all areas to prevent hearing

loss. In 1990, the United Kingdom implemented The

Household Appliances (Noise Emission) Regulations [6]

to help control indoor noise from modern appliances.

Noise has physiologic impacts aside from the potential to

reduce hearing ability. According to the American SpeechLanguage-Hearing Association [7], these effects include

elevated blood pressure; negative cardiovascular effects;

increased breathing rates, digestion, and stomach

disturbances; ulcers; negative effects on developing

fetuses; difficulty sleeping after the noise stops; plus the

intensification of the effects of drugs, alcohol, aging, and

carbon monoxide. In addition, noise can reduce attention

to tasks and impede speech communication. Finally, noise

can hamper performance of daily tasks, increase fatigue,

and cause irritability.

Household noise can be controlled in various ways.

Approaching the problem during initial construction is

the simplest, but has not become popular. For example, in

early 2003, only about 30% of homebuilders offered

sound-attenuating blankets for interior walls. A soundattenuating blanket is a lining of noise abatement

products (the thickness depends on the material being used).

Spray-in-place soft foam insulation can also be used as a

sound dampener, as can special walking mats for floors.

Actions that can help reduce household noise include

installing new, quieter appliances and isolating washing

machines to reduce noise and water passing through pipes. 

The ninth and final physiologic need is for adequate

space for exercise and play. Before industrialization in the

United States and England, a preponderance of the

population lived and worked in more rural areas with

very adequate areas for exercise and play. As

industrialization impacted demographics, more people

were in cities without ample space for play and exercise.

In the 19th century, society responded with the

development of playgrounds and public parks. Healthful

housing should include the provision of safe play and

2-2 Basic Principles of Healthy Housing
exercise areas. Many American neighborhoods are severely

deficient, with no area for children to safely play. New

residential areas often do not have sidewalks or street

lighting, nor are essential services available by foot

because of highway and road configurations. 

Fundamental Psychologic Needs

Seven fundamental psychologic needs for healthy housing

include the following:

1. adequate privacy for the individual,

2. opportunities for normal family life,

3. opportunities for normal community life,

4. facilities that make possible the performance of

household tasks without undue physical and

mental fatigue,

5. facilities for maintenance of cleanliness of the

dwelling and of the person,

6. possibilities for aesthetic satisfaction in the home

and its surroundings, and 

7. concordance with prevailing social standards of

the local community.

Privacy is a necessity to most people, to some degree and

during some periods. The increase in house size and the

diminishing family size have, in many instances, increased

the availability of privacy. Ideally, everyone would have

their own rooms, or, if that were not possible, would

share a bedroom with only one person of the same sex,

excepting married couples and small children. Psychiatrists

consider it important for children older than 2 years to

have bedrooms separate from their parents. In addition,

bedrooms and bathrooms should be accessible directly

from halls or living rooms and not through other bedrooms.

In addition to the psychologic value of privacy, repeated

studies have shown that lack of space and quiet due to

crowding can lead to poor school performance in children.

Coupled with a natural desire for privacy is the social

desire for normal family and community life. A wholesome

atmosphere requires adequate living room space and

adequate space for withdrawal elsewhere during periods of

entertainment. This accessibility expands beyond the walls

of the home and includes easy communication with centers

of culture and business, such as schools, churches,

entertainment, shopping, libraries, and medical services.

Protection Against Disease 

Eight ways to protect against contaminants include the

following:

1. provide a safe and sanitary water supply;

2. protect the water supply system against pollution;

3. provide toilet facilities that minimize the danger

of transmitting disease;

4. protect against sewage contamination of the interior

surfaces of the dwelling;

5. avoid unsanitary conditions near the dwelling;

6. exclude vermin from the dwelling, which may

play a part in transmitting disease;

7. provide facilities for keeping milk and food

fresh; and 

8. allow sufficient space in sleeping rooms to

minimize the danger of contact infection.

According to the U.S. EPA [8], there are approximately

160,000 public or community drinking water systems in the

United States. The current estimate is that 42 million

Americans (mostly in rural America) get their water from

private wells or other small, unregulated water systems.

The presence of adequate water, sewer, and plumbing

facilities is central to the prevention, reduction, and possible

elimination of water-related diseases. According to the

Population Information Program [9], water-related diseases

can be organized into four categories: 

• waterborne diseases, including those caused by

both fecal-oral organisms and those caused by toxic

substances;

• water-based diseases; 

• water-related vector diseases; and 

• water-scarce diseases. 

Numerous studies link improvements in sanitation and the

provision of potable water with significant reductions in

morbidity and mortality from water-related diseases.

Clean water and sanitation facilities have proven to

reduce infant and child mortality by as much as 55%

in Third World countries according to studies from the

Healthy Housing Reference Manual 2-3
1980s. Waterborne diseases are often referred to as “dirtywater” diseases and are the result of contamination from

chemical, human, and animal wastes. Specific diseases

in this group include cholera, typhoid, shigella, polio,

meningitis, and hepatitis A and E. Water-based diseases

are caused by aquatic organisms that spend part of their

life cycle in the water and another part as parasites of

animals. Although rare in the United States, these

diseases include dracunculiasis, paragonimiasis,

clonorchiasis, and schistosomiasis. The reduction in these

diseases in many countries has not only led to decreased rates

of illness and death, but has also increased productivity

through a reduction in days lost from work. 

Water-related diseases are linked to vectors that breed and

live in or near polluted and unpolluted water. These vectors are

primarily mosquitoes that infect people with the disease

agents for malaria, yellow fever, dengue fever, and

filariasis. While the control of vectorborne diseases is a

complex matter, in the United States, most of the control

focus has been on controlling habitat and breeding areas

for the vectors and reducing and controlling human cases

of the disease that can serve as hosts for the vector.

Vectorborne diseases have recently become a more of a

concern to the United States with the importation of the

West Nile virus. The transmission of West Nile virus

occurs when a mosquito vector takes a blood meal from a bird

or incidental hosts, such as a dog, cat, horse, or other

vertebrate. The human cases of West Nile virus in

2003 numbered 9,862, with 264 deaths. Finally,

water-scarce diseases are diseases that flourish where

sanitation is poor due to a scarcity of fresh water. Diseases

included in this category are diphtheria, leprosy, whooping

cough, tetanus, tuberculosis, and trachoma. These

diseases are often transmitted when the supply of fresh

water is inadequate for hand washing and basic hygiene.

These conditions are still rampant in much of the world,

but are essentially absent from the United States due to

the extensive availability of potable drinking water. 

In 2000, USCB [10] reported that 1.4% of U.S. homes

lacked plumbing facilities. This differs greatly from the

1940 census, when nearly one-half of U.S. homes lacked

complete plumbing. The proportion has continually

dropped, falling to about one-third in 1950 and then to

one-sixth in 1960. Complete plumbing facilities are

defined as hot and cold piped water, a bathtub or shower,

and a flush toilet. The containment of household sewage

is instrumental in protecting the public from waterborne

and vectorborne diseases. The 1940 census revealed that

more than a third of U.S. homes had no flush toilet, with

70% of the homes in some states without a flush toilet.

Of the 13 million housing units at the time without flush

toilets, 11.8 million (90.7%) had an outside toilet or

privy, another 1 million (7.6%) had no toilet or privy,

and the remainder had a nonflush toilet in the structure. 

In contrast to these figures, the 2000 census data demonstrate

the great progress that has been made in providing sanitary

sewer facilities. Nationally, 74.8% of homes are served by

a public sewer, with 24.1% served by a septic tank or cesspool,

and the remaining 1.1% using other means. 

Vermin, such as rodents, have long been linked to

property destruction and disease. Integrated pest

management, along with proper housing construction, has

played a significant role in reducing vermin around the

modern home. Proper food storage, rat-proofing

construction, and ensuring good sanitation outside the

home have served to eliminate or reduce rodent problems

in the 21st century home.

Facilities to properly store milk and food have not only been

instrumental in reducing the incidence of some foodborne

diseases, but have also significantly changed the diet in

developed countries. Refrigeration can be traced to the

ancient Chinese, Hebrews, Greeks, and Romans. In the

last 150 years, great strides have been made in using

refrigeration to preserve and cool food. Vapor compression

using air and, subsequently, ammonia as a coolant was

first developed in the 1850s. In the early 1800s, natural

ice was extracted for use as a coolant and preserver of

food. By the late 1870s, there were 35 commercial ice

plants in the United States and, by 1909, there were 2,000.

However, as early as the 1890s, sources of natural ice 

began to be a problem as a result of pollution and sewage

dumped into bodies of water. Thus, the use of natural ice as

a refrigerant began to present a health problem. Mechanical

manufacture of ice provided a temporary solution, which

eventually resulted in providing mechanical refrigeration. 

Refrigeration was first used by the brewing and meat-packing

industries; but most households had iceboxes (Figure 2.1),

which made the ice wagon a popular icon of the late

1800s and early 1900s. In 1915, the first refrigerator, the

Guardian, was introduced. This unit was the predecessor of

the Frigidaire. The refrigerator became as necessary to the

household as a stove or sewing machine. By 1937, nearly

6 million refrigerators were manufactured in the United

States. By 1950, in excess of 80% of American farms and

more than 90% of urban homes had a refrigerator.

Adequate living and sleeping space are also important in

protecting against contagion. It is an issue not only of

2-4 Basic Principles of Healthy Housing
privacy but of adequate room to reduce the potential for the

transmission of contagion. Much improvement has been

made in the adequacy of living space for the U.S. family

over the last 30 years. According to USCB [11], the

average size of new single homes has increased from a

1970 average of 1,500 square feet to a 2000 average of

2,266 square feet. USCB [11] says that slightly less than

5% of U.S. homes were considered crowded in 1990; that

is, they had more than one person per room. However,

this is an increase since the 1980 census, when the figure

was 4.5%. This is the only time there has been an

increase since the first housing census was initiated in

1940, when one in five homes was crowded. During the

1940 census, most crowded homes were found in

southern states, primarily in the rural south. Crowding

has become common in a few large urban areas, with

more than one-fourth of all crowded units located in four

metropolitan areas: Houston, Los Angeles, Miami, and

New York. The rate for California has not changed

significantly between 1940 (13%) and 1990 (12%).

Excessive crowding in homes has the potential to increase

not only communicable disease transmission, but also the

stress level of occupants because modern urban

individuals spend considerably more time indoors than

did their 1940s counterparts.

Protection Against Injury

A major provision for safe housing construction is

developing and implementing building codes. According

to the International Code Council one- and two-family

dwelling code, the purpose of building codes is to provide

minimum standards for the protection of life, limb,

property, environment, and for the safety and welfare of

the consumer, general public, and the owners and

occupants of residential buildings regulated by this

code [12]. 

However, as with all types of codes, the development of

innovative processes and products must be allowed to take

a place in improving construction technology. Thus,

according to the International Code Council one- and

two-family dwelling code, building codes are not

intended to limit the appropriate use of materials,

appliances, equipment, or methods by design or

construction that are not specifically prescribed by the

code if the building official determines that the proposed

alternate materials, appliances, equipment or methods of

design or construction are at least equivalent of that

prescribed in this code. While the details of what a code

should include are beyond the scope of this section,

additional information can be found at

http://www.iccsafe.org/, the Web site of the International

Code Council (ICC). ICC is an organization formed by

the consolidation of the Building Officials and Code

Administrators International, Southern Building Code

Congress International, Inc., and the International

Conference of Building Officials [12].

According to the Home Safety Council (HSC) [13], the

leading causes of home injury deaths in 1998 were falls

and poisonings, which accounted for 6,756 and

5,758 deaths, respectively. As expected, the rates and

national estimates of the number of fall deaths were

highest among those older than 64 years, and stairs or steps

were associated with 17% of fall deaths. Overall, falls were

the leading cause of nonfatal, unintentional injuries

occurring at home and accounted for 5.6 million injuries.

Similar to the mortality statistics, consumer products most

often associated with emergency department visits included

stairs and steps, accounting for 854,631 visits, and floors,

accounting for 556,800 visits. A national survey by HSC

found that one-third of all households with stairs did not

have banisters or handrails on at least one set of stairs.

Related to this, homes with older persons were more

likely to have banisters or handrails than were those where

young children live or visit. The survey also revealed that

48% of households have windows on the second floor or

above, but only 25% have window locks or bars to

prevent children from falling out. Bathtub mats or

nonskid strips to reduce bathtub falls were used in 63%

of American households. However, in senior households

Healthy Housing Reference Manual 2-5

Figure 2.1. Circa 1890 Icebox 

Source: Robert R. McCormick Museum, Wheaton, Illinois
(age 70 years and older), 79% used mats or nonskid strips.

Nineteen percent of the total number of homes surveyed

had grab bars to supplement the mats and strips. Significantly,

only 39% of the group most susceptible to falls (people aged

70 years and older) used both nonskid surfaces and grab bars.

Protection Against Fire

An important component of safe housing is to control

conditions that promote the initiation and spread of fire.

Between 1992 and 2001, an average of 4,266 Americans

died annually in fires and nearly 25,000 were injured.

This fact and the following information from the United

States Fire Administration (USFA) [14] demonstrate the

impact that fire safety and the lack of it have in the United

States. The United States has one of the highest fire death

rates in the industrialized world, with 13.4 deaths per

million people. At least 80% of all fire deaths occur in

residences. Residential fires account for 23% of all fires

and 76% of structure fires. In one- and two-family

dwellings, fires start in the kitchen 25.5% of the time and

originate in the bedroom 13.7% of the time. Apartment

fires most often start in the kitchen, but at almost twice

the rate (48.5%), with bedrooms again being the second

most common place at 13.4%.

These USFA statistics also disclose that cooking is the

leading cause of home fires, usually a result of unattended

cooking and human error rather than mechanical failure

of the cooking units. The leading cause of fire deaths in

homes is careless smoking, which can be significantly

deterred by smoke alarms and smolder-resistant bedding

and upholstered furniture. Heating system fires tend to be

a larger problem in single-family homes than in

apartments because the heating systems in family homes

frequently are not professionally maintained. 

A number of conditions in the household can contribute

to the creation or spread of fire. The USFA data indicate

that more than one-third of rural Americans use fireplaces,

wood stoves, and other fuel-fired appliances as primary sources

of heat. These same systems account for 36% of rural

residential fires. Many of these fires are the result of

creosote buildup in chimneys and stovepipes. These fires

could be avoided by

• inspecting and cleaning by a certified chimney

specialist;

• clearing the area around the hearth of debris,

decorations, and flammable materials;

• using a metal mesh screen with fireplaces and

leaving glass doors open while burning a fire;

• installing stovepipe thermometers to monitor flue

temperatures;

• leaving air inlets on wood stoves open and never

restricting air supply to the fireplaces, thus

helping to reduce creosote buildup;

• using fire-resistant materials on walls around

wood stoves;

• never using flammable liquids to start a fire;

• using only seasoned hardwood rather than soft,

moist wood, which accelerates creosote buildup;

• building small fires that burn completely and

produce less smoke;

• never burning trash, debris, or pasteboard in a

fireplace;

• placing logs in the rear of the fireplace on an adequate

supporting grate;

• never leaving a fire in the fireplace unattended;

• keeping the roof clear of leaves, pine needles,

and other debris;

• covering the chimney with a mesh screen spark

arrester; and

• removing branches hanging above the chimney,

flues, or vents. 

USFA [14] also notes that manufactured homes can be

susceptible to fires. More than one-fifth of residential fires

in these facilities are related to the use of supplemental

room heaters, such as wood- and coal-burning stoves,

kerosene heaters, gas space-heaters, and electrical heaters.

Most fires related to supplemental heating equipment result

from improper installation, maintenance, or use of the

appliance. USFA recommendations to reduce the chance

of fire with these types of appliances include the following:

• placing wood stoves on noncombustible surfaces

or a code-specified or listed floor surface;

2-6 Basic Principles of Healthy Housing
• placing noncombustible materials around the

opening and hearth of fireplaces;

• placing space heaters on firm, out-of-the-way

surfaces to reduce tipping over and subsequent

spillage of fuel and providing at least 3 feet of air

space between the heating device and walls, chairs,

firewood, and curtains;

• placing vents and chimneys to allow 18 inches of air

space between single-wall connector pipes and

combustibles and 2 inches between insulated

chimneys and combustibles; and 

• using only the fuel designated by the

manufacturer for the appliance.

The ability to escape from a building when fire has been

discovered or detected is of extreme importance. In the

modern home, three key elements can contribute to a safe

exit from a home during the threat of fire. The first of

these is a working smoke alarm system. The average

homeowner in the 1960s had never heard of a smoke

alarm, but by the mid-1980s, laws in 38 states and in

thousands of municipalities required smoke alarms in all

new and existing residences. By 1995, 93% of all singlefamily and multifamily homes, apartments, nursing

homes, and dormitories were equipped with alarms. The

cost decreased from $1,000 for a professionally installed unit

for a three-bedroom home in the 1970s to an ownerinstalled $10 unit. According to the EPA [15],

ionization chamber and photoelectric are the two most

common smoke detectors available commercially.

Helmenstein [16] states that a smoke alarm uses one or

both methods, and occasionally uses a heat detector, to

warn of a fire. These units can be powered by a 9-volt battery,

a lithium battery, or 120-volt house wiring. Ionization

detectors function using an ionization chamber and a minute

source of ionizing radiation. The radiation source is

americium-241 (perhaps 1/5,000th of a gram), while the

ionization chamber consists of two plates separated by about a

centimeter. The power source (battery or house current)

applies voltage to the plates, resulting in one plate being

charged positively while the other plate is charged negatively.

The americium constantly releases alpha particles that knock

electrons off the atoms in the air, ionizing the oxygen and

nitrogen atoms in the chamber. The negative plate attracts

the positively charged oxygen and nitrogen atoms, while the

electrons are attracted to the positive plate, generating a

small, continuous electric current. If smoke enters the

ionization chamber, the smoke particles attach to the ions

and neutralize them, so they do not reach the plate. The

alarm is then triggered by the drop in current between the

plates [16]. 

Photoelectric devices function in one of two ways. First, smoke

blocks a light beam, reducing the light reaching the photocell,

which sets off the alarm. In the second and more

common type of photoelectric unit, smoke particles

scatter the light onto a photocell, initiating an alarm. Both

detector types are effective smoke sensors and both must

pass the same test to be certified as Underwriters Laboratories

(UL) smoke detectors. Ionization detectors respond more

quickly to flaming fires with smaller combustion particles,

while photoelectric detectors respond more quickly to

smoldering fires. Detectors can be damaged by steam or high

temperatures. Photoelectric detectors are more expensive

than ionization detectors and are more sensitive to minute

smoke particles. However, ionization detectors have a

degree of built-in security not inherent to photoelectric

detectors. When the battery starts to fail in an ionization

detector, the ion current falls and the alarm sounds,

warning that it is time to change the battery before the

detector becomes ineffective. Backup batteries may be used

for photoelectric detectors that are operated using the

home’s electrical system. 

According to USFA [14], a properly functioning smoke

alarm diminishes the risk for dying in a fire by

approximately 50% and is considered the single most

important means of preventing house and apartment fire

fatalities. Proper installation and maintenance, however,

are key to their usefulness. Figure 2.2 shows a typical smoke

alarm being tested. 

Following are key issues regarding installation and

maintenance of smoke alarms. (Smoke alarms should be

installed on every level of the home including the

basement, both inside and outside the sleeping area.)

• Smoke alarms should be installed on the ceiling or

6–8 inches below the ceiling on side walls.

• Battery replacement is imperative to ensuring proper

operation. Typically, batteries should be replaced at

least once a year, although some units are

manufactured with a 10-year battery. A “chirping”

noise from the unit indicates the need for battery

replacement. A battery-operated smoke alarm has a

life expectancy of 8 to 10 years. 

• Battery replacement is not necessary in units that

are connected to the household electrical system.

Healthy Housing Reference Manual 2-7
• Regardless of the type, it is crucial to test every smoke

alarm monthly. Data from HSC [13] revealed that

only 83% of individuals with fire alarms test them

at least once a year; while only 19% of households

with at least one smoke alarm test them quarterly.

A second element impacting escape from a building is a

properly installed fire-suppression system. According to USFA

[14], sprinkler systems began to be used over 100 years ago in

New England textile mills. Currently, few homes are protected

by residential sprinkler systems. However, UL-listed home

systems are available and are designed to protect homes much

faster than standard commercial or industrial sprinklers. Based

on approximately 1% of the total building price in new

construction, sprinkler systems can be installed for a

reasonable price. These systems can be retrofitted to

existing construction and are smaller than commercial

systems. In addition, homeowner insurance discounts for

such systems range between 5% and 15% and are

increasing in availability.

The final element in escaping from a residential fire is having a

fire plan. A 1999 survey conducted by USFA [14] found

that 60% of Americans have an escape plan, with 42% of

these individuals having practiced the plan. Surprisingly,

26% of Americans stated they had never thought about

practicing an escape plan, and 3% believed escape

planning to be unnecessary. In addition, of the people

who had a smoke alarm sound an alert over the past year

before the study, only 8% believed it to be a fire and

thought they should evacuate the building. 

Protection from electrical shocks and burns is also a vital

element in the overall safety of the home. According to

the National Fire Protection Association (NFPA) [17],

electrical distribution equipment was the third-leading

cause of home fires and the second-leading cause of fire

deaths in the United States between 1994 and 1998.

Specifically, NFPA reported that 38,300 home electrical

fires occurred in 1998, which resulted in 284 deaths,

1,184 injuries, and approximately $670 million in direct

property damage. The same report indicated that the

leading cause of electrical distribution fires was ground

fault or short-circuit problems. A third of the home

electrical distribution fires were a result of problems with

fixed wiring, while cords and plugs were responsible for

17% of these fires and 28% of the deaths.

Additional investigation of these statistics reveals that

electrical fires are one of the leading types of home fires in

manufactured homes. USFA [14] data demonstrate that

many electrical fires in homes are associated with

improper installation of electrical devices by do-ityourselfers. Errors attributed to this amateur electrical

work include use of improperly rated devices such as

switches or receptacles and loose connections leading to

overheating and arcing, resulting in fires. Recommendations

to reduce the risk of electrical fires and electrocution

include the following:

1. Use only the correct fuse size and do not use

pennies behind a fuse.

2. Install ground fault circuit interrupters (GFCI) on

all outlets in kitchens, bathrooms, and anywhere

else near water. This can also be accomplished by

installing a GFCI in the breaker box, thus

protecting an entire circuit.

3. Never place combustible materials near light

fixtures, especially halogen bulbs that get very hot.

4. Use only the correct bulb size in a light fixture.

5. Use only properly rated extension cords for the

job needed.

6. Never use extension cords as a long-term solution

to the need for an additional outlet. Size the

extension cord to the wattage to be used.

7. Never run extension cords inside walls or under

rugs because they generate heat that must be able

to dissipate. 

2-8 Basic Principles of Healthy Housing

Figure 2.2. Smoke Alarm Testing

Source: Federal Emergency Management Agency
Fire Extinguishers

A fire extinguisher should be listed and labeled by an

independent testing laboratory such as FM (Factory

Mutual) or UL. Fire extinguishers are labeled according to

the type of fire on which they may be used. Fires involving

wood or cloth, flammable liquids, electrical, or metal sources

react differently to extinguishers. Using the wrong type of

extinguisher on a fire could be dangerous and could worsen

the fire. Traditionally, the labels A, B, C, and D have been

used to indicate the type of fire on which an extinguisher

is to be used. 

Type A—Used for ordinary combustibles such as cloth,

wood, rubber, and many plastics. These types of fire

usually leave ashes after they burn: Type A extinguishers

for ashes. The Type A label is in a triangle on the

extinguisher.

Type B—Used for flammable liquid fires such as oil,

gasoline, paints, lacquers, grease, and solvents. These

substances often come in barrels: Type B extinguishers for

barrels. The Type B label is in a square on the

extinguisher.

Type C—Used for electrical fires such as in wiring, fuse boxes,

energized electrical equipment, and other electrical sources.

Electricity travels in currents; Type C extinguishers for

currents. The Type C label is in a circle on the

extinguisher.

Type D—Used for metal fires such as magnesium,

titanium, and sodium. These types of fires are very dangerous

and seldom handled by the general public; Type D means

don’t get involved. The Type D label is in a star on the

extinguisher.

The higher the rating number on an A or B fire extinguisher,

the more fire it can put out, but high-rated units are often

the heavier models. Extinguishers need care and must be

recharged after every use—a partially used unit might as

well be empty. An extinguisher should be placed in the

kitchen and in the garage or workshop. Each extinguisher

should be installed in plain view near an escape route and

away from potential fire hazards such as heating appliances.

Recently, pictograms have come into use on fire extinguishers.

These picture the type of fire on which an extinguisher is

to be used. For instance, a Type A extinguisher has a

pictogram showing burning wood. A Type C extinguisher has 

a pictogram showing an electrical cord and outlet. These

pictograms are also used to show what not to use. For

example, a Type A extinguisher also show a pictogram of

an electrical cord and outlet with a slash through it (do not

use it on an electrical fire).

Fire extinguishers also have a number rating. For Type A

fires, 1 means 11⁄4 gallons of water; 2 means 21⁄2 gallons of

water, 3 means 33⁄4 gallons of water, etc. For Type B and

Type C fires, the number represents square feet. For example,

2 equals 2 square feet, 5 equals 5 square feet, etc. 

Fire extinguishers can also be made to extinguish more

than one type of fire. For example, you might have an

extinguisher with a label that reads 2A5B. This would

mean this extinguisher is good for Type A fires with a

21⁄2-gallon equivalence and it is also good for Type B fires

with a 5-square-foot equivalency. A good extinguisher to

have in each residential kitchen is a 2A10BC fire extinguisher.

You might also get a Type A for the living room and

bedrooms and an ABC for the basement and garage. 

PASS is a simple acronym to remind you how to operate most

fire extinguishers—pull, aim, squeeze, and sweep. Pull the

pin at the top of the cylinder. Some units require the

releasing of a lock latch or pressing a puncture lever. Aim

the nozzle at the base of the fire. Squeeze or press the

handle. Sweep the contents from side to side at the base

of the fire until it goes out. Shut off the extinguisher and

then watch carefully for any rekindling of the fire.

Protection Against Toxic Gases

Protection against gas poisoning has been a problem since

the use of fossil fuels was combined with relatively tight

housing construction. NFPA [17] notes that National

Safety Council statistics reflect unintentional poisonings

by gas or vapors, chiefly carbon monoxide (CO),

numbering about 600 in 1998. One-fourth of these

involved heating or cooking equipment in the home. The

U.S. Consumer Product Safety Commission [18] states

that in 2001 an estimated 130 deaths occurred as a result

of CO poisoning from residential sources; this decrease in

deaths is related to the increased use of CO detectors. In

addition, approximately 10,000 cases of CO-related injuries

occur each year. NFPA [17] also notes that, similar to fire

deaths, unintentional CO deaths are highest for ages 4 years

and under and ages 75 years and older. Additional information

about home CO monitoring can be found in Chapter 5. 

References

1. Ehlers VE, Steel EW. Municipal and rural

sanitation. Sixth edition. New York: McGraw-Hill

Book Company; 1965. p. 462–4.

Healthy Housing Reference Manual 2-9
2. National Institute on Aging. Hyperthermia—too

hot for your health, fact sheet health information.

Bethesda, MD: US Department of Health and

Human Services; no date. Available from URL:

http://www.niapublications.org/engagepages/

hyperther.asp.

3. US Census Bureau. Historical census of housing

tables—house heating fuel. Washington, DC: US

Census Bureau; 2002. Available from URL:

http://www.census.gov/hhes/www/housing/

census/historic/fuels.html.

4. Zilber SA. Review of health effects of indoor

lighting. Architronic 1993;2(3). Available from URL:

http://architronic.saed.kent.edu/v2n3/v2n3.06.html.

5. US Environmental Protection Agency.

Information on levels of environmental noise

requisite to protect public health and welfare with

an adequate margin of safety. Washington, DC: US

Environmental Protection Agency; 1974.

6. Public Health, England and Wales. The Household

Appliances (Noise Emission) Regulations 1990.

London: Her Majesty’s Stationery Office; 1990.

7. American Speech-Language-Hearing-Association.

Noise: noise is difficult to define. Rockville, MD:

American Speech-Language-Hearing-Association;

2003. Available from URL: http://www.asha.org/ 

public/hearing/disorders/noise.htm.

8. US Environmental Protection Agency. Factoids:

drinking water and ground water statistics for

2002. Washington, DC: US Environmental

Protection Agency, Office of Ground Water and

Drinking Water; January 2003. Available from URL:

http://www.epa.gov/safewater.

9. Hinrichsen D, Robey B, Upadhyay UD. The health

dimension. In: Solutions for a water-short world.

Population Report, Series M, No. 14. Baltimore, MD:

Johns Hopkins School of Public Health, Population

Information Program; 1998. Available from URL:

http://www.infoforhealth.org/pr/m14/m14chap5.shtml

10. US Census Bureau. Historical census of housing

tables—plumbing facilities, 2002. Washington,

DC: US Census Bureau; 2003. Available from URL:

http://www.census.gov/hhes/www/housing/census/

historic/plumbing.html.

11. US Census Bureau. Historical census of housing

tables—crowded and severely crowded housing

units, 2002. Washington, DC: US Census

Bureau; 2003. Available from URL:

http://www.census.gov/hhes/ www/housing/ 

census/historic/crowding.html.

12. International Code Council. Fact sheet. Falls

Church, VA: International Code Council; no date.

Available from URL: http://www.iccsafe.org/news/pdf/

factssheet.pdf.

13. Home Safety Council. The state of home safety in

America—executive summary. Washington, DC:

The Home Safety Council; 2002.

14. US Fire Administration. Welcome to the U.S. Fire

Administration (USFA) Web site. Washington,

DC: Federal Emergency Management Agency,

Department of Homeland Security; 2003.

Available from URL: http://www.usfa.fema.gov/.

15. US Environmental Protection Agency. Smoke

detectors and radiation. Washington, DC: US

Environmental Protection Agency; 2003. Available

from URL: http://www.epa.gov/

radiation/sources/smoke_alarm.htm.

16. Helmenstein AM. How do smoke detectors work?

Photoelectric & ionization smoke detectors, what

you need to know about chemistry. New York:

About, Inc.; 2003. Available from URL:

http://chemistry.about.com/library/weekly/

aa071401a.htm.

17. National Fire Protection Association. NFPA fact

sheets—electrical safety. Quincy, MA: National

Fire Protection Association; 2003. Available from

URL: http://www.nfpa.org/Research/

NFPAFactSheets/Electrical/electrical.asp.

18. US Consumer Product Safety Commission.

Nonfire carbon monoxide deaths: 2001 annual

estimate. Washington, DC: US Consumer

Product Safety Commission; 2004. Available from

URL: http://www.cpsc.gov/LIBRARY/co04.pdf.

2-10 Basic Principles of Healthy Housing
Additional Sources of Information 

Barbalace RC. Environmental justice and the NIMBY

principle. Environmental Chemistry.com: Environmental,

Chemistry, and Hazardous Materials Information and

Resources. Portland, ME; no date. Available from URL:

http://environmentalchemistry.com/yogi/hazmat/articles/

nimby.html.

Bryant B. The role of SNRE in the environmental justice

movement. Ann Arbor, MI: University of Michigan; 1997.

Available from URL: http://www.umich.edu/~snre492/

history.html.

Bullard RD. Waste and racism: a stacked deck? Forum

Appl Res Public Pol spring 1993.

National Institute on Aging. Hypothermia: a cold weather

hazard, fact sheet health information. Bethesda, MD: US

Department of Health and Human Services; 2001.

Available from URL: http://www.niapublications.org/

engagepages/ hypother.asp.

National Weather Service. Natural hazard statistics; no

date. Silver Spring, MD: National Weather Service.

Available from URL: http://www.nws.noaa.gov/

om/hazstats.shtml.

US Census Bureau. New residential construction

(building permits, housing starts, and housing

completions). Washington, DC: US Census Bureau; no

date. Available from URL:

http://www.census.gov/newresconst.

Healthy Housing Reference Manual 2-11
2-12 Basic Principles of Healthy Housing
“The poorest man may in his cottage bid defiance to all the

force of the Crown. It may be frail—its roof may shake—the

wind may blow through it—the storm may enter, the rain

may enter—but the King of England cannot enter—all his

force dares not cross the threshold of the ruined tenement!”

William Pitt, March 1763

Introduction

William Pitt, arguing before the British Parliament against

excise officers entering private homes to levy the Cyder

Tax, eloquently articulated this long-held and cherished

notion of the sanctity of private property. However, a

person’s right to privacy is not absolute. There has always

been a tension between the rights of property owners to do

whatever they desire with their property and the ability of

the government to regulate uses to protect the safety,

health, and welfare of the community. Few, however,

would argue with the right and duty of a city government

to prohibit the operation of a munitions factory or a

chemical plant in the middle of a crowded residential

neighborhood. 

History 

The first known housing laws are in the Code of Laws of

Hammurabi [1], who was the King of Babylonia, circa

1792–1750 BC. These laws addressed the responsibility of the

home builder to construct a quality home and outlined the

implications to the builder if injury or harm came to the

owner as a result of the failure to do so. During the Puritan

period (about 1620–1690), housing laws essentially

governed the behavior of the members of the society. For

example, no one was allowed to live alone, so bachelors,

widows, and widowers were placed with other families as

servants or boarders. In 1652, Boston prohibited building

privies within 12 feet of the street. Around the turn of the

18th century, some New England communities

implemented local ordinances that specified the size of

houses. During the 17th century, additional public policies

on housing were established. Because the English tradition

of using wooden chimneys and thatched roofs led to fires

in many dwellings, several colonies passed regulations

prohibiting them. 

After the early 17th century came an era of very rapid

metropolitan growth along the East Coast. This growth

was due largely to immigration from Europe and was

spurred by the Industrial Revolution. The most serious

housing problems began in New York about 1840 when

the first tenements were built. In 1867, a report by the

New York Metropolitan Board of Health on living

conditions in tenements convinced the New York State

legislature to pass the Tenement Housing Act of 1867 [2].

The principal requirements of the act included the

following: 

• Every room occupied for sleeping, if it does not

communicate directly with the external air, must

have a ventilating or transom window of at least

3 square feet to the neighboring room or hall.

• A proper fire escape is necessary on every tenement

or lodging house.

• The roof is to be kept in repair and the stairs are to

have banisters.

• At least one toilet is required for every

20 occupants for all such houses, and those toilets

must be connected to approved disposal systems.

• Cleansing of every lodging house is to be to the

satisfaction of the Board of Health, which is to have

access at any time. 

• All cases of infectious disease are to be reported to

the Board by the owner or his agent; buildings are

to be inspected and, if necessary, disinfected or

vacated if found to be out of repair.

There were also regulations governing distances between

buildings, heights of rooms, and dimensions of windows.

Although this act had some beneficial influences on

overcrowding, sewage disposal, lighting, and ventilation,

perhaps its greatest contribution was in laying a foundation

for more stringent future legislation.

Jacob A. Riis, a Danish immigrant and a police reporter on

New York’s Lower East Side, published a book titled How

the Other Half Lives—Studies Among the Tenements of New

York [3], which swayed public opinion in the direction of

housing reform and resulted in the Tenement House Act of

1901. The basic principles established in the Tenement

House Act of 1901 still underlie much of the housing

efforts in New York City today [4]. Since 1909, with the

establishment of the Philadelphia Housing Association, that city

has had almost continual inspection and improvement.

Chicago enacted housing legislation as early as 1889 and

Chapter 3: Housing Regulations

Healthy Housing Reference Manual 3-1
health legislation as early as 1881. Regulations on

ventilation, light, drainage, and plumbing were put into

effect in 1896. 

Before 1892, all government involvement in housing was

at a local level. In 1892, however, the federal government

passed a resolution authorizing investigation of slum

conditions in cities with 200,000 or more inhabitants.

Congress appropriated only $20,000 (roughly equal to

$390,000 in 2003) to cover the expenses of this project,

which limited the number of investigations. 

No significant housing legislation was passed in the

20th century until 1929 [5], when the New York State

legislature passed its Multiple Dwelling Law. Other cities

and states followed New York’s example and permitted

less strict requirements in their codes. This decreased

what little emphasis there was on enforcement.

Conditions declined until, by the 1930s, President

Franklin D. Roosevelt’s shocking report to the people was

“that one-third of the nation is ill-fed, ill-housed, and illclothed.” In response to the overwhelming loss of homes

during the Great Depression, Congress passed the United

States Housing Act of 1937, which created the United

States Housing Authority (USHA). This act subsidized

construction of new public housing units and required

the elimination of at least an equivalent number of units

from the local housing supply that were determined to be

inferior. In 1942, the USHA was renamed the Federal

Public Housing Administration and, in 1947, was

renamed the Public Housing Administration. 

The federal government not only encouraged the

construction of public housing, but took on the role of

financing private housing. In 1938, the Federal National

Mortgage Association was created. (Fannie Mae became a

private organization in 1968 [6].) Its purpose was to

provide a secondary market for the FHA, created in 1934,

and Veterans Administration (VA) mortgage loans. The

Servicemen’s Readjustment Act of 1944, also known as

the GI Bill of Rights, created a VA loan program

guaranteeing home mortgage loans for veterans. This

legislation, in conjunction with the FHA loan program,

was the impetus for initiating the huge program of home

construction and subsequent suburban growth following

World War II. In 1946, the Farmers Home Administration,

housed in the United States Department of Agriculture

(USDA), was created to make loans and grants for

constructing and repairing farm homes and assisting rural

self-help housing groups.

The Housing Act of 1949 allowed “primarily residential”

and “blighted” urban areas to be condemned, cleared of

buildings, and sold for private development. In addition

to assisting in slum clearance, this act also provided for

additional public housing and authorized the USDA to

provide farmers with loans to construct, improve, repair

or replace dwellings to provide decent, safe, and sanitary

living conditions for themselves, their tenants, lessees,

sharecroppers, and laborers. 

Because the many housing responsibilities administered

by various agencies within the federal government proved

unwieldy, the Housing and Urban Development Act was

passed in 1965. The U.S. Department of Housing and

Urban Development (HUD) was created to centralize the

responsibilities of the Housing and Home Finance Agency

and incorporated the FHA, the Federal National

Mortgage Association, the Public Housing Administration,

Urban Development Administration, and the Community

Facilities Administration. 

Zoning, Housing Codes, and Building Codes

Housing is inextricably linked to the land on which it is

located. Changes in the patterns of land use in the United

States, shifting demographics, an awareness of the need

for environmental stewardship, and competing uses for

increasingly scarce (desirable) land have all placed added

stress on the traditional relationship between the property

owner and the community. This is certainly not a new

development. 

In the early settlement of this country, following the precedent

set by their forefathers from Great Britain, gunpowder

mills and storehouses were prohibited from the heavily

populated portions of towns, owing to the frequent fires and

explosions. Later, zoning took the form of fire districts

and, under implied legislative powers, wooden buildings

were prohibited from certain sections of a municipality.

Massachusetts passed one of the first zoning laws in 1692.

This law authorized Boston, Salem, Charlestown, and

certain other market towns in the province to restrict the

establishment of slaughterhouses and stillhouses for

currying leather to certain locations in each town.

Few people objected to such restrictions. Still, the tension

remained between the right to use one’s land and the

community’s right to protect its citizens. In 1926, the

United States Supreme Court took up the issue in Village

of Euclid, Ohio, v. Ambler Realty [7]. In this decision,

the Court noted,

3-2 Housing Regulations
“Until recent years, urban life was comparatively

simple; but with great increase and concentration of

population, problems have developed which require

additional restrictions in respect of the use and

occupation of private lands in urban communities.”

In explaining its reasoning, the Court said, 

“the law of nuisances may be consulted not for the

purpose of controlling, but for the helpful aid of its

analogies in the process of ascertaining the scope of the

police power. Thus the question of whether the

power exists to forbid the erection of a building of a

particular kind or a particular use is to be

determined, not by an abstract consideration of the

building or other thing considered apart, but by

considering it in connection with the circumstances

and the locality... A nuisance may be merely the

right thing in the wrong place—like a pig in the

parlor instead of the barnyard.”

Zoning, housing, and building codes were adopted to improve

the health and safety of people living in communities.

And, to some extent, they have performed this function.

Certainly, housing and building codes, when enforced,

have resulted in better constructed and maintained

buildings. Zoning codes have been effective in

segregating noxious and dangerous enterprises from

residential areas. However, as the U.S. population has

grown and changed from a rural to an urban then to a

suburban society, land use and building regulations

developed for the 19th and early 20th centuries are

creating new health and safety problems not envisioned in

earlier times. 

Zoning and Zoning Ordinances

Zoning is essentially a means of ensuring that a community’s

land uses are compatible with the health, safety, and

general welfare of the community. Experience has shown

that some types of controls are needed to provide orderly

growth in relation to the community plan for development.

Just as a capital improvement program governs public

improvements such as streets, parks and other recreational

facilities, schools, and public buildings, so zoning governs

the planning program with respect to the use of public

and private property.

It is very important that housing inspectors know the general

nature of zoning regulations because properties in

violation of both the housing code and the zoning ordinance

must be brought into full compliance with the zoning

ordinance before the housing code can be enforced. In

many cases, the housing inspector may be able to

eliminate violations or properties in violation of housing

codes through enforcement of the zoning ordinance.

Zoning Objectives

As stated earlier, the purpose of a zoning ordinance is to

ensure that the land uses within a community are

regulated not only for the health, safety, and welfare of the

community, but also are in keeping with the

comprehensive plan for community development. The

provisions in a zoning ordinance that help to achieve

development that provides for health, safety, and welfare

are designed to do the following:

• Regulate height, bulk, and area of structure. To

provide established standards for healthful housing

within the community, regulations dealing with

building heights, lot coverage, and floor areas must

be established. These regulations then ensure that

adequate natural lighting, ventilation, privacy, and

recreational areas for children will be realized.

These are all fundamental physiologic needs

necessary for a healthful environment. Safety from

fires is enhanced by separating buildings to meet

yard and open-space requirements. Through

requiring a minimum lot area per dwelling unit,

population density controls are established.

• Avoid undue levels of noise, vibration, glare, air

pollution, and odor. By providing land-use

category districts, these environmental stresses upon

the individual can be reduced. 

• Lessen street congestion by requiring off-street

parking and off-street loading.

• Facilitate adequate provision of water, sewerage,

schools, parks, and playgrounds.

• Provide safety from flooding.

• Conserve property values. Through careful

enforcement of the zoning ordinance provisions,

property values can be stabilized and conserved.

To understand more fully the difference between zoning

and subdivision regulations, building codes, and housing

ordinances, the housing inspector must know what cannot

be accomplished by a zoning ordinance. Items that

cannot be accomplished by a zoning ordinance include

the following: 

Healthy Housing Reference Manual 3-3
• Overcrowding or substandard housing. Zoning

is not retroactive and cannot correct existing

conditions. These are corrected through

enforcement of a minimum standards housing code.

• Materials and methods of construction. Materials

and methods of construction are enforced through

building codes rather than through zoning.

• Cost of construction. Quality of construction,

and hence construction costs, are often regulated

through deed restrictions or covenants. Zoning

does, however, stabilize property values in an area

by prohibiting incompatible development, such as

heavy industry in the midst of a well-established

subdivision.

• Subdivision design and layout. Design and layout

of subdivisions, as well as provisions for parks and

streets, are controlled through subdivision

regulations. 

Content of the Zoning Ordinance 

Zoning ordinances establish districts of whatever size,

shape, and number the municipality deems best for

carrying out the purposes of the zoning ordinance. Most

cities use three major districts: residential (R), commercial

(C), and industrial (I). These three may then be

subdivided into many subdistricts, depending on local

conditions; e.g., R-1 (single-unit dwellings), R-2

(duplexes), R-3 (low-rise apartment buildings), and so on.

These districts specify the principal and accessory uses,

exceptions, and prohibitions [8].

In general, permitted land uses are based on the intensity

of land use—a less intense land use being permitted in a

more intense district, but not vice versa. For example, a

single-unit residence is a less intense land use than a multiunit

dwelling (defined by HUD as more than four living

units) and hence would be permitted in a residential

district zoned for more intense land use (e.g., R-3). A

multiunit dwelling would not, however, be permitted in

an R-1 district. While intended to promote the health,

safety, and general welfare of the community, housing

trends in the last half of the 20th century have led a

number of public health and planning officials to

question the blind enforcement of zoning districts. These

individuals, citing such problems as urban sprawl, have

stated that municipalities need to adopt a more flexible

approach to land use regulation—one that encourages

creating mixed-use spaces, increasing population densities,

and reducing reliance on the automobile. 

These initiatives are often called smart growth programs.

It is imperative, if this approach is taken, that both

governmental officials and citizens be involved in the

planning stage. Without this involvement, the community

may end up with major problems, such as overloaded

infrastructure, structures of inappropriate construction

crowded together, and fire and security issues for

residents. Increased density could strain the existing water,

sewer and waste collection systems, as well as fire and

police services, unless proper planning is implemented. 

In recent years, some ordinances have been partially based

on performance standards rather than solely on land-use

intensity. For example, some types of industrial developments

may be permitted in a less intense use district provided

that the proposed land use creates no noise, glare, smoke,

dust, vibration, or other environmental stress exceeding

acceptable standards and provided further that adequate

off-street parking, screening, landscaping, and similar

measures are taken.

Bulk and Height Requirements. Most early zoning

ordinances stated that, within a particular district, the

height and bulk of any structure could not exceed certain

dimensions and specified dimensions for front, side, and

rear yards. Another approach was to use floor-area ratios

for regulation. A floor-area ratio is the relation between

the floor space of the structure and the size of the lot on

which it is located. For example, a floor-area ratio of

1 would permit either a two-story building covering 50%

of the lot, or a one-story building covering 100% of the lot, as

demonstrated in Figure 3.1. Other zoning ordinances

specify the maximum amount of the lot that can be

covered or merely require that a certain amount of open

space must be provided for each structure, and leave the

builder the flexibility to determine the location of the

structure. Still other ordinances, rather than specify a

particular height for the structure, specify the angle of

light obstruction that will assure adequate air and light to

the surrounding structures, as demonstrated in Figure 3.2.

Yard Requirements. Zoning ordinances also contain

minimum requirements for front, rear, and side yards. These

requirements, in addition to stating the lot dimensions,

usually designate the amount of setback required. Most

ordinances permit the erection of auxiliary buildings in

rear yards provided that they are located at stated

distances from all lot lines and provided sufficient open

space is maintained. If the property is a corner lot,

additional requirements are established to allow visibility

for motorists.

3-4 Housing Regulations
Off-street Parking. Space for off-street parking and offstreet loading, especially for commercial buildings, is also

contained in zoning ordinances. These requirements are

based on the relationship of floor space or seating capacity

to land use. For example, a furniture store would require

fewer off-street parking spaces in relation to the floor area

than would a movie theater. 

Exceptions to the Zoning Code

Nonconforming Uses

Because zoning is not retroactive, all zoning ordinances

contain a provision for nonconforming uses. If a use has

already been established within a particular district before the

adoption of the ordinance, it must be permitted to

continue, unless it can be shown to be a public nuisance. 

Provisions are, however, put into the ordinance to aid in

eliminating nonconforming uses over time. These

provisions generally prohibit a) an enlargement or

expansion of the nonconforming use, b) reconstruction of

the nonconforming use if more than a certain portion of

the building should be destroyed, c) resumption of the

use after it has been abandoned for a period of specified

time, and d) changing the use to a higher classification or to

another nonconforming use. Some zoning ordinances

further provide a period of amortization during which

nonconforming land use must be phased out.

Variances 

Zoning ordinances contain provisions for permitting

variances and providing a method for granting these

variances, subject to certain specified provisions. A

variance may be granted when, owing to the specific conditions

or use of a particular lot, an undue hardship would be

imposed on the owner if the exact content of the

ordinance is enforced. A variance may be granted due to

the shape, topography, or other characteristic of the lot.

For example, suppose an irregularly shaped lot is located

in a district having a side yard requirement of 20 feet on a

side and a total lot size requirement of 10,000 square feet.

Further suppose that this lot contains 10,200 square feet

(and thus meets the total size requirement); however, due

to the irregular shape of the lot, there would be sufficient

space for only a 15-foot side yard. Because a hardship

would be imposed on the owner if the exact letter of the

law is applied, the owner of the property could apply to

the zoning adjustment board for a variance. Because the

total area of the lot is sufficient and a lessening of the

Healthy Housing Reference Manual 3-5

Figure 3.1. Example of a Floor Area

Figure 3.2. Example of an Angle of Light Obstruction
ordinance requirements would not be detrimental to the

surrounding property, nor would it interfere with neighboring

properties, a variance would probably be granted. Note

that a variance is granted to the owner under specific

conditions. Should use of the property change, the

variance would be voided.

Exceptions

An exception is often confused with a variance. In every

city there are some necessary uses that do not correspond

to the permitted land uses within the district. The zoning

code recognizes, however, that if proper safeguards are

provided, these uses would not have a detrimental effect

on the district. An example would be a fire station that

could be permitted in a residential area, provided the

station house is designed and the property is properly

landscaped to resemble or fit in with the characteristics of the

neighborhood in which it is located. 

Administration

Zoning inspectors are essential to the zoning process

because they have firsthand knowledge of a case. Often,

the zoning inspector may also be the building inspector or

housing inspector. Because the building inspector or

housing inspector is already in the field making

inspections, it is relatively easy for that individual to

check compliance with the zoning ordinances. Compliance

is determined by comparing the actual land use with that

allowed for the area and shown on the zoning map.

Each zoning ordinance has a map detailing the permitted

usage for each block. Using a copy of this map, the

inspector can make a preliminary check of the land use in

the field. If the use does not conform, the inspector must

then contact the Zoning Board to see whether the property in

question was a nonconforming use at the time of the

passage of the ordinance and whether an exception or variance

has been granted. In cities where up-to-date records are

maintained, the inspector can check the use in the field.

When a violation is observed, and the property owners

are duly notified of the violation, they have the right to

request a hearing before the Zoning Board of Adjustment

(also called the Zoning Board of Appeals in some cities).

The board may uphold the zoning enforcement officer or

may rule in favor of the property owner. If the action of

the zoning officer is upheld, the property owner may, if

desired, seek relief by appealing the decision to the courts;

otherwise, the violation must be corrected to conform to

the zoning code.

It is critical for the housing or building inspector and the

zoning inspector to work closely in municipalities where

these positions and responsibilities are separate. Experience

has shown that illegally converted properties are often

among the most substandard encountered in the municipality

and often contain especially dangerous housing code violations.

In communities where the zoning code is enforced effectively,

the resulting zoning compliance helps to advance, as well

as sustain, many of the minimum standards of the

housing code such as occupancy, ventilation, light, and

unimpeded egress. By the same token, building or

housing inspectors can often aid the zoning inspector by

helping eliminate some nonconforming uses through code

enforcement.

Housing Codes

A housing code, regardless of who promulgates it, is basically

an environmental health protection code. Housing codes

are distinguished from building codes in that they cover

houses, not buildings in general. For example, the housing

code requires that walls support the weight of the roof,

any floors above, and the furnishings, occupants, etc.,

within a building. 

Early housing codes primarily protected only physical health;

hence, they were enforced only in slum areas. In the

1970s, it was realized that, if urban blight and its associated

human suffering were to be controlled, housing codes

must consider both physical and mental health and must

be administered uniformly throughout the community.

In preparing or revising housing codes, local officials must

maintain a level of standards that will not merely be

minimal. Standards should maintain a living environment

that contributes positively to healthful individual and

family living. The fact that a small portion of housing

fails to meet a desirable standard is not a legitimate reason

for retrogressive modification or abolition of a standard.

The adoption of a housing ordinance that establishes low

standards for existing housing serves only to legalize and

perpetuate an unhealthy living environment. Wherever

local conditions are such that immediate enforcement of

some standards within the code would cause undue

hardship for some individuals, it is better to allow some

time for compliance than to eliminate an otherwise

satisfactory standard. When immediate health or safety

hazards are not involved, it is often wise to attempt to

create a reasonable timetable for accomplishing necessary

code modifications.

3-6 Housing Regulations
History

To assist municipalities with developing legislation necessary

to regulate the quality of housing, the American Public

Health Association (APHA) Committee on the Hygiene

of Housing prepared and published in 1952 a proposed

housing ordinance. This provided a prototype on which

such legislation might be based and has served as the

basis for countless housing codes enacted in the United

States since that time. Some municipalities enacted it without

change. Others made revisions by omitting some portions,

modifying others, and sometimes adding new provisions [9].

The APHA ordinance was revised in 1969 and 1971. In 1975,

APHA and the CDC jointly undertook the job of

rewriting and updating this model ordinance. The new

ordinance was entitled the APHA-CDC Recommended

Housing Maintenance and Occupancy Ordinance [10]. The

most recent model ordinance was published by APHA in

1986 as Housing and Health: APHA-CDC Recommended

Minimum Housing Standards [11]. This new ordinance is

one of several model ordinances available to communities

when they are interested in adopting a housing code.

A community should read and consider each element

within the model code to determine its applicability to

their community. A housing code is merely a means to an

end. The end is the eventual elimination of all substandard

conditions within the home and the neighborhood. This end

cannot be achieved if the community adopts an

inadequate housing code.

Objectives

The Housing Act of 1949 [12] gave new impetus to

existing local, state, and federal housing programs

directed toward eliminating poor housing. In passing

this legislation, Congress defined a new national

objective by declaring that “the general welfare and

security of the nation and the health and living

standards of its people...require a decent home and a

suitable living environment for every American family.”

This mandate generated an awareness that the quality of

housing and residential environment has an enormous

influence upon the physical and mental health and the

social well-being of each individual and, in turn, on the

economic, political, and social conditions in every

community. Consequently, public agencies, units of

government, professional organizations and others sought

ways to ensure that the quality of housing and the

residential environment did not deteriorate.

It soon became apparent that ordinances regulating the

supplied utilities and the maintenance and occupancy of

dwellings were needed. Commonly called housing codes,

these ordinances establish minimum standards to make

dwellings safe, sanitary, and fit for human habitation by

governing their condition and maintenance, their

supplied utilities and facilities, and their occupancy. The

2003 International Code Council (ICC) [13,14]

International Residential Code-One- and Two-Family

Dwellings (R101.3) states 

“the purpose of this code is to provide minimum

requirements to safeguard the public safety, health

and general welfare, through affordability, structural

strength, means of egress, facilities, stability, sanitation,

light and ventilation, energy conservation, safety to

fire and property from fire and other hazards

attributed to the built environment.”

Critical Requirements of an Effective Housing Program

A housing code is limited in its effectiveness by several

factors. First, if the housing code does not contain standards

that adequately protect the health and well-being of the

individuals, it cannot be effective. The best-trained

housing inspector, if not armed with an adequate housing

code, can accomplish little good in the battle against

urban blight.

A second issue in establishing an effective housing code is

the need to establish a baseline of current housing conditions.

A systems approach requires that you establish where you

are, where you are going, and how you plan to achieve your

goals. In using a systems approach, it is essential to know

where the program started so that the success or failure of

various initiatives can be established. Without this

information, success cannot be replicated, because you

cannot identify the obstacles navigated nor the elements

of success. Many initiatives fail because program

administrators are without the necessary proof of success

when facing funding shortfalls and budget cuts.

A third factor affecting the quality of housing codes is

budget. Without adequate funds and personnel, the

community can expect to lose the battle against urban

blight. It is only through a systematic enforcement effort

by an adequately sized staff of properly trained inspectors

that the battle can be won.

A fourth factor is the attitude of the political bodies

within the area. A properly administered housing program

will require upgrading substandard housing throughout the

community. Frequently, this results in political pressures

being exerted to prevent the enforcement of the code in

certain areas of the city. If the housing effort is backed

Healthy Housing Reference Manual 3-7
properly by all political elements, blight can be controlled

and eventually eliminated within the community. If, however,

the housing program is not permitted to choke out the

spreading influence of substandard conditions, urban

blight will spread like a cancer, engulfing greater and

greater portions of the city. Similarly, an effort directed at

only the most seriously blighted blocks in the city will

upgrade merely those blocks, while the blight spreads

elsewhere. If urban blight is to be controlled, it must be

cut out in its entirety.

A fifth element that limits housing programs is whether

they are supported fully by the other departments within

the city. Regardless of which city agency administers the

housing program, other city agencies must support the

activities of the housing program. In addition, great effort

should be expended to obtain the support and

cooperation of the community. This can be accomplished

through public awareness and public information

programs, which can result in considerable support or

considerable resistance to the efforts of the program.

A sixth limitation is an inadequately or improperly

trained inspection staff. Inspectors should be capable of

evaluating whether a serious or a minor problem exists in

matters ranging from the structural stability of a building

to the health and sanitary aspects of the structure. If they

do not have the authority or expertise, they should

develop that expertise or establish effective and efficient

agreements with overlapping agencies to ensure timely

and appropriate response. 

A seventh item that frequently restricts the effectiveness of

a housing program is the fact that many housing groups

fail to do a complete job of evaluating housing

problems. The deterioration of an area may be due to

factors such as housing affordability, tax rates, or issues

related to investment cost and return. In many cases, the

inspection effort is restricted to merely evaluating the

conditions that exist, with little or no thought given to

why these conditions exist. If a housing effort is to be

successful, as part of a systems approach, the question of

why the homes deteriorated must be considered. Was

it because of environmental stresses within the

neighborhood that need to be eliminated or was it

because of apathy on the part of the occupants? In either

case, if the causative agent is not removed, then the

inspector faces an annual problem of maintaining the

quality of that residence. It is only by eliminating the

causes of deterioration that the quality of the

neighborhood can be maintained. Often the regulatory

authority does not have adequate authority within the

enabling legislation of the code needed to resolve the

problem or there are gaps in jurisdiction.

Content of a Housing Code

Although all comprehensive housing codes or ordinances

contain a number of common elements, the provisions of

communities will usually vary. These variations stem from

differences in local policies, preferences, and, to a lesser

extent, needs. They are also influenced by the standards

set by the related provisions of the diverse building,

electrical, and plumbing codes in use in the municipality.

Within any housing code there are generally five features: 

1. Definitions of terms used in the code. 

2. Administrative provisions showing who is

authorized to administer the code and the basic

methods and procedures that must be followed in

implementing and enforcing the sections of the

code. Administrative provisions deal with items

such as reasonable hours of inspections, whether

serving violation notices is required, how to notify

absentee owners or resident-owners or tenants, how to

process and conduct hearings, what rules to follow

in processing dwellings alleged to be unfit for

human habitation, and how to occupy or use

dwellings finally declared fit.

3. Substantive provisions specifying the various types

of health, building, electrical, heating, plumbing,

maintenance, occupancy, and use conditions that

constitute violations of the housing code. These

provisions can be and often are grouped into three

categories: minimum facilities and equipment for

dwelling units; adequate maintenance of dwellings

and dwelling units, as well as their facilities and

equipment; and occupancy conditions of dwellings

and dwelling units.

4. Court and penalty sections outlining the basis for

court action and thepenalty or penalties to which

the alleged violator will be subjected if proved

guilty of violating one or more provisions of the code.

5. Enabling, conflict, and unconstitutionality

clauses providing the date a new or amended code

will take effect, prevalence of more stringent

provision when there is a conflict of two codes,

severability of any part of the ordinance that

might be found unconstitutional, and retention of

all other parts in full course and effect. In any city

3-8 Housing Regulations
following the format of the APHA-CDC Recommended

Housing Maintenance and Occupancy Ordinance

[10] the housing officer or other supervisor in

charge of housing inspections will also adopt

appropriate housing rules and regulations from

time to time to clarify or further refine the

provisions of the ordinance. When rules and

regulations are used, care should be taken that the

department is not overburdened with a number of

minor rules and regulations. Similarly, a housing

ordinance that encompasses all rules and regulations

might have difficulty because any amendments to

it will require action by the political element of

the community. Some housing groups, in

attempting to obtain amendments to an

ordinance, have had the entire ordinance thrown

out by the political bodies.

Administrative Provisions of a Housing Code

The administrative procedures and powers of the housing

inspection agency, its supervisors, and its staff are similar to

other provisions in that all are based on the police power of

the state to legislate for public health and safety. In

addition, the administrative provisions, and to a lesser

extent, the court and penalty provisions, outline how the

police power is to be exercised in administering and

enforcing the code.

Generally, the administrative elements deal with

procedures for ensuring that the constitutional doctrines of

reasonableness, equal protection under the law and due

process of law are observed. They also must guard against

violation of prohibitions against unlawful search and seizure,

impairment of obligations of contract, and unlawful

delegation of authority. These factors encompass items of

great importance to housing inspection supervisors such

as the inspector’s right of entry, reasonable hours of

inspection, proper service, and the validity of the provisions

of the housing codes they administer. 

Owner of Record. It is essential to file legal actions

against the true owners of properties in violation of

housing codes. With the advent of the computer, this is

often much easier than in the past. Databases that provide

this information are readily available from many offices of

local government such as the tax assessment office. The

method of obtaining the name and address of the legal

owner of a property in violation varies from place to

place. Ordinarily, a check of the city tax records will

suffice unless there is reason to believe these are not up to

date. In this case, a further check of county or parish

records will turn up the legal owner if state law requires

deed registration there. If it does not, the advice of the

municipal law department should be sought about the next

steps to follow.

Due Process Requirements. Every notice, complaint,

summons, or other type of legal paper concerning alleged

housing code violations in a given dwelling or dwelling

unit must be legally served on the proper party to be valid

and to prevent harassment of innocent parties. This might

be the owner, agent, or tenant, as required by the code. It

is customary to require that the notice to correct existing

violations and any subsequent notices or letters be served by

certified or registered mail with return receipt requested. The

receipt serves as proof of service if the case has to be taken

to court.

Due process requirements also call for clarity and

specificity with respect to the alleged violations, both in

the violation notices and the court complaint-summons.

For this reason, special care must be taken to be complete

and accurate in listing the violations and charges. To

illustrate, rather than direct the violator to repair all

windows where needed, the violator should be told

exactly which windows and what repairs are involved. 

The chief limitation on the due process requirement, with

respect to service of notices, lies in cases involving

immediate threats to health and safety. In these instances,

the inspection agency or its representative may, without

notice or hearing, issue an order citing the existence of

the emergency and requiring that action deemed

necessary to meet the emergency be taken.

In some areas housing courts on the municipal level have

advocates that assist both plaintiffs and defendants

prepare for the court process or to resolve the issue to

avoid court.

Hearings and Condemnation Power. The purpose of a

hearing is to give the alleged violator an opportunity to be

heard before further action is taken by the housing inspection

agency. These hearings may be very informal, involving

meetings between a representative of the agency and the

person ordered to take corrective action. They also may

be formal hearings at which the agency head presides and

at which the city and the defendant both are entitled to

be represented by counsel and expert witnesses. 

Informal Hearings. A violator may have questions about a

violation notice or the notice may be served at a time

when personal hardship or other factors prevent a violator

from meeting the terms of the notice. Therefore, many

Healthy Housing Reference Manual 3-9
housing codes provide the opportunity for a hearing at

which the violator may discuss questions or problems and

seek additional time or some modification of the order.

Administered in a firm but understanding manner, these

hearings can serve as invaluable aids in relieving needless

fears of those involved, in showing how the inspection

program is designed to help them and in winning their

voluntary compliance.

Formal Hearings. Formal hearings are often quasijudicial

hearings (even though the prevailing court rules of

evidence do not always apply) from which an appeal may

be taken to court. All witnesses must therefore be sworn

in, and a record of the proceedings must be made. The

formal hearing is used chiefly as the basis for determining

whether a dwelling is fit for human habitation,

occupancy, or use. In the event it is proved unfit, the

building is condemned and the owner is given a

designated amount of time either to rehabilitate it

completely or to demolish it. Where local funds are

available, a municipality may demolish the building and

place a lien against the property to cover demolition costs

if the owner fails to obey the order within the time

specified. This type of condemnation hearing is a very

effective means of stimulating prompt and appropriate

corrective action when it is administered fairly and firmly. 

Procedures for Coping With Common Problems. Several

states and local communities have developed innovative

ways to resolve code violation issues.

Limitation of Occupancy Notification. This technique

was pioneered in Wilmington, Delaware. It makes it

mandatory for property owners in the community to

obtain a legal notice from the housing inspection agency

specifying the maximum number of persons that may

occupy each of their properties. It also requires these owners

to have a residence, place of business, or an agent for their

properties within the community. The agent should be

empowered to take remedial action on any of the

properties found in violation. In addition, if the property

is sold, the new owner must obtain a new Limitation of

Occupancy Notification. 

Request for Inspections. Several states permit their

municipalities to offer a request for inspection service. For

a fee, the housing inspector will inspect a property for

violations of the housing code before its sale so that the

buyer can learn its condition in advance. Many states and

localities now require owners to notify prospective

purchasers of any outstanding notice of health risk or

violations they have against their property before the sale.

If they fail to do so, some codes will hold the owner liable

to the purchaser and the inspection agency for violations.

Tickets for Minor Offenses. Denver, Colorado, has used

minimal financial fines to prod minor violators and first

offenders into correcting violations without the city

resorting to court action. There are mixed views about

this technique because it is akin to formal police action.

Nevertheless, the action may stimulate compliance and

reduce the amount of court action needed to achieve it.

Forms and Form Letters. A fairly typical set of forms and

form letters are described below. It should be stressed that

inspection forms to be used for legal notices must satisfy

legal standards of the code, be meaningful to the owner

and sufficiently explicit about the extent and location of

particular defects, be adaptable to statistical compilation

for the governing body reports, and be written in a manner

that will facilitate clerical and other administrative usage.

The Daily Report Form. This form gives the inspection

agency an accurate basis for reporting, evaluating, and, if

necessary, improving the productivity and performance of

its inspectors.

Complaint Form. This form helps obtain full information

from the complainant and thus makes the relative

seriousness of the problem clear and reduces the number

of crank complaints.

No-entry Notice. This notice advises occupants or owners

that an inspector was there and that they must return a

call to the inspector.

Inspection Report Form. This is the most important form

in an agency. It comes in countless varieties, but if designed

properly, it will ensure more productivity and more

thoroughness by the inspectors, reduce the time spent in

writing reports, locate all violations correctly, and reduce

the time required for typing violation notices. Forms may

vary widely in sophistication from a very simple form to

one whose components are identified by number for use

in processing the case by automation. Some forms are a

combined inspection report and notice form in triplicate so

that the first page can be used as the notice of violation, the

second as the office record, and the third as the guide for

reinspection. A covering form letter notifies the violator of

the time allowed to correct the conditions listed in the

report form.

Violation Notice. This is the legal notice that housing

code violations exist and must be corrected within the

3-10 Housing Regulations
indicated amount of time. The notice may be in the form

of a letter that includes the alleged violations or has a

copy of these attached. It may be a standard notice form,

or it may be a combined report-notice. Regardless of the

type of notice used, it should make the location and

nature of all violations clear and specify the exact section

of the code that covers each one. The notice must advise

violators of their right to a hearing. It should also indicate

that the violator has a right to be represented by counsel

and that failure to obtain counsel will not be accepted as

grounds for postponing a hearing or court case.

Hearing Forms. These should include a form letter

notifying the violator of the date and time set for the hearing,

a standard summary sheet on which the supervisor can

record the facts presented at an informal hearing, and a

hearing-decision letter for notifying all concerned of the

hearing results. The latter should include the names of the

violator, inspector, law department, and any other city

official or agency that may be involved in the case.

Reinspection Form Letters or Notices. These have the

same characteristics as violation notices except that they

cover the follow-up orders given to the violator who has

failed to comply with the original notice within the time

specified. Some agencies may use two or three types of

these form letters to accommodate different degrees of

response by the violator. Whether one or several are used,

standardization of these letters or notices will expedite the

processing of cases.

Court Complaint and Summons Forms. These forms

advise alleged violators of the charges against them and

summon them to appear in court at the specified time

and place. It is essential that the housing inspection

agency work closely with the municipal law department

in preparing these forms so that each is done in exact

accord with the rules of court procedure in the relevant

state and community.

Court Action Record Form. This form provides an accurate

running record of the inspection agency’s court actions and

their results.

Substantive Provisions of a Housing Code

A housing code is the primary tool of the housing

inspector. The code spells out what the inspector may or

may not do. An effort to improve housing conditions can be

no better than the code allows. The substantive provisions of

the code specify the minimal housing conditions acceptable

to the community that developed them.

Dwelling units should have provisions for preparing at least

one regularly cooked meal per day. Minimum equipment

should include a kitchen sink in good working condition

and properly connected to the water supply system

approved by the appropriate authority. It should provide,

at all times, an adequate amount of heated and unheated

running water under pressure and should be connected to

a sewer system approved by the appropriate authority.

Cabinets or shelves, or both, for storing eating, drinking,

and cooking utensils and food should be provided. These

surfaces should be of sound construction and made of

material that is easy to clean and that will not have a toxic

or deleterious effect on food.

In addition, a stove and refrigerator should be provided.

Within every dwelling there should be a room that affords

privacy and is equipped with a flush toilet in good working

condition.

Within the vicinity of the flush toilet, a sink should be

provided. In no case should a kitchen sink substitute as a

lavatory sink. In addition, within each dwelling unit there

should be, within a room that affords privacy, either a bathtub

or shower or both, in good working condition. Both the

lavatory sink and the bathtub or shower or both should be

equipped with an adequate amount of heated and

unheated water under pressure. Each should be connected

to an approved sewer system. 

Within each dwelling unit two or more means of egress should

be provided to safe and open space at ground level. Provisions

should be incorporated within the housing code to meet the

safety requirements of the state and community involved. The

housing code should spell out minimum standards for lighting

and ventilation within each room in the structure. In addition,

minimum thermal standards should be provided.

Although most codes merely provide the requirement of a

given temperature at a given height above floor level, the

community should give consideration to the use of

effective temperatures. The effective temperature is a means of

incorporating not only absolute temperature in degrees, but

also humidity and air movement, giving a better indication of

the comfort index of a room.

The code should provide that no person shall occupy or

let for occupancy any dwelling or dwelling units that do

not comply with stated requirements. Generally, these

requirements specify that the foundation, roof, exterior walls,

doors, window space and windows of the structure be

sound and in good repair; that it be moisture-free,

watertight and reasonably weather tight and that all

structural surfaces be sound and in good repair.

Healthy Housing Reference Manual 3-11
HUD defines a multifamily dwelling unit as one that contains

four or more dwelling units in a single structure. A

dwelling unit is further defined as a single unit of

residence for a family of one or more persons in which

sleeping accommodations are provided but toileting or

cooking facilities are shared by the occupants.

Building Codes

Building codes define what materials and methods are

tobe used in the construction of various buildings. Model

building codes have been published by various trade

organizations such as the Southern Building Code Congress

International (SBCCI), Building Officials and Code

Administrators (BOCA), and the International Conference of

Building Officials (ICBO). Each of these groups

published a model building code that was widely used or

adapted regionally in the United States. BOCA national

codes were used mostly in eastern and Great Lakes states,

ICBO uniform codes in western and Midwest states, and

SBCCI standard codes in southern states. As a result, the

construction industry often faced the challenge, and cost,

of building to different codes in different areas of the country.

In 1994, BOCA, ICBO, and SBCCI created the

International Code Council (ICC) to develop a single set of

comprehensive, coordinated model construction codes that

could be used throughout the United States and around

the world. The first I-Code published was the

International Plumbing Code in 1995. By 2000, a

complete family of I-Codes was available, including the

International Building Code. The ICC Performance Code for

Buildings and Facilities joined the I-Code family in 2001. 

On February 1, 2003, the three organizations (BOCA,

SBCCI, and ICBO) were consolidated into the ICC

[13,14]. According to ICC Board president, Paul E. Myers, 

“The ICC International Codes (I Codes) combine

the strengths of the regional codes without regional

limitations. The ICC is a nonprofit organization

dedicated to developing a single set of comprehensive

and coordinated national codes to make compliance

easier and more cost-effective. I Codes respond to the

needs of the construction industry and public safety.

A single set of codes has strong support from

government, code enforcement officials, fire officials,

architects, engineers, builders, developers, and

building owners and managers.”

References

1. Hammurabi’s Code of Laws. Translated by L.W.

King. Available from URL:

http://eawc.evansville.edu/anthology/hammurabi.htm.

2. Claghorn KH. The foreign immigrant in New

York City. Reports of the Industrial Commission,

Volume XV. Washington, DC: US Government

Printing Office; 1901.p. 465-92. Available from

URL: http://tenant.net/Community/LES/clag2.html.

3. Riis J. How the other half lives—studies among

the tenements of New York. New York: Charles

Scriber’s Sons; 1890. Available from URL:

http://www.bartleby.com/208/.

4. New York City Department of City Planning. New

York City zoning: zoning history. New York City:

New York City Department of City Planning; no

date. Available from URL:

http://www.nyc.gov/html/dcp/html/

zone/zonehis.html. 

5. New York State Multiple Dwelling Law: chapter

713 of the Laws of 1929, as amended. Available

from URL: http://tenant.net/Other_Laws/

MDL/mdltoc.html.

6. Understanding Fannie Mae: our history.

Washington, DC: Fannie Mae; 2005. Available

from URL: http://www. fanniemae.com/aboutfm/

understanding/history.jhtml?p=About+Fannie+

Mae&s=Understanding+Fannie+

Mae&t=Our+History.

7. Paulson PB. Protecting zoning laws. Atlanta:

North Buckhead Civic Association; 2000 18 Mar.

Available from URL:

http://www.nbca.org/TAP_AJC_3-18.htm.

8. Municipal Code Corporation. Municipal building

codes (online library). Tallahassee, FL: Municipal

Code Corporation. Available from URL:

http://www.municode.com/resources/

online_codes.asp.

9. American Public Health Association. Housing

ordinance. Am J Public Health 1952

Jan;42(1):76–7.

10. US Public Health Service. APHA-CDC

recommended housing maintenance and occupancy

3-12 Housing Regulations
ordinance. Atlanta: US Department of Health and

Human Services; 1975.

11. American Public Health Association. Housing

and health: APHA-CDC recommended minimum

housing standards. Washington, DC: American

Public Health Association; 1986. 

12. Lang RE, Sohmer RR, editors. Legacy of the

Housing Act of 1949: The past, present, and

future of federal housing and urban policy.

Housing Policy Debate 2000;11(2): 291–7.

Available from URL:

http://www.fanniemaefoundation.org/programs/

hpd/pdf/ hpd_ 1102_edintro.pdf.

13. International Code Council. International

residential code 2003. Country Club Hills, IL:

ICC; 2003.

14. International Code Council. International

building code 2003. Country Club Hills, IL:

ICC; 2003.

Additional Sources of Information

American Planning Association. Available from URL:

http://www.planning.org/.

Arendt R. “Open Space” zoning: what it is and why it

works. Planners Commission Journal 1992. Available

from URL: http://www.plannersweb.com/articles/are015.html.

Bookmark, Inc. Available from URL: http://www.

bookmarki.com.

International Code Council. Available from URL:

http://www.iccsafe.org.

Rosenberg M. Zoning: residential, commercial, or

industrial? New York: About, Inc.; no date. Available

from URL: http://geography.about.com/library/weekly/

aa072801a.htm?iam=sherlock_abc/.

US Department of Energy, Land Use Planning. Smart

Communities Network. Washington, DC: US Department

of Energy; no date. Available from URL: http://www.

smartcommunities.ncat.org/landuse/luintro.shtml. 

US Department of Housing and Urban Development.

Available from URL: http://www.hud.gov/.

US Department of Housing and Urban Development. Final

report of HUD review of model building codes.

Washington, DC: US Department of Housing and Urban

Development; no date. Available from URL:

http://www.hud.gov/offices/fheo/disabilities/

modelcodes/chapter5.html.

Healthy Housing Reference Manual 3-13
3-14 Housing Regulations
Chapter 4—Disease Vectors and Pests

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Disease Vectors and Pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Rodents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Cockroaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Fleas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

Flies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7

Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8

Fire Ants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-13

Mosquitoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-15

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-17

Figure 4.1. Field Identification of Domestic Rodents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Figure 4.2. Norway Rat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Figure 4.3. Roof Rat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-2

Figure 4.4. Signs of Rodent Infestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

Figure 4.5. Rodent Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Figure 4.6. Live Trap for Rats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Figure 4.7. Kill Traps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4

Figure 4.8. American, Oriental, German, and Brown-banded Cockroaches . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.9. American Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.10. Oriental Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.11. German Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.12. Brown-banded Cockroaches, Various Stages and Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.13. Wood Cockroach, Adult Male . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5

Figure 4.14. Reported Human Plague Cases (1970–1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

Figure 4.15. Flea Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6

Figure 4.16. Housefly (Musca domestica) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7

Figure 4.17. Life Cycle of the Fly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8

Figure 4.18. Termite Tube Extending From Ground to Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9

Figure 4.19. Termite Mud Shelter Tube Constructed Over A Brick Foundation . . . . . . . . . . . . . . . . . . . .4-9

Figure 4.20. Differences Between Ants and Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9

Figure 4.21. Life Cycle of the Subterranean Termite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-10

Figure 4.22. Subterranean Termite Risk in the United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-11

Figure 4.23. Typical Points of Attack by Termites in the Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-12

Figure 4.24. Construction Techniques That Discourage Termite Attacks . . . . . . . . . . . . . . . . . . . . . . . . . .4-14

Figure 4.25. Fire Ants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-14

Figure 4.26. Range Expansion of Red Imported Fire Ants (RIFA) in the United States, 1918–1998 . . . . .4-15

Figure 4.27. Fire Ant Mound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-15

Healthy Housing Reference Manual 1

Contents
“Sometimes poor housing is a shorthand way of describing

living conditions of poor people. The poor include the aged,

deprived, ethnic minority groups, the infirmed, and families

headed by unemployed women. In other words, the people

most at risk for illness often live in inferior housing.

Therefore, it is a matter of conjecture whether many people

live in poor housing because they are sick or are sick because

they live in poor housing.”

Carter L. Marshall, M.D.

Dynamics of Health and Disease 

Appleton, Century Crofts 1972

Introduction

The most immediate and obvious link between housing and

health involves exposure to biologic, chemical, and

physical agents that can affect the health and safety of the

occupants of the home. Conditions such as childhood lead

poisoning and respiratory illnesses caused by exposure to

radon, asbestos, tobacco smoke, and other pollutants are

increasingly well understood and documented. However,

even 50 years ago, public health officials understood that

housing conditions were linked to a broader pattern of

community health. For example, in 1949, the Surgeon

General released a report comparing several health status

indicators among six cities having slums. The publication

reported that: 

• the rate of deaths from communicable disease in

these areas was the same as it was for the rest of

the country 50 years ago (i.e., around 1900);

• most of the tuberculosis cases came from 25% of

the population of these cities; and

• the infant mortality rate was five times higher

than in the rest of the country, approximately

equal to what it was 50 years ago.

Housing-related health concerns include asthma episodes

triggered by exposure to dust mites, cockroaches, pets,

and rodents. The existence of cockroaches, rats, and mice

mean that they can also be vectors for significant

problems that affect health and well-being. They are

capable of transmitting diseases to humans. According to

a 1997 American Housing Survey, rats and mice infested

2.7 million of 97 million housing units. A CDC-sponsored

survey of two major American cities documented that

nearly 50% of the premises were infected with rats and mice. 

This chapter deals with disease vectors and pests as

factors related to the health of households.

Disease Vectors and Pests 

Integrated pest management (IPM) techniques are

necessary to reduce the number of pests that threaten

human health and property. This systems approach to

the problem relies on more than one technique to reduce

or eliminate pests. It can be visualized best as concentric

rings of protection that reduce the need for the most

risky and dangerous options of control and the potential

for pests to evolve and develop. It typically involves using

some or all of the following steps:

• monitoring, identifying, and determining the

level of threat from pests;

• making the environment hostile to pests;

• building the pests out by using pest-proof building

materials;

• eliminating food sources, hiding areas, and

other pest attractants;

• using traps and other physical elimination devices; and 

• when necessary, selecting appropriate poisons

for identified pests.

The above actions are discussed in more detail in the

following section on the four basic strategies for

controlling rodents. 

Most homeowners have encountered a problem with

rodents, cockroaches, fleas, flies, termites, or fire ants.

These pests destroy property or carry disease, or both,

and can be a problem for rich and poor alike. 

Rodents

Rodents destroy property, spread disease, compete for human

food sources, and are aesthetically displeasing. Rodentassociated diseases affecting humans include plague, murine

typhus, leptospirosis, rickettsialpox, and rat-bite fever. The

three primary rodents of concern to the homeowner are the

Norway rat (Rattus norvegicus), roof rat (Rattus rattus), and the

house mouse (Mus musculus). The term “commensal” is

applied to these rodents, meaning they live at people’s expense.

The physical traits of each are demonstrated in Figure 4.1. 

Chapter 4: Disease Vectors and Pests

Healthy Housing Reference Manual 4-1
Barnett [1] notes that the house mouse is abundant

throughout the United States. The Norway rat

(Figure 4.2) is found throughout the temperate regions

of the world, including the United States. The roof rat

is found mainly in the South, across the entire nation to

the Pacific coast. As a group, rodents have certain

behavioral characteristics that are helpful in

understanding them. They are perceptive to touch,

with sensitive whiskers and guard hairs on their bodies.

Thus, they favor running along walls and between

objects that allow them

constant contact with

vertical surfaces. They are

known to have poor

eyesight and are alleged to

be colorblind.

Contrastingly, they have an

extremely sharp sense of

smell and a keen sense of

taste. The word rodent is

derived from the Latin verb

rodere, meaning “to gnaw.” 

The gnawing tendency leads to structural damage to

buildings and initiates fires when insulation is chewed

from electrical wires. Rodents will gnaw to gain entrance

and to obtain food.

The roof rat (Figure 4.3) is a slender, graceful, and very

agile climber. The roof rat prefers to live aboveground:

indoors in attics, between floors, in walls, or in enclosed

spaces; and outdoors in trees and dense vine growth.

Contrasted with the

roof rat, the Norway rat

is at home below the

ground, living in a

burrow. The house

mouse commonly is

found living in human

quarters, as suggested by

its name. Signs indicative

of the presence of

rodents—aside from seeing live or dead rats and hearing

rats—are rodent droppings, runways, and tracks

(Figure 4.4). Other signs include nests, gnawings, food

scraps, rat hair, urine spots, and rat body odors. Note

that waste droppings from rodents are often confused

with cockroach egg packets, which are smooth,

segmented, and considerably smaller than a mouse dropping.

According to the Military Pest Management Handbook

(MPMH) [2], rats and mice are very suspicious of any

new objects or food found in their surroundings. This

characteristic is one reason rodents can survive in dangerous

environments. This avoidance reaction accounts for

prebaiting (baiting without poisoning) in control programs.

4-2 Disease Vectors and Pests

Figure 4.1. Field Identification of Domestic Rodents [2]

Figure 4.2. Norway Rat [3]

Figure 4.3. Roof Rat [4]
Initially, rats or mice begin by taking only small amounts

of food. If the animal becomes ill from a sublethal dose of

poison, its avoidance reaction is strengthened, and a

poisoning program becomes extremely difficult to

complete. If rodents are hungry or exposed to an environment

where new objects and food are commonly found, such

as a dump, their avoidance reaction may not be as strong;

in extreme cases of hunger, it may even be absent. 

The first of four basic strategies for controlling rodents is

to eliminate food sources. To accomplish this, it is

imperative for the homeowner or occupant to do a good

job of solid waste management. This requires proper

storing, collecting, and disposing of refuse. 

The second strategy is to eliminate breeding and nesting

places. This is accomplished by removing rubbish from

near the home, including excess lumber, firewood, and

similar materials. These items should be stored above

ground with 18 inches of clearance below them. This

height does not provide a habitat for rats, which have a

propensity for dark, moist places in which to burrow.

Wood should not be stored directly on the ground, and

trash and similar rubbish should be eliminated.

The third strategy is to construct buildings and other

structures using rat-proofing methods. MPMH notes

that it is much easier to manage rodents if a structure is

built or modified in a way that prevents easy access by

rodents. Tactics for rodent exclusion include building or

covering doors and windows with metal. Rats can gnaw

through wooden doors and windows in a very short time

to gain entrance. All holes in a building’s exterior should

be sealed. Rats are capable of enlarging openings in

masonry, especially if the mortar or brick is of poor

quality. All openings more than 3⁄4-inch wide should be

closed, especially around pipes and conduits. Cracks

around doors, gratings, windows, and other such

openings should be covered if they are less than 4 feet

above the ground or accessible from ledges, pipes, or

wires (Figure 4.5). 

Additional tactics include using proper materials for rat

proofing. For example, sheet metal of at least 26-gauge,

1⁄4-inch or 1⁄2-inch hardware cloth, and cement are all

suitable rat-resistant materials. However, 1⁄2-inch

hardware cloth has little value against house mice. Tight

fittings and self-closing doors should be constructed.

Rodent runways can be behind double walls; therefore,

spaces between walls and floor-supporting beams should

be blocked with fire stops. A proper rodent-proofing

strategy must bear in mind that rats can routinely jump

2 feet vertically, dig 4 feet or more to get under a

foundation, climb rough walls or smooth pipes up to

3 inches in diameter, and routinely travel on electric

or telephone wires. 

The first three strategies—good sanitation techniques,

habitat denial, and rat proofing—should be used initially

in any rodent management program. Should they fail, the

fourth strategy is a killing program, which can vary from

a family cat to the professional application of

rodenticides. Cats can be effective against mice, but

typically are not useful against a rat infestation. Over-thecounter rodenticides can be purchased and used by the

homeowner or occupant. These typically are in the red

squill or warfarin groups. 

A more effective alternative is trapping. There are a

variety of devices to choose from when trapping rats or

mice. The two main groups of rat and mouse traps are

live traps (Figure 4.6) and kill traps (Figure 4.7). Traps

usually are placed along walls, near runways and burrows,

and in other areas. Bait is often used to attract the

rodents to the trap. To be effective, traps must be

monitored and emptied or removed quickly. If a rat

caught in a trap is left there, other rats may avoid the traps.

A trapping strategy also may include using live traps to

remove these vermin. 

Healthy Housing Reference Manual 4-3

Figure 4.4. Signs of Rodent Infestation [2]
Cockroaches 

Cockroaches have become well adapted to living with and

near humans, and their hardiness is legendary. In light of

these facts, cockroach control may become a homeowner’s

most difficult task because of the time and special

knowledge it often involves. The cockroach is considered

an allergen source and an asthma trigger for residents.

Although little evidence exists to link the cockroach to

specific disease outbreaks, it has bee demonstrated to

carry Salmonella typhimurium, Entamoeba histolytica, and

the poliomyelitis virus. In addition, Kamble and Keith [6]

note that most cockroaches produce a repulsive odor that

can be detected in infested areas. The sight of cockroaches

can cause considerable psychologic or emotional distress

in some individuals. They do not bite, but they do have

heavy leg spines that may scratch. 

According to MPMH [2], there are 55 species of

cockroaches in the United States. As a group, they tend to

prefer a moist, warm habitat because most are tropical in

origin. Although some tropical cockroaches feed only on

vegetation, cockroaches of public health interest tend to

live in structures and are customarily scavengers.

Cockroaches will eat a great variety of materials, including

cheese and bakery products, but they are especially fond

of starchy materials, sweet substances, and meat products. 

Cockroaches are primarily nocturnal. Daytime sightings

may indicate potentially heavy infestations. They tend to

hide in cracks and crevices and can move freely from

room to room or adjoining housing units via wall spaces,

plumbing, and other utility installations. Entry into

homes is often accomplished through food and beverage

boxes, grocery sacks, animal food, and household goods

carried into the home. The species of public health

Figure 4.7. Kill Traps for Rats [2]

Figure 4.5. Rodent Prevention [2]

Figure 4.6. Live Traps for Rats [5]

4-4 Disease Vectors and Pests
interest that commonly inhabit human dwellings

(Figures 4.8–4.13) include the following: German

cockroach (Blattella germanica); American cockroach

(Periplaneta americana); Oriental cockroach (Blatta

orientalis); brown-banded cockroach (Supella longipalpa);

Australian cockroach (Periplaneta australasiae); smokybrown cockroach (Periplaneta fuliginosa); and brown

cockroach (Periplaneta brunnea).

Four management strategies exist for controlling

cockroaches. The first is prevention. This strategy

includes inspecting items being carried into the home

and sealing cracks and crevices in kitchens, bathrooms,

exterior doors, and windows. Structural modifications

would include weather stripping and pipe collars. The

second strategy is sanitation. This denies cockroaches food,

water, and shelter. These efforts include quickly cleaning

food particles from shelving and floors; timely washing of

dinnerware; and routine cleaning under refrigerators,

stoves, furniture, and similar areas. If pets are fed indoors,

pet food should be stored in tight containers and not left

in bowls overnight. Litter boxes should be cleaned

routinely. Access should be denied to water sources by

fixing leaking plumbing, drains, sink traps, and purging

clutter, such as papers and soiled clothing and rags. The

third strategy is trapping. Commercially available cockroach

Figure 4.8. American, Oriental, German, and Brown- banded

Cockroaches [7]

Figure 4.9. American Cockroaches, Various Stages and Ages [7]

Figure 4.10. Oriental Cockroaches, Various Stages and Ages [7]

Figure 4.11. German Cockroaches, Various Stages and Ages [7]

Figure 4.12. Brown-banded Cockroaches, Various Stages and

Ages [7]

Figure 4.13. Wood Cockroach, Adult Male [7]

Healthy Housing Reference Manual 4-5
traps can be used to capture roaches and serve as a

monitoring device. The most effective trap placement is

against vertical surfaces, primarily corners, and under

sinks, in cabinets, basements, and floor drains. The fourth

strategy is chemical control. The use of chemicals

typically indicates that the other three strategies have been

applied incorrectly. Numerous insecticides are available

and appropriate information is obtainable from EPA. 

Fleas

The most important fleas as disease vectors are those that

carry murine typhus and bubonic plague. In addition,

fleas serve as intermediate hosts for some species of dog and

rodent tapeworms that occasionally infest people. They also

may act as intermediate hosts of filarial worms

(heartworms) in dogs. In the United States, the most

important disease related to fleas is the bubonic plague.

This is primarily a concern of residents in the southwestern

and western parts of the country (Figure 4.14). 

Of approximately 2,000 species of flea, the most common

flea infesting both dogs and cats is the cat flea

Ctenocephalides felis. Although numerous animals, both

wild and domestic, can have flea infestations, it is from

the exposure of domestic dogs and cats that most

homeowners inherit flea infestation problems. According to

MPMH [2], fleas are wingless insects varying from 1 to

81⁄2 millimeters (mm) long, averaging 2 to 4 mm, and

feed through a siphon or tube. They are narrow and

compressed laterally with backwardly directed spines,

which adapt them for moving between the hairs and

feathers of mammals and birds. They have long, powerful

legs adapted for jumping. Both sexes feed on blood, and

the female requires a blood meal before she can produce

viable eggs. Fleas tend to be host-specific, thus feeding on

only one type of host. However, they will infest other

species in the absence of the favored host. They are found

in relative abundance on animals that live in burrows and

sheltered nests, while mammals and birds with no

permanent nests or that are exposed to the elements tend

to have light infestations. 

MPMH [2] notes that fleas undergo complete metamorphosis

(egg, larva, pupa, and adult). The time it takes to

complete the life cycle from egg to adult varies according

to the species, temperature, humidity, and food

availability. Under favorable conditions, some species can

complete a generation in as little as 2 or 3 weeks.

Figure 4.15 shows the life cycle of the flea. 

4-6 Disease Vectors and Pests

Figure 4.14. Reported Human Plague Cases (1970–1997) [8]

Figure 4.15. Flea Life Cycle [2]
Flea eggs usually are laid singly or in small groups among

the feathers or hairs of the host or in a nest. They are

often laid in carpets of living quarters if the primary host

is a household pet. Eggs are smooth, spherical to oval,

light colored, and large enough to be seen with the naked 

eye. An adult female flea can produce up to 2,000 eggs in

a lifetime. Flea larvae are small (2 to 5 mm), white, and

wormlike with a darker head and a body that will appear

brown if they have fed on flea feces. This stage is mobile

and will move away from light, thus they typically will be

found in shaded areas or under furniture. In 5 to 12 days,

they complete the three larval stages; however, this may

take several months depending on environmental

conditions. The larvae, after completing development,

spin a cocoon of silk encrusted with granules of sand or

various types of debris to form the pupal stage. The pupal

stage can be dormant for 140 to 170 days. In some areas

of the country, fleas can survive through the winter. The

pupae, after development, are stimulated to emerge as

adults by movement, pressure, or heat. The pupal form of

the flea is resistant to insecticides. An initial treatment,

while killing egg, larvae, and adult forms, will not kill the

pupae. Therefore, a reapplication will often be necessary.

The adult forms are usually ready to feed about 24 hours

after they emerge from the cocoon and will begin to feed

within 10 seconds of landing on a host. Mating usually

follows the initial blood meal, and egg production is

initiated 24 to 48 hours after consuming a blood meal.

The adult flea lives approximately 100 days, depending

on environmental conditions.

Following are some guidelines for controlling fleas:

• The most important principle in a total flea control

program is simultaneously treating all pets and their

environments (indoor and outdoor).

• Before using insecticides, thoroughly clean the

environment, removing as many fleas as possible,

regardless of the form. This would include indoor

vacuuming and carpet steam cleaning. Special

attention should be paid to source points where pets

spend most of their time.

• Outdoor cleanup should include mowing, yard raking,

and removing organic debris from flowerbeds and

under bushes.

• Insecticide should be applied to the indoor and

outdoor environments and to the pet.

• Reapplication to heavily infested source points in

the home and the yard may be needed to eliminate pre-emerged adults.

Flies

The historical attitude of Western society toward flies has

been one of aesthetic disdain. The public health view is to

classify flies as biting or nonbiting. Biting flies include

sand flies, horseflies, and deerflies. Nonbiting flies include

houseflies, bottleflies, and screwworm flies. The latter

group is often referred to as synanthropic because of their

close association with humans. In general, the presence of

flies is a sign of poor sanitation. The primary concern of

most homeowners is nonbiting flies. 

According to

MPMH [2], the

housefly (Musca

domestica) (Figure

4.16) is one of the

most widely

distributed insects,

occurring

throughout the

United States, and

is usually the

predominant fly species in homes and restaurants. M.

domestica is also the most prominent human-associated

(synanthropic) fly in the southern United States. Because

of its close association with people, its abundance, and its

ability to transmit disease, it is considered a greater threat

to human welfare than any other species of nonbiting fly.

Each housefly can easily carry more than 1 million bacteria

on its body. Some of the disease-causing agents transmitted

by houseflies to humans are Shigella spp. (dysentery and

diarrhea = shigellosis), Salmonella spp. (typhoid fever),

Escherichia coli, (traveler’s diarrhea), and Vibrio cholera

(cholera). Sometimes these organisms are carried on the

fly’s tarsi or body hairs, and frequently they are

regurgitated onto food when the fly attempts to liquefy it

for ingestion. 

The fly life cycle is similar across the synanthropic group.

MPMH [2] notes that the egg and larval stages develop in

animal and vegetable refuse. Favorite breeding sites

include garbage, animal manure, spilled animal feed, and soil

contaminated with organic matter. Favorable

environmental conditions will result in the eggs hatching

in 24 hours or less. Normally, a female fly will produce

500 to 600 eggs during her lifetime. 

The creamy, white larvae (maggots) are about 1⁄2-inch

long when mature and move within the breeding material

Healthy Housing Reference Manual 4-7

Figure 4.16. Housefly [Musca domestica] [9]
to maintain optimum temperature and moisture

conditions. This stage lasts an average of 4 to 7 days in

warm weather. The larvae move to dry parts of the

breeding medium or move out of it onto the soil or

sheltered places under debris to pupate, with this stage

usually lasting 4 to 5 days. When the pupal stage is

accomplished, the adult fly exits the puparium, dries, hardens,

and flies away to feed, with mating occurring soon after

emergence. Figure 4.17 demonstrates the typical fly life

cycle. 

The control of the housefly is hinged on good sanitation

(denying food sources and breeding sites to the fly). This

includes the proper disposal of food wastes by placing

garbage in cans with close-fitting lids. Cans need to be

periodically washed and cleaned to remove food debris.

The disposal of garbage in properly operated sanitary

landfills is paramount to fly control. 

The presence of adult flies can be addressed in various

ways. Outside methods include limited placement of

common mercury vapor lamps that tend to attract flies.

Less-attractive sodium vapor lamps should be used near

the home. Self-closing doors in the home will deny

entrance, as will the use of proper-fitting and wellmaintained screening on doors and windows. 

Larger flies use homes for shelter from the cold, but do

not reproduce inside the home. Caulking entry points

and using fly swatters is effective and much safer than the

use of most pesticides. Insecticide “bombs” can be used in

attics and other rooms that can be isolated from the rest

of the house. However, these should be applied to areas

away from food, where flies rest. 

The blowfly is a fairly large, metallic green, gray, blue,

bronze, or black fly. They may spend the winter in homes

or other protected sites, but will not reproduce during

this time. Blowflies breed most commonly on decayed

carcasses (e.g., dead squirrels, rodents, birds) and in

droppings of dogs or other pets during the summer; thus,

removal of these sources is imperative. Small animals, on

occasion, may die inside walls or under the crawl space of

a house. A week or two later, blowflies or maggots may

appear. The adult blowfly is also attracted to gas leaks. 

Termites

According to Gold et al. [11], subterranean termites are

the most destructive insect pests of wood in the United

States, causing more than $2 billion in damage each year.

Annually, this is more property damage than that caused

by fire and windstorms combined. In the natural world,

these insects are beneficial because they break down dead

trees and other wood materials that would otherwise

accumulate. This biomass breakdown is recycled to the

soil as humus. MPMH [2], on the other hand, notes that

these insects can damage a building so severely it may

have to be replaced. Termites consume wood and other

cellulose products, such as paper, cardboard, and

fiberboard. They will also destroy structural timbers,

pallets, crates, furniture, and other wood products. In

addition, they will damage many materials they do not

normally eat as they search for food. The tunneling efforts

of subterranean termites can penetrate lead- and plasticcovered electric cable and cause electrical system failure.

In nature, termites may live for years in tree stumps or

lumber beneath concrete buildings before they penetrate

hairline cracks in floors and walls, as well as expansion

joints, to search for food in areas such as interior door

frames and immobile furniture. Termite management costs to

homeowners are exceeded only by cockroach control costs. 

Lyon [12] notes that termites are frequently mistaken by

the homeowner as ants and often are referred to

erroneously as white ants. Typical signs of termite

infestations occur in March through June and in

September and October. Swarming is an event where a

group of adult males and female reproductives leave the

nest to establish a new colony. If the emergence happens

inside a building, flying termites may constitute a

considerable nuisance. These pests can be collected with a

vacuum cleaner or otherwise disposed of without using

pesticides. Each homeowner should be aware of the

following signs of termite infestation:

• Pencil-thin mud tubes extending over the inside

and outside surfaces of foundation walls, piers,

sills, joists, and similar areas (Figures 4.18 and 4.19).

4-8 Disease Vectors and Pests

Figure 4.17. Life Cycle of the Fly [10]
• Presence of winged termites or their shed wings

on windowsills and along the edges of floors.

• Damaged wood hollowed out along the grain and

lined with bits of mud or soil. According to Oi

et al. [15], termite tubes and nests are made of

mud and carton. Carton is composed of partially

chewed wood, feces, and soil packed together.

Tubes maintain the high humidity required for

survival, protect termites from predators, and

allow termites to move from one spot to another. 

Differentiating the ant from the dark brown or black

termite reproductives can be accomplished by noting the

respective wings and body shape. MPMH [2] states that a

termite has four wings of about equal length and that the

wings are nearly twice as long as the body. By comparison, ant

wings that are only a little longer than the body and the

hind pair is much shorter than the front. Additionally,

ants typically have a narrow waist, with the abdomen

connected to the thorax by a thin petiole. Termites do

not have a narrow or pinched waist. Figure 4.20a and b

demonstrates the differences between the ant and termite.

Entomologists refer to winged ants and termites as alates. 

Figure 4.21 shows the life cycle of the termite. In each

colony, there are three castes or forms of individuals

known as reproductives, workers, and soldiers. According

to Lyon [12], the reproductives can be winged or

wingless, with the latter found in colonies to serve as

replacements for the primary reproductives. The primary

reproductives (alates) vary in color from pale yellowbrown to coal black, are 1⁄2-inch to 3/8-inch in length, are

flattened dorsa-ventrally, and have pale or smoke-gray to

brown wings. The secondary reproductives have short

wing buds and are white to cream colored. The workers

are the same size as the primary reproductives and are

white to grayish-white, with a yellow-brown head, and

are wingless. In addition, the soldiers resemble workers,

in that they are wingless, but soldiers have large,

rectangular, yellowish, and brown heads with large jaws.

MPMH [2] states there are five families of termites found

in the world, with four of them occurring in the United

States. The families in the United States are

Hodotermitidae (rotten-wood termites), Kalotermitidae

(dry-wood termites), Rhinotermitidae (subterranean

Healthy Housing Reference Manual 4-9

Figure 4.20a. Ant (Elbowed Antennae: Fore Wings Larger Than Hind;

Constricted Waist) [16]

Figure 4.20b. Termite (Beaded Antennae; All Wings Equal) [16]

Figure 4.18. Termite Tube Extending from Ground to Wall [Red

Arrows] [13]

Figure 4.19. Termite Mud Shelter Tube Constructed Over a Brick

Foundation [14]
termites) and Termitidae (desert termites). Subterranean

termites typically work in wood aboveground, but must

have direct contact with the ground to obtain moisture.

Nonsubterranean termites colonize above the ground and

feed on cellulose; however, their life cycles and methods

of attack, and consequently methods of control, are quite

different. Nonsubterranean termites in the United States

are commonly called drywood termites. 

In the United States, according to MPMH [2], native

subterranean termites are the most important and the

most common. These termites include the genus

Reticulitermes, occurring primarily in the continental

United States, and the genus Heterotermes, occurring in

the Virgin Islands, Puerto Rico, and the deserts of California

and Arizona. The appearance, habits, and type of damage

they cause are similar. The Formosan termite (Coptotermes

formosanus) is the newest species to become established in

the United States. It is a native of the Pacific Islands and

spread from Hawaii and Asia to the United States during

the 1960s. It is now found along the Gulf Coast, in

California, and in South Carolina, and is expected to

spread to other areas as well. Formosan termites cause

greater damage than do native species because of their

more vigorous and aggressive behavior and their ability to

rapidly reproduce, build tubes and tunnels, and seek out

new items to infest. They have also shown more resistance

to some soil pesticides than native species. Reproductives

(swarmers) are larger than native species, reaching up to

5/8-inch in length, and are yellow to brown in color.

Swarmers have hairy-looking wings and swarm after dusk,

unlike native species, which swarm in the daytime.

Formosan soldiers have more oval-shaped heads than do

native species. On top of the head is an opening that

emits a sticky, whitish substance.

Dry-wood termites (Cryptotermes spp.) live entirely in

moderately to extremely dry wood. They require contact

with neither the soil nor any other moisture source and

may invade isolated pieces of furniture, fence posts,

utility poles, firewood, and structures. Dry-wood termite

colonies are not as large as other species in the United

States, so they can occupy small wooden articles, which

are one way these insects spread to different locations.

They are of major economic importance in southern

California, Arizona, and along the Gulf Coast. The West

Indian dry-wood termite is a problem in Puerto Rico, the

U.S. Virgin Islands, Hawaii, parts of Florida and

Louisiana, and a number of U.S. Pacific Island territories.

Dry-wood termites are slightly larger than most other

species, ranging from 1⁄2 inch to 5/8 inch long, and are

generally lighter in color. 

Damp-wood termites do not need contact with damp

ground like subterranean termites do, but they do require

higher moisture content in wood. However, once

established, these termites may extend into slightly drier wood. 

Termites of minor importance are the tree-nesting groups.

The nests of these termites are found in trees, posts, and,

occasionally, buildings. Their aboveground nests are

connected to soil by tubes. Tree-nesting termites may be a

problem in Puerto Rico and the U.S. Virgin Islands. 

The risk for encountering subterranean termites in the

United States is greater in the southeastern states and in

southwestern California. In the United States, the risk for

termite infestations tends to decrease as the latitude

increases northward. 

Figure 4.22 portrays the geographic risk of subterranean

termites in the United States. Subterranean termites are

found in all states except Alaska and are most abundant

in the south and southeastern United States [18].

According to Potter [19], homeowners can reduce the risk

for termite attack by adhering to the following suggestions:

• Eliminate wood contact with the ground. Earthto-wood contact provides termites with

simultaneous access to food, moisture, and shelter

in conjunction with direct, hidden entry into the

structure. In addition, the homeowner or

occupant should be aware that pressure-treated

wood is not immune to termite attack because

termites can enter through the cut ends and build

tunnels over the surfaces.

4-10 Disease Vectors and Pests

Figure 4.21. Life Cycle of the Subterranean Termite [17]
• Do not allow moisture to accumulate near the

home’s foundation. Proper drainage, repair of

plumbing, and proper grading will help to reduce

the presence of moisture, which attracts termites.

• Reduce humidity in crawl spaces. Most building

codes state that crawl space area should be vented

at a rate of 1 square foot per 150 square feet of

crawl space area. This rate can be reduced for

crawl spaces equipped with a polyethylene or

equivalent vapor barrier to one square foot per

300 to 500 square feet of crawl space area. Vent

placement design includes positioning one vent

within 3 feet of each building corner. Trimming

and controlling shrubs so that they do not

obstruct the vents is imperative. Installling a 4-

to 6-mil polyethylene sheeting over a minimum of

75% of the crawl space will reduce the crawlspace moisture. Covering the entire floor of the

crawl space with such material can reduce two

potential home problems at one time: excess

moisture and radon (Chapter 5). The barrier will

reduce the absorption of moisture from the air

and the release of moisture into the air in the

crawl space from the underlying soil. 

• Never store firewood, lumber, or other wood debris

against the foundation or inside the crawl space.

Termites are both attracted to and fed by this type

of storage. Wood stacked in contact with a

dwelling and vines, trellises, and dense plant

material provide a pathway for termites to bypass

soil barrier treatment. 

• Use decorative wood chips and mulch sparingly.

Cellulose-containing products attract termites,

especially materials that have moisture-holding

properties, such as mulch. The homeowner should

never allow these products to contact wood

components of the home. The use of crushed

stone or pea gravel is recommended as being less

attractive to termites and helpful in diminishing

other pest problems.

• Have the structure treated by a professional pest

control treatment. The final, and most effective,

strategy to prevent infestation is to treat the soil

around and beneath the building with termiticide.

The treated ground is then both a repellant and

toxic to termites.

Healthy Housing Reference Manual 4-11

Figure 4.22. Subterranean Termite Risk in the United States [18]
Figure 4.23 demonstrates some typical points of attack by

subterranean termites and some faulty construction practices

that can contribute to subterranean termite infestations. 

Lyon [12] notes the following alternative termite control

measures:

• Nematodes. Certain species of parasitic round

worms (nematodes) will infest and kill termites

and other soil insects. Varying success has been

experienced with this method because it is

dependent on several variables, such as soil

moisture and soil type.

• Sand as a physical barrier. This would require

preconstruction planning and would depend on

termites being unable to manipulate the sand to

create tunnels. Some research in California and

Hawaii has indicated early success.

• Chemical baits. This method uses wood or

laminated texture-flavored cellulose impregnated

with a toxicant and/or insect growth regulator.

The worker termite feeds on the substance and

carries it back to the nest, reducing or eliminating

the entire colony. According to HomeReports.com

[20], an additional system is to strategically

place a series of baits around the house. The

intention is for termite colonies to encounter one

or more of the baits before approaching the

house. Once termite activity is observed, the bait

wood is replaced with a poison. The termites

bring the poison back to the colony and the

colony is either eliminated or substantially

reduced. This system is relatively new to the

market. Its success depends heavily on the

termites finding the bait before finding and

damaging the house.

Additional measures include construction techniques that

discourage termite attacks, as demonstrated in Figure 4.24.

Termites often invade homes by way of the foundation,

either by crawling up the exterior surface where their

activity is usually obvious or by traveling inside hollow

block masonry. One way to deter their activity is to block

their access points on or through the foundation. Metal

termite shields have been used for decades to deter

termite movement along foundation walls and piers on

up to the wooden structure. Metal termite shields should

extend 2 inches from the foundation and 2 inches down.

Improperly installed (i.e., not soldered/sealed properly),

damaged, or deteriorated termite shields may allow

Figure 4.23. Typical Points of Attack by Termites in the Home [2]

4-12 Disease Vectors and Pests
termites to reach parts of the wooden floor system.

Shields should be made of noncorroding metal and have

no cracks or gaps along the seams. If a house is being

built with metal termite shielding, the shielding should

extend at least 2 inches out and 2 inches down at a 45°

angle from the foundation wall. An alternative to using

termite shields on a hollow-block foundation is to fill the

block with concrete or put in a few courses of solid or

concrete-filled brick (which is often done anyway to level

foundations). These are referred to as masonry caps. The

same approach can be used with support piers in the

crawl space. Solid caps (i.e., a continuously poured

concrete cap) are best at stopping termites, but are not

commonly used. Concrete-filled brick caps should deter

termite movement or force them through small gaps, thus

allowing them to be spotted during an inspection [21]. 

Fire Ants

According to MPMH [2], ants are one of the most

numerous species on earth. Ants are in the same order as

wasps and bees and, because of their geographic

distribution, they are universally recognized (Figure 4.25).

The life cycle of the fire ant begins with the mating of the

winged forms (alates) some 300 to 800 feet in the air,

typically occurring in the late spring or early summer. The

male dies after the mating; and the newly mated queen

finds a suitable moist site, drops her wings, and burrows

in the soil, sealing the opening behind her. Ants undergo

complete metamorphosis and, therefore, have egg, larval,

pupal and adult stages. The new queen will begin laying

eggs within 24 hours. Once fully developed, she will

produce approximately 1,600 eggs per day over a

maximum life span of 7 years. Soft, whitish, legless larvae

are produced from the hatching. These larvae are fed by

the worker ants. Pupae resemble adults in form, but are

soft, nonpigmented, and lack mobility. There are at least

three distinct castes of ants: workers, queens, and males.

Typically, the males have wings, which they retain until

death. Queens, the largest of the three castes, normally

have wings, but lose them after mating. The worker,

which is also a female, is never winged, except as a rare

abnormality. Within this hierarchy, mature colonies

contain males and females that are capable of flight and

reproduction. These are known as reproductives, and an

Healthy Housing Reference Manual 4-13

1. Cracks in foundation permit hidden points of 

entry from soil to sill.

2. Posts through concrete in contact with 

substructural soil. Watch door frames and 

intermediate supporting posts.

3. Wood-framing members in contact with 

earthfill under concrete slab.

4. Form boards left in place contribute to 

termite food supply.

5. Leaking pipes and dripping faucets sustain soil 

moisture. Excess irrigation has same effect.

6. Shrubbery blocking air flow through vents.

7. Debris supports termite colony until large 

population attacks superstructure.

8. Heating unit accelerates termite development 

by maintaining warmth of colony on a yearround basis.

9. Foundation wall too low permits wood to 

contact soil. Adding topsoil often builds exterior 

grade up to sill level.

10. Footing too low or soil thrown against it causes 

wood-soil contact. There should be 8 inches 

of clean concrete between soil and pier block.

11. Stucco carried down over concrete foundation 

permits hidden entrance between stucco and 

foundation if bond fails.

12. Insufficient clearance for inspection also 

permits easy construction of termite shelter tubes 

from soil to wood.

13. Wood framing of crawl hole forming 

wood-soil contact.

14. Mud sill and/or posts in contact with soil.

15. Wood siding and skirting form soil contact. 

There should be a minimum of 3 inches 

clearance between skirting and soil.

16. Porch steps in contact with soil. Also watch for 

ladders and other wooden materials.

17. Downspouts should carry water away from

the building.

18. Improper maintenance of soil piled against pier 

footing. Also makes careful inspection impossible.

19. Wall girder entering recess and foundation wall.

Should have a 1-inch free air space on both 

sides and end and be protected with a moistureimpervious seal.

20. Vents placed between joists tunnel air through 

space without providing good substructural 

aeration. Vents placed in foundation wall give 

better air circulation.

Key to Figure 4.23
average colony may produce approximately 4,500 of these

per year. A healthy nest usually produces two nuptial

flights of reproductives each year and a healthy, mature

colony may contain more than 250,000 ants. Though

uncommon among ants, multiple queen colonies (10 to

100) occur somewhat frequently in fire ants, resulting in

more numerous mounds per acre.

There are many species of fire ants in the United States.

The most important are four species in the genus

Solenopsis. Of these, the number one fire ant pest is the

red imported fire ant (RIFA) Solenopsis invicta

(Figure 4.25). This ant was imported inadvertently from

South America in the 1930s through the port of Mobile,

Alabama. RIFAs are now found in more than 275 million

acres in 11 southern states and Puerto Rico. The second

most important species is the black imported fire ant,

S. richteri, which was introduced into the United States 

in the 1920s from Argentina or Uruguay. It is currently

limited in distribution to a small area of northern

Mississippi and Alabama. There are two native species

of fire ants: the tropical or native fire ant, S. geminata,

ranging from South Carolina to Florida and west to

Texas; and the Southern fire ant, S. xyloni, which occurs

from North Carolina south to northern Florida, along the

Gulf Coast, and west to California. The most important

extension of the RIFA range is thought to have occurred

during the 1950s housing boom as a result of the

transportation of sod and nursery plants (Figure 4.26).

RIFAs prefer open and sun-exposed areas. They are found

in cultivated fields, cemeteries, parks, and yards, and even

inside cars, trucks, and recreational vehicles. RIFAs are

attracted to electrical currents and are known to nest in

and around heat pumps, junction boxes, and similar

areas. They are omnivorous; thus they will attack most

things, living or dead. Their economic effects are felt by

their destruction of the seeds, fruit, shoots, and seedlings

of numerous native plant species. Fire ants are known to

tend pests, such as scale insects, mealy bugs, and aphids,

for feeding on their sweet waste excretion (honeydew).

RIFAs transport these insects to new feeding sites and

protect them from predators. The positive side of RIFA

infestation is that the fire ant is a predator of ticks and

controls the ground stage of horn flies.

4-14 Disease Vectors and Pests

Figure 4.24. Construction Techniques That Discourage Termite Attacks: Thin Metal Termite Shield Should Extend 2 Inches Beyond Foundation and 2 Inches

Down [2]

Figure 4.25. Fire Ants [22]
The urban dweller with a RIFA infestation may find

significant damage to landscape plants, with reductions in

the number of wild birds and mammals. RIFAs can

discourage outdoor activities and be a threat to young

animals or small confined pets. RIFA nests typically are

not found indoors, but around homes, roadways, and

structures, as well as under sidewalks. Shifting of soil after

RIFAs abandon sites has resulted in collapsing structures.

Figure 4.27 shows a fire ant mound with fire ants and a

measure of their relative size. 

The medical complications of fire ant stings have been

noted in the literature since 1957. People with disabilities,

reduced feeling in their feet and legs, young children, and

those with mobility issues are at risk for sustaining

numerous stings before escaping or receiving assistance.

Fatalities have resulted from attacks on the elderly and on

infants. Control of the fire ant is primarily focused on the

mound by using attractant bait consisting 

of soybean oil, corn grits, or chemical agents. The bait is

picked up by the worker ants and taken deep into the

mound to the queen. These products typically require

weeks to work. 

Individual mound treatment is usually most effective in

the spring. The key is to locate and treat all mounds in

the area to be protected. If young mounds are missed, the

area can become reinfested in less than a year. 

Mosquitoes 

All mosquitoes have four stages of development—egg,

larva, pupa, and adult—and spend their larval and pupal

stages in water. The females of some mosquito species

deposit eggs on moist surfaces, such as mud or fallen

leaves, that may be near water but dry. Later, rain or high

tides reflood these surfaces and stimulate the eggs to

hatch into larvae. The females of other species deposit

their eggs directly on the surface of still water in such

places as ditches, street catch basins, tire tracks, streams

that are drying up, and fields or excavations that hold

water for some time. This water is often stagnant and

close to the home in discarded tires, ornamental pools,

Healthy Housing Reference Manual 4-15

Figure 4.26. Range Expansion of Red Imported Fire Ants [RIFAs] in the United States, 1918–1998 [23]

Figure 4.27. Fire Ant Mound

Source: CAPT Craig Shepherd, U.S. PHS; used with permission.
unused wading and swimming pools, tin cans, bird baths,

plant saucers, and even gutters and flat roofs. The eggs

soon hatch into larvae. In the hot summer months, larvae

grow rapidly, become pupae, and emerge 1 week later as

flying adult mosquitoes. A few important spring species

have only one generation per year. However, most species

have many generations per year, and their rapid increase

in numbers becomes a problem.

When adult mosquitoes emerge from the aquatic stages,

they mate, and the female seeks a blood meal to obtain

the protein necessary for the development of her eggs.

The females of a few species may produce a first batch of

eggs without this first blood meal. After a blood meal is

digested and the eggs are laid, the female mosquito again

seeks a blood meal to produce a second batch of eggs.

Depending on her stamina and the weather, she may

repeat this process many times without mating again. The

male mosquito does not take a blood meal, but may feed

on plant nectar. He lives for only a short time after

mating. Most mosquito species survive the winter, or

overwinter, in the egg stage, awaiting the spring thaw,

when waters warm and the eggs hatch. A few important

species spend the winter as adult, mated females, resting

in protected, cool locations, such as cellars, sewers, crawl

spaces, and well pits. With warm spring days, these

females seek a blood meal and begin the cycle again.

Only a few species can overwinter as larvae.

Mosquitoborne diseases, such as malaria and yellow fever,

have plagued civilization for thousands of years. Newer threats

include Lyme disease and West Nile virus. Organized mosquito

control in the United States has greatly reduced the

incidence of these diseases. However, mosquitoes can still

transmit a few diseases, including eastern equine encephalitis

and St. Louis encephalitis. The frequency and extent of

these diseases depend on a complex series of factors.

Mosquito control agencies and health departments cooperate

in being aware of these factors and reducing the chance

for disease. It is important to recognize that young adult

female mosquitoes taking their first blood meal do not

transmit diseases. It is instead the older females, who, if they

have picked up a disease organism in their first blood meals,

can then transmit the disease during the second blood meal. 

The proper method to manage the mosquito problem in

a community is through an organized integrated pest

management system that includes all approaches that safely

manage the problem. The spraying of toxic agents is but

one of many approaches.

When mosquitoes are numerous and interfere with living,

recreation, and work, you can use the various measures

described in the following paragraphs to reduce their

annoyance, depending on location and conditions.

How to Reduce the Mosquito Population

The most efficient method of controlling mosquitoes is

by reducing the availability of water suitable for larval

and pupal growth. Large lakes, ponds, and streams that have

waves, contain mosquito-eating fish, and lack aquatic

vegetation around their edges do not contain mosquitoes;

mosquitoes thrive in smaller bodies of water in protected

places. Examine your home and neighborhood and take the

following precautions recommended by the New Jersey

Agricultural Experiment Station [24]:

• dispose of unwanted tin cans and tires; 

• clean clogged roof gutters and drain flat roofs; 

• turn over unused wading pools and other

containers that tend to collect rainwater;

• change water in birdbaths, fountains, and troughs

twice a week; 

• clean and chlorinate swimming pools; 

• cover containers tightly with window screen or

plastic when storing rainwater for garden use

during drought periods; 

• flush sump-pump pits weekly; and 

• stock ornamental pools with fish.

If mosquito breeding is extensive in areas such as woodland

pools or roadside ditches, the problem may be too great

for individual residents. In such cases, call the organized

mosquito control agency in your area. These agencies

have highly trained personnel who can deal with the

problem effectively.

Several commercially available insecticides can be effective

in controlling larval and adult mosquitoes. These chemicals

are considered sufficiently safe for use by the public.

Select a product whose label states that the material is

effective against mosquito larvae or adults. For safe and

effective use, read the label and follow the instructions for

applying the material. The label lists those insects that the

EPA agrees are effectively controlled by the product. 

4-16 Disease Vectors and Pests
For use against adult mosquitoes, some liquid insecticides

can be mixed according to direction and sprayed lightly

on building foundations, hedges, low shrubbery, ground

covers, and grasses. Do not overapply liquid insecticides—

excess spray drips from the sprayed surfaces to the ground,

where it is ineffective. The purpose of such sprays is to

leave a fine deposit of insecticide on surfaces where mosquitoes

rest. Such sprays are not effective for more than 1 or 2 days.

Some insecticides are available as premixed products or

aerosol cans. These devices spray the insecticide as very

small aerosol droplets that remain floating in the air and

hit the flying mosquitoes. Apply the sprays upwind, so

the droplets drift through the area where mosquito

control is desired. Rather than applying too much of

these aerosols initially, it is more practical to apply them

briefly but periodically, thereby eliminating those

mosquitoes that recently flew into the area.

Various commercially available repellents can be

purchased as a cream or lotion or in pressurized cans, then

applied to the skin and clothing. Some manufacturers also

offer clothing impregnated with repellents; coarse,

repellent-bearing particles to be scattered on the ground;

and candles whose wicks can be lit to release a repellent

chemical. The effectiveness of all repellents varies from

location to location, from person to person, and from

mosquito to mosquito. Repellents can be especially

effective in recreation areas, where mosquito control may

not be conducted. All repellents should be used according

to the manufacturers’ instructions. Mosquitoes are

attracted by perspiration, warmth, body odor, carbon

dioxide, and light. Mosquito control agencies use some of

these attractants to help determine the relative number of

adult mosquitoes in an area. Several devices are sold that

are supposed to attract, trap, and destroy mosquitoes and

other flying insects. However, if these devices are

attractive to mosquitoes, they probably attract more

mosquitoes into the area and may, therefore, increase

rather than decrease mosquito annoyance.

References 

1. Barnett DB. Vectors and their control. In: Morgan

MT, editor. Environmental health. 3rd ed.

Englewood, CO: Wadsworth Publishing Co.;

2002. p. 137–50.

2. Armed Forces Pest Management Board. Military

pest management handbook. Washington, DC:

Armed Forces Pest Management Board; no date.

Available from URL: http://www.afpmb.org/

MPMH/toc.htm. 

3. Indiana Department of Natural Resources.

Rodent pictures. Lafayette, IN: Indiana

Department of Natural Resources; no date.

Available from URL: http://www.entm.purdue.edu/

wildlife/rat_pictures.htm.

4. Arrow Services, Inc. Rats: roof rats. Plymouth,

IN: Arrow Services, Inc.; no date. Available from

URL: http://www.arrowpestcontrol.com/

pages/rod/roofpic.html.

5. Cobb County Extension Service. Fact sheet on

rodents: rats and mice. Marietta, GA: Cobb

County Extension Service; 2003. Available from

URL: http://www.griffin.peachnet.edu/ga/cobb/

Horticulture/Factsheets/peskycritters/ratsmice.htm.

6. Kamble ST, Keith DL. Cockroaches and their

control. Lincoln, NE: University of Nebraska

Cooperative Extension; 1995. 

7. University of Nebraska-Lincoln. Cockroach

picture gallery. Lincoln, NE: University of

Nebraska-Lincoln; no date. Available from URL:

http://pested.unl.edu/roachind.htm.

8. Centers for Disease Control and Prevention.

Reported human plague cases by county: United

States, 1970–1997. Atlanta: US Department of

Health and Human Services; no date. Available

from URL: http://www.cdc.gov/ncidod/

dvbid/plague/plagwest.htm.

9. Leslie M, editor. Netwatch: flys in the Web.

Science 2004;306:1269. Available from URL:

http://www.sel.barc.usda.gov/diptera/names/image

s/ science1104.pdf.

10. Oderkirk A. Fly control in poultry barns: poultry

fact sheet. Truro, Nova Scotia, Canada: Nova Scotia

Department of Agriculture and Marketing; 2001. 

11. Gold RE, Howell HN Jr, Glenn GJ. Subterranean

termites. College Station, TX: Texas Agricultural

Extension Service; 1999. Available from URL:

http://insects.tamu.edu/extension/bulletins/

b6080.html.

12. Lyon WF. Termite control: HYG-2092-03.

Columbus, OH: The Ohio State University

Extension; 2003. Available from URL:

http://ohioline.osu.edu/hyg-fact/2000/2092.html.

Healthy Housing Reference Manual 4-17
13. Austin AR. Sample photos of structural

foundation defects and deficiences. Houston:

Diligent Home Inspections; no date. 

14. Fumapest Group. Western subterranean termites.

Revesby, New South Wales, Australia: Fumapest

Group Pty.; no date. Available from URL:

http://www.termite.com/termites/westernsubterranean-termite.html.

15. Oi FM, Castner JL, Koehler PG. The Eastern

subterranean termite. Gainesville, FL: University

of Florida Cooperative Extension Service; 1997.

Available from URL: http://edis.ifas.ufl.edu/

BODY_IN031.

16. Ferster B, Deyrup M, Scheffrahn RH. How to tell

the difference between ant and termite alates. Fort

Lauderdale, FL: University of Florida; no date.

Available from URL: http://flrec.ifas.ufl.edu/

entomo/ants/Ant%20vs%20Termite.htm.

17. Su N-Y. Life cycle of the Formosan subterranean

termite, Coptotermes formosanus Shiraki.

Gainesville, FL: University of Florida; no date.

Available from URL: http://creatures.ifas.ufl.edu/

urban/termites/fst10.htm.

18. Suiter DR, Jones SC, Forschler BT. Biology of

subterranean termites in the Eastern United

States. Bulletin 1209. Columbus, OH: The Ohio

State University Extension; no date. Available

from URL: http://ohioline.osu.edu/b1209/.

19. Potter MF. Protecting your home against termites.

Lexington, KY: University of Kentucky

Department of Entomology; 2004. Available from

URL: http://www.uky.edu/Agriculture/

Entomology/entfacts/struct/ef605.htm.

20. HomeReports.com. Pest and termite control

companies. Atlanta: HomeReports.com; no date.

Available from URL: http://www.homereports.com/ge/

PestControl.htm.

21. North Carolina Cooperative Extension Service.

Termite prevention: approaches for new

construction. Raleigh, NC: North Carolina

Cooperative Extension Service; no date. Available

from URL: http://www.ces.ncsu.edu/

depts/ent/notes/Urban/termites/pre-con.htm.

22. Core J. Update: hot on the trail of fire ants. Agric 

Res 2003; 51:20-23. Available from URL:

http://ars.usda. gov/is/AR/archive/

Feb03/ants0203.htm.

23. California Department of Food and Agriculture.

First reported occurrence of red imported fire ant;

Solenopsis invicta. Sacramento, CA: California

Department of Food and Agriculture; no date.

Available from URL: www.cdfa.ca.gov/phpps/pdep/

rifa/html/english/facts/rifaTIME.htm. 

24. Sutherland DJ, Crans WJ.Mosquitoes in your life.

New Jersey Agricultural Experiment Station

Publication SA220-5M-86. New Brunswick, NJ:

New Jersey Agricultural Experiment Station,

Cook College, Rutgers, The State University of

New Jersey; no date. Available at URL:

http://www.rci.rutgers.edu/~insects/moslife.htm.

4-18 Disease Vectors and Pests
Chapter 5—Indoor Air Pollutants and Toxic Materials

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Indoor Air Pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Biologic Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

Chemical Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

Toxic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-13

Asbestos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-13

Lead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-15

Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-19

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-20

Figure 5.1. Mold Growth in the Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7

Figure 5.2. Home Carbon Monoxide Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7

Figure 5.3. Environmental Tobacco Smoke and Children’s Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8

Figure 5.4. Wood Products Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-10

Figure 5.5. EPA Map of Radon Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-10

Figure 5.6. Radon Entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-11

Figure 5.7. Home Radon Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12

Figure 5.9. Radon-resistant Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-12

Figure 5.10. Arsenic Label. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-19

Healthy Housing Reference Manual 1

Contents
“Walking into a modern building can sometimes be

compared to placing your head inside a plastic bag that is

filled with toxic fumes.”

John Bower

Founder, Healthy House Institute 

Introduction

We all face a variety of risks to our health as we go about

our day-to-day lives. Driving in cars, flying in airplanes,

engaging in recreational activities, and being exposed to

environmental pollutants all pose varying degrees of risk.

Some risks are simply unavoidable. Some we choose to

accept because to do otherwise would restrict our ability

to lead our lives the way we want. Some are risks we

might decide to avoid if we had the opportunity to make

informed choices. Indoor air pollution and exposure to

hazardous substances in the home are risks we can do

something about.

In the last several years, a growing body of scientific

evidence has indicated that the air within homes and

other buildings can be more seriously polluted than the

outdoor air in even the largest and most industrialized

cities. Other research indicates that people spend

approximately 90% of their time indoors. Thus, for

many people, the risks to health from exposure to indoor

air pollution may be greater than risks from outdoor

pollution.

In addition, people exposed to indoor air pollutants for

the longest periods are often those most susceptible to

their effects. Such groups include the young, the elderly,

and the chronically ill, especially those suffering from

respiratory or cardiovascular disease [1]. 

Indoor Air Pollution

Numerous forms of indoor air pollution are possible in

the modern home. Air pollutant levels in the home

increase if not enough outdoor air is brought in to dilute

emissions from indoor sources and to carry indoor air

pollutants out of the home. In addition, high temperature and

humidity levels can increase the concentration of some

pollutants. Indoor pollutants can be placed into two

groups, biologic and chemical.

Biologic Pollutants

Biologic pollutants include bacteria, molds, viruses,

animal dander, cat saliva, dust mites, cockroaches, and

pollen. These biologic pollutants can be related to some

serious health effects. Some biologic pollutants, such as

measles, chickenpox, and influenza are transmitted

through the air. However, the first two are now

preventable with vaccines. Influenza virus transmission,

although vaccines have been developed, still remains of

concern in crowded indoor conditions and can be

affected by ventilation levels in the home. 

Common pollutants, such as pollen, originate from

plants and can elicit symptoms such as sneezing, watery

eyes, coughing, shortness of breath, dizziness, lethargy,

fever, and digestive problems. Allergic reactions are the

result of repeated exposure and immunologic

sensitization to particular biologic allergens. 

Although pollen allergies can be bothersome, asthmatic

responses to pollutants can be life threatening. Asthma is

a chronic disease of the airways that causes recurrent and

distressing episodes of wheezing, breathlessness, chest

tightness, and coughing [2]. Asthma can be broken

down into two groups based on the causes of an attack:

extrinsic (allergic) and intrinsic (nonallergic). Most

people with asthma do not fall neatly into either type,

but somewhere in between, displaying characteristics of

both classifications. Extrinsic asthma has a known cause,

such as allergies to dust mites, various pollens, grass or

weeds, or pet danders. Individuals with extrinsic asthma

produce an excess amount of antibodies when exposed to

triggers. Intrinsic asthma has a known cause, but the

connection between the cause and the symptoms is not

clearly understood. There is no antibody hypersensitivity

in intrinsic asthma. Intrinsic asthma usually starts in

adulthood without a strong family history of asthma.

Some of the known triggers of intrinsic asthma are

infections, such as cold and flu viruses, exercise and cold

air, industrial and occupational pollutants, food additives

and preservatives, drugs such as aspirin, and emotional

stress. Asthma is more common in children than in

adults, with nearly 1 of every 13 school-age children

having asthma [3]. Low-income African-Americans and

certain Hispanic populations suffer disproportionately,

with urban inner cities having particularly severe

problems. The impact on neighborhoods, school

systems, and health care facilities from asthma is severe

because one-third of all pediatric emergency room visits

are due to asthma, and it is the fourth most prominent

cause of physician office visits. Additionally, it is the

leading cause of school absenteeism—14 million school

Chapter 5: Indoor Air Pollutants and Toxic Materials

Healthy Housing Reference Manual 5-1
days lost each year—from chronic illness [4]. The U.S.

population, on the average, spends as much as 90% of its

time indoors. Consquently, allergens and irritants from

the indoor environment may play a significant role in

triggering asthma episodes. A number of indoor

environmental asthma triggers are biologic pollutants.

These can include rodents (discussed in Chapter 4),

cockroaches, mites, and mold.

Cockroaches

The droppings, body parts, and saliva of cockroaches can

be asthma triggers. Cockroaches are commonly found in

crowded cities and in the southern United States.

Allergens contained in the feces and saliva of cockroaches

can cause allergic reactions or trigger asthma symptoms. A

national study by Crain et al. [5] of 994 inner-city allergic

children from seven U.S. cities revealed that cockroaches

were reported in 58% of the homes. The Community

Environmental Health Resource Center reports that

cockroach debris, such as body parts and old shells,

trigger asthma attacks in individuals who are sensitized to

cockroach allergen [6]. Special attention to cleaning must

be a priority after eliminating the presence of cockroaches

to get rid of the presence of any allergens left that can be

asthma triggers.

House Dust Mites

Another group of arthropods linked to asthma is house

dust mites. In 1921, a link was suggested between

asthmatic symptoms and house dust, but it was not until

1964 that investigators suggested that a mite could be

responsible. Further investigation linked a number of mite

species to the allergen response and revealed that humid

homes have more mites and, subsequently, more allergens.

In addition, researchers established that fecal pellets

deposited by the mites accumulated in home fabrics and

could become airborne via domestic activities such as

vacuuming and dusting, resulting in inhalation by the

inhabitants of the home. House dust mites are distributed

worldwide, with a minimum of 13 species identified from

house dust. The two most common in the United States

are the North American house dust mite

(Dermatophagoides farinae) and the European house dust

mite (D. pteronyssinus). According to Lyon [7], house dust

mites thrive in homes that provide a source of food and

shelter and adequate humidity. Mites prefer relative

humidity levels of 70% to 80% and temperatures of 75°F

to 80°F (24°C to 27°C). Most mites are found in

bedrooms in bedding, where they spend up to a third of

their lives. A typical used mattress may have from

100,000 to 10 million mites in it. In addition, carpeted

floors, especially long, loose pile carpet, provide a

microhabitat for the accumulation of food and moisture

for the mite, and also provide protection from removal by

vacuuming. The house dust mite’s favorite food is human

dander (skin flakes), which are shed at a rate of

approximately 0.20 ounces per week. 

A good microscope and a trained observer are imperative

in detecting mites. House dust mites also can be detected

using diagnostic tests that measure the presence and

infestation level of mites by combining dust samples

collected from various places inside the home with

indicator reagents [7]. Assuming the presence of mites,

the precautions listed below should be taken if people

with asthma are present in the home:

• Use synthetic rather than feather and down pillows.

• Use an approved allergen barrier cover to enclose

the top and sides of mattresses and pillows and

the base of the bed.

• Use a damp cloth to dust the plastic mattress

cover daily.

• Change bedding and vacuum the bed base and

mattress weekly.

• Use nylon or cotton cellulose blankets rather than

wool blankets.

• Use hot (120°F–130°F [49°C–54°C]) water to

wash all bedding, as well as room curtains.

• Eliminate or reduce fabric wall hangings, curtains,

and drapes.

• Use wood, tile, linoleum, or vinyl floor covering

rather than carpet. If carpet is present, vacuum

regularly with a high-efficiency particulate air

(HEPA) vacuum or a household vacuum with a

microfiltration bag. 

• Purchase stuffed toys that are machine washable.

• Use fitted sheets to help reduce the accumulation

of human skin on the mattress surface.

HEPA vacuums are now widely available and have also

been shown to be effective [8]. A conventional vacuum

tends to be inefficient as a control measure and results in

a significant increase in airborne dust concentrations, but

can be used with multilayer microfiltration collection

5-2 Indoor Air Pollutants and Toxic Materials
bags. Another approach to mite control is reducing

indoor humidity to below 50% and installing central

air conditioning. 

Two products are available to treat house dust mites and

their allergens. These products contain the active

ingredients benzyl benzoate and tannic acid. 

Pets

According to the U.S. Environmental Protection Agency

(EPA) [9], pets can be significant asthma triggers because

of dead skin flakes, urine, feces, saliva, and hair. Proteins

in the dander, urine, or saliva of warm-blooded animals

can sensitize individuals and lead to allergic reactions or

trigger asthmatic episodes. Warm-blooded animals

include dogs, cats, birds, and rodents (hamsters, guinea

pigs, gerbils, rats, and mice). Numerous strategies, such as

the following, can diminish or eliminate animal allergens

in the home:

• Eliminate animals from the home.

• Thoroughly clean the home (including floors and

walls) after animal removal.

• If pets must remain in the home, reduce pet

exposure in sleeping areas. Keep pets away from

upholstered furniture, carpeted areas, and stuffed

toys, and keep the pets outdoors as much

as possible.

However, there is some evidence that pets introduced

early into the home may prevent asthma. Several studies

have shown that exposure to dogs and cats in the first

year of life decreases a child’s chances of developing

allergies [10] and that exposure to cats significantly

decreases sensitivity to cats in adulthood [11]. Many

other studies have shown a decrease in allergies and

asthma among children who grew up on a farm and were

around many animals [12].

Mold

People are routinely exposed to more than 200 species of

fungi indoors and outdoors [13]. These include moldlike

fungi, as well as other fungi such as yeasts and

mushrooms. The terms “mold” and “mildew” are

nontechnical names commonly used to refer to any fungus

that is growing in the indoor environment. Mold colonies

may appear cottony, velvety, granular, or leathery, and

may be white, gray, black, brown, yellow, greenish, or

other colors. Many reproduce via the production and

dispersion of spores. They usually feed on dead organic

matter and, provided with sufficient moisture, can live off

of many materials found in homes, such as wood,

cellulose in the paper backing on drywall, insulation,

wallpaper, glues used to bond carpet to its backing, and

everyday dust and dirt. 

Certain molds can cause a variety of adverse human

health effects, including allergic reactions and immune

responses (e.g., asthma), infectious disease (e.g.,

histoplasmosis), and toxic effects (e.g., aflatoxin-induced

liver cancer from exposure to this mold-produced toxin in

food) [14]. A recent Institute of Medicine (IOM) review

of the scientific literature found sufficient evidence for an

association between exposure to mold or other agents in

damp indoor environments and the following conditions:

upper respiratory tract symptoms, cough, wheeze,

hypersensitivity pneumonitis in susceptible persons, and

asthma symptoms in sensitized persons [15]. A previous

scientific review was more specific in concluding that

sufficient evidence exists to support associations between

fungal allergen exposure and asthma exacerbation and

upper respiratory disease [13]. Finally, mold toxins can

cause direct lung damage leading to pulmonary diseases

other than asthma [13]. 

The topic of residential mold has received increasing

public and media attention over the past decade. Many

news stories have focused on problems associated with

“toxic mold” or “black mold,” which is often a reference

to the toxin-producing mold, Stachybotrys chartarum. This

might give the impression that mold problems in homes

are more frequent now than in past years; however, no

good evidence supports this. Reasons for the increasing

attention to this issue include high-visibility lawsuits

brought by property owners against builders and

developers, scientific controversies regarding the degree to

which specific illness outbreaks are mold-induced, and an

increase in the cost of homeowner insurance policies due

to the increasing number of mold-related claims. Modern

construction might be more vulnerable to mold problems

because tighter construction makes it more difficult for

internally generated water vapor to escape, as well as the

widespread use of paper-backed drywall in construction

(paper is an excellent medium for mold growth when

wet), and the widespread use of carpeting. 

Allergic Health Effects. Many molds produce numerous

protein or glycoprotein allergens capable of causing

allergic reactions in people. These allergens have been

measured in spores as well as in other fungal fragments.

An estimated 6%–10% of the general population and

15%–50% of those who are genetically susceptible are

Healthy Housing Reference Manual 5-3
sensitized to mold allergens [13]. Fifty percent of the

937 children tested in a large multicity asthma study

sponsored by the National Institutes of Health showed

sensitivity to mold, indicating the importance of mold as

an asthma trigger among these children [16]. Molds are

thought to play a role in asthma in several ways. Molds

produce many potentially allergenic compounds, and

molds may play a role in asthma via release of irritants

that increase potential for sensitization or release of toxins

(mycotoxins) that affect immune response [13]. 

Toxics and Irritants. Many molds also produce

mycotoxins that can be a health hazard on ingestion,

dermal contact, or inhalation [14]. Although common

outdoor molds present in ambient air, such as

Cladosporium cladosporioides and Alternaria alternata, do

not usually produce toxins, many other different mold

species do [17]. Genera-producing fungi associated with

wet buildings, such as Aspergillus versicolor, Fusarium

verticillioides, Penicillium aiurantiorisen, and S. chartarum,

can produce potent toxins [17]. A single mold species

may produce several different toxins, and a given

mycotoxin may be produced by more than one species of

fungi. Furthermore, toxin-producing fungi do not

necessarily produce mycotoxins under all growth

conditions, with production being dependent on the

substrate it is metabolizing, temperature, water content,

and humidity [17]. Because species of toxin-producing

molds generally have a higher water requirement than do

common household molds, they tend to thrive only under

conditions of chronic and severe water damage [18]. For

example, Stachybotrys typically only grows under continuously

wet conditions [19]. It has been suggested that very

young children may be especially vulnerable to certain

mycotoxins [19,20]. For example, associations have been

reported for pulmonary hemorrhage (bleeding lung)

deaths in infants and the presence of S. chartarum [21–24]. 

Causes of Mold. Mold growth can be caused by any

condition resulting in excess moisture. Common moisture

sources include rain leaks (e.g., on roofs and wall joints);

surface and groundwater leaks (e.g., poorly designed or

clogged rain gutters and footing drains, basement leaks);

plumbing leaks; and stagnant water in appliances (e.g.,

dehumidifiers, dishwashers, refrigerator drip pans, and

condensing coils and drip pans in HVAC systems).

Moisture problems can also be due to water vapor

migration and condensation problems, including uneven

indoor temperatures, poor air circulation, soil air entry

into basements, contact of humid unconditioned air with

cooled interior surfaces, and poor insulation on indoor

chilled surfaces (e.g., chilled water lines). Problems can

also be caused by the production of excess moisture

within homes from humidifiers, unvented clothes dryers,

overcrowding, etc. Finished basements are particularly

susceptible to mold problems caused by the combination

of poorly controlled moisture and mold-supporting

materials (e.g., carpet, paper-backed sheetrock) [15].

There is also some evidence that mold spores from damp

or wet crawl spaces can be transported through air currents

into the upper living quarters. Older, substandard

housing low income families can be particularly prone to

mold problems because of inadequate maintenance (e.g.,

inoperable gutters, basement and roof leaks), overcrowding,

inadequate insulation, lack of air conditioning, and poor

heating. Low interior temperatures (e.g., when one or two

rooms are left unheated) result in an increase in the

relative humidity, increasing the potential for water to

condense on cold surfaces. 

Mold Assessment Methods. Mold growth or the

potential for mold growth can be detected by visual

inspection for active or past microbial growth, detection

of musty odors, and inspection for water staining or

damage. If it is not possible or practical to inspect a

residence, this information can be obtained using

occupant questionnaires. Visual observation of mold

growth, however, is limited by the fact that fungal

elements such as spores are microscopic, and that their

presence is often not apparent until growth is extensive

and the fact that growth can occur in hidden spaces (e.g.,

wall cavities, air ducts). 

Portable, hand-held moisture meters, for the direct

measurement of moisture levels in materials, may also be

useful in qualitative home assessments to aid in

pinpointing areas of potential biologic growth that may

not otherwise be obvious during a visual inspection [14]. 

For routine assessments in which the goal is to identify

possible mold contamination problems before

remediation, it is usually unnecessary to collect and

analyze air or settled dust samples for mold analysis

because decisions about appropriate intervention

strategies can typically be made on the basis of a visual

inspection [25]. Also, sampling and analysis costs can be

relatively high and the interpretation of results is not

straightforward. Air and dust monitoring may, however,

be necessary in certain situations, including 1) if an

individual has been diagnosed with a disease associated

with fungal exposure through inhalation, 2) if it is

suspected that the ventilation systems are contaminated,

or 3) if the presence of mold is suspected but cannot be

identified by a visual inspection or bulk sampling [26].

5-4 Indoor Air Pollutants and Toxic Materials
Generally, indoor environments contain large reservoirs of

mold spores in settled dust and contaminated building

materials, of which only a relatively small amount is

airborne at a given time. 

Common methods for sampling for mold growth include

bulk sampling techniques, air sampling, and collection of

settled dust samples. In bulk sampling, portions of

materials with visual or suspected mold growth (e.g., sections

of wallboard, pieces of duct lining, carpet segments, or

return air filters) are collected and directly examined to

determine if mold is growing and to identify the mold

species or groups that are present. Surface sampling in

mold contamination investigations may also be used

when a less destructive technique than bulk sampling is

desired. For example, nondestructive samples of mold may

be collected using a simple swab or adhesive tape [14]. 

Air can also be sampled for mold using pumps that pull

air across a filter medium, which traps airborne mold

spores and fragments. It is generally recommended that

outdoor air samples are collected concurrent with indoor

samples for comparison purposes for measurement of

baseline ambient air conditions. Indoor contamination

can be indicated by indoor mold distributions (both

species and concentrations) that differ significantly from

the distributions in outdoor samples [14]. Captured mold

spores can be examined under a microscope to identify

the mold species/groups and determine concentrations or

they can be cultured on growth media and the resulting

colonies counted and identified. Both techniques require

considerable expertise.

Dust sampling involves the collection of settled dust

samples (e.g., floor dust) using a vacuum method in

which the dust is collected onto a porous filter medium

or into a container. The dust is then processed in the

laboratory and the mold identified by culturing viable spores.

Mold Standards. No standard numeric guidelines exist

for assessing whether mold contamination exists in an

area. In the United States, no EPA regulations or

standards exist for airborne mold contaminants [26].

Various governmental and private organizations have,

however, proposed guidance on the interpretation of

fungal measures of environmental media in indoor

environments (quantitative limits for fungal

concentrations). 

Given evidence that young children may be especially

vulnerable to certain mycotoxins [18] and in view of the

potential severity or diseases associated with mycotoxin

exposure, some organizations support a precautionary

approach to limiting mold exposure [19]. For example,

the American Academy of Pediatrics recommends that

infants under 1 year of age are not exposed at all to

chronically moldy, water-damaged environments [18]. 

Mold Mitigation. Common intervention methods for

addressing mold problems include the following:

• maintaining heating, ventilating, and air

conditioning (HVAC) systems; 

• changing HVAC filters frequently, as

recommended by manufacturer;

• keeping gutters and downspouts in working order

and ensuring that they drain water away from the

foundation;

• routinely checking, cleaning, and drying drip pans

in air conditioners, refrigerators, and

dehumidifiers;

• increasing ventilation (e.g., using exhaust fans or

open windows to remove humidity when cooking,

showering, or using the dishwasher);

• venting clothes dryers to the outside; and 

• maintaining an ideal relative humidity level in the

home of 40% to 60%.

• locating and removing sources of moisture

(controlling dampness and humidity and repairing

water leakage problems);

• cleaning or removing mold-contaminated

materials;

• removing materials with severe mold growth; and

• using high-efficiency air filters.

Moisture Control. Because one of the most important

factors affecting mold growth in homes is moisture level,

controlling this factor is crucial in mold abatement

strategies. Many simple measures can significantly control

moisture, for example maintaining indoor relative

humidity at no greater than 40%–60% through the use

of dehumidifiers, fixing water leakage problems,

increasing ventilation in kitchens and bathrooms by using

exhaust fans, venting clothes dryers to the outside,

Healthy Housing Reference Manual 5-5
reducing the number of indoor plants, using air

conditioning at times of high outdoor humidity, heating

all rooms in the winter and adding heating to outside wall

closets, sloping surrounding soil away from building

foundations, fixing gutters and downspouts, and using a

sump pump in basements prone to flooding [27]. Vapor

barriers, sump pumps, and aboveground vents can also be

installed in crawlspaces to prevent moisture problems [28]. 

Removal and Cleaning of Mold-contaminated Materials.

Nonporous (e.g., metals, glass, and hard plastics) and

semiporous (e.g., wood and concrete) materials

contaminated with mold and that are still structurally

sound can often be cleaned with bleach-and-water

solutions. However, in some cases, the material may not

be easily cleaned or may be so severely contaminated that

it may have to be removed. It is recommended that

porous materials (e.g., ceiling tiles, wallboards, and

fabrics) that cannot be cleaned be removed and discarded

[29]. In severe cases, clean-up and repair of moldcontaminated buildings may be conducted using methods

similar to those used for abatement of other hazardous

substances such as asbestos [30]. For example, in

situations of extensive colonization (large surface areas

greater than 100 square feet or where the material is

severely degraded), extreme precautions may be required,

including full containment (complete isolation of work

area) with critical barriers (airlock and decontamination

room) and negative pressurization, personnel trained to

handle hazardous wastes, and the use of full-face

respirators with HEPA filters, eye protection, and

disposable full-body covering [26]. 

Worker Protection When Conducting Mold Assessment

and Mitigation Projects. Activities such as cleaning or

removal of mold-contaminated materials in homes, as well

as investigations of mold contamination extent, have the

potential to disturb areas of mold growth and release

fungal spores and fragments into the air. Recommended

measures to protect workers during mold remediation

efforts depend on the severity and nature of the mold

contamination being addressed, but include the use of

well fitted particulate masks or respirators that retain

particles as small as 1 micrometer or less, disposable

gloves and coveralls, and protective eyewear [31].

Following are examples of guidance documents for

remediation of mold contamination:

• New York City Department of Health and Mental

Hygiene. Guidelines on Assessment and

Remediation of Fungi in Indoor Environments

(available from URL: http://www.nyc.gov/html/

doh/html/epi/moldrpt1.shtml).

• American Conference of Governmental Industrial

Hygienists (ACGIH) 1999 document,

Biosaerosols: Assessment and Control (can be

ordered at URL http://www.acgih.org/home.htm). 

• American Industrial Hygiene Association (AIHA)

2004 document, Assessment, Remediation, and

Post-Remediation Verification of Mold in

Buildings (can be ordered at URL www.aiha.org)

• Environmental Protection Agency guidance, Mold

Remediation in Schools and Commercial Buildings

(includes many general principles also applicable

to residential mold mitigation efforts; available at

URL: http://www.epa.gov/iaq/molds/

mold_remediation.html)

• Environmental Protection Agency guidance, A

Brief Guide to Mold, Moisture, and Your Home

(for homeowners and renters on how to clean up

residential mold problems and how to prevent

mold growth; available at URL: http://www.epa.gov/

iaq/molds/images/moldguide.pdf) 

• Canada Mortgage and Housing Corporation,

Clean-up Procedures for Mold in Houses,

(provides qualitative guidance for mold

mitigation; can be ordered at URL:

https://www.cmhc-schl.gc.ca:50104/b2c/b2c/

init.do?language=en). 

Figure 5.1 shows mold growth in the home.

Chemical Pollutants

Carbon Monoxide 

Carbon monoxide (CO) is a significant combustion

pollutant in the United States. CO is a leading cause of

poisoning deaths [32]. According to the National Fire

Protection Association (NFPA), CO-related nonfire

deaths are often attributed to heating and cooking

equipment. The leading specific types of equipment

blamed for CO-related deaths include gas-fueled space

heaters, gas-fueled furnaces, charcoal grills, gas-fueled

ranges, portable kerosene heaters, and wood stoves.

As with fire deaths, the risk for unintentional CO death is

highest for the very young (ages 4 years and younger) and

the very old (ages 75 years and older). CO is an odorless,

colorless gas that can cause sudden illness and death. It is

5-6 Indoor Air Pollutants and Toxic Materials
a result of the incomplete combustion of carbon.

Headache, dizziness, weakness, nausea, vomiting, chest

pain, and confusion are the most frequent symptoms of

CO poisoning. According to the American Lung

Association (ALA) [33], breathing low levels of CO can

cause fatigue and increase chest pain in people with

chronic heart disease. Higher levels of CO can cause

flulike symptoms in healthy people. In addition,

extremely high levels of CO cause loss of consciousness

and death. In the home, any fuel-burning appliance that

is not adequately vented and maintained can be a

potential source of CO. The following steps should be

followed to reduce CO (as well as sulfur dioxide and

oxides of nitrogen) levels:

• Never use gas-powered equipment, charcoal grills,

hibachis, lanterns, or portable camping stoves in

enclosed areas or indoors.

• Install a CO monitor (Figure 5.2) in appropriate

areas of the home. These monitors are designed to

provide a warning before potentially lifethreatening levels of CO are reached.

• Choose vented appliances when possible and keep

gas appliances properly adjusted to decrease the

combustion to CO. (Note: Vented appliances are

always preferable for several reasons: oxygen levels,

carbon dioxide buildup, and humidity management).

• Only buy certified and tested combustion

appliances that meet current safety standards, as

certified by Underwriter’s Laboratories (UL),

American Gas Association (AGA) Laboratories, or

equivalent.

• Assure that all gas heaters

possess safety devices that

shut off an improperly

vented gas heater. Heaters

made after 1982 use a

pilot light safety system

known as an oxygen

depletion sensor. When

inadequate fresh air exists,

this system shuts off the

heater before large

amounts of CO can

be produced.

• Use appliances that have

electronic ignitions instead

of pilot lights. These

appliances are typically more energy efficient and

eliminate the continuous low-level pollutants

from pilot lights.

• Use the proper fuel in kerosene appliances. 

• Install and use an exhaust fan vented to the

outdoors over gas stoves.

• Have a trained professional annually inspect,

clean, and tune up central heating systems

(furnaces, flues, and chimneys) and repair them

as needed.

• Do not idle a car inside a garage.

The U.S. Consumer Product Safety Commission (CPSC)

recommends installing at least one CO alarm per household

near the sleeping area. For an extra measure of safety,

another alarm should be placed near the home’s heating

source. ALA recommends weighing the benefits of using

models powered by electrical outlets versus models powered by

batteries that run out of power and need replacing.

Battery-powered CO detectors provide continuous protection

and do not require recalibration in the event of a power

outage. Electric-powered systems do not provide protection

during a loss of power and can take up to 2 days to

recalibrate. A device that can be easily self-tested and reset

to ensure proper functioning should be chosen. The product

should meet Underwriters Laboratories Standard UL 2034.

Ozone

Inhaling ozone can damage the lungs. Inhaling small amounts

of ozone can result in chest pain, coughing, shortness of

breath, and throat irritation. Ozone can also exacerbate

Healthy Housing Reference Manual 5-7

Figure 5.1. Mold Growth in the Home Figure 5.2. Home Carbon

Monoxide Monitor

Source: U.S. Navy
chronic respiratory diseases such as asthma. Susceptibility

to the effects of ozone varies from person to person, but

even healthy people can experience respiratory difficulties

from exposure. 

According to the North Carolina Department of Health

and Human Services [34], the major source of indoor

ozone is outdoor ozone. Indoor levels can vary from 10% of

the outdoor air to levels as high as 80% of the outdoor air.

The Food and Drug Administration has set a limit of

0.05 ppm of ozone in indoor air. In recent years, there

have been numerous advertisements for ion generators that

destroy harmful indoor air pollutants. These devices create

ozone or elemental oxygen that reacts with pollutants.

EPA has reviewed the evidence on ozone generators and

states: “available scientific evidence shows that at

concentrations that do not exceed public health standards,

ozone has little potential to remove indoor air contaminants,”

and “there is evidence to show that at concentrations that

do not exceed public health standards, ozone is not

effective at removing many odor causing chemicals” [35].

Ozone is also created by the exposure of polluted air to

sunlight or ultraviolet light emitters. This ozone produced

outside of the home can infiltrate the house and react

with indoor surfaces, creating additional pollutants.

Environmental Tobacco Smoke or Secondhand Smoke

Like CO, environmental tobacco smoke (ETS; also

known as secondhand smoke), is a product of

combustion. The National Cancer Institute (NCI) [36],

states that ETS is the combination of two forms of smoke

from burning tobacco products:

• Sidestream smoke, or smoke that is emitted

between the puffs of a burning cigarette, pipe, or

cigar; and

• Mainstream smoke, or the smoke that is exhaled

by the smoker.

The physiologic effects of ETS are numerous. ETS can

trigger asthma; irritate the eyes, nose, and throat; and

cause ear infections in children, respiratory illnesses, and

lung cancer. ETS is believed to cause asthma by irritating

chronically inflamed bronchial passages. According to the

EPA [37], ETS is a Group A carcinogen; thus, it is a

known cause of cancer in humans. Laboratory analysis

has revealed that ETS contains in excess of

4,000 substances, more than 60 of which cause cancer

in humans or animals. The EPA also estimates that

approximately 3,000 lung cancer deaths occur each year

in nonsmokers due to ETS. Additionally, passive smoking

can lead to coughing, excess phlegm, and chest

discomfort. NCI also notes that spontaneous abortion

(miscarriage), cervical cancer, sudden infant death

syndrome, low birth weight, nasal sinus cancer, decreased

lung function, exacerbation of cystic fibrosis, and negative

cognitive and behavioral effects in children have been

linked to ETS [36].

The EPA [37] states that, because of their relative body

size and respiratory rates, children are affected by ETS

more than adults are. It is estimated that an additional

7,500 to 15,000 hospitalizations resulting from increased

respiratory infections occur in children younger than

18 months of age due to ETS exposure. Figure 5.3 shows

the ETS exposure levels in homes with children under age

7 years. The following actions are recommended in the

home to protect children from ETS:

• if individuals insist on smoking, increase

ventilation in the smoking area by opening

windows or using exhaust fans; and

• refrain from smoking in the presence of children

and do not allow babysitters or others who work

in the home to smoke in the home or near children.

Volatile Organic Compounds

In the modern home, many organic chemicals are used as

ingredients in household products. Organic chemicals

that vaporize and become gases at normal room

temperature are collectively known as VOCs.

Examples of common items that can release VOCs

include paints, varnishes, and wax, as well as in many

cleaning, disinfecting, cosmetic, degreasing, and hobby

products. Levels of approximately a dozen common

VOCs can be two to five times higher inside the home, as

opposed to outside, whether in highly industrialized areas

5-8 Indoor Air Pollutants and Toxic Materials

Figure 5.3. Environmental Tobacco Smoke and Children’s Exposure [37]
or rural areas. VOCs that frequently pollute indoor air

include toluene, styrene, xylenes, and trichloroethylene.

Some of these chemicals may be emitted from aerosol

products, dry-cleaned clothing, paints, varnishes, glues,

art supplies, cleaners, spot removers, floor waxes, polishes,

and air fresheners. The health effects of these chemicals

are varied. Trichlorethylene has been linked to childhood

leukemia. Exposure to toluene can put pregnant women

at risk for having babies with neurologic problems,

retarded growth, and developmental problems. Xylenes

have been linked to birth defects. Styrene is a suspected

endocrine disruptor, a chemical that can block or mimic

hormones in humans or animals. EPA data reveal that

methylene chloride, a common component of some paint

strippers, adhesive removers, and specialized aerosol spray

paints, causes cancer in animals [38]. Methylene chloride

is also converted to CO in the body and can cause

symptoms associated with CO exposure. Benzene, a

known human carcinogen, is contained in tobacco smoke,

stored fuels, and paint supplies. Perchloroethylene, a

product uncommonly found in homes, but common to

dry cleaners, can be a pollution source by off-gassing from

newly cleaned clothing. Environmental Media Services

[39] also notes that xylene, ketones, and aldehydes are

used in aerosol products and air fresheners. 

To lower levels of VOCs in the home, follow these steps:

• use all household products according to directions;

• provide good ventilation when using these products;

• properly dispose of partially full containers of old

or unneeded chemicals;

• purchase limited quantities of products; and

• minimize exposure to emissions from products

containing methylene chloride, benzene, and

perchlorethylene.

A prominent VOC found in household products and

construction products is formaldehyde. According to

CPSC [40], these products include the glue or adhesive

used in pressed wood products; preservatives in paints,

coating, and cosmetics; coatings used for permanent-press

quality in fabrics and draperies; and the finish on paper

products and certain insulation materials. Formaldehyde

is contained in urea-formaldehyde (UF) foam insulation

installed in the wall cavities of homes as an energy

conservation measure. Levels of formaldehyde increase

soon after installation of this product, but these levels

decline with time. In 1982, CPSC voted to ban UF foam

insulation. The courts overturned the ban; however, the

publicity has decreased the use of this product.

More recently, the most significant source of

formaldehyde in homes has been pressed wood products

made using adhesives that contain UF resins [41]. The

most significant of these is medium-density fiberboard,

which contains a higher resin-to-wood ratio than any

other UF pressed wood product. This product is generally

recognized as being the highest formaldehyde-emitting

pressed wood product. Additional pressed wood products

are produced using phenol-formaldehyde resin. The latter

type of resin generally emits formaldehyde at a

considerably slower rate than those containing UF resin.

The emission rate for both resins will change over time

and will be influenced by high indoor temperatures and

humidity. Since 1985, U.S. Department of Housing and

Urban Development (HUD) regulations (24 CFR 3280.308,

3280.309, and 3280.406) have permitted only the use of

plywood and particleboard that conform to specified

formaldehyde emission limits in the construction of

prefabricated and manufactured homes [42]. This limit was

to ensure that indoor formaldehyde levels are below 0.4 ppm. 

CPSC [40] notes that formaldehyde is a colorless, strongsmelling gas. At an air level above 0.1 ppm, it can cause

watery eyes; burning sensations in the eyes, nose, and

throat; nausea; coughing; chest tightness; wheezing; skin

rashes; and allergic reactions. Laboratory animal studies

have revealed that formaldehyde can cause cancer in

animals and may cause cancer in humans. Formaldehyde

is usually present at levels less than 0.03 ppm indoors and

outdoors, with rural areas generally experiencing lower

concentrations than urban areas. Indoor areas that

contain products that release formaldehyde can have levels

greater than 0.03 ppm. CPSC also recommends the

following actions to avoid high levels of exposure to

formaldehyde:

• Purchase pressed wood products that are labeled

or stamped to be in conformance with American

National Standards Institute criteria ANSI

A208.1-1993. Use particleboard flooring marked

with ANSI grades PBU, D2, or D3. Mediumdensity fiberboard should be in conformance with

ANSI A208.2-1994 and hardwood plywood with

ANSI/HPVA HP-1-1994 (Figure 5.4).

• Purchase furniture or cabinets that contain a high

percentage of panel surface and edges that are

laminated or coated. Unlaminated or uncoated

Healthy Housing Reference Manual 5-9
(raw) panels of pressed wood panel products will

generally emit more formaldehyde than those that

are laminated or coated.

• Use alternative products, such as wood panel

products not made with UF glues, lumber, or metal.

• Avoid the use of foamed-in-place insulation

containing formaldehyde, especially UF foam

insulation.

• Wash durable-press fabrics before use. 

CPSC also recommends the following actions to reduce 

existing levels of indoor formaldehyde:

• Ventilate the home well by opening doors and

windows and installing an exhaust fan(s).

• Seal the surfaces of formaldehyde-containing

products that are not laminated or coated with

paint, varnish, or a layer of vinyl or polyurethanelike materials.

• Remove products that release formaldehyde in the

indoor air from the home. 

Radon

According to the EPA [43], radon is a colorless, odorless

gas that occurs naturally in soil and rock and is a decay

product of uranium. The U.S. Geological Survey (USGS)

[44] notes that the typical uranium content of rock and

the surrounding soil is between 1 and 3 ppm. Higher

levels of uranium are often contained in rock such as

light-colored volcanic rock, granite, dark shale, and

sedimentary rock containing phosphate. Uranium levels

as high as 100 ppm may be present in various areas of the

United States because of these rocks. The main source of

high-level radon pollution in buildings is surrounding

uranium-containing soil. Thus, the greater the level of

uranium nearby, the greater the chances are that buildings

in the area will have high levels of indoor radon.

Figure 5.5 demonstrates the geographic variation in radon

levels in the United States. Maps of the individual states

and areas that have proven high for radon are available at

http://www.epa.gov/iaq/radon/ zonemap.html. A free

video is available from the U.S. EPA: call 1-800-438-

4318 and ask for EPA 402-V-02-003 (TRT 13.10).

Radon, according to the California Geological Survey

[45], is one of the intermediate radioactive elements

formed during the radioactive decay of uranium-238,

uranium-235, or thorium-232. Radon-222 is the radon

isotope of most concern to public health because of its

longer half-life (3.8 days). The mobility of radon gas is

much greater than are uranium and radium, which are

solids at room temperature. Thus, radon can leave rocks

and soil, move through fractures and pore spaces, and

ultimately enter a building to collect in high concentrations.

When in water, radon moves less than 1 inch before it

decays, compared to 6 feet or more in dry rocks or soil.

USGS [44] notes that radon near the surface of soil

typically escapes into the atmosphere. However, 

where a house is present, soil air often flows toward the

house foundation because of

5-10 Indoor Air Pollutants and Toxic Materials

Figure 5.4. Wood Products Label [42]

Figure 5.5. EPA Map of Radon Zones [43]

Zone 1: predicted average indoor radon screening level greater than

4 pCi/L [picocuries per liter] 

Zone 2: predicted average indoor radon screening level between 2 and

4 pCi/L 

Zone 3: predicted average indoor radon screening level less than 2 pCi/L 

Important: Consult the EPA Map of Radon Zones document [EPA-402-R93-071] before using this map. This document contains information on

radon potential variations within counties. 

EPA also recommends that this map be supplemented with any available

local data to further understand and predict the radon potential of a

specific area.
• differences in air pressure between the soil and the

house, with soil pressure often being higher;

• presence of openings in the house’s foundation; and

• increases in permeability around the basement

(if present).

Houses are often constructed with loose fill under a basement

slab and between the walls and exterior ground. This fill

is more permeable than the original ground. Houses

typically draw less than 1% of their indoor air from the

soil. However, houses with low indoor air pressures,

poorly sealed foundations, and several entry points for soil

air may draw up to 20% of their indoor air from the soil. 

USGS [44] states that radon may also enter the home

through the water systems. Surface water sources typically

contain little radon because it escapes into the air. In

larger cities, radon is released to the air by municipal

processing systems that aerate the water. However, in

areas where groundwater is the main water supply for

communities, small public systems and private wells are

typically closed systems that do not allow radon to escape.

Radon then enters the indoor air from showers, clothes

washing, dishwashing, and other uses of water. Figure 5.6

shows typical entry points of radon.

Health risks of radon stem from its breakdown into

“radon daughters,” which emit high-energy alpha

particles. These progeny enter the lungs, attach

themselves, and may eventually lead to lung cancer. This

exposure to radon is believed to contribute to between

15,000 and 21,000 excess lung cancer deaths in the

United States each year. The EPA has identified levels

greater than 4 picocuries per liter as levels at which

remedial action should be taken. Approximately 1 in

15 homes nationwide have radon above this level,

according to the U.S. Surgeon General’s recent advisory

[46]. Smokers are at significantly higher risk for radonrelated lung cancer. 

Radon in the home can be measured either by the

occupant or by a professional. Because radon has no odor

or color, special devices are used to measure its presence.

Radon levels vary from day to day and season to season.

Short-term tests (2 to 90 days) are best if quick results are

needed, but long-term tests (more than 3 months) yield

better information on average year-round exposure.

Measurement devices are routinely placed in the lowest

occupied level of the home. The devices either measure 

the radon gas directly or the daughter products. The

simplest devices are passive, require no electricity, and

include a charcoal canister, charcoal liquid scintillation

device, alpha tract detector, and electret ion detectors [47].

All of these devices, with the exception of the ion

detector, can be purchased in hardware stores or by mail.

The ion detector generally is only available through

laboratories. These devices are inexpensive, primarily used

for short-term testing, and require little to no training.

Active devices, however, need electrical power and include

continuous monitoring devices. They are customarily

more expensive and require professionally trained testers

for their operation. Figure 5.7 shows examples of the

charcoal tester (a; left) and the alpha tract detector (b; right). 

After testing and evaluation by a professional, it may be

necessary to lower the radon levels in the structure. The

Pennsylvania Department of Environmental Protection

[48] states that in most cases, a system with pipes and a

fan is used to reduce radon. This system, known as a subslab

depressurization system, requires no major changes to the

home. The cost typically ranges from $500 to $2,500 and

averages approximately $1,000, varying with geographic

region. The typical mitigation system usually has only one

pipe penetrating through the basement floor; the pipe also

may be installed outside the house. The Connecticut

Department of Public Health [49] notes that it is more

cost effective to include radon-resistant techniques while

constructing a building than to install a reduction system

in an existing home. Inclusion of radon-resistant

techniques in initial construction costs approximately

$350 to $500 [50]. Figure 5.8 shows examples of radonresistant construction techniques. 

Healthy Housing Reference Manual 5-11

Figure 5.6. Radon Entry [30]
A passive radon-resistant system has five major parts: 

1. A layer of gas-permeable material under the

foundation.

2. The foundation (usually 4 inches of gravel).

3. Plastic sheeting over the foundation, with all

openings in the concrete foundation floor sealed

and caulked.

4. A gas-tight, 3- or 4-inch vent pipe running from

under the foundation through the house to the roof.

5. A roughed-in electrical junction box for the future

installation of a fan, if needed. 

These features create a physical barrier to radon entry.

The vent pipe redirects the flow of air under the

foundation, preventing radon from seeping into the house.

Pesticides

Much pesticide use could be reduced if integrated pest

management (IPM) practices were used in the home.

IPM is a coordinated approach to managing roaches,

rodents, mosquitoes, and other pests that integrates

inspection, monitoring, treatment, and evaluation, with

special emphasis on the decreased use of toxic agents.

However, all pest management options, including natural,

biologic, cultural, and chemical methods, should be

considered. Those that have the least impact on health

and the environment should be selected. Most household

pests can be controlled by eliminating the habitat for the

pest both inside and outside, building or screening them

out, eliminating food and harborage areas, and safely

using appropriate pesticides if necessary.

EPA [51] states that 75% of U.S. households used at least

one pesticide indoors during the past year and that 80% of

most people’s exposure to pesticides occurs indoors.

Measurable levels of up to a dozen pesticides have been

found in the air inside homes. Pesticides used in and

around the home include products to control insects

(insecticides), termites (termiticides), rodents (rodenticides),

fungi (fungicides), and microbes (disinfectants). These

products are found in sprays, sticks, powders, crystals,

balls, and foggers.

Delaplane [52] notes that the ancient Romans killed

insect pests by burning sulfur and controlled weeds with

salt. In the 1600s, ants were controlled with mixtures of

honey and arsenic. U.S. farmers in the late 19th century

used copper actoarsenite (Paris green), calcium arsenate,

nicotine sulfate, and sulfur to control insect pests in field

crops. By World War II and afterward, numerous

pesticides had been introduced, including DDT, BHC,

aldrin, dieldrin, endrin, and 2,4-D. A significant factor

with regard to these pesticides used in and around the

home is their impact on children. According to a 2003

EPA survey, 47% of all households with children under

the age of 5 years had at least one pesticide stored in an

unlocked cabinet less than 4 feet off the ground. This is

within easy reach of children. Similarly, 74% of

households without children under the age of 5 also

stored pesticides in an unlocked cabinet less than 4 feet

off the ground. This issue is significant because 13% of all

pesticide poisoning incidents occur in homes other than

the child’s home. The EPA [53] notes a report by the

American Association of Poison Control Centers

indicating that approximately 79,000 children were

involved in common household pesticide poisonings or

exposures. 

The health effects of pesticides vary with the product.

However, local effects from most of the products will be

on eyes, noses, and throats; more severe consequences,

such as on the central nervous system and kidneys and on

Figure 5.7. Home Radon Dectectors [31]

Figure 5.8. Radon-resistant Construction [50]

5-12 Indoor Air Pollutants and Toxic Materials
cancer risks, are possible. The active and inert ingredients

of pesticides can be organic compounds, which can

contribute to the level of organic compounds in indoor

air. More significantly, products containing cyclodiene

pesticides have been commonly associated with

misapplication. Individuals inadvertently exposed during

this misapplication had numerous symptoms, including

headaches, dizziness, muscle twitching, weakness, tingling

sensations, and nausea. In addition, there is concern that

these pesticides may cause long-term damage to the liver

and the central nervous system, as well as an increased

cancer risk. Cyclodiene pesticides were developed for use

as insecticides in the 1940s and 1950s. The four main

cyclodiene pesticides—aldrin, dieldrin, chlordane, and

heptachlor—were used to guard soil and seed against

insect infestation and to control insect pests in crops.

Outside of agriculture they were used for ant control;

farm, industrial, and domestic control of fleas, flies, lice,

and mites; locust control; termite control in buildings, fences,

and power poles; and pest control in home gardens. No

other commercial use is permitted for cyclodiene or

related products. The only exception is the use of

heptachlor by utility companies to control fire ants in

underground cable boxes. 

An EPA survey [53] revealed that bathrooms and kitchens

are areas in the home most likely to have improperly stored

pesticides. In the United States, EPA regulates pesticides under

the pesticide law known as the Federal Insecticide, Fungicide,

and Rodenticide Act. Since 1981, this law has required

most residential-use pesticides to bear a signal word such

as “danger” or “warning” and to be contained in childresistant packaging. This type of packaging is designed to

prevent or delay access by most children under the age of

5 years. EPA offers the following recommendations for

preventing accidental poisoning:

• store pesticides away from the reach of children in

a locked cabinet, garden shed, or similar location;

• read the product label and follow all directions

exactly, especially precautions and restrictions;

• remove children, pets, and toys from areas before

applying pesticides;

• if interrupted while applying a pesticide, properly

close the package and assure that the container is

not within reach of children; 

• do not transfer pesticides to other containers that

children may associate with food or drink;

• do not place rodent or insect baits where small

children have access to them;

• use child-resistant packaging properly by closing

the container tightly after use;

• assure that other caregivers for children are aware

of the potential hazards of pesticides;

• teach children that pesticides are poisons and

should not be handled; and 

• keep the local Poison Control Center telephone

number available.

Toxic Materials

Asbestos

Asbestos, from the Greek word meaning “inextinguishable,”

refers to a group of six naturally occurring mineral fibers.

Asbestos is a mineral fiber of which there are several

types: amosite, crocidiolite, tremolite, actinolite,

anthrophyllite, and chrysotile. Chrysotile asbestos, also

known as white asbestos, is the predominant commercial

form of asbestos. Asbestos is strong, flexible, resistant to

heat and chemical corrosion, and insulates well. These

features led to the use of asbestos in up to 3,000 consumer

products before government agencies began to phase it

out in the 1970s because of its health hazards. Asbestos

has been used in insulation, roofing, siding, vinyl floor

tiles, fireproofing materials, texturized paint and

soundproofing materials, heating appliances (such as

clothes dryers and ovens), fireproof gloves, and ironing

boards. Asbestos continues to be used in some products,

such as brake pads. Other mineral products, such as talc

and vermiculite, can be contaminated with asbestos. 

The health effects of asbestos exposure are numerous and

varied. Industrial studies of workers exposed to asbestos in

factories and shipyards have revealed three primary health

risk concerns from breathing high levels of asbestos fibers:

lung cancer, mesothelioma (a cancer of the lining of the

chest and the abdominal cavity), and asbestosis (a condition in

which the lungs become scarred with fibrous tissue).

The risk for all of these conditions is amplified as the

number of fibers inhaled increases. Smoking also

enhances the risk for lung cancer from inhaling asbestos

fibers by acting synergistically. The incubation period (from

time of exposure to appearance of symptoms) of these

diseases is usually about 20 to 30 years. Individuals who

develop asbestosis have typically been exposed to high

levels of asbestos for a long time. Exposure levels to

asbestos are measured in fibers per cubic centimeter of air.

Most individuals are exposed to small amounts of asbestos

Healthy Housing Reference Manual 5-13
in daily living activities; however, a preponderance of

them do not develop health problems. According to the

Agency for Toxic Substances and Disease Registry

(ATSDR), if an individual is exposed, several factors

determine whether the individual will be harmed [54].

These factors include the dose (how much), the duration

(how long), and the fiber type (mineral form and

distribution). ATSDR also states that children may be

more adversely affected than adults [54]. Children breathe

differently and have different lung structures than adults;

however, it has not been determined whether these

differences cause a greater amount of asbestos fibers to

stay in the lungs of a child than in the lungs of an adult.

In addition, children drink more fluids per kilogram of

body weight than do adults and they can be exposed

through asbestos-contaminated drinking water. Eating

asbestos-contaminated soil and dust is another source of

exposure for children. Certain children intentionally eat

soil and children’s hand-to-mouth activities mean that all

young children eat more soil than do adults. Family

members also have been exposed to asbestos that was

carried home on the clothing of other family members

who worked in asbestos mines or mills. Breathing asbestos

fibers may result in difficulty in breathing. Diseases

usually appear many years after the first exposure to

asbestos and are therefore not likely to be seen in

children. But people who have been exposed to asbestos

at a young age may be more likely to contract diseases

than those who are first exposed later in life. In the small

number of studies that have specifically looked at asbestos

exposure in children, there is no indication that younger

people might develop asbestos-related diseases more

quickly than older people. Developing fetuses and infants

are not likely to be exposed to asbestos through the

placenta or breast milk of the mother. Results of animal

studies do not indicate that exposure to asbestos is likely

to result in birth defects. 

A joint document issued by CPSC, EPA, and ALA, notes

that most products in today’s homes do not contain

asbestos. However, asbestos can still be found in products

and areas of the home. These products contain asbestos

that could be inhaled and are required to be labeled as

such. Until the 1970s, many types of building products

and insulation materials used in homes routinely

contained asbestos. A potential asbestos problem both

inside and outside the home is that of vermiculite. According

to the USGS [55], vermiculite is a claylike material that

expands when heated to form wormlike particles. It is

used in concrete aggregate, fertilizer carriers, insulation,

potting soil, and soil conditioners. This product ceased

being mined in 1992, but old stocks may still be available.

Common products that contained asbestos in the past

and conditions that may release fibers include the following:

• Steam pipes, boilers, and furnace ducts insulated

with an asbestos blanket or asbestos paper tape.

These materials may release asbestos fibers if

damaged, repaired, or removed improperly.

• Resilient floor tiles (vinyl asbestos, asphalt, and

rubber), the backing on vinyl sheet flooring, and

adhesives used for installing floor tile. Sanding

tiles can release fibers, as may scraping or sanding

the backing of sheet flooring during removal.

• Cement sheet, millboard, and paper used as

insulation around furnaces and wood-burning

stoves. Repairing or removing appliances may

release asbestos fibers, as may cutting, tearing,

sanding, drilling, or sawing insulation.

• Door gaskets in furnaces, wood stoves, and coal

stoves. Worn seals can release asbestos fibers

during use.

• Soundproofing or decorative material sprayed on

walls and ceilings. Loose, crumbly, or waterdamaged material may release fibers, as will

sanding, drilling, or scraping the material.

• Patching and joint compounds for walls, ceilings,

and textured paints. Sanding, scraping, or drilling

these surfaces may release asbestos.

• Asbestos cement roofing, shingles, and siding.

These products are not likely to release asbestos

fibers unless sawed, drilled, or cut.

• Artificial ashes and embers sold for use in gasfired fireplaces in addition to other older

household products such as fireproof gloves,

stove-top pads, ironing board covers, and certain

hair dryers.

• Automobile brake pads and linings, clutch facings,

and gaskets. 

Homeowners who believe material in their home may be

asbestos should not disturb the material. Generally,

material in good condition will not release asbestos fibers,

and there is little danger unless the fibers are released and

inhaled into the lungs. However, if disturbed, asbestos

material may release asbestos fibers, which can be inhaled

into the lungs. The fibers can remain in the lungs for a

5-14 Indoor Air Pollutants and Toxic Materials
long time, increasing the risk for disease. Suspected

asbestos-containing material should be checked regularly

for damage from abrasions, tears, or water. If possible,

access to the area should be limited. Asbestos-containing

products such as asbestos gloves, stove-top pads, and

ironing board covers should be discarded if damaged or

worn. Permission and proper disposal methods should be

obtainable from local health, environmental, or other

appropriate officials. If asbestos material is more than

slightly damaged, or if planned changes in the home

might disturb it, repair or removal by a professional is

needed. Before remodeling, determine whether asbestos

materials are present. 

Only a trained professional can confirm suspected

asbestos materials that are part of a home’s construction. This

individual will take samples for analysis and submit them

to an EPA-approved laboratory.

If the asbestos material is in good shape and will not be

disturbed, the best approach is to take no action and

continue to monitor the material. If the material needs

action to address potential exposure problems, there are

two approaches to correcting the problem: repair and removal. 

Repair involves sealing or covering the asbestos material.

Sealing or encapsulation involves treating the material

with a sealant that either binds the asbestos fibers together

or coats the material so fibers are not released. This is an

approach often used for pipe, furnace, and boiler

insulation; however, this work should be done only by a

professional who is trained to handle asbestos safely.

Covering (enclosing) involves placing something over or

around the material that contains asbestos to prevent release

of fibers. Exposed insulated piping may be covered with a

protective wrap or jacket. In the repair process, the

approach is for the material to remain in position

undisturbed. Repair is a less expensive process than is removal. 

With any type of repair, the asbestos remains in place.

Repair may make later removal of asbestos, if necessary,

more difficult and costly. Repairs can be major or minor.

Both major and minor repairs must be done only by a

professional trained in methods for safely handling asbestos. 

Removal is usually the most expensive and, unless

required by state or local regulations, should be the last

option considered in most situations. This is because

removal poses the greatest risk for fiber release. However,

removal may be required when remodeling or making

major changes to the home that will disturb asbestos

material. In addition, removal may be called for if

asbestos material is damaged extensively and cannot be

otherwise repaired. Removal is complex and must be done

only by a contractor with special training. Improper

removal of asbestos material may create more of a

problem than simply leaving it alone. 

Lead

Many individuals recognize lead in the form often seen in

tire weights and fishing equipment, but few recognize its

various forms in and around the home. The MerriamWebster Dictionary [56] defines lead as “a heavy soft malleable

ductile plastic but inelastic bluish white metallic element

found mostly in combination and used especially in pipes,

cable sheaths, batteries, solder, and shields against

radioactivity.” Lead is a metal with many uses. It melts easily

and quickly. It can be molded or shaped into thin sheets

and can be drawn out into wire or threads. Lead also is

very resistant to weather conditions. Lead and lead

compounds are toxic and can present a severe hazard to

those who are overexposed to them. Whether ingested or

inhaled, lead is readily absorbed and distributed

throughout the body.

Until 1978, lead compounds were an important component

of many paints. Lead was added to paint to promote

adhesion, corrosion control, drying, and covering. White

lead (lead carbonate), linseed oil, and inorganic pigments

were the basic components for paint in the 18th and 19th

centuries, and continued until the middle of the 20th century.

Lead was banned by CPSC in 1978. Lead-based paint was

used extensively on exteriors and interior trim-work, window

sills, sashes, window frames, baseboards, wainscoting,

doors, frames, and high-gloss wall surfaces, such as those

found in kitchens and bathrooms. The only way to determine

which building components are coated with lead paint is

through an inspection for lead-based paint. Almost all

painted metals were primed with red lead or painted with

lead-based paints. Even milk (casein) and water-based

paints (distemper and calcimines) could contain some

lead, usually in the form of hiding agents or pigments.

Varnishes sometimes contained lead. Lead compounds also

were used as driers in paint and window-glazing putty. 

Lead is widespread in the environment. People absorb

lead from a variety of sources every day. Although lead

has been used in numerous consumer products, the most

important sources of lead exposure to children and others

today are the following:

• contaminated house dust that has settled on

horizontal surfaces,

• deteriorated lead-based paint,

Healthy Housing Reference Manual 5-15
• contaminated bare soil, 

• food (which can be contaminated by lead in the

air or in food containers, particularly leadsoldered food containers), 

• drinking water (from corrosion of plumbing

systems), and 

• occupational exposure or hobbies.

Federal controls on lead in gasoline, new paint, food

canning, and drinking water, as well as lead from industrial air

emissions, have significantly reduced total human exposure

to lead. The number of children with blood lead levels above

10 micrograms per deciliter (μg/dL), a level designated as

showing no physiologic toxicity, has declined from

1.7 million in the late 1980s to 310,000 in 1999–2002.

This demonstrates that the controls have been effective,

but that many children are still at risk. CDC data show

that deteriorated lead-based paint and the contaminated

dust and soil it generates are the most common sources of

exposure to children today. HUD data show that the

number of houses with lead paint declined from 64 million

in 1990 to 38 million in 2000 [57].

Children are more vulnerable to lead poisoning than are

adults. Infants can be exposed to lead in the womb if

their mothers have lead in their bodies. Infants and

children can swallow and breathe lead in dirt, dust, or

sand through normal hand-to-mouth contact while they

play on the floor or ground. These activities make it easier

for children to be exposed to lead. Other sources of

exposure have included imported vinyl miniblinds,

crayons, children’s jewelry, and candy. In 2004, increases

in lead in water service pipes were observed in Washington,

D.C., accompanied by increases in blood lead levels in

children under the age of 6 years who were served by the

water system [58].

In some cases, children swallow nonfood items such as

paint chips. These may contain very large amounts of lead,

particularly in and around older houses that were painted

with lead-based paint. Many studies have verified the

effect of lead exposure on IQ scores in the United States.

The effects of lead exposure have been reviewed by the

National Academy of Sciences [59]. 

Generally, the tests for blood lead levels are from drawn

blood, not from a finger-stick test, which can be unreliable if

performed improperly. Units are measured in micrograms

per deciliter and reflect the 1991 guidance from the Centers

of Disease Control [60]: 

• Children: 10 μg/dL (level of concern)—find

source of lead;

• Children: 15 μg/dL and above—environmental

intervention, counseling, medical monitoring;

• Children: 20 μg/dL and above—medical treatment;

• Adults: 25 μg/dL (level of concern)—find source

of lead; and 

5-16 Indoor Air Pollutants and Toxic Materials

Lead in paint. Differing methods report results in differing units. Lead is considered a potential hazard if

above the following levels, but can be a hazard at lower levels if improperly handled. Below are the current

action levels identified by HUD [62] and EPA (40 CFR Part 745):

Lab analysis of samples: 

5,000 milligram per kilogram (mg/kg) or 5,000 parts per million (ppm) 

0.5% lead by weight.

X-ray fluorescence: 

1 milligram per square centimeter (mg/cm2)

Lead in dust: Lead in soil: 

Floors, 40 micrograms per square foot (μg/ft2) High-contact bare play areas: 400 ppm 

Window sills, 250 μg/ft2 Other yard areas: 1,200 ppm

Window troughs, 400 μg/ft2 (clearance only)

Action Levels for Lead
• Adults: 50 μg/dL—Occupational Safety and

Health Administration (OSHA) standard for

medical removal from the worksite.

Adults are usually exposed to lead from occupational

sources (e.g., battery construction, paint removal) or at

home (e.g., paint removal, home renovations). 

In 1978, CPSC banned the use of lead-based paint in

residential housing. Because houses are periodically

repainted, the most recent layer of paint will most likely

not contain lead, but the older layers underneath

probably will. Therefore, the only way to accurately

determine the amount of lead present in older paint is to

have it analyzed. 

It is important that owners of homes built before 1978 be

aware that layers of older paint can contain a great deal of

lead. Guidelines on identifying and controlling lead-based

paint hazards in housing have been published by HUD [61]. 

Controlling Lead Hazards

The purpose of a home risk assessment is to determine,

through testing and evaluation, where hazards from lead

warrant remedial action. A certified inspector or risk

assessor can test paint, soil, or lead dust either on-site or

in a laboratory using methods such as x-ray fluorescence

(XRF) analyzers, chemicals, dust wipe tests, and atomic

absorption spectroscopy. Lists of service providers are

available by calling 1-800-424-LEAD. Do-it-yourself test

kits are commercially available; however, these kits do not

tell you how much lead is present, and their reliability at

detecting low levels of lead has not been determined.

Professional testing for lead in paint is recommended.

The recommended sampling method for dust is the

surface wet wipe. Dust samples are collected from

different surfaces, such as bare floors, window sills, and

window wells. Each sample is collected from a measured

surface area using a wet wipe, which is sent to a

laboratory for testing. Risk assessments can be fairly lowcost investigations of the location, condition, and severity

of lead hazards found in house dust, soil, water, and

deteriorating paint. Risk assessments also will address

other sources of lead from hobbies, crockery, water, and

work environments. These services are critical when

owners are seeking to implement measures to reduce

suspected lead hazards in housing and day-care centers or

when extensive rehabilitation is planned. 

HUD has published detailed protocols for risk

assessments and inspections [61].

It is important from a health standpoint that future tenants,

painters, and construction workers know that lead-based

paint is present, even under treated surfaces, so they can

take precautions when working in areas that will generate

lead dust. Whenever mitigation work is completed, it is

Healthy Housing Reference Manual 5-17

Deteriorated lead-based paint: Paint known to contain lead above the regulated level that shows signs of

peeling, chipping, chalking, blistering, alligatoring, or otherwise separating from its substrate. 

Dust removal: The process of removing dust to avoid creating a greater problem of spreading lead particles;

usually through wet or damp collection and use of HEPA vacuums.

Hazard abatement: Long-term measures to remove the hazards of lead-based paint through replacement of

building components, enclosure, encapsulation, or paint removal. 

Interim control: Short-term methods to remove lead dust, stabilize deteriorating painted surfaces, treat

friction and impact surfaces that generate lead dust, and repaint surfaces. Maintenance can ensure that

housing remains lead-safe. 

Lead-based paint: Any existing paint, varnish, shellac, or other coating that is equal to or greater than

1.0 milligrams per square centimeter (mg/cm2) or greater than 0.5% by weight (5,000 ppm, 5,000

micrograms per gram [μg/g], or 5,000 milligrams per kilogram [mg/kg]). For new paint, CPSC has

established 0.06% as the maximum amount of lead allowed in new paint. Lead in paint can be measured by

x-ray fluorescence analyzers or laboratory analysis by certified personnel and approved laboratories. 

Risk assessment: An on-site investigation to determine the presence and condition of lead-based paint,

including limited test samples and an evaluation of the age, condition, housekeeping practices, and uses of a

residence. 

Definitions Related to Lead
important to have a clearance test using the dust wipe

method to ensure that lead-laden dust generated during

the work does not remain at levels above those established

by the EPA and HUD. Such testing is required for

owners of most housing that is receiving federal financial

assistance, such as Section 8 rental housing. A building or

housing file should be maintained and updated whenever

any additional lead hazard control work is completed.

Owners are required by law to disclose information about

lead-based paint or lead-based paint hazards to buyers or

tenants before completing a sales or lease contract [62].

All hazards should be controlled as identified in a

risk assessment.

Whenever extensive amounts of lead must be removed

from a property, or when methods of removing toxic

substances will affect the environment, it is extremely

important that the owner be aware of the issues surrounding

worker safety, environmental controls, and proper disposal.

Appropriate architectural, engineering, and environmental

professionals should be consulted when lead hazard

projects are complex. 

Following are brief explanations of the two approaches for

controlling lead hazard risks. These controls are

recommended by HUD in HUD Guidelines for the

Evaluation and Control of Lead-Based Paint Hazards in

Housing [61], and are summarized here to focus on

special considerations for historic housing: 

Interim Controls. Short-term solutions include thorough

dust removal and thorough washdown and cleanup, paint

film stabilization and repainting, covering of leadcontaminated soil, and informing tenants about lead

hazards. Interim controls require ongoing maintenance

and evaluation. 

Hazard Abatement. Long-term solutions are defined as

having an expected life of 20 years or more and involve

permanent removal of hazardous paint through chemicals,

heat guns, or controlled sanding or abrasive methods;

permanent removal of deteriorated painted features

through replacement; removal or permanent covering of

contaminated soil; and the use of enclosures (such as

drywall) to isolate painted surfaces. The use of specialized

encapsulant products can be considered as permanent

abatement of lead. 

Reducing and controlling lead hazards can be successfully

accomplished without destroying the character-defining

features and finishes of historic buildings. Federal and

state laws generally support the reasonable control of leadbased paint hazards through a variety of treatments,

ranging from modified maintenance to selective substrate

removal. The key to protecting children, workers, and the

environment is to be informed about the hazards of lead,

to control exposure to lead dust and lead in soil and lead

paint chips, and to follow existing regulations. 

The following summarizes several important regulations

that affect lead-hazard reduction projects. Owners should

be aware that regulations change, and they have a

responsibility to check state and local ordinances as well.

Care must be taken to ensure that any procedures used to

release lead from the home protect both the residents and

workers from lead dust exposure.

Residential Lead-Based Paint Hazard Reduction Act of

1992, Title X [62]. Part of the Housing and Community

Development Act of 1992 (Public Law 102-550) [63]. It

established that HUD issue Guidelines for the Evaluation

and Control of Lead-Based Paint Hazards in Housing [61]

to outline risk assessments, interim controls, and

abatement of lead-based paint hazards in housing. Title X

calls for the reduction of lead in federally supported

housing. It outlines the federal responsibility toward its

own residential units and the need for disclosure of lead

in residences, even private residences, before a sale. Title X

also required HUD to establish regulations for federally

assisted housing (24 CFR Part 35) and EPA to establish

standards for lead in paint, dust, and soil, as well as

standards for laboratory accreditation (40 CFR Part 745).

EPA’s residential lead hazard standards are available at

http://www.epa.gov/lead/leadhaz.htm.

Interim Final Rule on Lead in Construction (29 Code of

Federal Regulations [CFR] 1926.62) [64]. Issued by

OSHA, these regulations address worker safety, training,

and protective measures. The regulations are based in part

on personal-air sampling to determine the amount of lead

dust exposure to workers. 

State Laws. States generally have the authority to regulate

the removal and transportation of lead-based paint and

the generated waste through the appropriate state

environmental and public health agencies. Most

requirements are for mitigation in the case of a leadpoisoned child, for protection of children, or for oversight

to ensure the safe handling and disposal of lead waste.

When undertaking a lead-based paint reduction program,

it is important to determine which laws are in place that

may affect the project.

5-18 Indoor Air Pollutants and Toxic Materials
Local Ordinances. Check with local health departments,

poison control centers, and offices of housing and

community development to determine whether any laws

require compliance by building owners. Determine

whether projects are considered abatements and will

require special contractors and permits. 

Owner’s Responsibility. Owners are ultimately

responsible for ensuring that hazardous waste is properly

disposed of when it is generated on their own sites.

Owners should check with their state government to

determine whether an abatement project requires a

certified contractor. Owners should establish that the

contractor is responsible for the safety of the crew, to

ensure that all applicable laws are followed, and that

transporters and disposers of hazardous waste have

liability insurance as a protection for the owner. The

owner should notify the contractor that lead-based paint

may be present and that it is the contractor’s

responsibility to follow appropriate work practices to

protect workers and to complete a thorough cleanup to

ensure that lead-laden dust is not present after the work is

completed. Renovation contractors are required by EPA

to distribute an informative educational pamphlet

(Protect Your Family from Lead in Your Home) to

occupants before starting work that could disturb leadbased paint (http://www.epa.gov/lead/

leadinfo.htm#remodeling).

Arsenic

Lead arsenate was used legally up to 1988 in most of the

orchards in the United States. Often 50 applications or

more of this pesticide were applied each year. This toxic

heavy metal compound has accumulated in the soil

around houses and under the numerous orchards in the

country, contaminating both wells and land. These

orchards are often turned into subdivisions as cities

expand and sprawl occurs. Residues from the pesticide

lead arsenate, once used heavily on apple, pear, and other

orchards, contaminate an estimated 70,000 to 120,000 acres

in the state of Washington alone, some of it in areas

where agriculture has been replaced with housing,

according to state ecology department officials and others. 

Lead arsenate, which was not banned for use on food

crops until 1988, nevertheless was mostly replaced by the

pesticide dichlorodiphenyltrichloroethane (DDT) and its

derivatives in the late 1940s. DDT was banned in the

United States in 1972, but is used elsewhere in the world. 

For more than 20 years, the wood industry has infused

green wood with heavy doses of arsenic to kill bugs and

prevent rot. Numerous studies show that arsenic sticks to

children’s hands when they play on treated wood, and it is

absorbed through the skin and ingested when they put

their hands in their mouths. Although most uses of

arsenic wood treatments were phased out by 2004, an

estimated 90% of existing outdoor structures are made of

arsenic-treated wood [65].

In a study conducted by the University of North Carolina

Environmental Quality Institute in Asheville, wood

samples were analyzed and showed that 

• Older decks and play sets (7 to 15 years old) that

were preserved with chromated copper arsenic

expose people to just as much arsenic on the

wood surface as do newer structures (less than

1 year old). The amount of arsenic that testers

wiped off a small area of wood about the size of a

4-year-old’s handprint typically far exceeds what

EPA allows in a glass of water under the Safe

Drinking Water Act standard. Figure 5.9 shows a

safety warning label placed on wood products. 

• Arsenic in the soil from two of every five

backyards or parks tested exceeded EPA’s

Superfund cleanup level of 20 ppm. 

Arsenic is not just poisonous in the short term, it causes

cancer in the long term. Arsenic is on EPA’s short list of

chemicals known to cause cancer in humans. According to the

National Academy of Sciences, exposure to arsenic causes

lung, bladder, and skin cancer in humans, and is suspected as

a cause of kidney, prostate, and nasal passage cancer. 

Healthy Housing Reference Manual 5-19

Figure 5.9. Arsenic Label 
References

1. US Environmental Protection Agency and the US

Consumer Product Safety Commission. The

inside story: a guide to indoor air quality.

Washington, DC: US Environmental Protection

Agency and the US Consumer Product Safety

Commission, Office of Radiation and Indoor Air;

1995. Document #402-K-93-007. Available from

URL: http://www.epa.gov/iaq/pubs/insidest.html.

2. Centers for Disease Control and Prevention.

Asthma: speaker’s kit for health care professionals;

preface. Atlanta: US Department of Health and

Human Services; no date. Available from URL:

http://www.cdc.gov/asthma/speakit/intro.htm.

3. US Environmental Protection Agency.

Washington, DC: US Environmental Protection

Agency; 2004. Asthma facts. EPA #402-F-04-019.

Available from URL: http://www.epa.gov/

asthma/pdfs/asthma_fact_sheet_en.pdf.

4. Centers for Disease Control and Prevention.

Asthma: speaker’s kit for health care professionals;

epidemiology. Atlanta: US Department of Health

and Human Services; no date. Available from

URL: http://www.cdc.gov/asthma/speakit/epi.htm.

5. Crain EF, Walter M, O’Connor GT, Mitchell H,

Gruchalla RS, Kattan M, et al. Home and allergic

characteristics of children with asthma in seven

U.S. urban communities and design of an environmental intervention: The Inner-City Asthma

Study. Environ Health Perspect

2002;119:939–45.

6. Community Environmental Health Resource

Center. Cockroaches: tools for detecting hazards.

Washington, DC: Community Environmental

Health Resource Center; no date. Available from

URL: http://www.cehrc.org/tools/

cockroaches/index.cfm.

7. Lyon WF. Entomology, House Dust Mites HYG

2157-97. Columbus, OH: The Ohio State

University Extension; 1997. Available from URL:

http://ohioline.osu.edu/hyg-fact/2000/2157.html.

8. Morgan WJ, Crain EF, Gruchalla RS, O’Connor

GT, Kattan M, et al. Results of a home-based

environmental intervention among urban children

with asthma. N Engl J Med 2004;351:1068–80.

9. US Environmental Protection Agency. Sources of

indoor air pollution—biological pollutants.

Washington, DC: US Environmental Protection

Agency; no date. Available from URL:

http://www.epa.gov/iaq/biologic.html.

10. Ownby DR. Exposure to dogs and cats in the first

year of life and risk of allergic sensitization at 6 to

7 years of age. JAMA 2002;288(8):963–72.

11. Roost HP. Role of current and childhood exposure to cat and atopic sensitization. J Allergy Clin

Immunol 1999;104(5):94.

12. Downs SH. Having lived on a farm and protection against allergic diseases in Australia. Clin Exp

Allergy 2001;31(4):570–5.

13. Institute of Medicine. Clearing the air: asthma

and indoor air exposures. Washington, DC:

National Academies Press; 2000.

14. American Conference of Governmental and

Industrial Hygienists. Macher J, editor.

Bioaerosols: assessment and control. Cincinnati,

OH: American Conference of Governmental and

Industrial Hygienists; 1999. 

15. Institute of Medicine. Damp indoor spaces and

health. Washington, DC: National Academies

Press; 2004.

16. Morgan WJ, Crain EF, Gruchalla RS, O’Connor

GT, Kattan M, Evans R 3rd, et al. Results of

home-based environmental intervention among

urban children with asthma. N Engl J Med

2004;351:1068–80.

17. Burge HA, Ammann HA. Fungal toxins and β

(1J3)-D-glucans. In: Macher J, editor.

Bioaerosols: assessment and control. Cincinnati,

OH: American Conference of Governmental and

Industrial Hygienists; 1999.

18. American Academy of Pediatrics, Committee on

Environmental Health. Toxic effects of indoor

molds. Pediatrics 1998;101:712–14.

19. Burge HA, Otten JA. 1999. Fungi. In: Macher J,

editor. Bioaerosols: assessment and control.

Cincinnati, OH: American Conference of

Governmental and Industrial Hygienists; 1999.

5-20 Indoor Air Pollutants and Toxic Materials
20. Etzel RA. The “fatal four” indoor air pollutants.

Pediatr Ann 2000;29(6):344–50.

21. Dearborn DG, Smith PG, Dahms BB, Allan TM,

Sorenson WG, Montana E, et al. Clinical profile

of thirty infants with acute pulmonary hemorrhage in Cleveland. Pediatrics 2002;110:627–37.

22. Etzel RA, Montana E, Sorenson WG, Kullman

GJ, Allan TM, Dearborn DG. Acute pulmonary

hemorrhage in infants associated with exposure to

Stachybotrys atra and other fungi. Arch Pediatr

Adolesc Med 1998;152:757–62.

23. Flappan SM, Portnoy J, Jones P, Barnes C. Infant

pulmonary hemorrhage in a suburban home with

water damage and mold (Stachybotrys atra).

Environ Health Perspect 1999;107:927–30.

24. Vesper S, Dearborn DG, Yike I, Allan T,

Sobolewski J, Hinkley SF, et al. Evaluation of

Stachybotrys chartarum in the house of an infant

with pulmonary hemorrhage: quantitative assessment before, during, and after remediation. J.

Urban Health Bull N Y Acad Med

2000;77(1):68–85.

25. US Environmental Protection Agency. A brief

guide to mold, moisture, and your home (EPA

402-K-02-003). Washington, DC: US

Environmental Protection Agency; 2002.

Available from URL: http://www.epa.gov/

iaq/molds/images/moldguide.pdf. 

26. NYC. 2000. Guidelines on assessment and remediation of fungi in indoor environments. New

York City Department of Health, Bureau of

Environmental & Occupational Disease

Epidemiology. Available from URL:

http://www.ci.nyc.ny.us/html/doh/html/epi/

moldrpt1.shtml. 

27. Bush RK, Portnoy JM. The role and abatement of

fungal allergens in allergic diseases. J Allerg Clin

Immunol Suppl 2001;107(3 pt 2):430.

28. Department of Housing and Urban Development,

Office of Native American Programs. Mold detection and prevention: a guide for housing authorities in Indian Country. Washington, DC:

Department of Housing and Urban Development;

2001. Available from URL: http://www2.ihs.gov/

IEH/documents/HUD%20Mold%20

Detection.pdf. 

29. US Environmental Protection Agency. Mold

remediation in schools and commercial buildings

(EPA 402-K-01-001). Washington, DC: US

Environmental Protection Agency; 2001.

30. Shaughnessy RJ, Morey PR. Remediation of

microbial contamination. In: Macher J, editor.

Bioaerosols: assessment and control. Cincinnati,

OH: American Conference of Governmental and

Industrial Hygienists; 1999.

31. National Institute of Environmental Health

Sciences. Interim final guidelines for the protection and training of workers engaged in maintenance and remediation work associated with

mold. Report of a national technical workshop,

National Institute of Environmental Health

Sciences, New York City, 2004 Jan 27–28.

32. Mott JA, Wolfe MI, Alverson CJ, Macdonald SC,

Bailey CR, Ball LB, et al. National vehicle emissions policies and practices and declining US carbon monoxide mortality. JAMA 2002;288:988–95.

33. American Lung Association. Carbon monoxide

fact sheet. New York: American Lung Association;

2004. Available from URL:

http://www.lungusa.org/site/

pp.asp?c=dvLUK9O0E&b=35375.

34. North Carolina Department of Health and

Human Services. Indoor ozone. Raleigh, NC:

North Carolina Department of Health and

Human Services; 2003. Available from URL:

http://www.epi.state.nc.us/epi/oee/

ozone/indoor.html.

35. US Environmental Protection Agency. Ozone

generators that are sold as air cleaners: an assessment of effectiveness and health consequences.

Washington, DC: US Environmental Protection

Agency; no date. Available from URL:

http://www.epa.gov/iaq/pubs/ozonegen.html.

36. National Cancer Institute. Secondhand smoke:

questions and answers. Bethesda, MD: National

Cancer Institute; no date. Available from URL:

http://www.cancer.gov/cancertopics/factsheet/

Tobacco/ETS.

Healthy Housing Reference Manual 5-21
37. US Environmental Protection Agency. What you

can do about secondhand smoke as parents, decision-makers, and building occupants.

Washington, DC: US Environmental Protection

Agency; 1993. Available from URL: http://

www.epa.gov/smokefree/pubs/etsbro.html.

38. US Environmental Protection Agency. Methylene

chloride (dichloromethane). Washington, DC: US

Environmental Protection Agency; 1992.

Available from URL: http://www.epa.gov/

ttnatw01/hlthef/methylen.html. 

39. Environmental Media Services. Four to avoid.

Washington, DC: Environmental Media Services;

2002. 

40. US Consumer Product Safety Commission. An

update on formaldehyde: 1997 revision.

Washington, DC: Consumer Product Safety

Commission; 1997. CPSC Document 725.

Available from URL: http://www.cpsc.gov/

cpscpub/pubs/725.html.

41. US Environmental Protection Agency. Sources of

indoor air pollution—formaldehyde. Washington,

DC: US Environmental Protection Agency.

Available from URL: http://www.epa.gov/

iaq/formalde.html.

42. US Department of Housing and Urban

Development. Formaldehyde emission controls

for certain wood products. 24 CFR3280.308.

Washington, DC: US Department of Housing

and Urban Development; 2001. Available from

URL: http://www.hudclips.org/cgi/index.cgi. 

43. US Environmental Protection Agency. Assessment

of risks from radon in homes. Washington, DC:

US Environmental Protection Agency; 2003.

Available from URL: http://www.epa.gov/radon/

risk_assessment.html. 

44. US Geological Survey. The geology of radon.

Reston, VA: US Geological Survey; 1995.

Available from URL: http://energy.cr.usgs.gov/

radon/georadon/3.html.

45. California Geological Survey. Radon. Sacramento,

CA: California Geological Survey; no date.

Available from URL: http://www.consrv.ca.gov/

cgs/minerals/hazardous_minerals/radon/.

46. US Department of Health and Human Services.

Surgeon General releases national health advisory

on radon. Washington, DC: US Department of

Health and Human Services; 2005. Available from

URL: http://www.hhs.gov/surgeongeneral/

pressreleases/sg01132005.html.

47. Brain M, Freudenrich C. How radon works.

Atlanta: How Stuff Works; no date. Available

from URL: http://home.howstuffworks.com/

radon.htm.

48. Pennsylvania Department of Environmental

Protection. Mitigating your home or office.

Harrisburg, PA: Pennsylvania Department of

Environmental Protection; no date. Available

from URL: http://www.dep.state.pa.us/dep/

deputate/airwaste/rp/radon_division/

Mitigation_Info.htm.

49. Connecticut Department of Public Health. Why

should you build homes with radon-resistant techniques? Hartford, CT: Connecticut Department

of Public Health Radon Program; no date.

Available from URL: http://www.dph.state.ct.us/

BRS/radon/radon_techniques.htm.

50. US Environmental Protection Agency. Radonresistant new construction. Washington, DC: US

Environmental Protection Agency; no date.

Available from URL: http://www.epa.gov/

radon/construc.html.

51. US Environmental Protection Agency. Pesticides

and child safety. Washington, DC: US

Environmental Protection Agency; no date.

Available from URL: http://www.epa.gov/pesticides/factsheets/childsaf.htm.

52. Delaplane KS. Pesticide usage in the United

States: history, benefits, risks, and trends. Athens,

GA: Cooperative Extension Service, The

University of Georgia College of Agriculture and

Environmental Sciences; no date. Available from

URL: http://pubs.caes.uga.edu/

caespubs/pubcd/B1121.htm.

53. US Environmental Protection Agency. Sources of

indoor air pollution—pesticides. Washington,

DC: US Environmental Protection Agency; no

date. Available from URL: http://www.epa.gov/

iaq/pesticid.html.

5-22 Indoor Air Pollutants and Toxic Materials
54. Agency for Toxic Substances and Disease Registry.

Public health statement for asbestos. Atlanta: US

Department of Health and Human Services;

2001. Available from URL:

http://www.atsdr.cdc.gov/toxprofiles/phs61.html.

55. US Geological Survey. Some facts about asbestos.

USGS fact sheet FS-012-01, online version 1.1.

Reston, VA: US Geological Survey; March 2001.

Available from URL:

http://pubs.usgs.gov/fs/fs012-01/.

56. Merriam-Webster, Inc. Merriam-Webster dictionary. Springfield, MA: Merriam-Webster, Inc.; no

date. Available from URL: http://www.m-w.com/

home.htm.

57. Jacobs DE, Clickner RP, Zhou JY, Viet SM,

Marker DA, Rogers JW, et al. The prevalence of

lead-based paint hazards in U.S. housing. Environ

Health Perspect 2002;100:A599–606.

58. Centers for Disease Control and Prevention.

Blood lead levels in residents of homes with elevated lead in tap water—District of Columbia,

2004. MMWR 2004; 53(12):268–70. Available

from URL: http://www.cdc.gov/mmwr/preview/

mmwrhtml/mm5312a6.htm.

59. National Research Council. Measuring lead exposure in infants, children and other sensitive populations. Washington, DC: National Academy

Press; 1993.

60. Centers for Disease Control. Preventing lead poisoning in young children. Report No. 99-2230.

Atlanta: US Department of Health and Human

Services; 1991.

61. US Department of Housing and Urban

Development. HUD technical guidelines for the

evaluation and control of lead-based paint hazards

in housing. Washington, DC: US Department of

Housing and Urban Development; 1995.

Available from URL: http://www.hud.gov/

offices/lead/guidelines/hudguidelines/index.cfm. 

62. US Department of Housing and Urban

Development. The lead-based paint disclosure

rule (Section 1018 of the Residential Lead-Based

Paint Hazard Reduction Act of 1992).

Washington, DC: US Department of Housing

and Urban Development; no date. Available from

URL: http://www.hud.gov/offices/lead/

disclosurerule/index.cfm. 

63. Residential Lead-Based Paint Hazard Reduction

Act of 1992, Title X of the Housing and

Community Development Act of 1992, Pub. L.

No. 102-550 (Oct 28, 1992).

64. Occupational Safety and Health Administration.

Lead exposure in construction: interim final rule.

Fed Reg 1993;58:26590–649.

65. Environmental Working Group. Nationwide consumer testing of backyard decks and play sets

shows high levels of arsenic on old wood.

Washington, DC: Environmental Working

Group; 2002. Available from URL:

http://www.ewg.org/reports/allhandsondeck/.

Healthy Housing Reference Manual 5-23
5-24 Indoor Air Pollutants and Toxic Materials
Chapter 6—Housing Structure

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

New Housing Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Old Housing Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-8

Vapor Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Crawl Space Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Vapor Barriers for Concrete Slab Homes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Wall and Ceiling Vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

House Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Foundation Sills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Flooring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Studs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Interior Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Stairways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Roof Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Rafters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Collar Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Purlin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Ridge Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Hip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Roof Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Dormer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Asphalt Shingle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

EPDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Asphalt Built-up Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Coal Tar Pitch Built-up Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Slate Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Tile Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Copper Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Galvanized Iron Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Wood Shingle Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Roof Flashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Gutters and Leaders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Exterior Walls and Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-21

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-22

Figure 6.1. Housing Structure Terminology, Typical House Built Today . . . . . . . . . . . . . . . . . .6-1

Figure 6.2. Housing Structure Terminology, Typical House Built Between 1950 and 1980 . . . .6-6

Figure 6.3. Foundation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Figure 6.4. Foundation Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Healthy Housing Reference Manual 1

Contents
Figure 6.5. Interior Stairway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Figure 6.6. Classifications of Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Figure 6.7. Three-dimensional View of a Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Figure 6.8. Window Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Figure 6.9. Wall Framing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

2 Contents
Chapter 6: Housing Structure

“The Palace of Fine Arts in Mexico City has sunk more

than 10 feet into the ground since it was built 60 years

ago and the most noticeable effect is that the grand stone

stairway has disappeared and the entrance is now at

street level.” 

C.B. Crawford, 

Canadian Building Digest

Introduction

The principal function of a house is to provide

protection from the elements. Our present society,

however, requires that a home provide not only shelter,

but also privacy, safety, and reasonable protection of our

physical and mental health. A living facility that fails to

offer these essentials through adequately designed and

properly maintained interiors and exteriors cannot be

termed “healthful housing.”

In this chapter, the home is considered in terms of the

parts that have a bearing on its soundness, state of repair,

and safety. These are some of the elements that the

housing inspector must examine when making a

thorough housing inspection.

Figure 6.1 shows a typical house being built and

inspected today and includes a terminology key. Both the

figure and the key are available in an interactive format

in the glossary on the U.S. Inspect Web site [1]. 

Figure 6.2 shows a typical house built between 1950 and

1980 and also includes a terminology key. The figures

show the complexity and the numerous components of a

home. These components form the vocabulary that is

necessary to discuss housing structure inspection issues.

Key to Figure 6.1 (New Housing Terminology)

1. Ash dump (see 35)—A door or opening in the

firebox that leads directly to the ash pit, through

which the ashes are swept after the fire is burned out.

All fireboxes are not equipped with an ash dump.

2. Attic space—The open space within the attic area. 

3. Backfill—The material used to refill an excavation

around the outside of a foundation wall or pipe

trench.

4. Baluster—One of a series of small pillars that is

Figure 6.1. Housing Structure Terminology, Typical House Being Built Today [1]

Healthy Housing Reference Manual 6-1
attached to and runs between the stairs and the

handrails. The spacing between the balusters should

be less than 4 inches to prevent small children from

getting stuck between the balusters. Balusters are

considered a safety item and provide an additional

barrier.

5. Baseboard trim—Typically a wood trim board that is

placed against the wall around the perimeter of a

room next to the floor. The intent is to conceal the

joint between the floor and wall finish.

6. Basement window—A window opening installed in

the basement wall. Basement windows are

occasionally below the finish grade level and will be

surrounded on the exterior by a window well.

7. Blind or shutter—A lightweight frame in the form of

a door located on each side of a window. They are

most commonly constructed of wood (solid or

louvered panels) or plastic. Originally they were

designed to close and secure over the windows for

security and foul weather. Most shutters now are more

likely decorative pieces that are secured to the house

beside the windows.

8. Bridging—Small pieces of wood or metal strapping

placed in an X-pattern between the floor joists at

midspan to prevent the joists from twisting and

squeaking and to provide reinforcement and

distribution of stress.

9. Building paper/underlayment—Building material,

usually a felt paper that is used as a protective barrier

against air and moisture passage from the area

beneath the flooring as well as providing a

movement/noise isolator in hardwood flooring.

10. Ceiling joist—A horizontally placed framing

members at the ceiling of the top-most living space of

a house that provides a platform to which the finished

ceiling material can be attached.

11. Chair rail (not shown)—Decorative trim applied

around the perimeter of a room such as a formal

dining room or kitchen/breakfast nook at the

approximate same height as the back of a chair. It is

sometimes used as a cap trim for wainscoting (see

wainscoting).

12. Chimney—A masonry or in more modern

construction wood framed enclosure that surrounds

and contains one or more flues and extends above the

roofline. 

13. Chimney cap—The metal or masonry protective

coveringat the top of the chimney that seals the

chimney shaft from water entry between the chimney

enclosure and the flue tiles. 

14. Chimney flues—The space or channel in a chimney

that carries off the smoke and other combustion gases

to the outside air. Most homes will have a terra cotta

tile flue or a metal flue.

15. Collar beam/tie—A horizontal piece of framing

lumber that provides intermediate support for

opposite rafters. They are usually located in the

middle to upper third portion of the rafters. It is also

known as a collar beam or collar brace.

16. Concrete slab floor—Typically approximately

4 inches thick, the concrete slab floor provides a

number of uses. It creates a solid level surface to walk

and work on. It provides a separation between the

grade/soil and a potentially livable area. It also

provides lateral compression resistance for the

foundation walls, preventing soil pressure from

outside the foundation from pushing the foundation

walls and footings inward. 

17. Corner brace—Diagonal braces placed at the corners

of framed walls to stiffen them and provide extra strength.

18. Cornice—An overhang of a pitched roof at the eave

line that usually consists of a fascia board, a soffit, and

any appropriate moldings or vents.

19. Cornice molding—The individual pieces of wood

trim that are applied to the cornice area at the eaves.

20. Door casing/trim—The finish trim details around the

perimeter of the door on the interior finished wall.

21. Door frame/jamb—The top and sides of the door to

include the wall framing as well as the actual door

frame and trim. 

22. Downspout—A pipe, usually of metal or vinyl, that is

connected to the gutters and is used to carry the roofwater runoff down and away from the house. 

23. Downspout gooseneck—Segmented section of

downspout that is bent at a radius to allow the

6-2 Housing Structure
downspout to be attached to the house and to follow

the bends and curves of the eaves and ground. 

24. Downspout shoe—The bottom downspout

gooseneck that directs the water from the downspout

to the extension or splash block at the grade. 

25. Downspout strap—Strap used to secure the

downspout to the side of the house. 

26. Drain tile—A tube or cylinder that is normally

installed around the exterior perimeter of the

foundation footings that collects and directs ground

water away from the foundation of the house. The tile

can be individual sections of clay or asphalt tubing or,

in more recent construction, a perforated-plastic drain

tile that is approximately 4 inches in diameter. The

drain tile leads either towards a sump or to an exterior

discharge away from the house. 

27. Entrance canopy—A small overhanging roof that

shelters the front entrance.

28. Entrance stoop—An elevated platform constructed of

wood framing or masonry at the front entry that

allows visitors to stand above or out of the elements.

The platform should be wide enough to allow

someone to stand on the platform while opening an

outward swinging door such as a storm door even if

one is not present. 

29. Exterior siding—The decorative exterior finish on a

house. Its primary function is to protect the shell of

the house from the elements. The choice of siding

materials varies widely to include wood, brick, metal,

vinyl, concrete, stucco, and a variety of manufactured 

compositions such as compressed wood, compressed

cellulose (paper), fiber-reinforced cement, and

synthetic stucco. 

30. Fascia—The visible flat front board that caps the

rafter tail ends and encloses the overhang under the

eave that runs along the roof edge. The gutter is

usually attached at this location. 

31. Fascia/rake board—The visible flat front board that

caps the rafter tail ends and encloses the overhang

under the eave that runs along the roof edge and at

the edge of the roofing at the gables. The gutter is

usually attached to this board at the eaves. 

32. Finish flooring (not shown)—The final floor covering

inside the living space of a house. The most common

types of finishes are carpeting; hardwood flooring;

ceramic, composite, or laminate stone tile; parquet

panels; or vinyl sheet flooring.

33. Finished grade line—A predetermined line indicating the

proposed elevation of the ground surface around a

building.

34. Firebox—The cavity in the open face of the fireplace

in which the fire is maintained. The firebox leads

directly to the fireplace flue. The firebox is constructed of

fire or refractory brick set in fireclay or reinforced

mortar in traditional masonry fireplaces. The firebox

may also be constructed of metal or ceramic-coated

metal panels in more modern prefabricated fireplaces.

The walls of the firebox are usually slanted toward the

living space both to direct smoke up toward the flue

and to reflect heat into the room.

35. Fireplace cleanout door—The access door to the ash

pit beneath the fireplace. On a fireplace that is located

inside the house, the cleanout door is usually located

in the lowest accessible level of the house such as the

basement or crawl space. On a fireplace that is located

at the outside of the house, the cleanout door will be

located at the exterior of the chimney. Not all

fireplaces are equipped with a cleanout door.

36. Fireplace hearth—The inner or outer floor of a

fireplace, usually made of brick, tile, or stone.

37. Flashing (not shown)—The building component

used to connect and cover portions of a deck, roof, or

siding material to another surface such as a wall, a

chimney, a vent pipe, or anywhere that runoff is

heavy or where two dissimilar materials meet. The

flashing is mainly intended to prevent water entry and

is usually made of rubber, tar, asphalt, or various metals.

38. Floor joists—The main subfloor framing members

that support the floor span. Joists are usually made of

engineered wood I-beams or 2×8 or larger lumber. 

39. Foundation footing—The base on which the

foundation walls rests. The foundation is wider than

the foundation wall to spread out the load it is

bearing and to help prevent settling.

40. Foundation wall—The concrete block, concrete slab

or other nonwood material that extends below or

Healthy Housing Reference Manual 6-3
partly below grade, which provides support for

exterior walls and other structural pans of the building. 

41. Framing studs—A 2×4 or 2×6 vertical framing

member used to construct walls and partitions,

usually spaced 12 to 24 inches apart. 

42. Gable framing—The vertical and horizontal framing

members that make up and support the end of a building

as distinguished from the front or rear side. A gable is

the triangular end of an exterior wall above the eaves.

43. Garage door—The door for the vehicle passage into

the garage area. Typical garage doors consist of

multiple jointed panels of wood, metal, or fiberglass. 

44. Girder—A large beam supporting floor joists at the same

level as the sills. A larger or principal beam used to support

concentrated loads at isolated points along its length.

45. Gravel fill—A bed of coarse rock fragments or

pebbles that is laid atop the existing soil before

pouring the concrete slab. The gravel serves a dual

purpose of breaking surface tension on the concrete

slab and providing a layer that interrupts capillary

action of subsurface moisture from reaching the

concrete slab. Typically, a polyethylene sheeting will

be installed between the gravel fill and the concrete

slab for further moisture proofing.

46. Gutter—A channel used for carrying water run-off.

Usually located at the eaves of a house and connected

to a downspout. The primary purpose of the gutters

and downspouts is to carry roof water run-off as far

away from the house as possible. 

47. Insulation—A manufactured or natural material that

resists heat flow that is installed in a house’s shell to

keep the heat in a house in the winter and the

coolness in the house in the summer. The most

common form of insulation is fiberglass, whether in

batts or blown-in material, along with cellulose, rigid

foam boards, sprayed-in foam, and rock wool.

48. Jack/king stud—The framing stud, sometimes called

the trimmer, that supports the header above a

window, door, or other opening within a bearing wall.

Depending on the size of the opening, there may be

several jack studs on either side of the opening.

49. Mantel—The ornamental or decorative facing around

a fireplace including a shelf that is attached to the

breast or backing wall above the fireplace.

50. Moisture/vapor barrier—A nonporous material, such

as plastic or polyethylene sheeting, that is used to

retard the movement of water vapor into walls and

attics and prevent condensation in them. A vapor

barrier is also installed in crawl space areas to prevent

moisture vapor from entering up through the ground.

51. Newel post—The post at the top and bottom of the

handrails and anywhere along the stair run that

creates a directional change in the handrails is called

the newel post. The newel post is securely anchored

into the underlying floor framing or the stair stringer

to provide stability to the handrails.

52. Reinforcing lath—A strip of wood or metal attached

to studs and used as a foundation for plastering,

slating or tiling. Lath has been replaced by gypsum

board in most modern construction.

53. Ridge board/beam—The board placed on edge at the

top-most point of the roof framing, into which the

upper ends of the rafters are joined or attached.

54. Roofing—The finished surface at the top of the house

that must be able to withstand the effects of the

elements (i.e., wind, rain, snow, hail, etc.). A wide

variety of materials are available, including asphalt

shingles, wood shakes, metal roofing, ceramic and

concrete tiles, and slate, with asphalt shingles making

up the bulk of the material used.

55. Roof rafters—Inclined structural framing members

that support the roof, running from the exterior wall

the to the ridge beam. Rafters directly support the

roof sheathing and create the angle or slope of the roof. 

56. Roof sheathing—The material used to cover the

outside surface of the roof framing to provide lateral

and rack support to the roof, as well as to provide a

nailing surface for the roofing material. This material

most commonly consists of plywood OSB or

horizontally laid wood boards. 

57. Sidewalk—A walkway that provides a direct, allweather approach to an entry. The sidewalk can be

constructed of poured concrete, laid stone, concrete

pavers, or gravel contained between borders or curbs.

6-4 Housing Structure
58. Sill plate—The horizontal wood member that is

anchored to the foundation masonry to provide a

nailing surface for floors or walls built above.

59. Silt fabric—A porous fabric that acts as a barrier

between the backfilled soil (see backfill) and the gravel

surrounding the drain tile. This barrier prevents soil

particles from blocking the movement of groundwater

to the drain tile.

60. Soffit/lookout block—Rake cross-bracing between

the fly rafters and end gable rafters that the soffit is

nailed to.

61. Stair rail—A sturdy handhold and barrier that follows

the outside, and sometimes inside, perimeter of the

stairs. The stair rail is used to prevent falls and to

provide a means of additional support when walking

up or down the stairs.

62. Stair riser—The vertical boards that close the space

between each stair tread on a set of stairs (see stair

stringer and stair tread).

63. Stair stringer—The supporting members in a set of

stairs that are cut or notched to accept the individual

treads and risers (see stair riser and stair tread).

64. Stair tread—The horizontal board in a stairway that

is walked upon (see stair riser and stair stringer).

65. Subfloor—Boards or plywood, installed over joists,

on which the finish floor rests. 

66. Support post—A vertical framing member usually

designed to carry or support a beam or girder. In

newer construction a metal lally (pronounced “lolly”)

column is commonly used, as well as 4×4- or 6×6-

inch wood posts.

67. Tar—Otherwise known as asphalt, tar is a very thick,

dark brown/black substance that is used as a sealant or

waterproofing agent. It is usually produced naturally

by the breakdown of animal and vegetable matter that

has been buried and compressed deep underground.

Tar is also manufactured—a hydrocarbon by-product

or residue that is left over after the distillation of

petroleum. It is commonly used as a sealant or patch for

roof penetrations, such as plumbing vents and chimney

flashing. Tar is also used as a sealer on concrete and

masonry foundation walls before they have been

backfilled.

68. Termite shield—A metal flashing that is installed

below the sill plate that acts as a deterrent to keep

termites from reaching the sill plate. 

69. Top plate—The topmost horizontal framing members

of a framed wall. Most construction practices require

the top plate to be doubled in thickness.

70. Wainscoting—The wooden paneling of the lower

part of an interior wall up to approximately waistheight or between 36 and 48 inches from the floor.

71. Wall insulation—A manufactured or natural material

that resists heat flow that is installed in a house’s shell

to keep the heat in a house in the winter and the

coolness in the house in the summer. Fiberglass batts

are the most common form of wall insulation.

72. Wall sheathing—The material used to cover the

outside surface of the wall framing that provides lateral

and shear support to the wall as well as a nailing

surface for the exterior siding.

73. Window casing/trim—The finish trim details around

the perimeter of the window on the interior finished wall. 

74. Window cripple—Short studs placed between the

header and a top plate or between a sill and sole plate.

75. Window frame/jamb—The top and sides of the

window, to include the wall framing and the actual

window frame and trim.

76. Window header—A beam placed perpendicular to

wall studs above doors, windows, or other openings to

carry the weight of structural loads above the window

or door. 

77. Window sash—The framework that holds the glass in

a door or window.

78. Window well (not shown)—An excavation around a

basement window that prevents the surrounding soils

from collapsing into the window. The window well

surround is normally constructed of formed

corrugated galvanized metal, built-up masonry, or

pressure-treated wood. 

Healthy Housing Reference Manual 6-5
Key to Figure 6.2 (Old Housing Terminology)

Fireplace

1. Chimney—A vertical masonry shaft of reinforced

concrete or other approved noncombustible, heat

resisting material enclosing one or more flues. It

removes the products of combustion from solid,

liquid or gaseous fuel.

2. Flue liner—The flue is the hole in the chimney. The

liner, made of terra cotta or metal, protects the brick

from harmful smoke gases.

3. Chimney cap—This top is generally of concrete. It

protects the brick from weather.

4. Chimney flashing—Sheet metal flashing provides a

tight joint between chimney and roof.

5. Firebrick—An ordinary brick cannot withstand the

heat of direct fire, and so special firebrick is used to

line the fireplace. In newer construction, fireplaces are

constructed of prefabricated metal inserts.

6. Ash dump—A trap door to let the ashes drop to a pit

below, where they may be easily removed.

7. Cleanout door—The door to the ash pit or the bottom of

a chimney through which the chimney can be cleaned.

8. Chimney breast—The inside face or front of a

fireplace chimney.

9. Hearth—The floor of a fireplace that extends into the

room for safety purposes.

Roof

10. Ridge—The top intersection of two opposite

adjoining roof surfaces.

11. Ridge board—The board that follows along under

the ridge.

12. Roof rafters—The structural members that support

the roof.

6-6 Housing Structure

Figure 6.2. Housing Structure and Terminology, Typical House Built Between 1950 and 1980 [2]
13. Collar beam—Not a beam at all; this tie keeps the

roof from spreading and connects similar rafters on

opposite sides of the roof.

14. Roof insulation—An insulating material (usually rock

wool or fiberglass) in a blanket form placed between

the roof rafters to keep a house warm in the winter

and cool in the summer.

15. Roof sheathing—The boards that provide the base

for the finished roof. In newer construction, roof

sheathing is composed of sheets of plywood, or

oriented strand board (OSB).

16. Roofing—The wood, asphalt or asbestos shingles—or

tile, slate, or metal—that form the outer protection

against the weather.

17. Cornice—A decorative element made of molded

members, usually placed at or near the top of an

exterior or interior wall.

18. Gutter—The trough that gathers rainwater from a roof.

19. Downspout—The pipe that leads the water down

from the gutter.

20. Storm sewer tile—The underground pipe that

receives the water from the downspouts and carries it

to the sewer. In newer construction, plastic-type

material have replaced tile. 

21. Gable—The triangular end of a building with a

sloping roof.

22. Barage board—The fascia or board at the gable just

under the edge of the roof.

23. Louvers—A series of slanted slots arranged to keep

out rain, yet allow ventilation.

Walls and Floors

24. Corner post—The vertical member at the corner of

the frame, made up to receive inner and outer covering

materials.

25. Studs—The vertical wood members of the house,

usually 2×4s at minimum and spaced every 16 inches.

26. Sill—The board that is laid first on the foundation,

and on which the frame rests.

27. Plate—The board laid across the top ends of the

studs to hold them even and tight.

28. Corner bracing—Diagonal strips to keep the frame

square and plumb.

29. Sheathing—The first layer of outer wall covering

nailed to the studs.

30. Joist—The structural members or beams that hold up

the floor or ceiling, usually 2×10s or 2×12s spaced 

16 inches apart.

31. Bridging—Cross-bridging or solid. Members at the

middle or third points of joist spans to brace one to

the next and to prevent them from twisting.

32. Subflooring—Typically plywood or particle wood

that is laid over the joists.

33. Flooring paper—A felt paper laid on the rough floor

to stop air infiltration and, to some extent, noise.

34. Finish flooring—Hardwood, of tongued and grooved

strips, carpet, or vinyl products (tile, linoleum).

35. Building paper or sheathing—Paper or plasticized

material placed outside the sheathing, not as a vapor

barrier, but to prevent water and air from leaking in.

Building paper is also used as a tarred felt under

shingles or siding to keep out moisture or wind.

36. Beveled siding—Sometimes called clapboards, with a

thick butt and a thin upper edge lapped to shed

water. In newer construction, vinyl, aluminum, or

fiber cement siding and stucco are more prevalent.

37. Wall insulation—A blanket of wool or reflective foil

placed inside the walls.

38. Metal lath—A mesh made from sheet metal onto

which plaster or other composite surfacing materials

can be applied. In newer construction, plaster

sheetrock 4-×8-foot sheets have replaced lath.

Foundation and Basement 

39. Finished grade line—The top of the ground at the

foundation.

40. Foundation wall—The wall of poured concrete

(shown) or concrete blocks that rests on the footing

and supports the remainder of the house.

Healthy Housing Reference Manual 6-7
41. Termite shield—A metal baffle to prevent termites

from entering the frame.

42. Footing—The concrete pad that carries the entire

weight of the house upon the earth.

43. Footing drain tile—A pipe with cracks at the joints,

or perforated plastic pipe to allow underground water

to drain away before it gets into the basement.

44. Basement floor slab—The 4- or 5-inch layer of

concrete that forms the basement floor.

45. Gravel fill—Placed under the slab to allow drainage

and to guard against a damp floor.

46. Girder—A main beam upon which floor joists rest.

Usually of steel, but also of wood.

47. Backfill—Earth, once dug out, that has been replaced

and tamped down around the foundation.

48. Areaway—An open space to allow light and air to a

window. Also called a light well.

49. Area wall—The wall, of metal or concrete, that forms

the open area.

Windows and Doors

50. Window—An opening in a building for admitting

light and air. It usually has a pane or panes of glass

and is set in a frame or sash that is generally movable

for opening and shutting.

51. Window frame—The lining of the window opening.

52. Window sash—The inner frame, usually movable,

that holds the glass.

53. Lintel—The structural beam over a window or door

opening.

54. Window casing—The decorative strips surrounding a

window opening on the inside.

Stairs and Entry

55. Entrance canopy—A roof extending over the

entrance door.

56. Furring—Falsework or framework necessary to bring

the outer surface level to the inner surface.

57. Stair tread—The horizontal part of a step that the

foot hits when climbing up or down the stairs.

58. Stair riser—The vertical board connecting one tread

to the next.

59. Stair stringer—The sloping board that supports the

ends of the steps.

60. Newel—The post that terminates the railing.

61. Stair rail—The bar used for a handhold when using

the stairs.

62. Balusters—Vertical rods or spindles supporting a rail.

Foundation

The word “foundation” is used to mean

• construction below grade, such as footings, cellar,

or basement;

• the composition of the earth on which the

building rests; and

• special construction, such as pilings and piers used

to support the building.

The foundation bed may be composed of solid rock,

sand, gravel, or unconsolidated sand or clay. Rock, sand,

or gravel are the most reliable foundation materials.

Figure 6.3 shows the three most common foundations for

homes. Unconsolidated sand and clay, though found in

many sections of the country, are not as desirable for

foundations because they are subject to sliding and

settling [1]. Capillary breaks have been identified as a key

way of reducing moisture incursion in new construction [3].

The footing distributes the weight of the building over a

sufficient area of ground to ensure that the foundation

walls will stand properly. Footings are usually concrete;

however, in the past, wood and stone have been used.

Some older houses were constructed without footings.

Although it is usually difficult to determine the condition

of a footing without excavating the foundation, a footing

in a state of disrepair or lack of a footing will usually be

indicated either by large cracks or by settlement in the

foundation walls. This type of crack is called a “Z” crack.

Foundation wall cracks are usually diagonal, starting from

the top, the bottom, or the end of the wall (Figure 6.4).

6-8 Housing Structure
Cracks that do not extend to at least one edge of the wall

may not be caused by foundation problems. Such wall

cracks may be due to other structural problems and

should also be reported. 

The foundation walls support the weight of the structure

and transfer this weight to the footings. The foundation

walls may be made of stone, brick, concrete, or concrete

blocks. The exterior should be moisture proofed with

either a membrane of waterproof material or a coating of

portland cement mortar. The membrane may consist of

plastic sheeting or a sandwich of standard roofing felt

joined and covered with tar or asphalt. The purpose of

waterproofing the foundation and walls is to prevent

water from penetrating the wall material and leaving the

basement or cellar walls damp. 

Holes in the foundation

walls are common in many

old houses. These holes

may be caused by missing

bricks or blocks. Holes and

cracks in a foundation wall

are undesirable because

they make a convenient

entry for rats and other

rodents and also indicate

the possibility of further

structural deterioration.

Basement problems are a

major complaint of

homeowners [4–9].

Concrete is naturally

porous (12%–18% air).

When it cures, surplus

water creates a network of

interconnected capillaries.

These pores let in liquid

water, water vapor, and

radon gas. Like a sponge,

concrete draws water from

several feet away. As concrete ages, the pores get bigger as

a result of freezing, thawing, and erosion.

Concrete paints, waterproofing sealers, or cement coatings

are a temporary fix. They crack or peel and cannot stop

gases such as water vapor and radon.

Damp basement air spreads mold and radon through the

house. Efflorescence (white powder stains) and musty

odors are telltale signs of moisture problems. 

Basement remodeling traps invisible water vapor, causing

mold and mildew. Most basements start leaking within

10 to 15 years. The basement walls and floors should be

sealed and preserved before they deteriorate. The basement

floor should be concrete placed on at least 6 inches of

gravel. The gravel distributes groundwater movement

under the concrete floor, reducing the possibility of the

water penetrating the floor. A waterproof membrane, such as

plastic sheeting, should be laid before the concrete is

placed for additional protection against flooding and the

infiltration of radon and other gases.

The basement floor should be gradually, but uniformly,

sloped from all directions toward a drain or a series of

drains. These drains permit the basement or cellar to drain if

it becomes flooded.

Healthy Housing Reference Manual 6-9

Figure 6.4. Foundation Cracks [4]

Figure 6.3. Foundation [3]
Water or moisture marks on the floor and walls are signs

of ineffective waterproofing or moisture proofing. Cellar

doors, hatchways, and basement windows should be

weather-tight and rodent-proof. A hatchway can be inspected

by standing at the lower portion with the doors closed; if

daylight can be seen, the door needs to be sealed or repaired.

Vapor Barriers

Crawl Space Vapor Barriers

Throughout the United States, even in desert areas, there

is moisture in the ground from groundwater being

absorbed. Even in an apparently dry crawl space, a large

amount of water is entering. The moisture is drying out

as fast as it is entering, which causes high moisture levels

in the crawl space and elsewhere in the house. A solid

vapor barrier is recommended in all crawl spaces and

should be required if moisture problems exist [10]. This

vapor barrier, if properly installed, also reduces the

infiltration of radon gas. Of course, if the moisture is

coming from above ground, a vapor barrier will collect

and hold the moisture. Therefore, any source of moisture

must be found and eliminated. The source may be as

obvious as sweating pipes, or may be more difficult to

spot, such as condensation on surfaces. The solution can

be as simple as applying insulation to exposed sections of

the piping or complex enough to require power exhaust

fans and the addition of insulation and vapor barriers. 

The more common causes of moisture problems in a new

home are moisture trapped within the structure during

construction and a continuing source of excess moisture

from the basement, crawl space, or slab. To resolve this

potential problem, 6-mil plastic sheets should be laid as

vapor barriers over the entire crawl space floor. The sheets

should overlap each other by at least 6 inches and should

be taped in place. The plastic should extend up the

perimeter walls by about 6 inches. The plastic sheets

should be attached to the interior walls of the crawl space

with mastic or batten strips. All of the perimeter walls

should be insulated, and insulation should be between the

joists at the top of the walls. Vents, which may need to be

opened in the late spring and closed in the fall, should

not be blocked. If not properly managed, moisture

originating in the crawl space can cause problems with

wood flooring and create many biologic threats to health

and property. A properly placed vapor barrier can prevent

or reduce problem moisture from entering the home. 

Vapor Barriers for Concrete Slab Homes

Strip flooring and related products should be protected

from moisture migration by a slab. Proper on-grade or

above-grade construction requires that a vapor barrier be

placed beneath the slab. Moisture tests should be done to

determine the suitability of the slab before installing

wood products. A vapor barrier equivalent to 4- or 6-mil

polyethylene should be installed on top of the slab to further

protect the wood products and the residents of the home.

Wall and Ceiling Vapor Barriers

Wall and ceiling vapor barriers should go on the heated

side of the insulation and are necessary in cold climates.

Water vapor flows from areas of high pressure (indoors in

winter) through the wall to an area of low pressure

(outdoors in winter). People and their pets produce

amazing quantities of water vapor by breathing. Additional

moisture in considerable quantities is created in the home

from everyday activities such as washing clothes, cooking,

and personal hygiene. The purpose of the vapor barrier is

to prevent this moisture from entering the wall and freezing,

then draining, causing damage. In addition, wet insulation has

very little insulating value. Insulation with the vapor

barrier misplaced will allow the vapor to condense in the

insulation and then freeze. In cold climates, this ice can

actually build up all winter and run out on the floor in

the spring. Such moisture buildup blisters paint, rots

sheathing, and destroys the insulating value of insulation. 

House Framing

Many types of house-framing systems are found in

various sections of the country; however, most framing

systems include the elements described in this section.

Foundation Sills

The purpose of the sill is to provide support or a bearing

surface for the outside walls of the building. The sill is the

first part of the frame to be placed and rests directly on

the foundation wall. It is often bolted to the foundation

wall by sill anchors. In many homes, metal straps are

cemented into the foundation wall that are bent around

and secured to the sill. It is good practice to protect the

sill against termites by extending the foundation wall to at

least 18 inches above the ground and using a noncorroding

metal shield continuously around the outside top of the

foundation wall.

Flooring Systems

The flooring system is composed of a combination of

girders, joists, subflooring, and finished flooring that may

be made up of concrete, steel, or wood. Joists are laid

perpendicular to the girders, at about 16 inches on center, and

the subflooring is attached to them. If the subfloor is wood, it

may be nailed, glued, or screwed at either right angles or

diagonally to the joists. Many homes are built with wood

I-joists or trusses rather on than solid wood joists.

6-10 Housing Structure
In certain framing systems, a girder supports the joists

and is usually a larger section than the joists it supports.

Girders are found in framing systems where there are no

interior bearing walls or where the span between bearing

walls is too great for the joists. The most common application

of a girder is to support the first floor. Often a board known

as a ledger is applied to the side of a wood girder or beam

to form a ledge for the joists to rest upon. The girder, in

turn, is supported by wood posts or steel “lally columns”

that extend from the cellar or basement floor to the girder.

Studs

For years, wall studs were composed of wood and were

2×4 inches; but, with the demand for greater energy

efficiency in homes, that standard no longer holds true.

Frame studs up to 6 inches wide are used to increase the

area available for placing insulation material. The

increased size in the studs allow for larger spaces between

joists.

There are now alternatives to conventional wood studs,

specifically, insulated concrete forms, structural insulated

panels, light-gauge steel, and combined steel and wood

[11–13]. The advantages of light-gauge steel include the

following: 

• weighs 60% less than equivalent wood units and

has greater strength and durability; 

• is impervious to termites and other damagecausing pests; 

• stays true and does not warp; 

• is noncombustible; and 

• is recyclable. 

The disadvantages of steel include these: 

• steel is an excellent thermal conductor and

requires additional external insulation; 

• as a new product, it is unfamiliar to craftsmen,

engineers, and code officials; and 

• a different type of construction tools are required. 

The combined steel and wood framing system includes

light-gauge steel studs with 6-inch wooden stud pieces

attached to the top and bottom to allow easy attachment

to traditional wood frame materials. 

There are two types of walls or partitions: bearing and

nonbearing. A bearing wall is constructed at right angles

to support the joists. A nonbearing wall, or partition, acts

as a screen or enclosure; hence, the headers in it are often

parallel to the joists of the floor above.

In general, studs, like joists, are spaced 16 inches on

center. In light construction, such as garages and summer

cottages, wider spacing on studs is common.

Openings for windows or doors must be framed in studs.

This framing consists of horizontal members (headers)

and vertical members (trimmers or jack studs). 

Because the vertical spaces between studs can act as flues

to transmit flames in the event of a fire, fire stops are

important in preventing or retarding fire from spreading

through a building by way of air passages in walls, floors,

and partitions. Fire stops are wood obstructions placed

between studs or floor joists to block fire from spreading

in these natural flue spaces.

Interior Walls

Many types of materials are used for covering interior

walls and ceilings, but the principal type is drywall. The

generic term “drywall” is typically used when talking

about gypsum board. It is also called wallboard or referred

to by the brand name Sheetrock. Gypsum board is a sheet

material composed of a gypsum filler faced with paper. In

drywall construction, gypsum boards are fastened to the

studs either vertically or horizontally and then painted.

The edges along the length of the sheet are slightly

recessed to receive joint cement and tape.

Drywall finish, composed of gypsum board, is a material

that requires little, if any, wait for application. Other

drywall finishes include plywood, fiberboard, or wood in

various sizes and forms. Plaster was once quite popular for

interior walls. Plaster is a mixture (usually of lime, sand,

and water) applied in two or three coats to lath to form a

hard-wall surface. A plaster finish requires a base on

which plaster can be spread. Wood lath at one time was

the plaster base most commonly used, but today gypsumboard lath is more popular. Gypsum lath may be

perforated to improve the bond and thus lengthen the

time the plaster can remain intact when exposed to fire.

Building codes in some cities require that gypsum lath be

perforated. Expanded-metal lath also may be used as a

plaster base. Expanded-metal lath consists of sheet metal

slit and expanded to form openings to hold the plaster.

Plaster is applied over the base to a minimum thickness of

1⁄2 inch. Because wood-framing members may dry after

Healthy Housing Reference Manual 6-11
the house is completed, some shrinkage can be expected,

which, in turn, may cause plaster cracks to develop

around openings and in corners. Strips of lath embedded

in the plaster at these locations prevent cracks. Bathrooms

have unique moisture exposure problems and local code

approved cement board should be used around bath and

shower enclosures.

Stairways

The purpose of stairway dimension standards is to ensure

adequate headroom and uniformity in riser and tread size.

Interior stairways (Figure 6.5) should be no less than

44 inches wide. The width of a stairway may be reduced

to 36 inches when permitted by local or state code in

one- and two-family dwellings. Stairs with closed risers

should have maximum risers of 81⁄4 inches and minimum

treads of 9 inches plus 1 inch nosing. Basement stairs are

often constructed with open risers. These stairs should

have maximum risers of 81⁄4 inches and minimum treads

of 9 inches plus 1-inch nosing. The headroom in all parts

of the stair enclosure should be no less than 80 inches.

Dimensions of exterior stairways should be the same as

those of interior stairways, except that the headroom

requirement does not apply.

Staircases should have handrails that are between 11⁄4 and

25/8 inches wide, particularly if the staircases have more

than four steps. Handrails should be shaped so they can

be readily grasped for safety and placed so they are easily

accessible. Handrails should be 41/8 inches from the wall

and be 34 to 38 inches above the leading edge of the

stairway treads. Handrails should not end in any manner

or have projections that can snag clothing. 

Windows

The six general classifications of windows (Figure 6.6) are

as follows [1]:

• Double-hung sash windows that move up or

down, balanced by weights hung on chains, ropes,

or springs on each side;

• Casement sash windows that are hinged at the side

and can be hung so they will swing out or in; 

• Awning windows that usually have two or more

glass panes that are hinged at the top and swing

out horizontally; 

• Sliding windows that usually have two or more

glass panes that slide past one another on a

horizontal track; 

• Fixed windows that are generally for increased

light entry and decorative effect; and

• Skylight windows for increased room illumination

and decoration that can be built to open.

The principal parts of a window, shown in threedimensional view in Figure 6.7 and face-on and side view

in Figure 6.8, are the following: 

6-12 Housing Structure

Figure 6.6. Classifications of Windows [1]

Figure 6.5. Interior Stairway [4]
Drip cap—A separate piece of wood projecting over the

top of the window; a component of the window casing.

The drip cap protects against moisture.

Window trough—The cut or groove in which the sash of

the window slides or rests. 

Window sill—The shelf on the bottom edge of a

window, either a projecting part of the window frame or

the bottom of the wall recess that the window fits into. The

sill contains the trough and protects against moisture. 

Recent technological advancements—new materials,

coatings, design, and construction features—make it

possible to choose windows that allow you to balance

winter heating and summer cooling needs without

sacrificing versatility or style. To ensure that windows,

doors, or skylights selected are appropriate for the region

in which they are to be installed, Energy Star

Certification labels include a climate region map.

Some window glass is made of tempered glass to resist

breakage. Some windows are made of laminated glass,

which resists breakage, but if broken produces glass shards

too small to cause injury [14]. The glazing, or glass, can

be a solid glass sheet (single glazed) or have two layers of

glass (double glazed) separated by a spacer. Air trapped

between the glass layers provides some insulation value.

Triple-glazed windows have three pieces of glass, or two

layers of glass with a low

emissivity film suspended

between them. Tripleglazed windows have

advantages where

extremes in weather and

temperature are the

norm. They also can

reduce sound

transmission to a greater

degree than can single- or

double-glazed windows.

Doors

There are many styles of

doors both for exterior

and interior use. Exterior

doors must, in addition

to offering privacy,

protect the interior of the

structure from the

elements. Various parts of

a door are the same as the

corresponding parts of a

window. A door’s

function is best

determined by the material

from which it is made, how it looks, and how it operates.

When doors are used for security, they are typically made

from heavy materials and have durable, effective locks and

hinges. A door that lets in light or allows people to look

out onto the yard, such as a sliding glass door or a french

door, will have multiple panes (also called lights) or be made

almost completely of glass.

Houses have many exterior and interior door options.

Exterior doors are typically far sturdier than interior doors

and need to be weather tight and ensure security for the

home. Exterior doors are also more decorative than most

interior doors and may cost a considerable amount.

Typical exterior doors include front entry doors, back

doors, french doors, dutch doors, sliding glass doors,

patio doors, and garage doors.

French doors and sliding doors are examples of the two

primary ways doors open. French doors swing on hinges;

sliding doors glide along a track. Some doors, such as

dutch doors, have tops and bottoms that swing open

independently.

Most doors are made of wood or materials made to look

like wood. Fiberglass composite and steel doors often have

Healthy Housing Reference Manual 6-13

Figure 6.8. Window Details [3]

Figure 6.7. Three Dimensional View of a Window [1]
polymer or vinyl coatings embossed with wood grain;

some even have cellulose-based coatings that can be

stained like wood doors. Wood doors are made from

every kind of wood imaginable, hardwoods being the

most durable and elegant. Wood doors insulate better

than glass; composite and steel doors provide even more

insulation and durability, as well as better security than

does wood.

Garage Doors

Garage doors open in almost any configuration needed

for the design of the home. Installing most garage doors is

complex and dangerous enough that only a building

professional should attempt it. Garage doors often include

very strong springs that can come loose and severely

injure the unsuspecting installer. Garage door springs are

under extreme tension because of the heavy loads they

must lift, which makes them dangerous to adjust. A

garage door may suffer from any of several problems. The

most common problem is that the door becomes difficult

to lift and lower. This may be something that can be

resolved with simple adjustments, or it may be more

serious. If the door is connected to an electric opener, the

opener mechanism can be disconnected from the door by

pulling the release cord or lever. If the door then works

manually, the problem is with the electric opener. A door

that seems unusually hard to lift may have a problem with

spring tension. Wood doors should be properly painted or

stained both outside and inside. If only the outside of a

garage door is finished, the door may warp and moisture

may cause the paint to peel.

Rules issued by the Consumer Product Safety

Commission on December 3, 1992, specify entrapment

protection requirements for garage doors [15]. 

The rules require that residential garage door openers

contain one of the following: 

• An external entrapment protection device, such as

an electric eye that sees an object obstructing the

door without having actual contact with the

object. A door-edge sensor is a similar device. The

door-edge sensor acts much like the door-edge

sensors on elevator doors.

• A constant contact control button, which is a

wall-mounted button requiring a person to hold

in the control button continuously for the door to

close completely. If the button is released before

the door closes, the door reverses and opens to the

highest position. 

• A sticker on all newly manufactured garage door

openers warning consumers of the potential

entrapment hazard. The sticker is to be placed near

the wall-mounted control button. 

The variety of exterior door systems has increased

significantly over the past 5 to 10 years. Many combine

several different materials to make a realistic, if not actual

wood, door that provides both beauty and enhanced security.

Exterior House Doors

Exterior door frames are ordinarily of softwood plank,

with the side rabbitted to receive the door in the same

way as casement windows. At the foot is a sill, made of

hardwood or other material, such as aluminum, to

withstand the wear of traffic and sloped down and out to

shed water. Doors often come equipped with door sweeps

to conserve energy. 

The four primary categories of modern exterior doors are

steel, fiberglass, composites, and wood.

Steel—The most common exterior door sold today is

steel. Humidity will not cause a steel door to warp or twist.

Steel doors often have synthetic wood-grain embossed

finishes that accept stain. Just about every steel exterior door

is filled with some type of foam. This foam allows the doors

to achieve R-values almost five times that of an ordinary

wood door. Metal is often used as a veneer frame. In general,

the horizontal members are called rails and the vertical

members are called stiles. Every door has a top and

bottom rail, and some may have intermediate rails. There

are always at least two stiles, one on each side of the door.

Fiberglass—The second most frequently selected exterior

door is fiberglass. Fiberglass doors are similar to steel doors,

but tend to be much more resistant to denting. (Steel

doors can be dented quite easily.) Fiberglass doors also are

stainable and have rich, realistic wood graining. Fiberglass

doors are insulated with foam and have high R-values.

Composite materials—The third most common exterior

door is made of composite materials. These doors often

are of two materials blended together. Their composite

fiber-reinforced core can be twice as strong as wood. This

composite core will not rot, warp, or twist when subjected

to high levels of humidity.

Wood—The last major category of doors is wood. Solid

wood doors range from inexpensive to true works of art.

Their downside is that they can warp and bow if not sealed

properly from humidity and will then fit poorly in their frames. 

6-14 Housing Structure
Other types of wooden doors are described below.

• Batten doors are often found on older homes.

They are made of boards nailed together in

various ways. The simplest is two layers nailed to

each other at right angles, usually with each layer

at 45° to the vertical. Another type of batten door

consists of vertical boards nailed at right angles to

several (two to four) cross strips called ledgers,

with diagonal bracing members nailed between

the ledgers. If vertical members corresponding to

ledgers are added at the sides, the verticals are

called frames. Batten doors are often found in

cellars and other places where appearance is not a

factor and economy is desired.

• Solid flush doors are perfectly flat, usually on both

sides, although occasionally they are made flush

on one side and are paneled on the other. Flush

doors sometimes are solid planking, but they are

commonly veneered and possess a core of small

pieces of white pine or other wood. These pieces 

are glued together with staggered end joints. Along

the sides, top, and bottom are glued 3⁄4 inch edge

strips of the same wood, used to create a smooth

surface that can be cut or planed. The front and

back faces are then covered with a 1/8-inch to

1⁄4-inch layer of veneer. Solid flush doors may be

used on both the interior and exterior.

• Hollow-core doors, like solid flush doors, are

perfectly flat; but, unlike solid doors, the core

consists mainly of a grid of crossed wooden slats

or some other type of grid construction. Faces are

three-ply plywood instead of one or two plies of

veneer, and the surface veneer may be any species

of wood, usually hardwood. The edges of the core

are solid wood and are made wide enough at the

appropriate places to accommodate locks and

butts. Doors of this kind are considerably lighter

than solid flush doors. Hollow-core doors are

usually used as interior doors.

Many doors are paneled, with most panels consisting of

solid wood or plywood, either raised or flat, although

exterior doors frequently have one or more panels of glass.

One or more panels may be used, although some have as

many as nine panels. Paneled doors may be used both on

the interior or exterior.

The frame of a doorway is the portion to which the door

is hinged. It consists of two side jambs and a head jamb,

with an integral or attached stop against which the

door closes.

Roof Framing

Rafters

One of a series of structural roof members spanning from

an exterior beam or a ridge board. Rafters serve the same

purpose for the roof as joists do for floors, that is,

providing support for sheathing and roofing material.

They are typically placed on 16-inch centers. 

Collar Beam

Collar beams are ties between rafters on opposite sides of

the roof. If the attic is to be used for rooms, the collar

beam may double as the ceiling joist. 

Purlin

A purlin is the horizontal member that forms the support

for the rafters at the intersection of the two slopes of a

gambrel roof.

Ridge Board

A ridge board is a horizontal member that forms a lateral

tie to make rafters secure.

Hip

A hip is like a ridge, except that it slopes. It is the intersection

of two adjacent, rather than two opposite, roof planes.

Roof Sheathing

The manner in which roof sheathing is applied depends

upon the type of roofing material. Roof boards may vary

from tongue-and-groove lumber to plywood panels.

Dormer

The term “dormer window” is applied to all windows in

the roof of a building, whatever their size or shape.

Roofs

Asphalt Shingle

The principal damage to asphalt shingle roofs is caused by

strong winds on shingles nailed close to the ridge line of

the roof. Usually the shingles affected by winds are those

in the four or five courses nearest the ridge and in the

area extending about 5 feet down from the edge or rake of

the roof.

EPDM

Ethylene propylene diene monomer (EPDM) is a singleply roofing system. EPDM allows extreme structural

movement without splitting or cracking and retains its

pliability in a wide range of temperatures.

Healthy Housing Reference Manual 6-15
Asphalt Built-up Roofs

Asphalt roofs may be unsurfaced (a coating of bitumen

being exposed directly to the weather) or surfaced (with

slag or gravel embedded in the bituminous coating).

Using surfacing material is desirable as a protection

against wind damage and the elements. This type of roof

should have enough pitch to drain water readily.

Coal Tar Pitch Built-up Roofs

This type of roof must be surfaced with slag or gravel. A

coal tar pitch built-up roof should always be used on a

deck pitched less than 1⁄2 inch per foot; that is, where

water may collect and stand. This type of roof should be

inspected on completion, 6 months later, and then at least

once a year, preferably in the fall. When the top coating

of bitumen shows damage or has become badly

weathered, it should be renewed.

Slate Roofs

The most common problem with slate roofs is the

replacement of broken slates. Otherwise, slate roofs

normally render long service with little or no repair.

Tile Roofs

Replacement of broken shingle tiles is the main

maintenance problem with tile roofs. This is one of the most

expensive roofing materials. It requires very little maintenance

and gives long service.

Copper Roofs

Usually made of 16-ounce copper sheeting and applied to

permanent structures, copper roofs require practically no

maintenance or repair when properly installed. Proper

installation allows for expansion and contraction with

changes in temperature.

Galvanized Iron Roofs

The principal maintenance for galvanized iron roofs

involves removing rust and keeping the roof well painted.

Leaks can be corrected by renailing, caulking, or replacing

all or part of the sheet or sheets in disrepair. 

Wood Shingle Roofs

The most important factors of wood shingle roofs are their

high pitch and exposure, the character of wood, the kind of

nails used and the preservative treatment given the

shingles. At one time these roofs were treated with

creosote and coal tar preservatives. Because they are made

from a flammable material, insurance companies

frequently have higher rates for wood shingle roofs.

Roof Flashing

Valleys in roofs (such as gambrel roofs, which have two

pitches designed to provide more space on upper floors

and are steeper on their lower slope and flatter toward the

ridge) that are formed by the junction of two downward

slopes may be open or closed. In a closed valley, the slates,

tiles, or shingles of one side meet those of the other, and

the flashing below them may be comparatively narrow. In

an open valley, the flashing, which may be made of zinc,

copper, or aluminum, is laid in a continuous strip,

extending 12 to 18 inches on each side of the valley, while

the tiles or slates do not come within 4 to 6 inches of it.

The ridges built up on a sloping roof where it runs down

against a vertical projection, like a chimney or a skylight,

should be weatherproofed with flashing. Failure of roof

flashing is usually due to exposed nails that have come

loose. The loose nails allow the flashing to lift, resulting

in leakage. Flashings made of lead or coated with lead

should not be used. 

The use of a thin, self-sticking rubber ice and water shield

under flashings and on the edge of roofs is now common

practice. The shield helps reduce leakage and ice backup

in cold climates, preventing serious damage to this part of

the home. 

Gutters and Leaders

Gutters and leaders should be of noncombustible

materials and should not be made of lead, lead-coated

copper, or any other formulation containing lead. They

should be securely fastened to the structure and spill into

a storm sewer, not a sanitary sewer, if the neighborhood

has one. When there is no storm sewer, a concrete or

stone block placed on the ground beneath the leader

prevents water from eroding the lawn. This stone block is

called a splash block. Gutters should be checked every

spring and fall and cleaned when necessary. Gutters must

be placed or installed to ensure that water drainage is

taken away from the foundation of the house. Soil around

the home should be graded in a manner that also drains

the water away from the foundation of the home.

Exterior Walls and Trim

Exterior walls are enclosure walls whose purpose is not

only to make the building weather tight, but to also allow

the building to dry out. In most one- to three-story

buildings they also serve as bearing walls. These walls may

be made of many different materials (Figure 6.9). 

Brick is often used to cover framed exterior walls. In this

situation, the brick is only one course thick and is called a

brick veneer. It supports nothing but itself and is kept

6-16 Housing Structure
from toppling by ties

connected to the frame

wall. 

In frame construction,

the base material of the

exterior walls is called

sheathing. The sheathing

material may be squareedge, shiplap,

tongue-and-groove

boards, or plywood or

oriented strand board

(OSB). Sheathing, in

addition to serving as a

base for the finished

siding material, stiffens

the frame to resist sway

caused by wind. It is for

this reason that sheathing

is applied diagonally on

frame buildings. Its role

is to brace the walls

effectively to keep them

from racking.

Many types of sidings,

shingles, and other

exterior coverings are applied over the sheathing. Vinyl

siding; wood siding; brick, cedar, and other wood shingles

or shakes; asphalt; concrete; clapboard; common siding

(called bevel siding); composition siding; cement shingles;

fiber cement (e.g., Hardiplank); and aluminum siding are

commonly used for exterior coverings. In older homes,

asbestos-cement siding shingles can still be found as an

exterior application or underneath various types of

aluminum or vinyl siding. 

Clapboard and common siding differ only in the length

of the pieces. Composition siding is made of felt, grit,

and asphalt, which are often shaped to look like brick.

Asbestos and cement shingles, which were used until the

early 1970s, are rigid and produce a siding that is fireresistant, but also a health hazard. Cedar wood shingles

and aluminum are manufactured with a backer board that

gives insulation and fire-resistant qualities. Vinyl siding is

manufactured from polyvinyl chloride (PVC), a building

material that has replaced metal as the prime material for

many industrial, commercial, and consumer products.

PVC has many years of performance as a construction

material, providing impact-resistance, rigidity, and

strength. The use of vinyl siding is not without controversy,

because PVC is known to cause cancer in humans.

Accidental fires in vinyl-sided buildings are more dangerous

because vinyl produces toxic vapors when heated.

Putting It All Together

The next section shows a home being built by Habitat for

Humanity. 

This small, one-family home represents all of the

processes that would also be used for a far more expensive

and elaborate dwelling. The homebuilding demonstrated

by the following pictures was by an industrial arts class to

educate and train a new generation of construction specialists

and homebuilders. 

A. 

The foundation trench for a new home has horizontal metal

rods, also called reinforcement rods or rebar, to increase the

strength of the concrete. After the concrete hardens, a

perforated pipe 4 to 6 inches in diameter is placed beside it

to collect water and allow it to drain away from the

foundation. This pipe is the footing drain, and the poured

concrete beside it is the footer. The footing drain is

important in removing water from the base of the home. It

also serves the secondary purpose of moisture control in the

home and provides a venting route for radon gas. The holes

dug near the legs of the workers will be filled with concrete

and form the footer that will hold up the porch of the home. 

To assist in preventing capillary action from wicking water

from the foundation to the wooden structure, a polyethylene

sheet is placed over the footer before pouring the concrete

foundation, or building a cinderblock foundation.

Healthy Housing Reference Manual 6-17

Figure 6.9. Wall Framing [4]
6-18 Housing Structure

E. 

Gravel fill is placed outside the finished poured concrete

foundation. This ensures that moisture does not stand

around the foundation for any time. The moisture is routed

to the footing drain for fast dispersal.

B. 

The concrete on top of the footer is leveled to establish a

surface for the foundation of the home. Once the footer has

hardened, the perforated drainage pipe will be laid on the

outside of the poured foundation wall. The reinforcing rods

were positioned in the trench before pouring the concrete.

C. 

Concrete will be poured into this form on top of the footer

to create the foundation of the home. Again, reinforcing rods

are added to ensure that the concrete has both lateral

strength, as well as the strength to support the home. Once

the concrete has hardened and becomes seasoned, the forms

will be removed to reveal the finished poured concrete

foundation over the perforated drainage pipe. Not shown is a

newer technique of using insulating polystyrene forms and

ties in a building foundation.

D. 

Foundations are not always poured concrete, but are often

cinderblock or similar materials that are cemented in place

to form the load-bearing wall. The arrow shows the concrete

chute delivering concrete into the form. Long poles are

pushed into the freshly poured concrete to remove air

pockets that would weaken the foundation. 

Care must be taken to ensure that the forms are

appropriately supported before pouring the concrete. Often

tar, plastic, or other waterproof materials are placed on the

outside of the foundation to the ground level to further

divert moisture from the house to the footing drains.
Healthy Housing Reference Manual 6-19

F. 

A termite shield is established on top of the concrete wall

(foundation) just below the sill of the home. The sill is

typically made of pressure- and insecticide-treated wood to

ensure stability and long life. 

A cinderblock foundation will be used to support the storage

shed attached to the house. Note the potential for

inadvertent sabotage of the termite shield if a shield is not

installed on the top of the cinder block foundation. 

G. 

OSB subfloor, the joist supporting the floor, and the metal

bridging that is used to keep the joist from twisting can be

seen from the crawl space under the home.

If the material used for the flooring or external sheathing of

the home is made of plywood or a composition that is not

waterproof, the material must be protected from rain to

prevent deterioration and germination of mold spores. Some

glues or resins release toxic vapors for years if deterioration

is allowed to begin.

H. 

The flooring material of the

first floor of the home is OSB

applied to the subfloor with

both glue and wood screws.

Where possible, the screws

should extend into the subfloor

and the joist below the subfloor to prevent squeaking.

J. 

The exterior wall

framing is composed of

studs that are 2x6-inch

boards. The horizontal

member extending from

one exterior wall to the

other is called a girder

and is a prime support

for the second floor of the home. The larger studs in the

exterior wall are used both for greater strength and to provide

greater energy efficiency for the home.

The lintels above the windows and doors distribute the

weight of the second floor and roof across the studs that are

located on each side of the openings in the frame.

K. 

The joists above the first floor

are connected to the central

girder of the home by steel

brackets. These brackets

provide a far more effective

alternative than does

toenailing nails to hold the joists in place or to notching the

girder to hold them.

I. 

The interior wall framing is

composed of studs

traditionally referred to as

2×4s. The horizontal member

at the top of the studs is

called a girt or a ribbon. In

this case the builders

have used two 2×4s, placing

one on top of the other.

Because the outside walls

have used studs that are 2×6-inch boards, the girts or

ribbons on top of these are also double 2×6-inch boards.
6-20 Housing Structure

L. 

The subroof or roof

sheathing is applied from

the bottom up with

temporary traction boards

nailed to the subroof to

allow safe installation of the

material. 

The subroof is placed on the rafters up to the ridge board of

the roof. A waterproof material will be added to the subroof

before installing the final roofing material.

M. 

An interior wall is

installed to create

second-floor rooms. 

The subroof has been

installed.

The exterior wood of

the home has been

covered with plastic

sheathing or a

housewrap to protect it

from moisture.

N. 

Flashing material, such

as sheet metal, is

installed at critical

locations to make sure

that water does not

enter the home where

the joints and angles of

a roof meet:

• where the dormer roof meets the roof and the walls 

of the dormer meet the roof,

• where windows penetrate the walls,

• where the vent stack penetrates the roof,

• where the porch roof meets the front wall,

• skylights, and 

• eaves of the house.

O. 

A safety scaffold is standing at the rear of the home, and the

final roofing material has been applied, in addition to the

exterior vinyl siding.
References

1. US Inspect. Glossary of terms. Chantilly, VA: US

Inspect; no date. Available from URL:

http://www.usinspect.com/Glossary/glossary.asp.

2. Center for Disease Control. Housing construction

terminology. In: Basic housing inspection. Atlanta:

US Department of Health and Human Services;1976.

3. Building Science Corporation. Read this before

you design, build, or renovate. Westford, MA:

Building Science Corporation; 2004. 

4. Center for Disease Control. Basic housing

inspection. Atlanta: US Department of Health

and Human Services; 1976.

5. Wagner JD. Drying out a wet basement. New

York: This Old House Ventures, Inc.; no date.

Available from URL: http://www.thisoldhouse.com/

toh/knowhow/interiors/article/

0,16417,220912,00.html.

6. Friedman D. Inspecting foundations for structural

defects. Poughkeepsie, NY: Daniel Friedman;

2001. Available from URL: http://www.inspectny.com/structure/foundation.htm.

7. Association of Bay Area Governments. Foundations:

section 5. Oakland, CA: Association of Bay Area

Governments; 1998. Available from URL:

http://www.abag.ca.gov/bayarea/eqmaps/

fixit/ch5.

8. Crawford CB. CBD-148: foundation

measurements. Ottawa, Ontario, Canada:

National Research Council; 1972. Available from

URL: http://irc.nrc-cnrc.gc.ca/cbd/cbd148e.html.

9. Hamilton JJ. CBD-184: foundations on swelling

or shrinking subsoils. Ottawa, Ontario, Canada:

National Research Council; 1977. Available from

URL: http://irc.nrc-cnrc.gc.ca/pubs/

cbd/cbd184_e.html.

10. US Department of Housing and Urban

Development. Basements and crawl spaces.

Washington, DC: US Department of Housing

and Urban Development; 2000. Available from

URL: http://www.hud.gov/offices/hsg/sfh/

ref/sfhp1-25.cfm.

11. Bateman BW. Light-gauge steel verses

conventional wood framing in residential

construction. J Construction Educ

1997;2(2):99–108.

12. National Association of Home Builders Research

Center. Integrated steel/wood combination

framing. Upper Marlboro, MD: National

Association of Home Builders; no date. Available

from URL: http://www.toolbase.org/

tertiaryT.asp?DocumentID=

4249&CategoryID=1142.

13. Steel Wood Studs. Why use steel wood studs?

Reno, NV: Steel Wood Studs; 2001. 

14. Canadian Mortgage and Housing Corporation.

Understanding window terminology. Ottawa,

Ontario, Canada: Canadian Mortgage and

Housing Corporation; no date. Available from

URL: http://www.cmhc-schl.gc.ca/

en/burema/gesein/abhose/abhose_061.cfm.

15. US Consumer Product Safety Commission. Safety

commission publishes Final Rules for automatic

garage door openers. Washington, DC: US

Consumer Product Safety Commission; 1992.

Available from URL: http://www.cpsc.gov/

cpscpub/prerel/prhtml93/93024.html.

Healthy Housing Reference Manual 6-21

P. 

The front porch of the home is constructed of pressuretreated, insect-resistant lumber. The use of such lumber

should be carefully evaluated with respect to what chemicals

have been used and the potential for human exposure to the

treated wood. Composite wood products and plastic decking

materials, collectively called Trex, are available as an

alternative to pressure-treated wood. A proper hand railing

and balusters will be installed.
Additional Sources of Information

Carmody J, Christian J, Labs K, editors. Builder’s

foundation handbook. Oak Ridge, TN: Oak Ridge National

Laboratory; 1991. 

US Department of Housing and Urban Development.

Basements and crawl spaces. Washington, DC: US

Department of Housing and Urban Development; 2000.

Available from URL: http://www.hud.gov/offices/

hsg/sfh/ref/sfhp1-25.cfm.

6-22 Housing Structure
Chapter 7—Environmental Barriers

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1

Roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2

Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Siding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Fiber Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Brick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Stucco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Vinyl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

Asbestos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-6

Figure 7.1. Sources of Moisture and Air Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1

Figure 7.2. Blown Attic Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Figure 7.3. Depth of Attic Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Figure 7.4. Attic Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Figure 7.5. Brick Structural Defect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-4

Figure 7.6. Corrosion in Piping Resulting From Galvanic Response . . . . . . . . . . . . . . . . . . . . .7-5

Healthy Housing Reference Manual 1

Contents
“The physician can bury his mistakes, but the architect can

only advise his client to plant vines—so they should go as far

as possible from home to build their first buildings.”

Frank Lloyd Wright

New York Times, October 4, 1953

Introduction

Damaging moisture originates not only from outside a

home; it is created inside the home as well. Moisture is

produced by smoking; breathing; burning candles;

washing and drying clothes; and using fireplaces, gas

stoves, furnaces, humidifiers, and air conditioning. Leaks

from plumbing, unvented bathrooms, dishwashers, sinks,

toilets, and garbage disposal units also create moisture

problems because they are not always found before water

damage or mold growth occurs. Figure 7.1 provides an

overview of the sources of moisture and types of air

pollutants that can enter a home. 

Solving moisture problems is often expensive and timeconsuming. The first step is to do a moisture inventory

to eliminate problems in their order of severity. Problems

that are easiest and least expensive to resolve should be

addressed first. For example, many basement leaks have

been eliminated by making sure sump pumps and

downspouts drain away from the house. On the other

hand, moisture seeping though basement or foundation

walls often is very expensive to repair. Eliminating such

moisture is seldom as simple as coating the interior wall,

but often requires expert consultation and excavating

around the perimeter of the house to install or clean

clogged footing drains. Sealing the outside of the

basement walls and coating the exterior foundation wall

with tar or other waterproofing compounds are often the

only solutions to eliminate moisture. 

Moisture condensation occurs in both winter and summer.

The following factors increase the probability of

condensation: 

• Homes that are ineffectively insulated and are not

sealed against air infiltration in cold climates can

result in major moisture problems.

• Cool interior surfaces such as pipes, windows, tile

floors, and metal appliances; air conditioner coils

with poor outside drainage; masonry or concrete

surfaces; toilet tanks; and, in the winter, outside

walls and ceilings can result in moisture buildup

from condensation. If the temperature of an

interior surface is low enough to reach the dew

point, moisture in the air will condense on it and

enhance the growth of mold.

Chapter 7: Environmental Barriers

Figure 7.1. Sources of Moisture and Air Pollutants [1]

Healthy Housing Reference Manual 7-1
• Dehumidifiers used in regions where outside

humidity levels are normally 80% or higher have

a moisture-collecting tank that should be cleaned

and disinfected regularly to prevent the growth of

mold and bacteria. It is best if dehumidifiers have

a drain line continuously discharging directly to

the outside or into a properly plumbed trap. This

is also true in climates where air conditioning

units are used on a full-time or seasonal basis.

Their cooling pans provide an excellent

environment for the growth of allergenic or

pathogenic organisms.

• Moisture removed from clothing by clothes driers

ends up in the dryer vent if it is clogged by lint or

improperly configured. Moisture buildup in this

vent can result in mold growth and, if leakage

occurs, damage to the structure of the home. The

vent over the cooking area of the kitchen also

should be checked routinely for moisture or grease

buildup.

Roof

The control of moisture in a home is of paramount

importance. It is no surprise that moisture control begins

with the design and integrity of the roof. Many types of

surfacing materials are used for roofs-stone, composition

asphalt, plastic, or metal, for example. Some have

relatively short lives and some, such as slate and tile, have

extraordinarily long lives. As in nearly all construction

materials, tradeoffs must be made in terms of cost,

thermal efficiency, and longevity. However, all roofs have

two things in common: the need to shed moisture and

protect the interior from the environment.

When evaluating the roof of a home, the first thing to

observe is the roofline against the sky to see if the roof’s

ridge board is straight and level. If the roofline is not

straight, it could mean that serious deterioration has taken

place in the structure of the home as a result of improper

construction, weight buildup, a deteriorated or broken

ridge beam, or rotting rafters. Whatever the cause, the focus of

an inspection must be to locate the extent of the damage. 

The next area to inspect is around the flashing on the

roof. Flashing is used around any structure that penetrates

the surface of a roof or where the roofline takes another

direction. These areas include chimneys, gas vents, attic

vents, dormers, and raised and lowered roof surfaces. One

of the best ways to locate a leak around flashing is to go

into the attic and look carefully. Leaks often are

discovered when it rains; but if it is not raining, the

underside of the roof can be examined with the attic

lights off for pinpoints of daylight. 

Roofing material should lay relatively flat and should not

wave or ripple. The roof should be checked for missing or

damaged shingles, areas where flashing should be installed,

elevation changes in roof surfaces, and evidence of

decomposing or displaced surfaces around the edge of the

roof [1–3].

1) Is the roofline of the house straight?

2) Are there ripples or waves in the roof?

3) What is the condition of the gutters and downspouts?

4) What is the condition of the boards the gutters are attached to?

5) Does the flashing appear to be separated or damaged?

6) Is there any apparent damage in the attic or can sunlight be seen through the roof?

7) Is there mold or discoloration on the rafters or roof sheathing?

8) Is there evidence of corrosion between the gutter and downspouts and any metal roofing or 

aluminum siding?

9) Do the downspouts route the water away from the base or foundation of the home?

10) Are the gutters covered or free of leaves? Are they sagging or separating from the fascia?

11) Does the gutter provide a mosquito-breeding area by holding water?

Roof Inspection

7-2 Environmental Barriers
Insulation

A house must be able to breathe; therefore, air must not

be trapped inside, but must be allowed to exit the home

with its moisture. Moisture buildup in the home will lead

to both mold and bacteria growth. Figure 7.2 demonstrates

insulation blown into an attic, to a depth of approximately

12 inches (Figure 7.3). Figure 7.4 shows the area

extending from a house under the roof, known as the

soffit. The soffit is perforated so that air can flow into the

attic and up through the ridge vents to ventilate the attic. 

If insulation is too thick or installed improperly, it

restricts proper air turnover in the attic and moisture or

extreme temperatures could result in mold or bacteria

growth, as well as delamination of the plywood and

particleboards and premature aging of the roof’s

subsurface and shingles. 

Care also must be taken in cold climates to ensure that

the insulation has a vapor barrier and that it is installed

face down. When insulation is placed in the walls of a

home, a thin plastic vapor barrier should be placed over

the insulation facing the inside of the home. The purpose

of this vapor barrier is to keep moisture produced inside

the house from compromising the insulation. If the

barrier is not installed, warm, moist air will move through

the drywall and into the insulated wall cavity. When the

air cools, moisture will condense on the fibers of the

insulation making it wet; and, if it is cellulose insulation,

it will absorb and hold the moisture. Wetness reduces the

effectiveness of the insulation and provides a favorable

environment for the growth of bacteria and mold [4,5]. 

Siding

Good siding should be attractive, durable, insect- and

vermin-resistant, waterproof, and capable of holding a

weather-resistant coating. Fire-resistant siding and roofing

are important in many areas where wildfires are common

and are required by many local building codes. 

All exterior surfaces will eventually deteriorate, regardless

of manufacturer warranties or claims. Leaks in the home

from the outside occur in many predictable locations. The

exterior siding or brick should be checked for cracks or

gaps in protective surfaces. Where plumbing, air vents,

electrical outlets, or communication lines extend through

an exterior wall, they should be carefully checked to

ensure an airtight seal around those openings. The

exterior surface of the home has doors, windows, and

Healthy Housing Reference Manual 7-3

Figure 7.2. Blown Attic Insultation 

Figure 7.3. Depth of Attic Insulation 

Figure 7.4. Blown Attic Insultation 
other openings. These openings should be caulked

routinely, and the drainage gutters along the top should

be checked to ensure that they drain properly.

Exterior surface materials include stucco, vinyl, asbestos

shingles, brick, metal (aluminum), fiber cement, exterior

plywood, hardwood, painted or coated wood, glass, and

tile, some of which are discussed in this chapter [6,7].

Fiber Cement

Fiber cement siding is engineered composite-material

products that are extremely stable and durable. Fiber

cement siding is made from a combination of cellulose

fiber material, cement and silica sand, water, and other

additives. Fiber cement siding is fire resistant and useful

in high-moisture areas.

The fiber cement mixture is formed into siding or

individual boards, then dried and cured using superheated

steam under pressure. The drying and curing process

assures that the fiber cement siding has very low moisture

content, which makes the product is stable—no warping

or excessive movement—and its surface good for painting.

Weight is a minor concern with fiber cement products:

they weigh about 11⁄2 times what comparably sized

composite wood products do. Other concerns relate to

cutting fiber cement: cutting produces a fine dust with

microscopic silica fibers, so personal protective equipment

(respirator and goggles) are necessary. In addition, special

tools are needed for cutting. 

Brick

Brick homes may seem on the surface to be nearly

maintenance free. This is true in some cases, but, like all

surfaces, brick also degrades. Although this degradation

takes longer in brick than in other materials, repairing

brick is complex and quite expensive. There are two basic

types of brick homes. One is brick veneer, which is a thin

brick set to the outside of a wooden stud wall. The brick

is not actually the supporting wall. Brick veneer typically

has the same pattern of bricks around the doors and

windows; a true brick wall will have brick arches or heavy

steel plates above the doors and other openings of the

building. Some brick walls have wooden studs behind the

brick to provide an area for insulation, plumbing, vents,

and wiring. It is important that weep holes and flashing

be installed in brick homes to control moisture. 

Improperly constructed building footers can result in

major damage to the exterior brick surface of a home by

allowing moisture, insects, and vermin to enter. A crack,

such as the one in Figure 7.5, is

an example of such a failure. This

type of damage will require much

more than just a mortar patch.

Buildings constructed of concrete

block also experience footer

failure. The damage is reason to

not skimp when installing and inspecting the footing and

reinforces the need for appropriate concrete mix, rebar,

and footing drains. 

Stucco

Synthetic stucco (exterior insulation and finish system;

EIFS) is a multilayered exterior finish that has been used

in Europe since shortly after World War II, when

contractors found it to be a good repair choice for

buildings damaged during the war. North American

builders began using EIFS in the 1980s, first in

commercial buildings, then as an exterior finish to wood

frame houses.

EIFS has three layers:

• Inner layer—foam insulation board secured to the

exterior wall surface, often with adhesive;

• Middle layer—a polymer and cement base coat

applied to the top of the insulation, then

reinforced with glass fiber mesh; and 

• Exterior layer—a textured finish coat.

EIFS layers bond to form a covering that does not

breathe. If moisture seeps in, it can become trapped

behind the layers. With no place to go, constant exposure

to moisture can lead to rot in wood and other vulnerable

materials within the home. Ripples in the stucco could be

a sign of a problem. On the surface it may look like

nothing is wrong, but beneath the surface, the stucco may

have cracked from settling of the house. With a properly

installed moisture barrier, no moisture should be able to

seep behind the EIFS, including moisture originating

inside the home. Drains in the foundation can be

designed to enable moisture that does seep in to escape. 

Other signs of problems are mold or mildew on the

interior or exterior of the home, swollen wood around

door and window frames, blistered or peeling paint; and

cracked EIFS or cracked sealant.

7-4 Environmental Barriers

Figure 7.5. Brick

Structural Defect
Vinyl 

Standard vinyl siding is made from thin, flexible sheets of

plastic about 2 mm thick, precolored and bent into shape

during manufacturing. The sheets interlock as they are

placed above one another. Because temperature and

sunlight cause vinyl to expand and contract, it fits into

deep channels at the corners and around windows and

doors. The channels are deep enough that as the siding

contracts, it remains within the channel. 

Siding composed of either vinyl or aluminum will expand

and contract in response to temperature change. This

requires careful attention to the manufacturer’s specifications

during application. Cutting the siding too short causes

exposed surfaces when the siding contracts, resulting in

moisture damage and eventual leakage. Even small cracks

exposing the undersurface can create major damage.

Vinyl has some environmental and health concerns, as do

most exterior treatments. Vinyl chloride monomer, of which

polyvinyl chloride siding is made, is a strong carcinogen

and, when heated, releases toxic gases and vapors. Under

normal conditions, significant exposures to vinyl chloride

monomer are unlikely. 

Asbestos

Older homes were often sided with composites containing

asbestos. This type of siding was very popular in the early

1940s. It was heavily used through the 1950s and

decreasingly used up until the early 1960s. The siding is

typically white, although it may be painted. It is often

about 1⁄4-inch thick and very brittle and was sold in

sections of about 12×18 inches. The composite is quite

heavy and very slatelike in difficulty of application. As it

ages, it becomes even more brittle, and the surface erodes

and becomes powdery. This siding, when removed, must

be disposed of in accordance with local, state, and federal

laws regulating the disposal of asbestos materials. The

workers and the site must be carefully managed and

protected from contamination. The composite had several

virtues as siding. It was quite resistant to fire, was not

attractive to insects or vermin, provided very good

insulation, and did not grow mold readily. Because of its

very brittle nature, it could be damaged by children

playing and, as a result, often was covered later with

aluminum siding. 

Metal

If metal siding is used, the mounting fasteners (nails or

screws) must be compatible with the metal composition

of the siding, or the siding or fasteners will corrode. This

corrosion is due to galvanic response.

Galvanic response (corrosion) can produce devastating

results that often are only noticed when it is too late. It

should always be considered in inspections and is

preventable in nearly all cases.

When two dissimilar metals, such as aluminum and steel,

are coupled and subjected to a corrosive environment

(such as air, water, salt spray, or cleaning solutions), the

more active metal (aluminum) becomes an anode and

corrodes through exfoliation or pitting. This can happen with

plumbing, roofing, siding, gutters, metal venting, and

heating and air conditioning systems. 

When two metals are electrically connected to each other

in a conductive environment, electrons flow from the

more active metal to the less active because of the difference

in the electrical potential, the so-called “driving force.”

When the most active metal (anode) supplies current, it

will gradually dissolve into ions in the electrolyte and, at

the same time, produce electrons, which the least active

(cathode) will receive through the metallic connection with

the anode. The result is that the cathode will be negatively

polarized and hence be protected against corrosion. 

Thus, less noble metals are more susceptible to corrosion.

An example of protecting an appliance such as an ironbodied water heater would be to ensure that piping

Healthy Housing Reference Manual 7-5

Figure 7.6. Corrosion in Piping Resulting From Galvanic Response

1. Use like metals when possible

2. Use metals with similar electronegativity 

levels

3. Use dielectric unions for plumbing

4. Use anodes that are inexpensive to replace

Remember: Use metals with less susceptibility 

to protect metals that are more susceptible 

to corrosion.

Metal Corrosion Prevention
connections are of similar material when possible and

follow the manufacturer’s good practice and instructions on

using dielectric (not conductors of electricity) unions [8].

Figure 7.6 shows examples of electrochemical kinetics in

pipes that were connected to dissimilar metals.

References

1. Lawrence Berkeley National Laboratory. Cool

roofing materials database. Berkeley, CA:

Lawrence Berkeley National Laboratory,

Environmental Energy Technologies Division;

2000. Available from URL:

http://eetd.lbl.gov/coolroof/.

2. California Energy Commission. Roofing.

Sacramento: California Energy Commission; no

date. Available from URL: http://www.consumerenergycenter.org/homeandwork/homes/

construction/roofing.html.

3. Cazayoux EJ, Bilello RA. Roof materials. Baton

Rouge, LA: Louisiana State University; no date.

Available from URL: http://www.leeric.lsu.edu/

bgbb/7/ecep/carpntry/i/i.htm.

4. Department of Energy. Insulation fact sheet.

Washington, DC: Department of Energy; 2002.

Available from URL: http://www.ornl.gov/sci/

roofs+walls/insulation/ins_01.htm.

5. The Old House Web. Insulation: stories and more

from the Old House Web. Gardiner, ME: The

Old House Web; no date. Available from URL:

http://www.oldhouseweb.com/stories/HowTo/

HVAC_and_Insulation/Insulation/. 

6. The Old House Web. Siding: stories and more

from the Old House Web. Gardiner, ME: The

Old House Web; no date. Available from URL:

http://www.oldhouseweb.com/

stories/How-To/Siding/.

7. Vandervort D. House siding and architectural

details. Glendale, CA: Hometips.com; no date.

Available from URL: http://www.hometips.com/

home_improvement/siding.html.

8. University of Wisconsin-Stevens Point. Corrosion,

lead, copper: in-home water supplies—are you at

risk? Stevens Point, WI: University of WisconsinStevens Point; no date. Available from URL:

https://www.uwsp.edu/cnr/etf/corros.htm. 

7-6 Environmental Barriers
Chapter 8—Rural Water Supplies and Water-quality Issues

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Water Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Source Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2

Well Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Sanitary Design and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Pump Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Dug and Drilled Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Cisterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Disinfection of Water Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7

Chlorine Carrier Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Routine Water Chlorination (Simple) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Well Water Shock Chlorination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Backflow, Back-siphonage, and Other Water Quality Problems . . . . . . . . . . . . . . . .8-9

Backflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Back-siphonage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

Other Water Quality Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

Protecting the Groundwater Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-12

Figure 8.1. U.S. Water Supply by Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Figure 8.2. Cross Section of a Driven Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Figure 8.3. Well Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Figure 8.4. Converted Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Figure 8.5. Recapped and Sealed Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.6. Drilled Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.7. Typical Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.8. Sewage in Drainage Ditch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Figure 8.9. Drilled Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Figure 8.10. Spring Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources . . . . . . . .8-2

Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters . . . . . . . . .8-3

Table 8.3. Disinfection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7

Table 8.4. Chlorination Guide for Specific Water Conditions . . . . . . . . . . . . . . . . . . . . . . . . .8-8

Table 8.5. Preparing a 200-ppm Chlorine Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Table 8.6. Analyzing and Correcting Water Quality Problems . . . . . . . . . . . . . . . . . . . . . . . . .8-11

Healthy Housing Reference Manual 1

Contents
“We never know the worth of water till the well is dry.”

Thomas Fuller

Gnomologia, 1732

Introduction

One of the primary differences between rural and urban

housing is that much infrastructure that is often taken

for granted by the urban resident does not exist in the

rural environment. Examples range from fire and police

protection to drinking water and sewage disposal. This

chapter is intended to provide basic knowledge about the

sources of drinking water typically used for homes in the

rural environment. It is estimated that at least 15% of

the population of the United States is not served by

approved public water systems. Instead, they use individual

wells and very small drinking water systems not covered

by the Safe Water Drinking Act (SDWA); these wells and

systems are often untested and contaminated [1]. Many

of these wells are dug rather than drilled. Such shallow

sources frequently are contaminated with both chemicals

and bacteria. Figure 8.1 shows the change in water

supply source in the United States from 1970 to 1990.

According to the 2003 American Housing Survey, of the

105,843,000 homes in the United States, water is

provided to 92,324,000 (87.2%) by a public or private

business; 13,097,000 (12.4%) have a well (11,276,000

drilled, 919,000 dug, and 902,000 not reported) [3].

Water Sources

The primary sources of drinking water are groundwater

and surface water. In addition, precipitation (rain and

snow) can be collected and contained. The initial quality

of the water depends on the source. Surface water (lakes,

reservoirs, streams, and rivers), the drinking water source

for approximately 50% of our population, is generally of

poor quality and requires extensive treatment.

Groundwater, the source for the other approximately

50% of our population, is of better quality. However, it

still may be contaminated by agricultural runoff or

surface and subsurface disposal of liquid waste, including

leachate from solid waste landfills. Other sources, such as

spring water and rain water, are of varying levels of quality,

but each can be developed and treated to render it potable. 

Most water systems consist of a water source (such as a

well, spring, or lake), some type of tank for storage, and

a system of pipes for distribution. Means to treat the

water to remove harmful bacteria or chemicals may also be

required. The system can be as simple as a well, a pump,

and a pressure tank to serve a single home. It may be a

complex system, with elaborate treatment processes,

multiple storage tanks, and a large distribution system

serving thousands of homes. Regardless of system size,

the basic principles to assure the safety and potability of

water are common to all systems. Large-scale water

supply systems tend to rely on surface water resources,

and smaller water systems tend to use groundwater. 

Groundwater is pumped from wells drilled into aquifers.

Aquifers are geologic formations where water pools, often

deep in the ground. Some aquifers are actually higher

than the surrounding ground surface, which can result in

flowing springs or artesian wells. Artesian wells are often

Chapter 8: Rural Water Supplies and Water-quality Issues

Healthy Housing Reference Manual 8-1

Figure 8.1. U.S. Water Supply by Source [2]
drilled; once the aquifer is penetrated, the water flows

onto the surface of the ground because of the hydrologic

pressure from the aquifer.

SDWA defines a public water system as one that provides

piped water to at least 25 persons or 15 service connections

for at least 60 days per year. Such systems may be owned

by homeowner associations, investor-owned water

companies, local governments, and others. Water not

from a public water supply, and which serves one or only

a few homes, is called a private supply. Private water

supplies are, for the most part, unregulated. Community

water systems are public systems that serve people yearround in their homes. The U.S. Environmental Protection

Agency (EPA) also regulates other kinds of public water

systems-such as those at schools, factories, campgrounds,

or restaurants-that have their own water supply. 

The quantity of water in an aquifer and the water

produced by a well depend on the nature of the rock,

sand, or soil in the aquifer where the well withdraws

water. Drinking water wells may be shallow (50 feet or

less) or deep (more than 1,000 feet). 

On average, our society uses almost 100 gallons of

drinking water per person per day. Traditionally, water use

rates are described in units of gallons per capita per day

(gallons used by one person in 1 day). Of the drinking

water supplied by public water systems, only a small

portion is actually used for drinking. Residential water

consumers use most drinking water for other purposes,

such as toilet flushing, bathing, cooking, cleaning, and

lawn watering. 

The amount of water we use in our homes varies during

the day: 

• Lowest rate of use—11:30 PM to 5:00 AM,

• Sharp rise/high use—5:00 AM to noon (peak

hourly use from 7:00 AM to 8:00 AM),

• Moderate use—noon to 5:00 PM (lull around

3:00 PM), and 

• Increasing evening use—5:00 PM to 11:00 PM

(second minor peak, 6:00 PM to 8:00 PM). 

Source Location

The location of any source of water under consideration

as a potable supply, whether individual or community,

should be carefully evaluated for potential sources of

contamination. As a general practice, the maximum

distance that economics, land ownership, geology, and

topography will allow should separate a water source from

potential contamination sources. Table 8.1 details some of

the sources of contamination and gives minimum

distances recommended by EPA to separate pollution

sources from the water source.

Water withdrawn directly from rivers, lakes, or reservoirs

cannot be assumed to be clean enough for human

consumption unless it receives treatment. Water pumped

from underground aquifers will require some level of

treatment. Believing surface water or soil-filtered water

has purified itself is dangerous and unjustified. Clear

water is not necessarily safe water. To assess the level of

treatment a water source requires, follow these steps:

• Determine the quality needed for the intended

purpose (drinking water quality needs to be

evaluated under the SDWA).

• For wells and springs, test the water for

bacteriologic quality. This should be done with

several samples taken over a period of time to

8-2 Rural Water Supplies and Water-quality Issues

Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources (Horizontal Distance) [1]
establish a history on the source. With few

exceptions, surface water and groundwater sources

are always presumed to be bacteriologically unsafe

and, as a minimum, must be disinfected.

• Analyze for chemical quality, including both legal

(primary drinking water) standards and aesthetic

(secondary) standards.

• Determine the economical and technical restraints

(e.g., cost of equipment, operation and

maintenance costs, cost of alternative sources,

availability of power).

• Treat if necessary and feasible.

Well Construction

Many smaller communities obtain drinking water solely

from underground aquifers. In addition, according to the

last census with data on water supply systems, 15% of

people in the United States are on individual water supply

systems. In some sections of the country, there may be a

choice of individual water supply sources that will supply

water throughout the year. Some areas of the country may

be limited to one source. The various sources of water

include drilled wells, driven wells, jetted wells, dug wells,

bored wells, springs, and cisterns. Table 8.2 provides a

more detailed description of some of these wells.

Regardless of the choice for a water supply source, special

safety precautions must be taken to assure the potability

of the water. Drainage should be away from a well. The

casings of the well should be sealed with grout or some other

mastic material to ensure that surface water does not seep

along the well casing to the water source. In Figure 8.2,

the concrete grout has been reinforced with steel and a

drain away from the casing has been provided to assist in

protecting this water source. Additionally, research

suggests that a minimum of 10 feet of soil is essential to

filter unwanted biologic organisms from the water source. 

However, if the area of well construction has any sources

of chemical contamination nearby, the local public health

authority should be contacted. In areas with karst

topography (areas characterized by a limestone landscape

with caves, fissures, and underground streams), wells of

any type are a health risk because of the long distances

that both chemical and biologic contaminants can travel. 

When determining where a water well is to be located,

several factors should be considered:

• the groundwater aquifer to be developed, 

• depth of the water-bearing formations, 

• the type of rock formations that will be encountered, 

• freedom from flooding, and 

• relation to existing or potential sources 

of contamination. 

Figure 8.2. Cross Section of a Driven Well

Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters

Healthy Housing Reference Manual 8-3
The overriding concern is to protect any kind of well

from pollution, primarily bacterial contamination.

Groundwater found in sand, clay, and gravel formations is

more likely to be safer than groundwater extracted from

limestone and other fractured rock formations. Whatever

the strata, wells should be protected from

• surface water entering directly into the top of the well, 

• groundwater entering below ground level without

filtering through at least 10 feet of earth, and 

• surface water entering the space between the well

casing and surrounding soil.

Also, a well should be located in such a way that it is

accessible for maintenance, inspection, and pump or pipe

replacement when necessary. Driven wells (Figure 8.2) are

typically installed in sand or soil and do not penetrate

base rock. They are, as a result, hammered into the ground

and are quite shallow, resulting in frequent contamination by

both chemical and bacterial sources. 

Sanitary Design and Construction 

Whenever a water-bearing formation is penetrated (as in

well construction), a direct route of possible water

contamination exists unless satisfactory precautions are

taken. Wells should be provided with casing or pipe to an

adequate depth to prevent caving and to permit sealing of

the earth formation to the casing with watertight cement

grout or bentonite clay, from a point just below the

surface to as deep as necessary to prevent entry of

contaminated water. 

Once construction of the well is completed, the top of the

well casing should be covered with a sanitary seal, an

approved well cap, or a pump mounting that completely

covers the well opening (Figure 8.3). If pumping at the

design rate causes drawdown in the well, a vent through a

tapped opening should be provided. The upper end of the

vent pipe should be turned downward and suitably

screened to prevent the entry of insects and foreign matter. 

Pump Selection

A variety of pump types and sizes exist to meet the needs

of individual or community water systems. Some of the

factors to be considered in selecting a pump for a specific

application are well depth, system design pressure,

demand rate in gallons per minute, availability of power,

and economics. 

Dug and Drilled Wells

Dug wells (Figures 8.4 and 8.5) were one of the most

common types of wells for individual water supply in the

United States before the 1950s. They were often

constructed with one person digging the hole with a

shovel and another pulling the dirt from the hole with a

rope, pulley, and bucket. Of course, this required a hole

of rather large circumference, with the size increasing the

potential for leakage from the surface. The dug well also

was traditionally quite shallow, often less than 25 feet,

which often resulted in the water source being

8-4 Rural Water Supplies and Water-quality Issues

Figure 8.3. Well Seal Figure 8.4. Converted Dug Well [1]
contaminated by surface water as it ran through cracks

and crevices in the ground to the aquifer. Dug wells

provide potable water only if they are properly located

and the water source is free of biologic and chemical

contamination. The general rule is, the deeper the well,

the more likely the aquifer is to be free of contaminants,

as long as surface water does not leak into the well

without sufficient soil filtration. 

Two basic processes are used to remediate dug wells. One

is to dig around the well to a depth of 10 feet and install

a solid slab with a hole in it to accommodate a well casing

and an appropriate seal (Figures 8.4 and 8.5). The dirt is

then backfilled over the slab to the surface, and the casing

is equipped with a vent and second seal, similar to a

drilled well, as shown in Figure 8.6. This results in a

considerable reduction in the area of the casing that needs

to be protected. Experience has shown that the disturbed

dirt used for backfilling over the buried slab will continue

to release bacteria into the well for a short time after

modification. Most experts in well modification suggest

installing a chlorination system on all dug wells to

disinfect the water because of their shallow depth and

possible biologic impurity during changing drainage and

weather conditions above ground. Figure 8.7 shows a dug

well near the front porch of a house and within 5 feet of a

drainage ditch and 6 feet of a rural road. This well is

likely to be contaminated with the pesticide used to

termite-proof the home and from whatever runs off the

nearby road and drainage ditch. The well shown is about

15 feet deep. The brick structure around the well holds

the centrifugal pump and a heater to keep the water from

freezing. Although dangerous to drink from, this well is

Healthy Housing Reference Manual 8-5

Figure 8.5. Recapped and Sealed Dug Well [1]

Figure 8.6. Drilled Well [4]

Figure 8.7. Typical Dug Well
typical of dug wells used in rural areas of the United

States for drinking water. 

Samples should not be taken from such wells because they

instill a false sense of security if they are negative for both

chemicals and biologic organisms. The quality of the

water in such wells can change in just a few hours

through infiltration of drainage water. Figure 8.8 shows

the septic tank discharge in the drainage ditch 5 feet

upstream of the dug well in Figure 8.7. This potential

combination of drinking water and waste disposal presents

an extreme risk to the people serviced by the dug well.

Sampling is not the answer; the water source should be

changed under the supervision of qualified environmental

health professionals.

Figure 8.9 shows a drilled well. On the left side of the picture

is the corner of the porch of the home. The well appears

not to have a sanitary well seal and is likely open to the

air and will accept contaminants into the casing. Because the

well is so close to the house, the casing is open, and the land

slopes toward the well, it is a major candidate for

contamination and not a safe water source. 

Springs 

Another source of water for individual water supply is

natural springs. A spring is groundwater that reaches the

surface because of the natural contours of the land. 

Springs are common in rolling hillside and mountain

areas. Some provide an ample supply of water, but most

provide water only seasonally. Without proper precautions, the

water may be biologically or chemically contaminated and

not considered potable. 

To obtain satisfactory (potable) water from a spring, it is

necessary to

• find the source,

• properly develop the spring,

• eliminate surface water outcroppings above the

spring to its source,

• prevent animals from accessing the spring area, and

• provide continuous chlorination.

Figure 8.10 illustrates a properly developed spring. Note

that the line supplying the water is well underground, the

spring box is watertight, and surface water runoff is

diverted away from the area. Also be aware that the water

quality of a spring can change rapidly.

Cisterns

A cistern is a watertight, traditionally underground

reservoir that is filled with rainwater draining from the

8-6 Rural Water Supplies and Water-quality Issues

Figure 8.10. Spring Box [5]

Figure 8.8. Sewage in Drainage Ditch

Figure 8.9. Drilled Well
roof of a building. Cisterns will not provide an ample

supply of water for any extended period of time, unless

the amount of water used is severely restricted. Because

the water is coming off the roof, a pipe is generally

installed to allow redirection of the first few minutes of

rainwater until the water flows clear. Disinfection is,

nevertheless, of utmost importance. Diverting the first

flow of water does not assure safe, non-polluted water

because chemicals and biologic waste from birds and other

animals can migrate from catchment surfaces and from

windblown sources. In addition, rainwater has a low pH,

which can corrode plumbing pipes and fixtures if not treated.

Disinfection of Water Supplies

Water supplies can be disinfected by a variety of methods

including chlorination, ozonation, ultraviolet radiation,

heat, and iodination. The advantages and disadvantages of

each method are noted in Table 8.3. 

The understanding of certain terms (blue box, next page)

is necessary in talking about chlorination. 

Table 8.4 is a chlorination guide for specific water conditions.

Chlorine is the most commonly used water disinfectant.

It is available in liquid, powder, gas, and tablet form.

Chlorine gas is often used for municipal water

disinfection, but can be hazardous if mishandled.

Recommended liquid, powder, and tablet forms of

chlorine include the following:

• Liquid—Chlorine laundry bleach (about 5%

chlorine). Swimming pool disinfectant or

concentrated chlorine bleach (12%–17% chlorine).

• Powder—Chlorinated lime (25% chlorine), dairy

sanitizer (30% chlorine), and high-test calcium

hypochlorite (65%–75% chlorine). 

Table 8.3. Disinfection Methods 

Healthy Housing Reference Manual 8-7
8-8 Rural Water Supplies and Water-quality Issues

Table 8.4. Chlorination Guide for Specific Water Conditions 

Breakpoint chlorination—A process sometimes used to ensure the presence of free chlorine in public water supplies by

adding enough chlorine to the water to satisfy the chlorine demand and to react with all dissolved ammonia that might

be present. The concentrations of chlorine needed to treat a variety of water conditions are listed in Table 8.4. 

Chlorine concentration—The concentration (amount) of chlorine in a volume of water is measured in parts per million

(ppm). In 1 million gallons of water, a chlorine concentration of 1 ppm would require 8.34 pounds of 100% chlorine.

Contact time—The time, after chlorine addition and before use, given for disinfection to occur. For groundwater systems,

contact time is minimal. However, in surface water systems, a contact time of 20 to 30 minutes is common.

Dosage—The total amount of chlorine added to water. Given in parts per million (ppm) or milligrams per liter

(mg/L).

Demand—Chlorine solution used by reacting with particles of organic matter such as slimes or other chemicals and

minerals that may be present. The difference between the amount of chlorine applied to water and total available

chlorine remaining at the end of a specified contact period.

Parts per million—A weight-to-weight comparison; 1 ppm equals 1 pound per million pounds. Because water weighs

8.34 pounds per gallon, it takes 8.34 pounds of any substance per million gallons to equal 1 ppm. In water chemistry,

1 ppm equals 1 mg/L.

Residual—The amount of chlorine left after the demand is met; available (free) chlorine. This portion provides a ready

reserve for bactericidal action. Both combined and free chlorine make up chlorine residual and are involved in disinfection.

Total available chlorine = free chlorine + combined chlorine.

Definitions of Terms Related to Chlorination
• Tablets—High-test calcium hypochlorite

(65%–75% chlorine).

• Gas—Gas chlorine is an economical and

convenient way to use large amounts of chlorine.

It is stored in steel cylinders ranging in size from

100 to 2,000 pounds. The packager fills these

cylinders with liquid chlorine to approximately

85% of their total volume; the remaining 15% is

occupied by chlorine gas. These ratios are required

to prevent tank rupture at high temperatures. It is

important that direct sunlight never reaches gas

cylinders. It is also important that the user of

chlorine knows the maximum withdrawal rate of

gas per day per cylinder. For example, the

maximum withdrawal rate from a 150-pound

cylinder is approximately 40 pounds per day at room

temperature discharging to atmospheric pressure.

Chlorine Carrier Solutions

On small systems or individual wells, a high-chlorine carrier

solution is mixed in a tank in the pump house and pumped

by the chlorinator into the system. Table 8.5 shows how

to make a 200-ppm carrier solution. By using 200 ppm,

only small quantities of this carrier have to be added.

Depending on the system, other stock solutions may be

needed to better use existing chemical feed equipment.

Routine Water Chlorination (Simple)

Most chlorinated public water supplies use routine water

chlorination. Enough chlorine is added to the water to

meet the chlorine demand, plus enough extra to supply

0.2 to 0.5 ppm of free chlorine when checked after 20 minutes.

Simple chlorination may not be enough to kill certain

viruses. Chlorine as a disinfectant increases in

effectiveness as the chlorine residual is increased and as

the contact time is increased. 

Chlorine solutions should be mixed and chlorinators

adjusted according to the manufacturer’s instructions.

Chlorine solutions deteriorate gradually when standing.

Fresh solutions must be prepared as necessary to maintain

the required chlorine residual. Chlorine residual should be

tested at least once a week to assure effective equipment

operation and solution strengths. 

A dated record should be kept of solution preparation,

type, proportion of chlorine used, and residual-test results.

Sensing devices are available that will automatically shut off

the pump and activate a warning bell or light when the

chlorinator needs servicing. 

Well Water Shock Chlorination

Shock chlorination is used to control iron and sulfatereducing bacteria and to eliminate fecal coliform bacteria

in a water system. To be effective, shock chlorination

must disinfect the following: the entire well depth, the

formation around the bottom of the well, the pressure

system, water treatment equipment, and the distribution

system. To accomplish this, a large volume of superchlorinated water is siphoned down the well to displace

the water in the well and some of the water in the

formation around the well. Check specifications on the

water treatment equipment to ensure appropriate protection

of the equipment.

With shock chlorination, the entire system-from the

water-bearing formation through the well-bore and the

distribution system-is exposed to water that has a concentration

of chlorine strong enough to kill iron and sulfate-reducing

bacteria. The shock chlorination process is complex and

tedious. Exact procedures and concentrations of chlorine

for effective shock treatment are available [6,7].

Backflow, Back-siphonage, and Other Water

Quality Problems

In addition to contamination at its source, water can

become contaminated with biologic materials and toxic

construction or unsuitable joint materials as it flows

through the water distribution system in the home. Water

flowing backwards (backflow) in the pipes sucks materials

back (back-siphonage) into the water distribution system,

creating equally hazardous conditions. Other water quality

problems relate to hardness, dissolved iron and iron bacteria,

acidity, turbidity, color, odor, and taste.

Backflow

Backflow is any unwanted flow of nonpotable water into

a potable water system. The direction of flow is the

reverse of that intended for the system. Backflow may be

caused by numerous factors and conditions. For example,

the reverse pressure gradient may be a result of either a

loss of pressure in the supply main (back-siphonage) or

the flow from a pressurized system through an unprotected

Healthy Housing Reference Manual 8-9

Table 8.5. Preparing a 200-ppm Chlorine Solution 
cross-connection (back-pressure). A reverse flow in a

distribution main or in a customer’s system can be created

by a change of system pressure wherein the pressure at the

supply point becomes lower than the pressure at the point

of use. When this happens, the water at the point of use

will be siphoned back into the system, potentially

polluting or contaminating it. It is also possible that

contaminated or polluted water could continue to

backflow into the public distribution system. The point at

which nonpotable water comes in contact with potable

water is called a cross-connection. 

Examples of backflow causes include supplemental

supplies, such as a standby fire protection tank; fire

pumps; chemical feed pumps that overpower the potable

water system pressure; and sprinkler systems.

Back-Siphonage

Back-siphonage is a siphon action in an undesirable or

reverse direction. When there is a direct or indirect

connection between a potable water supply and water of

questionable quality due to poor plumbing design or

installation, there is always a possibility that the public

water supply may become contaminated. Some examples

of common plumbing defects are

• washbasins, sterilizers, and sinks with submerged

inlets or threaded hose bibs and hose;

• oversized booster pumps that overtax the supply

capability of the main and thus develop negative

pressure;

• submerged inlets and fire pumps (if the fire

pumps are directly connected into the water main,

a negative pressure will develop); and

• a threaded hose bib in a health-care facility (which

is technically a cross-connection). 

There are many techniques and devices for preventing 

back-flow and back-siphonage. Some examples are

• Vacuum breakers (nonpressure and pressure);

• Back-flow preventers (reduced pressure principle,

double gate-double check valves, swingconnection, and air gap-double diameter

separation);

• Surge tanks (booster pumps for tanks, fire system

make-up tank, and covering potable tanks); and 

• Color coding in all buildings where there is any

possibility of connecting two separate systems or

taking water from the wrong source (blue-potable,

yellow-nonpotable, and other-chemical and gases).

An air gap is a physical separation between the incoming

water line and maximum level in a container of at least

twice the diameter of the incoming water line. If an air

gap cannot be installed, then a vacuum breaker should be

installed. Vacuum breakers, unlike air gaps, must be

installed carefully and maintained regularly. Vacuum

breakers are not completely failsafe. 

Other Water Quality Problems

Water not only has to be safe to drink; it should also be

aesthetically pleasing. Various water conditions affect

water quality. Table 8.6 describes symptoms, causes,

measurements, and how to correct these problems.

Protecting the Groundwater Supply 

Follow these tips to help protect the quality of

groundwater supplies:

• Periodically inspect exposed parts of wells for

cracked, corroded, or damaged well casings;

broken or missing well caps; and settling and

cracking of surface seals.

• Slope the area around wells to drain surface runoff

away from the well.

• Install a well cap or sanitary seal to prevent

unauthorized use of, or entry into, a well.

• Disinfect wells at least once a year with bleach or

hypochlorite granules, according to the

manufacturer’s directions.

• Have wells tested once a year for coliform bacteria,

nitrates, and other constituents of concern.

• Keep accurate records of any well maintenance,

such as disinfection or sediment removal, that

require the use of chemicals in the well.

• Hire a certified well driller for new well construction,

modification, or abandonment and closure.

• Avoid mixing or using pesticides, fertilizers,

herbicides, degreasers, fuels, and other pollutants

near wells.

• Do not dispose of waste in dry or abandoned wells.

8-10 Rural Water Supplies and Water-quality Issues
• Do not cut off well casings below the land

surface.

• Pump and inspect septic systems as often as

recommended by local health departments.

• Never dispose of hazardous materials (e.g., paint,

paint stripper, floor stripper compounds) in a

septic system.

References

1. Rhode Island Department of Health and 

University of Rhode Island Cooperative Extension

Water Quality Program. Healthy drinking waters 

for Rhode Islanders. Kingston, RI: Rhode Island 

Department of Health and University of Rhode 

Island Cooperative Extension Water Quality 

Program; 2003. Available from URL: 

http://www.uri.edu/ce/wq/has/html/Drinking.pdf.

Healthy Housing Reference Manual 8-11

Table 8.6. Analyzing and Correcting Water Quality Problems (continues on next page)
2. US Census Bureau. Historical census of housing 

graphs: water supply. Washington, DC: US 

Census Bureau; no date. Available from URL: 

http://www.census.gov/hhes/www/housing/ 

census/historic/swgraph.html.

3. US Census Bureau. American housing survey. 

Washington, DC: US Census Bureau; 2003. 

Available from URL: http://www.census.gov/hhes/

www/housing/ahs/nationaldata.html.

4. National Ground Water Association. Well system 

material. Westerville, OH: National Ground 

Water Association; 2003. Available from URL: 

http://www.ngwa.org/pdf/wellsystemmaterials.pdf.

5. US Environmental Protection Agency. Spring 

development. Chicago: US Environmental 

Protection Agency; 2001. 

6. Government of Alberta. Shock chlorination—well

maintenance. Edmonton, Alberta, Canada: Alberta 

Agriculture, Food & Rural Development;2001.

Available from URL: http://www1.agric.gov.ab.ca/

$department/deptdocs.nsf/all/wwg411.

7. Boulder GNS Water Well Service and Supply. 

Chlorination of water systems. Boulder, CO: 

Boulder GNS Water Well Service and Supply; 

2002. Available from URL: http://www.waterwell.cc/

CHLORIN.HTM.

8. Iowa State University Diagnosing and solving 

common water-quality problems. Ames, IA: Iowa 

State University; 1994. Available from URL: 

http://www.abe.iastate.edu/HTMDOCS/

aen152.pdf.

Additional Sources of Information

American Water Works Association. Available from URL:

http://www.awwa.org.

Drexel University: Drinking water outbreaks. Available

from URL: http://water.sesep.drexel.edu/outbreaks/.

US Environmental Protection Agency: Ground water and

drinking water. Available from URL:

http://www.epa.gov/safewater. 

8-12 Rural Water Supplies and Water-quality Issues

Table 8.6. Analyzing and Correcting Water Quality Problems (continued)
Chapter 9—Plumbing

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Elements of a Plumbing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Water Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Hot and Cold Water Main Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-3

Water Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

Drainage System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

Corrosion Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Water Conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-14

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-15

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-16

Figure 9.1. Typical Home Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Figure 9.2. House Service Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2

Figure 9.3. Gas Water Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-7

Figure 9.4. Temperature-pressure Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

Figure 9.5. Branch Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-10

Figure 9.6. P-trap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-10

Figure 9.7. Types of S-traps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-10

Figure 9.8. Trap Seal: (a) Seal Intact; (b) Fixture Draining; (c) Loss of Gas Seal . . . . . . . . . . . .9-10

Figure 9.9. Loss of Trap Seal in Lavatory Sink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

Figure 9.10. Back-to-back Venting (Toilet). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

Figure 9.11. Back-to-back Venting (Sink). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-11

Figure 9.12. Wall-hung Fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Figure 9.13. Unit Vent Used in Bathtub Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Figure 9.14. Toilet Venting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Figure 9.15. Janitor’s Sink. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Figure 9.16. Common Y-trap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Figure 9.17. Hose Bib With Vacuum Breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

Table 9.1. Fixture Unit Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-9

Table 9.2. Sanitary House Drain Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-9

Table 9.3. Minimum Fixture Service Pipe Diameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

Healthy Housing Reference Manual 1

Contents
“The society which scorns excellence in plumbing as a

humble activity and tolerates shoddiness in philosophy

because it is an exalted activity will have neither good

plumbing nor good philosophy: neither its pipes nor its

theories will hold water.” 

John W. Gardner, Secretary, 

Department of Health, Education, and Welfare, 1965 

Introduction

Plumbing may be defined as the practice, materials, and

fixtures used in installing, maintaining, and altering

piping, fixtures, appliances, and appurtenances in

connection with sanitary or storm drainage facilities, a

venting system, and public or private water supply

systems. Plumbing does not include drilling water wells;

installing water soften ing equipment; or manufacturing

or selling plumbing fixtures, appliances, equipment, or

hardware. A plumbing system consists of three parts: an

adequate potable water supply system; a safe, adequate

drainage system; and ample fixtures and equipment.

The housing inspector’s prime concern while inspecting

plumbing is to ensure the provision of a safe water

supply system, an adequate drainage system, and ample

and proper fixtures and equipment that do not

contaminate water. The inspector must make sure that

the system moves waste safely from the home and

protects the occupants from backup of waste and

dangerous gases. This chapter covers the major features

of a residential plumbing system and the basic plumbing

terms and principles the inspector must know and

understand to identify housing code violations that

involve plumbing. It will also assist in identifying the

more complicated defects that the inspector should refer

to the appropriate agencies. This chapter is not a

plumbing code, but should provide a base of knowledge

sufficient to evaluate household systems. 

Elements of a Plumbing System 

The primary purposes of a plumbing system are

• To bring an adequate and potable supply of hot

and cold water to the inhabitants of a house, and

• To drain all wastewater and sewage discharge

from fixtures into the public sewer or a private

disposal system.

It is, therefore, very important that the housing inspector

be completely familiar with all elements of these systems

so that inade quacies of the structure’s plumbing and

other code violations will be recognized. To aid the

inspector in understanding the plumbing system, a schematic

of a home plumbing system is shown in Figure 9.1.

Water Service

The piping of a house service line should be as short as

possible. Elbows and bends should be kept to a minimum

because they reduce water pressure and, therefore, the

supply of water to fixtures in the house. The house

service line also should be protected from freezing.

Four feet of soil is a commonly accepted depth to bury

the line to prevent freezing. This depth varies, however,

across the country from north to south. The local or state

plumbing code should be consulted for recommended

depths. The minimum service line size should be 3⁄4 inch.

The minimum water supply pressure should be 40 pounds

per square inch (psi), no cement or concrete joints

should be allowed, no glue joints between different types

of plastic should be allowed, and no female threaded

PVC fittings should be used.

The materials used for a house service may be approved

plastic, copper, cast iron, steel, or wrought iron. The

connections used should be compatible with the type of

pipe used. A typical house service installation is pictured

in Figure 9.2. The elements of the service installation are

described below. 

Corporation stop—The corporation stop is connected to

the water main. This connection is usually made of brass

Chapter 9: Plumbing

Healthy Housing Reference Manual 9-1

Figure 9.1. Typical Home Water System [1]
and can be connected to the main with a special tool

without shutting off the municipal supply. The valve

incorporated in the corporation stop permits the pressure

to be maintained in the main while the service to the

building is completed. 

Curb stop—The curb stop is a similar valve used to

isolate the building from the main for repairs,

nonpayment, of water bills or flooded basements. Because

the corporation stop is usually under the street and it is

necessary to break the pavement to reach the valve, the

curb stop is used as the isolation valve.

Curb stop box—The curb stop box is an access box to

the curb stop for opening and closing the valve. A longhandled wrench is used to reach the valve.

9-2 Plumbing

Air chambers—Pressure-absorbing devices that eliminate water hammer. Air chambers should be installed as close as possible

to the valves or faucet and at the end of long runs of pipe.

Air gap (drainage system)—The unobstructed vertical distance through the free atmosphere between the outlet of a water

pipe and the flood level rim of the receptacle into which it is discharging.

Air gap (water distribution system)—The unobstructed vertical distance through the free atmosphere between the lowest

opening from any pipe or faucet supplying water to a tank, plumbing fixture, or other device and the flood level rim of the

receptacle.

Backflow—The flow of water or other liquids, mixtures, or substances into the distributing pipes of a potable water supply from any source or sources other than the intended source. Back siphonage is one type of backflow. 

Back siphonage—The flowing back of used, contaminated, or polluted water from a plumbing fixture or vessel into a

potable water supply because of negative pressure in the pipe. 

Branch—Any part of the piping system other than the main, riser, or stack.

Branch vent—A vent connecting one or more individual vents with a vent stack.

Building drain—Part of the lowest piping of a drainage system that receives the discharge from soil, waste, or other

drainage pipes inside the walls of the building (house) and conveys it to the building sewer beginning 3 feet outside the

building wall.

Cross connection—Any physical connection or arrangement between two otherwise separate piping systems (one of

which contains potable water and the other which contains either water of unknown or questionable safety or steam, gas,

or chemical) whereby there may be a flow from one system to the other, the direction of flow depending on the pressure differential between the two systems. (See Backflow and Back siphonage.)

Disposal field—An area containing a series of one or more trenches lined with coarse aggregate and conveying the effluent from a septic tank through vitrified clay pipe or perforated, nonmetallic pipe, laid in such a manner that the flow will

be distributed with reasonable uniformity into natural soil.

Drain—Any pipe that carries wastewater or waterborne waste in a building (house) drainage system.

Flood level rim—The top edge of a receptacle from which water overflows. 

Flushometer valve—A device that discharges a predetermined quantity of water to fixtures for flushing purposes and is

closed by direct water pressures. 

Flushometer toilet—a toilet using a flushometer valve that uses pressure from the water supply system rather than the

force of gravity to discharge water into the bowl, designed to use less water than conventional flush toilets.

Flush valve—A device located at the bottom of the tank for flushing toilets and similar fixtures.

Definitions of Terms Related to Home Water Systems

Figure 9.2. House Service Installation [1]
Meter stop—The meter stop is a valve placed on the

street side of the water meter to isolate it for installation

or maintenance. Many codes require a gate valve on the

house side of the meter to shut off water for plumbing

repairs. The curb and meter stops can be ruined in a short

time if used very frequently. 

The water meter is a device used to measure the amount

of water used in the house. It is usually the property of

the water provider and is a very delicate instrument that

should not be abused. In cold climates, the water meter is

often inside the home to keep it from freezing. When the

meter is located inside the home, the company providing

the water must make appointments to read the meter,

which often results in higher water costs unless the meter

is equipped with a signal that can be observed from the

outside. The water meter is not shown in Figure 9.2

because of regional differences in location of the unit. 

Because the electric system is sometimes grounded to an

older home’s water line, a grounding loop device should

be installed around the meter. Many meters come with a

yoke that maintains electrical continuity even though the

meter is removed.

Hot and Cold Water Main Lines

The hot and cold water main lines are usually hung from

the basement ceiling or in the crawl space of the home

and are attached to the water meter and hot water tank

on one side and the fixture supply risers on the other. These

pipes should be installed neatly and should be supported by

pipe hangers or straps of sufficient strength and number to

Healthy Housing Reference Manual 9-3

z

Grease trap—See Interceptor.

Hot water—Potable water heated to at least 120°F–130°F (49°C–54°C) and used for cooking, cleaning, washing dishes,

and bathing.

Insanitary—Unclean enough to endanger health.

Interceptor—A device to separate and retain deleterious, hazardous, or undesirable matter from normal waste and permit

normal sewage or liquid waste to discharge into the drainage system by gravity.

Main vent—The principal artery of the venting system, to which vent branches may be connected.

Leader—An exterior drainage pipe for conveying storm water from roof or gutter drains to the building storm drain,

combined building sewer, or other means of disposal.

Main sewer—See Public sewer.

Pneumatic—Pertaining to devices making use of compressed air as in pressure tanks boosted by pumps.

Potable water—Water having no impurities present in amounts sufficient to cause disease or harmful physiologic effects

and conforming in its bacteriologic and chemical quality to the requirements of the U.S. Environmental Protection

Agency’s Safe Drinking Water Act or meeting the regulations of other agencies having jurisdiction.

P & T (pressure and temperature) relief valve—A safety valve installed on a hot water storage tank to limit temperature

and pressure of the water.

P-trap—A trap with a vertical inlet and a horizontal outlet.

Public sewer—A common sewer directly controlled by public authority.

Relief vent—An auxiliary vent that permits additional circulation of air in or between drainage and systems.

Septic tank—A watertight receptacle that receives the discharge of a building’s sanitary drain system or part thereof and

is designed and constructed to separate solid from liquid, digest organic matter through a period of detention, and allow

the liquids to discharge into the soil outside of the tank through a system of open-joint or perforated piping or through a

seepage pit.

Sewerage system—A system comprising all piping, appurtenances, and treatment facilities used for the collection and 

disposal of sewage, except plumbing inside and in connection with buildings served, and the building drain.

Soil pipe—The pipe that directs the sewage of a house to the receiving sewer, building drain or building sewer.

Soil stack—The vertical piping that terminates in a roof vent and carries off the vapors of a plumbing system.

Stack vent—An extension of a solid or waste stack above the highest horizontal drain connected to the stack, sometimes

called a waste vent or a soil vent.

Definitions of Terms Related to Home Water Systems
prevent sagging. Older homes that have copper pipe with

soldered pipes can pose a lead poisoning risk, particularly

to children. In 1986, Congress banned lead solder

containing greater than 0.2% lead and restricted the lead

content of faucets, pipes, and other plumbing materials to

no more than 8%. The water should be tested to

determine the presence or level of lead in the water. Until

such tests can be conducted, the water should be run for

about 2 minutes in the morning to flush any such

material from the line. Hot and cold water lines should

be approximately 6 inches apart unless the hot water line

is insulated. This is to ensure that the cold water line does

not pick up heat from the hot water line [2].

The supply mains should have a drain valve stop and waste

valve to remove water from the system for repairs. These

valves should be on the low end of the line or on the end of

each fixture riser.

The fixture risers start at the basement main and rise

vertically to the fixtures on the upper floors. In a onefamily dwelling, riser branches will usually proceed from

the main riser to each fixture grouping. In any event, the

fixture risers should not depend on the branch risers for

support, but should be supported with a pipe bracket.

The size of basement mains and risers depends on the

number of fixtures supplied. However, a 3⁄4-inch pipe is

usually the minimum size used. This allows for deposits

on the pipe due to hardness in the water and will usually

give satisfactory volume and pressure.

In homes without basements, the water lines are

preferably located in the crawl space or under the slab.

The water lines are sometimes placed in the attic;

however, because of freezing, condensation, or leaks, this

placement can result in major water damage to the home.

In two-story or multistory homes, the water line

placement for the second floor is typically between the

studs and, then, for the shortest distance to the fixture,

between the joists of the upper floors.

Hot and Cold Water Piping Materials

Care must be taken when choosing the piping materials.

Some state and local plumbing codes prohibit using some

of the materials listed below in water distribution systems.

Polyvinyl Chloride (PVC). PVC is a white plastic pipe

used outside. It should be used only for cold water. Its

uses include water service between the meter and building

and irrigation [3]. PVC, or vinyl, is one of the most

commonly used materials in the marketplace. It is in

water pipes, packaging, construction and automotive

material, toys, and medical equipment. PVC is also

known as chloroethene, chloroethylene, and ethylene

monochloride. It is a known human carcinogen; PVC

causes liver cancer, angiosarcomas, and other health

problems in people who are exposed to it in their work

environment. Significant exposure can occur when the

material is heated or in the process of manufacturing the

material. As a result, PVC is closely regulated in the work

environment and not commonly recommended for use as

hot water piping. 

9-4 Plumbing

Storm sewer—A sewer used for conveying rain water, surface water, condensate, cooling water, or similar liquid waste.

Trap—A fitting or device that provides a liquid seal to prevent the emission of sewer gases without materially affecting

the flow of sewage or wastewater through it.

Vacuum breaker—A device to prevent backflow (back siphonage) by means of an opening through which air may be drawn

to relieve negative pressure (vacuum).

Vapor lock—A bubble of air that restricts the flow of water in a pipe.

Vent stack—The vertical vent pipe installed to provide air circulation to and from the drainage system and that extends

through one or more stories.

Water hammer—The loud thump of water in a pipe when a valve or faucet is suddenly closed.

Water service pipe—The pipe from the water main or other sources of potable water supply to the water-distributing 

system of the building served.

Water supply system—Consists of the water service pipe, the water-distributing pipes, the necessary connecting pipes, 

fittings, control valves, and all appurtenances in or adjacent to the building or premises.

Wet vent—A vent that receives the discharge of waste other than from water closets.

Yoke vent—A pipe connecting upward from a soil or waste stack to a vent stack to prevent pressure changes in the stacks.

Definitions of Terms Related to Home Water Systems
PVC also contains phthalates, which accumulate in body

tissues and can damage the liver and lungs. It has been

shown in lower mammals to damage reproductive organs.

Phthalates are freely given off by the plastics in which it is

used; and, because it is fat soluble, is found in meats and

cheeses packaged in PVC. Although phthalates show

almost no toxicity in adult humans in acute (short-term)

doses, even at high doses, the cumulative nature of

phthalate toxicity results in toxic effects even at very low

dosages with chronic exposure (over a long period of

time). Very young infants do not metabolize phthalates as

well as do adults, and so are at greater risk for harm. The

availability of phthalates in the consumer environment

causes inevitable chronic ingestion for almost all modern

industrial consumers. 

Lead is used as a hardening agent to manufacture PVC

materials. Therefore, it is very important that third-party

testing be done on PVC piping. PVC piping should have

the stamp of both the testing laboratory and a potable

water (PW) mark to indicate that it meets appropriate

standards for use as potable water piping. 

Chlorinated PVC (CPVC). CPVC is a slightly yellow

plastic pipe used inside homes. It has a long service life,

but is not quite as tough as copper. Some areas with

corrosive water will benefit by using chlorinated PVC

piping. CPVC piping is designed and recommended for

use in hot and cold potable water distribution systems [4].

Copper. Copper comes in three grades: 

• M for thin wall pipe (used mainly inside homes); 

• L for thicker wall pipe (used mainly outside for

water services); and 

• K, the thickest (used mainly between water mains

and the water meter). 

Copper lasts a long time, is durable, and connects well to

valves. It should not be installed if the water has a pH of

6.5 or less. Most public utilities supply water at a pH

between 7.2 and 8.0. Many utilities that have source

water with a pH below 6.5 treat the water to raise the

pH. Private well water systems often have a pH below

6.5. When this is the case, installing a treatment system

to make the water less acidic is a good idea [5].

Galvanized Steel. Galvanized pipe corrodes rather easily.

The typical life of this piping is about 40 years. One of

the primary problems with galvanized steel is that, in

saturated water, the pipe will become severely restricted

by corrosion that eventually fills the pipe completely.

Another problem is that the mismatch of metals between

the brass valves and the steel results in corrosion.

Whenever steel pipe meets copper or brass, the steel pipe

will rapidly corrode. Dielectric unions can be used

between copper and steel pipes; however, these unions

will close off flow in a short time. The problem with

dielectric unions is that they break the grounding effect if

a live electrical wire comes in contact with a pipe. Some

cities require the two pipes to be bonded electrically to

maintain the safety of grounded pipes. 

PEX. PEX is an acronym for a cross-formulated

polyethylene. “PE” refers to the raw material used to make

PEX (polyethylene), and “X” refers to the cross-linking of

the polyethylene across its molecular chains. The

molecular chains are linked into a three-dimensional

network that makes PEX remarkably durable within a wide

range of temperatures, pressures, and chemicals [6].

PEX is flexible and can be installed with fewer fittings

than rigid plumbing systems. It is a good choice for

repiping and for new homes and works well for corrosive

water conditions. PEX stretches to accommodate the

expansion of freezing water and then returns to its

original size when water thaws. Although it is highly

freeze-resistant, no material is freeze-proof. 

Kitec. Kitec is a multipurpose pressure pipe that uniquely

unites the advantages of both metal and plastic. It is made

of an aluminum tube laminated to interior and exterior

layers of plastic. Kitec provides a composite piping system

for a wide range of applications, often beyond the scope of

metal or plastic alone. Unlike copper and steel materials,

Kitec is noncorroding and resists most acids, salt

solutions, alkalis, fats, and oils. 

Poly. Poly pipe is a soft plastic pipe that comes in coils

and is used for cold water. It can crack with age or wear

through from rocks. Other weak points can be the

stainless steel clamps or galvanized couplings.

Polybutylene [Discontinued]. Polybutylene pipe is a soft

plastic pipe. This material is no longer recommended

because of early chemical breakdown. Individuals with a

house, mobile home, or other structure that has

polybutylene piping with acetal plastic fittings may be

eligible for financial relief if they have replaced that

plumbing system. For claims information, call 1-800-

392-7591 or go to www.pbpipe.com.

Healthy Housing Reference Manual 9-5
Hot Water Safety

In the United States, more than 112,000 people enter a

hospital emergency room each year with scald burns. Of

these, 6,700 (6%), have to be hospitalized. Almost 3,000 of

these scald burns come from tap water in the home. The

three high risk groups are children under the age of 5 years,

the handicapped, and adults over the age of 65 years. It

only takes 1 second to get a serious third-degree burn

from water that is 156°F (69°C). Tap water is too hot if

instant coffee granules melt in it.

Young children, some handicapped individuals, and

elderly people are particularly vulnerable to tap water

burns. Children cannot always tell the hot water faucets

from the cold water faucets. Children have delicate skin

and often cannot get out of hot water quickly, so they

suffer hot water burns most frequently. Elderly and

handicapped persons are less agile and more prone to falls

in the bath tub. They also may have diseases, such as

diabetes, that make them unable to feel heat in some

regions of the body, such as the hands and feet. Thirddegree burns can occur quickly—in 1 second at 156°F

(69°C), in 2 seconds at 149°F (65°C), in 5 seconds at

140°F (60°C), and in 15 seconds at 133°F (56°C).

A tap-water temperature of 120°F–130°F (49°C–54°C) is

hot enough for washing clothes, bedding, and dishes.

Even at 130°F (54°C), water takes only a few minutes of

constant contact to produce a third-degree burn. Few

people bathe at temperatures above 110°F (43°C), nor

should they. Water heater thermostats should be set at

about 120°F (49°C) for safety and to save 18% of the

energy used at 140°F (60°C). Antiscald devices for faucets

and showerheads to regulate water temperature can help

prevent burns. A plumber should install and calibrate

these devices. Most hot water tank installations now

require an expans ion tank to reduce pressure fluctuations

and a heat trap to keep hot water from escaping up pipes.

Types of Water Flow Controls

It is essential that valves be used in a water system to

allow the system to be controlled in a safe and efficient

manner. The number, type, and size of valves required

will depend on the size and complexity of the system. Most

valves can be purchased in sizes and types to match the

pipe sizes used in water system installations. Listed below

are some of the more commonly encountered valves with

a description of their basic functions.

Shutoff Valves. Shutoff valves should be installed between

the pump and the pressure tank and between the pressure

tank and service entry to a building. Globe, gate, and ball

valves are common shutoff valves. Gate and ball valves

cause less friction loss than do globe valves; ball valves last

longer and leak less than do gate valves. Shutoff valves

allow servicing of parts of the system without draining the

entire system.

Flow-control Valves. Flow-control valves provide uniform

flow at varying pressures. They are sometimes needed to

regulate or limit the use of water because of limited water

flow from low-yielding wells or an inadequate pumping

system. They also may be needed with some treatment

equipment. These valves are often used to limit flow to a

fixture. Orifices, mechanical valves, or diaphragm valves

are used to restrict the flow to any one service line or

complete system and to assure a minimum flow rate to all

outlets.

Relief Valves. Relief valves permit water or air to escape

from the system to relieve excess pressure. They are

spring-controlled and are usually adjustable to relieve

varying pressures, generally above 60 psi. Relief valves

should be installed in systems that may develop pressures

exceeding the rated limits of the pressure tank or

distribution system. Positive displacement and

submersible pumps and water heaters can develop these

excessive pressures. The relief valve should be installed

between the pump and the first shutoff valve and must be

capable of discharging the flow rate of the pump. A

combined pressure and temperature relief valve is needed

on all water heaters. Combination pressure and vacuum

relief valves also should be installed to prevent vacuum

damage to the system.

Pressure-reducing Valves. A pressure-reducing valve is

used to reduce line pressure. On main lines, this allows

the use of thinner walled pipe and protects house

plumbing. Sometimes these valves are installed on

individual services to protect plumbing.

Altitude Valves. Often an altitude valve is installed at the

base of a hot water tank to prevent it from overflowing.

Altitude valves sense the tank level through a pressure line

to the tank. An adjustable spring allows setting the level

so that the valve closes and prevents more inflow when

the tank becomes full.

Foot Valves. A foot valve is a special type of check valve

installed at the end of a suction pipe or below the jet in a

well to prevent backflow and loss of prime. The valve

should be of good quality and cause little friction loss.

9-6 Plumbing
Check Valves. Check valves have a function similar to

foot valves. They permit water flow in only one direction

through a pipe. A submersible pump may use several

check valves. One is located at the top of the pump to

prevent backflow from causing back spin of the impellers.

Some systems use another check valve and a snifter valve.

They will be in the drop pipe or pitless unit in the well

casing and allow a weep hole located between the two

valves to drain part of the pipe. When the pump is started,

it will force the air from the drained part of the pipe into

the pressure tank, thus recharging the pressure tank.

Frost-proof Faucets. Frost-proof faucets are installed

outside a house with the shutoff valve extending into the

heated house to prevent freezing. After each use, the water

between the valve and outlet drains, provided the hose is

disconnected, so water is not left to freeze.

Frost-proof Hydrants. Frost-proof hydrants make outdoor

water service possible during cold weather without the

danger of freezing. The shutoff valve is buried below the

frost line. To avoid submerging it, which might result in

contamination and back siphoning, the stop-and-waste

valve must drain freely into a rock bed. These hydrants

are sometimes prohibited by local or state health authorities.

Float Valves. Float valves respond to a high water level to

close an inlet pipe, as in a tank-type toilet.

Miscellaneous Switches. Float switches respond to a high

and/or low water level as with an intermediate storage

tank. Pressure switches with a low-pressure cutoff stop the

pump motor if the line pressure drops to the cutoff point.

Low-flow cutoff switches are used with submersible

pumps to stop the pump if the water discharge falls below

a predetermined minimum operating pressure. Highpressure cut-off switches are used to stop pumps if the

system pressure rises above a predetermined maximum.

Paddle-type flow switches detect flow by means of a

paddle placed in the pipe that operates a mechanical

switch when flow in the pipe pushes the paddle.

The inadvertent contamination of a public water supply

as a result of incorrectly installing plumbing fixtures is a

poten tial public health problem in all communities.

Continuous surveillance by environmental health

personnel is necessary to know whether such public

health hazards have developed as a result of additions or

alterations to an approved system. All environmental

health specialists should learn to recognize the three

general types of defects found in potable water supply

systems: backflow, back siphonage, and overhead leakage

into open potable water containers. If identified, these

conditions should be corrected immediately to prevent

the spread of disease or poisoning from high concentrations

of organic or inorganic chemicals in the water.

Water Heaters

Water heaters (Figure 9.3) are usually powered by

electricity, fuel oil, gas, or, in rare cases, coal or wood.

They consist of a space for heating the water and a

storage tank for providing hot water over a limited period

of time. All water heaters should be fitted with a

temperature-pressure (T&P) relief valve no matter what

fuel is used. The installation port for these valves may be

found on the top or on the side of the tank near the top.

T&P valves should not be placed close to a wall or door

jamb, where they would be inaccessible for inspection and

use. Hot water tanks sometimes are sold without the

T&P valve, and it must be purchased separately. This fact

alone should encourage individual permitting and

inspection by counties and municipalities to ensure that

they are installed. The T&P valve should be inspected at a

minimum of once per year.

A properly installed T&P valve will operate when either

the temperature or the pressure becomes too high due to

an interruption of the water supply or a faulty thermostat.

Figure 9.3 shows the correct installation of a gas water

Healthy Housing Reference Manual 9-7

Figure 9.3. Gas Water Heater [1]
heater. Particular care should be paid to the exhaust port

of the T&P valve. Figure 9.4 shows the placement of the

T&P valve. This vent should be directed to within

6 inches of the floor, and care must be taken to avoid

reducing the diameter of the vent and creating any

unnecessary bends in the discharge pipe. Most codes will

allow only one 90° bend in the vent. The point is to

avoid any constrictions that could slow down the steam

release from the tank to avoid explosive pressure buildup. 

Water heaters that are installed on wooden floors should

have water collection pans with a drainage tube that drains to

a proper drain. The pan should be checked on a regular basis.

Tankless Water Heaters 

A tankless unit has a heating device that is activated by

the flow of water when a hot water valve is opened. Once

activated, the heater delivers a constant supply of hot

water. The output of the heater, however, limits the rate

of the heated water flow. Demand water heaters are

available in propane (LP), natural gas, or electric models.

They come in a variety of sizes for different applications,

such as a whole-house water heater, a hot water source for

a remote bathroom or hot tub, or as a boiler to provide

hot water for a home heating system. They can also be

used as a booster for dishwashers, washing machines, and a

solar or wood-fired domestic hot water system [7]. 

The appeal of demand water heaters is not only the

elimination of the tank standby losses and the resulting

lower operating costs, but also the fact that the heater

delivers hot water continuously. Most tankless models

have a life expectancy of more than 20 years. In contrast,

storage tank water heaters last 10 to 15 years. Most

tankless models have easily replaceable parts that can

extend their life by many years more.

Drainage System

Water is brought into a house, used, and discharged

through the drainage system. This system is a sanitary

drainage system carrying just interior wastewater.

Sanitary Drainage System

The proper sizing of the sanitary drain or house drain

depends on the number of fixtures it serves. The usual

minimum size is 4 inches in diameter. The materials used

are usually cast iron, vitrified clay, plastic, and, in rare

cases, lead. The top two pipe choices for drain, waste, and

vent (DWV) systems are PVC or ABS. For proper flow in

the drain, the pipe should be sized and angled so that the

pipe is approximately half full. This ensures proper

scouring action so that the solids contained in the waste

will not be deposited in the pipe. 

Using PVC in DWV pipe is a two-step process needing a

primer and then cement. ABS uses cement only. In most

cases the decision will be made on the basis of which

material is sold in an area. Few areas stock both materials

because local contractors usually favor one or the other.

ABS costs more than PVC in many areas, but Schedule

40 PVC DWV solid core pipe is stronger than ABS.

Their durability is similar.

Size of House Drain. The Uniform Plumbing Code

Committee has developed a method of sizing house

drains in terms of fixture units. One fixture unit equals

approximately 71⁄2 gallons of water per minute. This is the

surge flow rate of water discharged from a wash basin in

one minute. 

All other fixtures have been related to this unit. Fixture

unit values are shown in Table 9.1.

Grade of House Drain. A house drain should be sloped

toward the sewer to ensure scouring of the drain. The

usual pitch of a house or building sewer is a 1⁄4-inch drop

in 1 foot of length. The size of the drain is based on the

fixture units flowing into the pipe and the slope of the

drain. Table 9.2 shows the required pipe size for the system.

9-8 Plumbing

Figure 9.4. Temperature-Pressure Valve
House Drain Installation. Typical branch connections to

the main are shown in Figure 9.5.

Fixture and Branch Drains. A branch drain is a waste

pipe that collects the waste from two or more fixtures and

conveys it to the sewer. It is sized in the same way as the

sewer, taking into account that all toilets must have a

minimum 3-inch diameter drain, and only two toilets

may connect into one 3-inch drain. All branch drains

must join the house drain with a Y-fitting as shown in

Figure 9.5. The same is true for fixture drains joining

branch drains. The Y-fitting is used to eliminate, as much

as possible, the deposit of solids in or near the

connection. A buildup of these solids will block the drain.

Recommended minimum sizes of fixture drains are shown

in Table 9.2. 

Traps 

A plumbing trap is a device used in a waste system to

prevent the passage of sewer gas into the structure and yet

not hinder the fixture’s discharge to any great extent. All

fixtures connected to a household plumbing system

should have a trap installed in the line. The effects of

sewer gases on the human body are well known; many of

the gases are extremely harmful. In addition, certain sewer

gases are explosive. 

P-trap. The most commonly used trap is the P-trap

(Figure 9.6). The depth of the seal in a trap is usually

2 inches. A deep seal trap has a 4-inch seal. 

As mentioned earlier, the purpose of a trap is to seal out

sewer gases from the structure. Because a plumbing

system is subject to wide variations in flow, and this flow

originates in many different sections of the system,

pressures vary widely in the waste lines. These pressure

differences tend to remove the water seal in the trap. The

waste system must be properly vented to prevent the traps

from siphoning dry, thus losing their water seal and

allowing gas from the sewer into the building. 

Objectionable Traps. The S-trap and the 3⁄4 S-trap

(Figure 9.7) should not be used in plumbing installations.

They are almost impossible to ventilate properly, and the

3⁄4 S-trap forms a perfect siphon. Mechanical traps were

introduced to counteract this problem. It has been found,

however, that the corrosive liquids flowing in the system

corrode or jam these mechanical traps. For this reason, most

plumbing codes prohibit mechanical traps.

Healthy Housing Reference Manual 9-9

Table 9.2. Sanitary House Drain Sizes 

Table 9.1. Fixture Unit Values 
The bag trap, an extreme form of S-trap, is seldom found. 

Figure 9.7 also shows this type of S-trap.

Traps are used only to prevent the escape of sewer gas into

the structure. They do not compensate for pressure

variations. Only proper venting will eliminate pressure

problems. 

Ventilation

A plumbing system is ventilated to prevent trap seal loss,

material deterioration, and flow retardation.

Trap Seal Loss. The seal in a plumbing trap may be lost

due to siphonage (direct and indirect or momentum),

back pressure, evaporation, capillary attraction, or wind 

effect. The first two are probably the most common

causes of loss. Figure 9.8 depicts this siphonage process;

Figure 9.9 depicts loss of trap seal. 

If a waste pipe is placed vertically after the fixture trap, as

in an S-trap, the wastewater continues to flow after the

fixture is emptied and clears

the trap. This is caused by the

pressure of air on the water of

the fixture being greater than

the pressure of air in the waste

pipe. The action of the water

discharging into the waste pipe

removes the air from that pipe

and thereby causes a negative

pressure in the waste line.

In the case of indirect or

momentum siphonage, the

flow of water past the entrance

to a fixture drain in the waste

pipe removes air from the

fixture drain. This reduces the

air pressure in the fixture

drain, and the entire assembly

acts as an aspirator. (Figures

9.10 and 9.11 show plumbing

configurations that would

allow this type of siphonage to

occur.) 

Back Pressure. The flow of

water in a soil pipe varies

according to the fixtures being

used. Small flows tend to cling

to the sides of the pipe, but

large ones form a slug of waste

as they drop. As this slug of

water falls down the pipe, the

air in front of it becomes

Figure 9.7. Types of S-traps

Figure 9.8. Trap Seal: [a]

Seal Intact; [b] Fixture

Draining; [c] Loss of Gas

Seal [1]

Figure 9.5. Branch Connections Figure 9.6. P-trap [1]

9-10 Plumbing
pressurized. As the pressure

builds, it seeks an escape

point. This point is either a

vent or a fixture outlet. If the

vent is plugged or there is no

vent, the only escape for this

air is the fixture outlet. 

The air pressure forces the

trap seal up the pipe into the

fixture. If the pressure is great

enough, the seal is blown out

of the fixture entirely. Figures

9.8 and 9.9 illustrate the

potential for this type of

problem. Large water flow past

the vent can aspirate the water

from the trap, while water

flow approaching the trap can

blow the water out of the trap.

Vent Sizing. Vent pipe installation is similar to that of soil

and waste pipe. The same fixture unit criteria are used.

Table 9.3 shows minimum vent pipe sizes.

Vent pipes of less than 11⁄4 inches in diameter should not

be used. Vents smaller than this diameter tend to clog and

do not perform their function.

Individual Fixture Ventilation. Figure 9.12 shows a

typical installation of a wall-hung plumbing unit. This

type of ventilation is generally used for sinks, drinking

fountains, and so forth. Air admittance valves are often

used for individual fixtures. Figure 9.13 shows a typical

installation of a bathtub or shower ventilation system.

Figure 9.14 shows the proper vent connection for toilet

fixtures and Figure 9.15 shows a janitor’s sink or slop sink

that has the proper P-trap. For the plumbing fixture to

work properly, it must be vented as in Figures 9.13 and 9.14.

Unit Venting. Figures 9.10 and 9.11 show a back-to-back

shared ventilation system for various plumbing fixtures.

The unit venting system is commonly used in apartment

buildings. This type of system saves a great deal of money

and space when fixtures are placed back-to-back in

separate apartments. It does, however, pose a problem if

the vents are undersized because they will aspirate the

water from the other trap. Figure 9.16 shows a double

combination Y-trap used for joining the fixtures to the

common soil pipe fixture on the other side of the wall.

Wet Venting. Bathroom fixture groupings are commonly

wet vented; that is, the vent pipe also is used as a waste line. 

Total Drainage System

The drain, soil waste, and vent systems are all connected, and

the inspector should remember the following fundamentals:

Working vents must provide air to all fixtures to ensure

the movement of waste into the sewer. Improperly vented

fixtures will drain slowly and clog often. They also present

a health risk if highly toxic and explosive sewer gases enter

the home. Correct venting is shown in Figures 9.10–9.15;

incorrect venting is shown in Figures 9.8 and 9.9. A wet

Healthy Housing Reference Manual 9-11

Figure 9.9. Loss of Trap Seal in

Lavatory Sink [1]

Figure 9.10. Back-to-back Venting [Toilet]

Figure 9.11. Back-to-back Venting [Sink]
vent can result in one of the traps siphoning the other dry

when large volumes of water are poured down the drain.

Wet vents are not permitted by many state plumbing

codes because of the potential for self-siphoning.

Backup of sewage into sinks, dishwashers, and other

appliances is always a possibility unless the system is

equipped with air gaps or vacuum breakers. All

connections to the potable water system must be a

minimum of two pipe diameters above the overflow of

the appliance and, in some cases, where flat surfaces are

near, two and one-half pipe diameters above the overflow

of the appliance.

A simple demonstration of how easily siphoning can

occur is to hold a glass of water with food coloring in it

with the tip of a faucet in the colored water. If the sink’s

vegetable sprayer is directed to a second glass and sprayed,

in most cases, the colored water will be aspirated into the

faucet and then out of the sprayer into the second glass.

Weed or pest killer attachments that hook to garden hoses

work on the same principle. Figure 9.17 shows an outside

hose bib equipped with a vacuum breaker. In the areas of

the United States that freeze, these vacuum breakers must

be removed because they trap water in the area of the line

that can freeze and burst. Many vacuum breakers sold

today automatically drain to prevent freeze damage. 

9-12 Plumbing

Figure 9.12. Wall-hung Fixtures 

Figure 9.13. Unit Vent Used in Bathtub Installation

Table 9.3. Minimum Fixture Service Pipe Diameters

Figure 9.14. Toilet Venting
Devices that pull water from a utility may create negative

pressures that can damage water piping and pull

dangerous substances into the line at the same time.

These devices include power sprayers that hook to the

home hose bib (outside faucets) and pressurize the spray

by creating a vacuum on the supply side.

Corrosion Control

To understand the proper maintenance procedures for the

prevention and elimination of water quality problems in

plumbing systems, it is necessary to understand the

process used to determine the chemical aggressiveness of

water. The process is used to determine when additional

treatment is needed. Water that is out of balance can

result in many negative outcomes, from toxic water to

damaged and ruined equipment. 

Water dissolves and carries materials when it is not

saturated. An equilibrium among pH, temperature,

alkalinity, and hardness controls water’s ability to create

scale or to dissolve material. If water is saturated with

harmless or beneficial substances, such as calcium, then

the threat of damage can be mitigated. The Langelier

method, developed in the early 1930s, is a process used in

boiler management,

municipal water

treatment, and

swimming pools to

provide this balance. In

the Langelier index,

saturation over 0.3 is

scale forming, and a

saturation below 0.3 is

corrosive.

The

susceptibility of

metal to

corrosion is as

follows (most

susceptible to

least susceptible):

magnesium, zinc,

aluminum,

cadmium, mild

steel, cast iron,

stainless steel (active), lead-tin solder, lead, tin, brass, gun

metal, aluminum bronze, copper, copper-nickel alloy,

Monel, titanium, stainless steel (passive), silver, gold, and

platinum.

Water Conservation

How much attention should be paid to fixtures that just

drip a little bit of water or that just will not quite shut

off? At 30 drops per minute, you will lose and pay for

54 gallons per month. At 60 drops per minute, you will

lose and pay for 113 gallons per month. At 120 drops per

minute, you will lose and pay for 237 gallons per month.

This is only a small loss of water considering the 5 to

7 gallons per flush used by a properly functioning toilet.

If the toilet is not properly maintained, the loss of water

and its effect on the monthly water bill can be incredible.

Lower flow toilets have been mandated to save precious

and limited resources. Most pre-1992 toilets used up to

7 gallons per flush. Toilets have since evolved to use 5.5,

then 3.5, and now 1.6 gallons per flush. 

With the changes in the water usage laws in 1992, there

were many customer complaints, and plumbers were in the

bad position of installing products that nobody wanted to

use. New and updated products now work better than the

old water wasters. 

According to the EPA, in 2000, a typical U.S. family of

four spent approximately $820 every year on water and sewer

fees, plus another $230 in energy for heating water. In

many cities, according to the U.S. EPA, water and sewer

costs can be more than twice those amounts. Many people do

not realize how much money they can save by taking simple

steps to save water, and they do not know the cumulative

effects small changes can have on water resources and

environmental quality. Fixing a leaky faucet, toilet, or

lawn-watering system can reduce water consumption.

Changing to water-efficient plumbing fixtures and

appliances can result in major water and energy savings [9,10].

Healthy Housing Reference Manual 9-13

Figure 9.15. Janitor’s Sink

Figure 9.16. Common Y-trap

Figure 9.17. Hose Bib With Vacuum Breaker
Summer droughts remind many of the need to appreciate

clean water as an invaluable resource. As the U.S. population

increases, the need for clean water supplies continues to

grow dramatically and puts additional stress on our limited

water resources. We can all take steps to save and conserve

this valuable resource.

The EPA [11] suggests the following steps homeowners

should take right away to save water and money:

• Stop leaks!—Check indoor water-using

appliances and devices for leaks. Pay particular

attention to toilets that leak.

• Take showers—Showers use considerably less

water than do baths.

• Replace shower heads—Replacement shower

heads are available that reduce water use.

• Turn the water off when not needed—While

brushing your teeth, turn the water off until you

need to rinse.

• Replace your old toilet—The largest water user

inside the home is the toilet. If a home was built

before 1992 and the toilet has never been

replaced, it is very likely that it is not a waterefficient, 1.6 gallons-per-flush toilet. Choose a

replacement toilet carefully to ensure that what

you make up per individual flush, you do not lose

because you must flush more often.

• Replace your clothes washer—The second largest

water user in the home is the washing machine.

Energy Star-rated washers that also have a water

factor at or lower than 9.5 use 35%–50% less

water and 50% less energy per load. This saves

money on both water and energy bills.

• Plant the right plants with proper landscape

design and irrigation—Select plants that are

appropriate for the local climate. Having a 100%

turf lawn in a dry desert climate uses a significant

amount of water. Also, home owners should consider

the benefits of a more natural landscape or wildscape.

• Water plants only as needed—Most water wasted

in the garden is by watering when plants do not

need it or by not maintaining the irrigation system.

If manually watering, set a timer and move the

hose promptly. Make sure the irrigation controller

has a rain shutoff device and that it is

appropriately scheduled. Drip irrigation should be

considered where practical. Newer irrigation

systems have sensors to prevent watering while it

is raining.

Putting It All Together

These photographs, taken during construction of a home

by Habitat for Humanity, show various plumbing

elements discussed in this chapter.

9-14 Plumbing

A. 

Hot and cold copper water lines and drain, p-trap and vent,

and vent for the washer drain shown. When a house is

vacant for awhile, the P-trap should be filled with water to

prevent sewer gas from entering the home. Mineral oil added

to the water can slow the loss of fluid in the trap.

B. 

Hot and cold water pipes, soil pipe, and vent shown.
References

1. US Environmental Protection Agency. United

States Environmental Protection Agency guidance

from hotline compendium: lead ban.

Washington, DC: US Environmental Protection

Agency; 1988. Available from URL:

http://www.epa.gov/safewater/wsg/wsg_H19.pdf.

2. Uni-Bell PVC Pipe Association. Handbook of

PVC pipe design and construction. Dallas: UniBell PVC Pipe Association; 2001. Available from

URL: http://www.uni-bell.org/pubs/

handbook.pdf.

3. Occupational Safety and Health Administration.

Safety hazard information bulletin on the use of

polyvinyl chloride (PVC) pipe in above ground

installations. Washington, DC: Occupational

Safety and Health Administration; 1988.

http://www.osha.gov/dts/hib/hib_data/

hib19880520.html.

4. Copper Development Association. Copper in

your home: plumbing, heating, cooling. New

York: Copper Development Association; no date.

Available from URL: http://www.copper.org/

copperhome/PHC/phc_home.html.

5. Plastic Pipe and Fittings Association. Cross-linked

polyethylene. Glen Ellyn, IL: Plastic Pipe and

Fittings Association; no date. Available from

URL:

http://www.ppfahome.org/pex/historypex.html.

6. NAMCO. Determine the total fixture unit load.

Dallas: NAMCO; no date. Available from URL:

http://www.namco-div.com/booster/

sel%20criteria/fixtureload.htm.

7. Energy Efficiency and Renewable Energy

Clearinghouse. Demand (tankless or

instantaneous) water heaters. Merrifield, VA:

Energy Efficiency and Renewable Energy

Clearinghouse; no date. Available from URL:

http://www.toolbase.org/tertiaryT.asp?

DocumentID=3206&&&CategoryID=0.

8. Public Health-Seattle and King County. Public

health plumbing program: water supply fixture

units (WSFU) and minimum fixture branch pipe

sizes. Seattle, WA: Public Health-Seattle and King

E. 

Polyethylene water

service pipe entering

the home through the

concrete basement wall

shown. White plastic

adapter shown

between polyethylene

water service pipe and

3⁄4 inch copper water

line. A short distance

above the adapter is a

pressure reducing

valve. To the right of

water line is the 4-inch PVC pipe waste water line.

Healthy Housing Reference Manual 9-15

C. 

Vent for the sink and toilet, soil pipe, and cap for toilet

connection shown. A wax or plastic seal shaped like a donut

will be placed on the cap before bolting down the toilet.

D. 

Mixing and antiscald water flow contro, vent for fixture, hot

and cold water lines, and bathtub overflow shown. At this

point in construction, insulation might be considered for the

hot water lines. Water service and waste water line.
County; no date. Available from URL: http://

www.metrokc.gov/health/plumbing/wsfu.htm.

9. US Environmental Protection Agency. Developing

water system financial capacity. Washington, DC:

US Environmental Protection Agency; 2002.

Available from URL:

http://www.epa.gov/safewater/dwa/

electronic/presentations/pwsoper/fincapacity.pdf. 

10. US Environmental Protection Agency. Water and

wastewater pricing. Washington, DC: US

Environmental Protection Agency; no date.

Available from URL: http://www.epa.gov/water/

infrastructure/pricing/.

11. US Environmental Protection Agency. Using

water wisely in the home. Washington, DC: US

Environmental Protection Agency; 2002.

Available from URL:

http://www.epa.gov/owm/water-efficiency/

waterconservation_final.pdf. 

Additional Sources of Information

American Backflow Prevention Association. Available

from URL: http://www.abpa.org.

American Society of Plumbing Engineers. Available from

URL: http://aspe.org.

American Society of Sanitary Engineering. Available from

URL: http://www.asse-plumbing.org.

American Water Works Association. Available from URL:

http://www.awwa.org.

National Sanitation Foundation. Available from URL:

http://www. nsf.org/international.

Plumbing-Heating-Cooling Contractors Association.

Available from URL: http://www.phccweb.org.

Underwriters Laboratories Inc. Available from URL:

http://www.ul.com.

For more water conservation tips and energy saving ideas

for businesses, industries, and individuals, visit the EPA’s

Water-use Efficiency Program Web site

(http://www.epa.gov/owm/water-effic iency/index.htm).

9-16 Plumbing
Chapter 10—On-site Wastewater Treatment

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

Treatment of Human Waste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

On-site Wastewater Treatment Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Septic Tank Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Alternative Septic Tank Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-6

Maintaining the On-site Wastewater Treatment Systems . . . . . . . . . . . . . . . . . . . .10-8

Symptoms of Septic System Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-9

Septic Tank Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-9

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-12

Figure 10.1. Conventional On-site Septic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

Figure 10.2. Straight Pipe Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-2

Figure 10.3. Clear Creek Water Contaminated With Sewage. . . . . . . . . . . . . . . . . . . . . . . . . . .10-2

Figure 10.4. Septic Tank System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Figure 10.5. Septic Tank. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-4

Figure 10.6. On-site Sewage Disposal System Site Evaluation Form . . . . . . . . . . . . . . . . . . . . .10-5

Figure 10.7. Cross-section of an Absorption Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-5

Figure 10.8. Mound System Cutaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-7

Figure 10.9. Low Pressure On-site System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-7

Figure 10.10. Plant-rock Filter System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-8

Figure 10.11. Sludge and Scum in Multicompartment Septic Tank . . . . . . . . . . . . . . . . . . . . . . .10-10

Table 10.1. Mound System Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . .10-6

Table 10.2. Low-pressure Pipe Systems Advantages and Disadvantages . . . . . . . . . . . . . . . . . .10-7

Table 10.3. Plant Rock Filter System Advantages and Disadvantages . . . . . . . . . . . . . . . . . . . .10-8

Table 10.4. Septic Tank System Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-10

Healthy Housing Reference Manual 1

Contents
“Technology has made large populations possible; 

large populations now make technology indispensable.”

Joseph Wood Krutch, Author, 1932

Introduction

The French are considered the first to use an

underground septic tank system in the 1870s. By the

mid 1880s, two-chamber, automatic siphoning septic

tank systems, similar to those used today, were being

installed in the United States. Even now, more than a

century later, septic tank systems represent a major

household wastewater treatment option. Fully one-fourth

to one-third of the homes in the United States use such a

system [1]. 

On-site sewage disposal systems are used in rural areas

where houses are spaced so far apart that a sewer system

would be too expensive to install, or in areas around

cities where the city government has not yet provided

sewers to which the homes can connect. In these areas,

people install their own private sewage treatment plants.

As populations continue to expand beyond the reach of

municipal sewer systems, more families are relying on

individual on-site wastewater treatment systems and

private water supplies. The close proximity of on-site

water and wastewater systems in subdivisions and other

developed areas, reliance on marginal or poor soils for

on-site wastewater disposal, and a general lack of

understanding by homeowners about proper septic tank

system maintenance pose a significant threat to public

health. The expertise on inspecting, maintaining, and

installing these systems generally rests with the

environmental health staff of the local county or city

health departments. 

These private disposal systems are typically called septic

tank systems. A septic tank is a sewage holding device

made of concrete, steel, fiberglass, polyethylene, or other

approved material cistern, buried in a yard, which may

hold 1,000 gallons or more of wastewater. Wastewater

flows from the home into the tank at one end and leaves

the tank at the other (Figure 10.1) [2]. 

Proper maintenance of septic tanks is a public health

necessity. Enteric diseases such as cryptospordiosis,

giardiasis, salmonellosis, hepatitis A, and shigellosis may

be transmitted through human excrement. Historically,

major epidemics of cholera and typhoid fever were

primarily caused by improper disposal of wastewater. The

earliest epidemiology lesson learned was through the

effort of Dr. John Snow of England (1813–1858) during

a devastating cholera epidemic in London [3]. Dr. Snow,

known as the father of field epidemiology, discovered

that the city's water supply was being contaminated by

improper disposal of human waste. He published a brief

pamphlet, On the Mode of Communication of Cholera,

suggesting that cholera is a contagious disease caused by

a poison that reproduces in the human body and is

found in the vomitus and stools of cholera patients. He

believed that the main, although not only, means of

transmission was water contaminated with this poison.

This differed from the commonly accepted belief at the

time that diseases were transmitted by inhaling vapors.

Treatment of Human Waste

Safe, sanitary, nuisance-free disposal of wastewater is a

public health priority in all population groups, small and

large, rural or urban. Wastewater should be disposed of

in a manner that ensures that

• community or private drinking water supplies are

not threatened;

• direct human exposure is not possible;

• waste is inaccessible to vectors, insects, rodents, 

or other possible carriers;

• all environmental laws and regulations are 

complied with; and

• odor or aesthetic nuisances are not created.

Chapter 10: On-site Wastewater Treatment

Healthy Housing Reference Manual 10-1

Figure 10.1. Conventional On-site Septic System [2] 

Effluent leaves home through a pipe, enters a septic tank, travels through a

distribution box to a trench absorption system composed of perforated pipe.
In Figure 10.2, a straight pipe from a nearby home

discharges untreated sewage that flows from a shallow

drainage ditch to a roadside mountain creek in which

many children and some adults wade and fish. The clear

water (Figure 10.3) is quite deceptive in terms of the

health hazard presented. A 4-mile walk along the creek

revealed 12 additional pipes that were also releasing

untreated sewage. Some people in the area reportedly

regard this creek as a source of drinking water.

Raw or untreated domestic wastewater (sewage) is

primarily water, containing only 0.1% of impurities that

must be treated and removed. Domestic wastewater

contains biodegradable organic materials and, very likely,

pathogens. The primary purpose of wastewater treatment

is to remove impurities and release the treated effluent

into the ground or a stream. There are various processes

for accomplishing this:

• Centralized treatment—Publicly owned

treatment works (POTWs) that use primary

(physical) treatment and secondary (biologic)

treatment on a large scale to treat flows of up to

millions of gallons or liters per day,

• Treatment on-site—Septic tanks and absorption

fields or variations thereof, and

• Stabilization ponds (lagoons)—Centralized

treatment for populations of 10,000 or less when

soil conditions are marginal and land space is ample. 

10-2 On-site Wastewater Treatment

Figure 10.2. Straight Pipe Discharge

Source: Donald Johnson; used with permission.

Figure 10.3. Clear Creek Water Contaminated With Sewage

Source: Donald Johnson; used with permission.

John Snow, a London physician, was among the

first to use anesthesia. It is his work in

epidemiology, however, that earned him his

reputation as a prototype for epidemiologists.

Dr. Snow’s brief 1849 pamphlet, On the Mode of Communication of Cholera, caused no great stir, and his theory that the city’s water supply was

contaminated was only one of many proposed

during the epidemic. 

Snow, however, was able to prove his theory in

1854, when another severe epidemic of cholera

occurred in London. Through painstaking

documentation of cholera cases and correlation of

the comparative incidence of cholera among

subscribers to the city’s two water companies, he

showed that cholera occurred much more

frequently in customers of one water company.

This company drew its water from the lower

Thames, which become contaminated with

London sewage, whereas the other company

obtained water from the upper Thames. Snow’s

evidence soon gained many converts. 

A striking incident during this epidemic has become

legendary. In one neighborhood, the intersection of Cambridge Street and Broad Street, the

concentration of cholera cases was so great that the

number of deaths reached over 500 in 10 days.

Snow investigated the situation and concluded that

the cases were clustered around the Broad Street

pump. He advised an incredulous but panicked

assembly of officials to have the pump handle

removed, and when this was done, the epidemic

was contained. Snow was a skilled practitioner as

well as an epidemiologist, and his creative use of

the scientific information of his time is an

appropriate example for those interested in disease

prevention and control [3].

Epidemiology
Not included are pit privies and compost toilets. 

Historically, wastewater disposal systems are categorized as

water-carrying and nonwater-carrying. Nonwater-carried

human fecal waste can be contained and decomposed onsite, the primary examples being a pit privy or compost

toilet. These systems are not practical for individual

residences because they are inconvenient and they expose

users to inclement weather, biting insects, and odors.

Because of the depth of the disposal pit for privies, they

may introduce waste directly into groundwater. It should

be noted that these types of systems are often used and

may be acceptable in low-water-use conditions such as

small campsites or along nature trails [4–6].

On-site Wastewater Treatment Systems

As urban sprawl continues and the population increases in

rural areas, the cost of building additional sewage disposal

systems increases. One of the prime reasons for

annexation is to increase the tax base without increasing

the cost of municipal government. The governments

involved often buy into short-term tax gains at massive

long-term costs for eventual infrastructure improvements

to annexed communities. Installing septic tank systems is

common to provide on-site disposal systems, but it is a

temporary solution at best. Because property size must be

sufficient to allow space for septic system replacement, the

cost to the municipality installing a centralized sewer

system will be dramatically increased because of the large

lot size.

Two microbiologic processes occur in all methods that

attempt to decompose domestic wastewater: anaerobic (by

bacteria that do not require oxygen) and aerobic (by

bacteria that require oxygen) decomposition. Aerobic

decomposition is generally preferred because aerobic

bacteria decompose organic matter (sewage) at a rate

much faster than do anaerobic bacteria and odors are less

likely. Centralized wastewater treatment facilities use

aerobic processes, as do most types of lagoons. Septic tank

systems use both processes. 

Septic Tank Systems

Approximately 21% of American homes are served by onsite sewage disposal systems. Of these, 95% are septic

tank field systems. Septic tank systems are used as a

means of on-site wastewater treatment in many homes,

both in rural and urban areas, in the United States. If

maintained and operated within acceptable parameters,

they are capable of properly treating wastewater for a

limited number of years and will need both routine

maintenance and eventually major repairs. Proper

placement and installation is a key to the successful

operation of any on-site wastewater treatment system, but

septic tank systems have a finite life expectancy and all

such systems will eventually fail and need to be replaced.

Figure 10.4 shows a typical rural home with a well and a

septic system. 

Septic tank systems generally are composed of the septic

tank, distribution box, absorption field (also known as the

soil drainfield), and leach field. The septic tank serves three

purposes: sedimentation of solids in the wastewater, storage of

solids, and anaerobic breakdown of organic materials.

To place the septic tank and absorption field in a way that

will not contaminate water wells, groundwater, or streams,

the system should be 10 feet from the house and other

structures, at least 5 feet from property lines, 50 feet from

water wells, and 25 feet from streams. The entire system

area should be easily identifiable. There have been

occasions when owners have paved or built over the area.

The local health code authorities must be consulted on

required distances in their area because of soil and

groundwater issues. 

Aerobic, or aerated, septic systems use a suspended

growth wastewater treatment process, and can remove

suspended solids that are not removed by simple

sedimentation. Under appropriate conditions, aerobic

units may also provide for nitrification of ammonia, as

well as significant pathogen reduction. Some type of

primary treatment usually precedes the aerated tank. The

tanks contain an aeration chamber, with either

mechanical aerators or blowers, or air diffusers, and an

area for final clarification/settling. Aerobic units may be

designed as either continuous flow or batch flow systems.

Healthy Housing Reference Manual 10-3

Figure 10.4. Septic Tank System [7]
The continuous flow type are the most commercially

available units. Effluent from the aerated tank is conveyed

either by gravity flow or pumping to either further

treatment/ pretreatment processes or to final treatment

and disposal in a subsurface soil disposal system. Various

types of pretreatment may be used ahead of the aerobic

units, including septic tanks and trash traps. 

The batch flow system collects and treats wastewater over

a period of time, then discharges the settled effluent at

the end of the cycle [8]. 

Aerobic units may be used by individual or clustered

residences and establishments for treating wastewater

before either further treatment/pretreatment or final onsite subsurface treatment and disposal. These units are

particularly applicable where enhanced pretreatment is

important, and where there is limited availability of land

suitable for final on-site disposal of wastewater effluent.

Because of their need for routine maintenance to ensure

proper operation and performance, aerobic units may be

well-suited for multiple-home or commercial applications,

where economies of scale tend to reduce maintenance

and/or repair costs per user. The lower organic and

suspended solids content of the effluent may allow a

reduction of land area requirements for subsurface

disposal systems. 

A properly functioning septic tank will remove

approximately 75% of the suspended solids, oil, and

grease from effluent. Because the detention time in the

tank is 24 hours or less, there is not a major kill of

pathogenic bacteria. The bacteria will be removed in the

absorption field (drainfield). However, there are soils and

soil conditions that prohibit the ability of a drainfield to

absorb effluent from the septic tank. 

Septic tanks are sized to retain the total volume of sewage

produced by a household in a 24-hour period. Normally a

1,000-gallon tank is the minimum size to use. State or

local codes generally require larger tanks as the potential

occupancy of the home increases (e.g., 1,250 gallons for

four bedrooms) and may require two tanks in succession

when inadequate soils require alternative system

installation. Figure 10.5 shows a typical septic tank.

Distribution boxes are not required by most on-site

plumbing codes or by the U.S. Environmental Protection

Agency. When used, distribution boxes provide a

convenient inspection port. In addition, if a split system

absorption field is installed (two separate absorption

trench systems), the distribution box is a convenient place

to install a diversion valve for annually alternating

absorption fields. 

Absorption Field Site Evaluation

The absorption field has a variety of names, including

leach field, tile field, drainfield, disposal field, and

nitrification field. The effluent from the septic tank is

directed to the absorption field for final treatment. The

suitability of the soil, along with other factors noted

below, determines the best way to properly treat and

dispose of the wastewater.

Most, but unfortunately not all, states require areas not

served by publicly owned sewers to be preapproved for

on-site wastewater disposal before home construction

through a permitting process. This process typically requires a

site evaluation by a local environmental health specialist,

soil scientist, or, in some cases, a private contractor. To

assist in the site evaluation process, soil survey maps from

the local soil conservation service office may be used to

provide general information about soils in the area. 

The form shown in Figure 10.6 is typical of those used in

conducting a soil evaluation.

Sites for on-site wastewater disposal are first evaluated for

use with a conventional septic tank system. Evaluation

factors include site topography, landscape position, soil

texture, soil structure, internal drainage, depth to rock or

other restrictive horizons, and useable area. If the criteria

are met, a permit is issued to allow the installation of a

conventional septic tank system. Areas that do not meet

the criteria for a conventional system may meet lessrestrictive criteria for an alternative type of system. 

10-4 On-site Wastewater Treatment

Figure 10.5. Septic Tank [9]
Many sites are unsuitable for any type of on-site

wastewater disposal system because of severe topographic

limitations, poor soils, or other evaluation criteria. Such

sites should not be used for on-site wastewater disposal

because of the high likelihood of system failure.

Some states and localities may require a percolation test as

part of the site evaluation process. As a primary

evaluation method, percolation tests are a poor indicator

of the ability of a soil to treat and move wastewater

throughout the year. However, information obtained by

percolation tests may be useful when used in conjunction

with a comprehensive soil analysis.

Absorption Field Trench

A conventional absorption field trench (Figure 10.7), also

known as a rock lateral system, is the most common

system used on level land or land with moderate slopes

with adequate soil depth above the water table or other

restrictive horizons. The effluent from the septic tank

flows through solid piping to a distribution box or, in many

cases, straight to an absorption field. With the conventional

system and most alternative systems, the effluent flows

through perforated pipes into gravel-filled trenches and

subsequently seeps through the gravel into the soil.

The local regulatory agency should be consulted about

the acceptable depth of the absorption field trench. Some

states require as much as 4 feet of separation beneath the

bottom of the trench and the groundwater. The depth of

absorption field trenches should be at least 18 inches, and

ideally no deeper than 24 inches. The absorption field

pipe should be laid flat with no slope. There should be a

minimum of 12 to 18 inches of acceptable soil below the

bottom of the trench to any bedrock, water table, or

restrictive horizon. The length of the trench should not

exceed 100 feet for systems using a distribution box.

Serpentine systems may be several hundred feet long and

should be filled with crushed or fragmented clean rock or

gravel in the bottom 6 inches of the trench. Perforated

4-inch-diameter pipe is laid on top of the gravel then

covered with an additional 2 inches of rock and leveled for

a total of 12 inches. A geotextile material or a biodegradable

material such as straw should be placed over the gravel

before backfilling the trench to prevent soil from clogging

the spaces between the rocks. 

One or more monitoring ports should be installed in the

absorption area extending to the bottom of the gravel to

allow measurement of the actual liquid depth in the

Healthy Housing Reference Manual 10-5

Figure 10.6. On-site Sewage Disposal System Site Evaluation Form

Figure 10.7. Cross-section of an Absorption Field [10]
gravel. This is essential for subsequent testing of the

adequacy of the system.

As a general rule, using longer and narrower trenches to

meet square footage requirements produces a better

working and longer lasting ground absorption sewage

disposal system. Studies have shown that as septic systems

age, the majority of effluent absorption by the soil is

provided by lateral movement through the trench

sidewalls. Longer and narrower trenches (such as 400 feet

long by 2 feet wide instead of 200 feet by 4 feet to obtain

800 square feet) greatly increase the sidewall area of the

system for lateral movement of wastewater. 

Alternative Septic Tank Systems 

As the cost of land for home building increases and the

availability of land decreases, land that was once

considered unsuitable is being developed. This land often

has poor soil and drainage properties. Such sites require a

considerable amount of engineering skill to design an

acceptable wastewater disposal system. In many cases,

sites are not acceptable for seepage systems within a

reasonable cost. These systems are primarily regulated by

state and local government and, before use, approval must

be obtained from the appropriate regulatory agencies.

Even if a site is approved in one state or county jurisdiction, a

similar site may not be approved in another.

The primary difficulty with septic tank systems is treating

effluent in slowly permeable or marginal soils. Low-wateruse devices, when installed, may make it possible to use a

small percentage of septic tank systems in marginal soil.

However, low-water-use devices are usually required as

part of a larger effort to develop a usable alternative

sewage disposal system. Alternative sewage disposal

methods that can be used if regular subsurface disposal is

not appropriate are numerous [11]. Some of the more

common alternative systems are described below.

Mound Systems

A mound system (Table 10.1) is elevated above the

natural soil surface to achieve the desired vertical

separation from a water table or impervious material. The

elevation is accomplished by placing sand fill material on

top of the best native soil stratum. At least 1 foot of

naturally occurring soil is necessary for a mound system to

function properly. Minimizing water usage in the home also

is critical to prevent effluent from weeping through the

sides of the mound (Figure 10.8).

When a mound system is constructed, the septic tank

usually receives wastewater from the house by gravity

flow. A lift station is located in the second compartment

or in a separate tank to pump the effluent up to the

distribution piping in the mound. Floats in the lift station

control the size of the pumped effluent dose. An alarm

should be installed to alert the homeowner of pump failure so

that repairs can be made before the pump tank overfills.

Low-Pressure Pipe Systems

Low-pressure pipe (LPP) systems may also be used where

the soil profile is shallow. These systems are similar to

mounds except that they use naturally occurring soil as it

exists on-site instead of elevating the disposal field with

soil fill material. LPP systems are installed with a

trenching machine at depths of 12 to 18 inches. The LPP

system consists of a septic tank, high-water alarm,

pumping tank, supply line, manifold, lateral line, and

submersible effluent pump (Figure 10.9).

10-6 On-site Wastewater Treatment

Table 10.1. Mound System Advantages and Disadvantages
When septic tank effluent rises to the level of the pump

control in the pumping tank, the pump turns on, and

effluent moves through the supply line and distribution

laterals. The laterals contain small holes and are typically

placed 3 to 8 feet apart. From the trenches, the effluent

moves into the soil where it is treated. The pump turns

off when the effluent falls to the lower control. Dosing

takes place one to two times daily, depending on the

amount of effluent generated. Pump malfunctions set off

an alarm to alert the homeowner. The time between doses

allows the effluent to be absorbed into the soil and also

allows oxygen to reenter the soil to break down solids that

may be left behind. If the pump malfunctions, an alarm

notifies the homeowner to contact a qualified septic

system contractor. The pump must be repaired or replaced

quickly to prevent the pump tank from overflowing.

Table 10.2 shows the advantages and disadvantages of LPP

systems.

Plant-rock Filter Systems (Constructed Wetlands)

Considered experimental in some states, plant-rock filter

systems are being used with great success in Kentucky,

Louisiana, and Michigan. Plant-rock filters generally

consist of a septic tank (two-compartment), a rock filter,

and a small overflow lateral (absorption) field. Overflow

from the septic tank is directed into the rock filter. The

rock filter is a long narrow trench (3 to 5 feet wide and

60 to 100 feet long) lined with leak-proof polyvinyl

chloride or butylplastic to which rock is added. A 2- to

4-inch-diameter rock is used below the effluent flow line

and larger rock above (Figure 10.10). 

Plant-rock filter systems are typically sized to allow

1.3 cubic feet of rock area per gallon of total daily waste

flow. A typical size for a three-bedroom house would be

468 square feet of interior area. Various width-to-length

ratios within the parameters listed above could be used to

obtain the necessary square footage. The trenches can

even be designed in an “L” shape to accommodate small

building lots.

Treatment begins in the septic tank. The partially treated

wastewater enters the lined plant-rock filter cell through

solid piping, where it is distributed across the cell. The

plants within the system introduce oxygen into the

Healthy Housing Reference Manual 10-7

Table 10.2. Low-pressure Pipe Systems Advantages and Disadvantages

Figure 10.9. Low Pressure On-site System [12]

Figure 10.8. Mound System Cutaway [3]
wastewater through their roots. As the wastewater

becomes oxygenated, beneficial microorganisms and fungi

thrive on and around the roots, which leads to digestion

of organic matter. In addition, large amounts of water are

lost through evapotranspiration. The kinds of plants most

widely used in these systems include cattails, bulrush,

water lilies, many varieties of iris, and nutgrass. Winter

temperatures have little effect because the roots are doing

the work in these systems, and they stay alive during the

winter months. Discharge from wetlands systems may

require disinfection. The advantages and disadvantages of

the plant-rock filter system are shown in Table 10.3. 

Maintaining On-site Wastewater Treatment

Systems

Dos and don’ts inside the house:

• Do conserve water. Putting too much water into

the septic system can eventually lead to system

failure. (Typical water use is about 60 gallons per

day for each person in the family.) The standard

drain field is designed for a capacity of

120 gallons per bedroom. If near capacity, systems

may not work. Water conservation will extend the

life of the system and reduce the chances of

system failure. 

• Do fix dripping faucets and leaking toilets.

• Do avoid long showers.

• Do use washing machines and dishwashers only

for full loads.

• Do not allow the water to run continually when

brushing teeth or while shaving.

• Do avoid disposing of the following items down

the sink drains or toilets: chemicals, sanitary

napkins, tissues, cigarette butts, grease, cooking

oil, pesticides, kitty litter, coffee grounds,

disposable diapers, stockings, or nylons.

• Do not install garbage disposals. 

• Do not use septic tank additives or cleaners. They

are unnecessary and some of the chemicals can

contaminate the groundwater. 

Dos and don’ts for outside maintenance:

• Do maintain adequate vegetative cover over the

absorption field. 

• Do not allow surface waters to flow over the tank

and drainfield areas. (Diversion ditches or

subsurface tiles may be used to direct water away

from system.) 

• Do not allow heavy equipment, trucks, or

automobiles to drive across any part of the system. 

10-8 On-site Wastewater Treatment

Figure 10.10. Plant-rock Filter System [12]

Table 10.3. Plant-rock Filter System Advantages and Disadvantages 
• Do not dig into the absorption field or build

additions near the septic system or the repair area. 

• Do make sure a concrete riser (or manhole) is

installed over the tank if not within 6 inches of

the surface, providing easy access for measuring

and pumping solids. (Note: All tanks should have

two manholes, one positioned over the inlet

device and one over the outlet device.) 

There is no need to add any commercial substance to

“start” or clean a tank to keep it operating properly. They

may actually hinder the natural bacterial action that takes

place inside a septic tank. The fecal material, cereal grain,

salt, baking soda, vegetable oil, detergents, and vitamin

supplements that routinely make their way from the

house to the tank are far superior to any additive.

Symptoms of Septic System Problems

These symptoms can mean you have a serious septic

system problem: 

• Sewage backup in drains or toilets (often a black

liquid with a disagreeable odor). 

• Slow flushing of toilets. Many of the drains will

drain much slower than usual, despite the use of

plungers or drain-cleaning products. This also can

be the result of a clogged plumbing vent or a

nonvented fixture.

• Surface flow of wastewater. Sometimes liquid

seeps along the surface of the ground near your

septic system. It may or may not have much of an

odor and will range from very clear to black in

color.

• Lush green grass over the absorption field, even

during dry weather. Often, this indicates that an

excessive amount of liquid from the system is

moving up through the soil, instead of down, as it

should. Although some upward movement of

liquid from the absorption field is good, too

much could indicate major problems. 

• The presence of nitrates or bacteria in the

drinking water well indicates that liquid from the

system may be flowing into the well through the

ground or over the surface. Water tests available

from the local health department will indicate

whether this is a problem. 

• Buildup of aquatic weeds or algae in lakes or

ponds adjacent to your home. This may indicate

that nutrient-rich septic system waste is leaching

into the surface water, which may lead to both

inconvenience and possible health problems. 

• Unpleasant odors around the house. Often, an

improperly vented plumbing system or a failing

septic system causes a buildup of disagreeable odors.

Table 10.4 is a guide to troubleshooting septic tank problems.

Septic Tank Inspection

The first priority in the inspection process is the safety of

the homeowner, neighbors, workers, and anyone else for

which the process could create a hazard. 

• Do not enter septic tanks or cesspools.

• Do not work alone on these tanks.

• Do not bend or lean over septic tanks or cesspools.

• Note and take appropriate action regarding unsafe

tank covers.

• Note unsanitary conditions or maintenance needs

(sewage backups, odor, seepage).

• Do not bring sewage-contaminated clothing into

the home.

• Have current tetanus inoculations if working in

septic tank inspection.

Methane and hydrogen sulfide gases are produced in a

septic tank. They are both toxic and explosive. Hydrogen

sulfide gas is quite deceptive. It can have a very strong

odor one moment, but after exposure, the odor may not

be noticed.

Inspection Process

As sewage enters a septic tank, the rate of flow is reduced

and heavy solids settle, forming sludge. Grease and other

light solids rise to the surface, forming a scum. The

sludge and scum (Figure 10.11) are retained and break

down while the clarified effluent (liquid) is discharged to

the absorption field.

Sludge eventually accumulates in the bottom of all septic

tanks. The buildup is slower in warm climates than in

colder climates. The only way to determine the sludge

Healthy Housing Reference Manual 10-9
10-10 On-site Wastewater Treatment

Table 10.4. Septic Tank System Troubleshooting 

Figure 10.11. Sludge and Scum in Multicompartment Septic Tank [13]
depth is to measure the sludge with a probe inserted through

an inspection port in the tank’s lid. Do not put this job off until

the tank fills and the toilet overflows. If this happens, damage

to the absorption field could occur and be expensive to repair. 

Scum Measurement

The floating scum thickness can be measured with a probe.

The scum thickness and the vertical distance from the

bottom of the scum to the bottom of the inlet can also be

measured. If the bottom of the scum gets within 3 inches

of the outlet, scum and grease can enter the absorption

field. If grease gets into the absorption field, percolation is

impaired and the field can fail. If the scum is near the

bottom of the tee, the septic tank needs to be cleaned out.

The scum thickness can best be measured through the

large inspection port. Scum should never be closer than 3

inches to the bottom of the baffle. The scum thickness is

observed by breaking through it with a probe, usually a pole.

Sludge Measurement

To measure sludge, make a sludge-measuring stick using a

long pole with at least 3 feet of white cloth (e.g., an old

towel) on the end. Lower the measuring stick into the

tank, behind the outlet baffle to avoid scum particles,

until it touches the tank bottom. It is best to pump each

tank every 2 to 3 years. Annual checking of sludge level is

recommended. The sludge level must never be allowed to

rise within 6 inches of the bottom of the outlet baffle. In

two-compartment tanks, be sure to check both compartments.

When a septic tank is pumped, there is no need to

deliberately leave any residual solids. Enough will remain

after pumping to restart the biologic processes. 

References

1. University of California Cooperative Extension,

Calaveras County. Septic tanks: the real poop. San

Andreas, CA: University of California Cooperative

Extension, Calaveras County; no date. Available

from URL: http://cecalaveras.ucdavis.edu/realp.htm.

2. University of Nebraska-Lincoln. Residential onsite wastewater treatment: septic system and

drainfield maintenance. Lincoln, NE: University

of Nebraska-Lincoln; 2000. Available from URL:

http://ianrpubs.unl.edu/wastemgt/g1424.htm.

3. Rosenberg CE. The cholera years. Chicago: The

University of Chicago Press; 1962.

4. Salvato J, Nemerow NL, Agardy FJ, editors.

Environmental engineering. 5th ed. New York:

John Wiley and Sons; 2003.

5. Advanced Composting Systems. Phoenix

composting toilet system. Whitefish, MT:

Advanced Composting Systems; no date. Available

from URL: http://www.compostingtoilet.com.

6. BioLet USA, Inc. Composting toilets.

Newcomerstown, OH: BioLet USA, Inc.; no date.

Available from URL: http://www.biolet.com.

7. Mankl K, Slater B. Septic system maintenance.

Columbus, OH: The Ohio State University 

Extension; no date. Available from URL:

http://ohioline.osu.edu/aex-fact/0740.html.

8. Hutzler NJ, Waldorf LE, Fancy J. Aerated tanks

(aerobic units). In: Performance of aerobic

treatment units. Madison, WI: University of

Wisconsin - Madison; no date. Available from

URL: http://www.ci.austin.tx.us/wri/treat5.htm.

9. Center for Disease Control. Basic housing

inspection. Atlanta: US Department of Health

and Human Services; 1976. 

10. Purdue Research Foundation. Environmental

education software series. West Lafayette, IN:

Purdue Research Foundation; 1989. Available

from URL: http://www.inspect-ny.com/

septic/trench.gif.

11. North Carolina Cooperative Extension Service.

On-site wastewater treatment websites.

Jacksonville, NC: North Carolina Cooperative

Extension Service; 2002. Available from URL:

http://www.ces.ncsu.edu/onslow/staff/drashash/

enved/sepsites.html. 

12. Clay Township Regional Waste District. Septic

systems. Indianapolis: Clay Township Regional

Waste District; 2004. Available from URL:

http://www.ctrwd.org/septics.htm. 

13. Jackson Purchase Resource Conservation and

Development Foundation, Inc. Septic systems: an

overview. Cynthiana, KY: Jackson Purchase Resource

Conservation and Development Foundation, Inc.;

no date. Available from URL:

http://www.jpf.org/LRV/septic.htm. 

Healthy Housing Reference Manual 10-11
Additional Sources of Information

Agency for Toxic Substances and Disease Registry. Science

page, Office of the Associate Administrator for Science.

Atlanta: US Department of Health and Human Services;

no date. Available from URL:

http://www.atsdr.cdc.gov/science/. 

American Society of Civil Engineers. Available from

URL: http://www.asce.org. 

Burks BD, Minnis MM. Onsite wastewater treatment

systems. Madison, WI: Hogarth House, Ltd.; 1994. Textbook

and reference manual on all aspects of on-site treatment. 

International Code Council. International private sewage

disposal code, 2000. Falls Church, VA: International

Code Council; 2000. 

National Onsite Wastewater Recycling Association

(NOWRA). Available from URL: http://www.nowra.org

or 1-800-966-2942.

National Small Flows Clearinghouse. Available from

URL: http://www.nesc.wvu.edu/nsfc/nsfc_index.htm or

1-800-624-8301. 

US Army Corps of Engineers. Available from URL:

http://www.usace.army.mil.

10-12 On-site Wastewater Treatment
Chapter 11—Electricity

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-1

Flow of Electric Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-2

Electric Service Entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Service Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Underground Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Electric Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Two- or Three-wire Electric Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Residential Wiring Adequacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Wire Sizes and Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Reducing Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Wire Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Wire Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Types of Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Flexible Cords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

The Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

The Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

Safety Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Open Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Concealed Knob and Tube Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Electric Service Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Over-Current Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-10

Circuit Breakers (Fuseless Service Panels) . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Ground Fault Circuit Interrupters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Arc-fault Circuit Interrupters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Fused Ampere Service Panel (Fuse Box) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Electric Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Outlet Switches and Junction Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Grounding Outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Polarized Plugs and Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-14

Common Electrical Violations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-14

Excessive or Faulty Fusing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-15

Cords Run Through Walls or Doorways and Hanging Cords or Wires . . . . .11-15

Temporary Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Excessively Long Extension Cords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Dead or Dummy Outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Aluminum Wiring Inside the Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

Inspection Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-16

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-17

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-17

Figure 11.1. Utility Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Figure 11.2. Entrance Head. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Figure 11.3. Armored Cable Service Entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Healthy Housing Reference Manual 1

Contents
Figure 11.4. Breakers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Figure 11.5. Thin-wall Conduit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Figure 11.6. Electric Meter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-5

Figure 11.7. Typical Service Entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-5

Figure 11.8. Grounding Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Figure 11.9. Grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Figure 11.10. Three-wire Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Figure 11.11. Two-wire Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-7

Figure 11.12. Wire Markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Figure 11.13. Armored Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-9

Figure 11.14. 200-Amp Service Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Figure 11.15. External Power Shutoff and Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Figure 11.16. Ground Fault Circuit Interruptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Figure 11.17. Arc Interrupter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Figure 11.18. Types of Fuses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-13

Figure 11.19. Appliance Ground and Grounded Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-14

2 Contents
'“To electrize plus or minus, no more needs to be known

than this, that the parts of the tube or sphere that are

rubbed, do, in the instant of the friction, attract the

electrical fire, and therefore take it from the thing rubbing;

the same parts immediately, as the friction upon them ceases,

are disposed to give the fire they have received to any body.”

Benjamin Franklin 

Franklin’s Discovery of the Positive 

and Negative States of Electricity, 1747

Introduction

Two basic codes concerned with residential wiring are

important to the housing inspector. The first is the local

electrical code. The purpose of this code is to safeguard

persons as well as buildings and their contents from

hazards arising from the use of electricity for light, heat,

and power. The electrical code contains basic minimum

provisions considered necessary for safety. Compliance

with this code and proper maintenance will result in an

installation essentially free from hazards, but not

necessarily efficient, convenient, or adequate for good

service or future expansion.

Most local electrical codes are modeled after the National

Electrical Code, published by the National Fire

Protection Association (NFPA). Reference to the “code”

in the remainder of this chapter will be to the National

Electrical Code, unless specified otherwise [1]. 

An electrical installation that was safe and adequate

under the provisions of the electrical code at the time of

installation is not necessarily safe and adequate today. An

example would be the grounding of a home electrical

system. In the past, electrical systems could be grounded

to the home’s plumbing system. Today, many plumbing

systems are no longer constructed of conductive material,

but are made of plastic or polyvinyl chloride-based

materials. Today, the recommendations for grounding a

home electrical system are to use two 8-foot by 5/8-inch

copper ground rods. These must be spaced 6 feet apart

and be connected by a continuous (unbroken) piece of

copper wire (the size of this wire corresponds to the size

of the system main). It is also highly recommended that

the system be grounded to the incoming water line if it is

conductive or to the nearest conductive cold water

supply line. Hazards often occur because of overloading

wiring systems or usage not in conformity with the code.

This occurs because initial wiring did not provide for

increases in the use of electricity. For this reason, it is

recommended that initial installations be adequate and

that reasonable provisions for system changes be made

for further increases in the use of electricity.

The other code that contains electrical provisions is the

local housing code. It establishes minimum standards for

artificial and natural lighting and ventilation, specifies

the minimum number of electric outlets and lighting

fixtures per room, and prohibits temporary wiring except

under certain circumstances. In addition, the housing

code usually requires that all components of an electrical

system be installed and maintained in a safe condition to

prevent fire or electric shock.

Chapter 11: Electricity

Healthy Housing Reference Manual 11-1

Ampere—The unit for measuring intensity of flow of electricity. Its symbol is “I.”

Bonding—Applies inert material to metal surfaces to eliminate electrical potential between metal components and

prevent components and piping systems from having an elevated voltage potential. 

Circuit—The flow of electricity through two or more wires from the supply source to one or more outlets and back to the

source.

Circuit breaker—A safety device used to break the flow of electricity by opening the circuit automatically in the event of

overloading or used to open or close the circuit manually.

Conductor—Any substance capable of conveying an electric current. In the home, copper wire is usually used.

• A bare conductor is one with no insulation or covering.

• A covered conductor is one covered with one or more layers of insulation.

Definitions of Terms Related to Electricity
Flow of Electric Current

Electricity is usually created by a generator that converts

mechanical energy into electrical energy. The electricity

may be the result of water, steam, or wind powering or

turning a generator. The electricity is then run through a

transformer, where voltage is increased to several hundred

thousand volts and, in some instances, to a million or

more volts. This high voltage is necessary to increase the

efficiency of power transmission over long distances. 

This high-transmission voltage is stepped down (reduced)

to normal 115/230-volt household current by a transformer

located near the point of use (residence). The electricity is

then transmitted to the house by a series of wires called a

service drop. In areas where the electric wiring is underground,

the wires leading to the building are buried in the ground.

For electric current to flow, it must travel from a higher

to a lower potential voltage. In an electrical system, the

11-2 Electricity

Conductor gauge—A numeric system used to label electric conductor sizes, given in American Wire Gauge (AWG). The

larger the AWG number, the smaller the wire size.

Current—The flow of electricity through a circuit. 

• Alternating current is an electric current that reverses its direction of flow at regular intervals. For example, it

would alternate 60 times every second in a 60-cycle system. This type of power is commonly found in homes.

• Direct current is an electric current flowing in one direction. This type of current is not commonly found in

today’s homes.

Electricity—Energy that can be used to run household appliances; it can produce light and heat, shocks, and numerous

other effects.

Fuse—A safety device that cuts off the flow of electricity when the current flowing through the fuse exceeds its rated

capacity.

Ground—To connect with the earth, as to ground an electric wire directly to the earth or indirectly through a water pipe

or some other conductor. Usually, a green-colored wire is used for grounding the whole electrical system to the earth. A

copper wire is usually used to ground individual electrical components of the whole system. (The home inspector should

never assume that insulation color wiring codes have been used appropriately.)

Ground fault circuit interrupter (GFCI)—A device intended to protect people from electric shock. It de-energizes a

circuit or portion of a circuit within an established very brief period of time when a current to ground exceeds some

predetermined value (less than that required to operate the over-current protected device of the supply circuit).

Hot wires—Those that carry the electric current or power to the load; they are usually black or red.

Insulator—A material that will not permit the passage of electricity.

Kilowatt-hour (KWH)—The amount of energy supplied by one kilowatt (1,000 watts) for 1 hour (3,600 seconds), equal

to 3,600,000 joule. Electric bills are usually figured by the number of KWHs consumed.

Neutral wire—The third wire in a three-wire distribution circuit; it is usually white or light gray and is connected to the

ground.

Resistance—A measure of the difficulty of electric current to pass through a given material; its unit is the ohm.

Service—The conductor and equipment for delivering energy from the electricity supply system to the wiring system of

the premises.

Service drop—The overhead service connectors from the last pole or other aerial support to and including the splices, if

any, connecting to the service entrance conductors at the building or other structure.

Service panel—Main panel or cabinet through which electricity is brought to the building and distributed. It contains the

main disconnect switch and fuses or circuit breakers.

Short circuit—A break in the flow of electricity through a circuit due to the load caused by improper connection between

hot and neutral wires. 

Volt—The unit for measuring electrical pressure of force, which is known as electromotive force. Its symbol is “E.”

Voltage drop—A voltage loss when wires carry current. The longer the cord, the greater the voltage drop.

Watt—The unit of electric power. Volts times amperes = watts.

Definitions of Terms Related to Electricity
hot wires (black or red) are at a higher potential than are

the neutral or ground wire (white or green). 

Voltage is a measure of the force at which electricity is

delivered. It is similar to pressure in a water supply system.

Current is measured in amperes and is the quantity of

flow of electricity. It is similar to measuring water in

gallons per second. A watt is equal to volts times amperes.

It is a measure of how much power is flowing. Electricity

is sold in quantities of kilowatt-hours.

The earth, by virtue of moisture contained within the

soil, serves as a very effective conductor. Therefore, in

power transmission, instead of having both the hot and

neutral wires carried by the transmission poles, one lead

of the generator is connected to the ground, which serves

as a conductor (Figure 11.1). All electrical utility wires are

carried by the transmission towers and are considered hot

or charged. At the house, or point where the electricity is

to be used, the circuit is completed by another

connection to ground.

The electric power utility provides a ground somewhere

in its local distribution system; therefore, there is a

ground wire in addition to the hot wires within the

service drop. In Figure 11.1 this ground can be seen at

the power pole that contains the step-down transformer.

In addition to the ground connection provided by the

electric utility, every building is required to have an

independent ground called a system ground. The system

ground is a connection to ground from one of the

current-carrying conductors of the electrical system.

System grounding, applied to limit overvoltages in the

event of a fault, provides personnel safety, provides a

positive means of detecting and isolating ground faults,

and improves service reliability. Therefore, the system

ground’s main purpose is to protect the electrical system

itself and offers limited protection to the user.

The system ground serves the same purpose as the power

company’s ground; however, it has a lower resistance

because it is closer to the building. The equipment

ground protects people from potential harm during the

use of certain electrical equipment. The system ground

should be a continuous wire of low resistance and of

sufficient size to conduct current safely from lightning

and overloads.

Electric Service Entrance

Service Drop

To prevent accidental contact by people, the entrance

head (Figure 11.2) should be attached to the building at

least 10 feet above ground. The conductor should clear all

roofs by at least 8 feet and residential driveways by 12 feet.

For public streets, alleys, roads, and driveways on other than

residential property, the clearance must be 18 feet.

The wires or conductor should be of sufficient size to carry

the load and not smaller than No. 8 copper wire or equivalent.

For connecting wire from the entrance head to the service

drop wires, the code requires that the service entrance

conductors be installed either below the level of the

service head or below the termination of the service

entrance cable sheath. Drip loops must be formed on

individual conductors. This will prevent water from

entering the electric service system. The wires that form

the entrance cable should extend 36 inches from the

entrance head to provide a sufficient length to connect

service drop wires to the building with insulators. The

entrance cable may be a special type of armored outdoor

cable, or it may be enclosed in a conduit. The electric

power meter may be located either inside or outside the

Healthy Housing Reference Manual 11-3

Figure 11.1. Utility Overview [2] Figure 11.2. Entrance Head 
building. In either instance, the meter must be located

before the main power disconnect.

Figure 11.3 shows an armored cable service entrance with

a fuse system. Newer construction will have circuit

breakers, as shown in Figure 11.4. The armored cable is

anchored to the building with metal straps spaced every

4 feet. The cable is run down the wall and through a hole

drilled through the building. The cable is then connected to

the service panel, which should be located within 1 foot of

where the cable enters the building. The ground wire

need not be insulated. This ground wire may be either

solid or stranded copper, or a material with an equivalent

resistance. 

Figure 11.5 shows the use of thin-wall conduit in a service

entrance.

Underground Service

When wires are run underground, they must be protected

from moisture and physical damage. The opening in the

building foundation where the underground service enters

the building must be moisture proof. Refer to local codes

for information about allowable materials for this type of

service entrance.

Electric Meter

The electric meter (Figure 11.6) may be located inside or

outside the building. The meter itself is weatherproof and

is plugged into a weatherproof socket. The electric power

company furnishes the meter; the socket may or may not

be furnished by the power company.

Grounding

The system ground consists of grounding the neutral

incoming wire and the neutral wire of the branch circuits.

The equipment ground consists of grounding the metal

parts of the service entrance, such as the service switch, as

well as the service entrance conduit, armor or cable. 

Figure 11.5. Thin-wall Conduit [2]

Figure 11.3. Armored Cable Service Entrance [2]

Figure 11.4. Breakers [2]

11-4 Electricity
Poor grounding at any point can result in a person

providing a more effective route to ground than the

intended ground, resulting in electrocution. This can

occur from damaged insulation allowing electricity to

flow into the case or cabinet of the appliance.

The system must be grounded by two 8 foot by 5/8-inch

copper ground rods of at least 8 feet in length driven into

the ground and connected by a continuous (unbroken)

piece of copper wire (the size of this wire corresponds to

the size of the system main). It is highly recommended

that the system also be grounded to the incoming water line

or nearest cold water supply line if it is metal. 

The usual ground connection is to a conductive water

pipe of the city water system. The connection should be

made to the street side of the water meter, as shown in

Figure 11.7. If the water meter is located near the street

curb, then the ground connection should be made to the

cold water pipe as close as possible to where it enters the

building. It is not unusual for a water meter to be

removed from the building for service. If the ground

connection is made at a point in the water piping system

on the building side of the water meter, the ground

circuit will be broken on removal of the meter. This

broken ground circuit is a shock hazard if both sides of

the water meter connections are touched simultaneously.

Local or state codes should be checked to determine

compliance with correct grounding protocols.

In increasing instances, the connections between the

water meters and pipes are electrically very poor. In this

case, if the ground connection is made on the building

side of the water meter, there may not be an effective

ground. To prevent the two aforementioned situations,

the code requires effective bonding by a properly sized

jumper-wire around any equipment that is likely to be

disconnected for repairs or replacement.

Often, the house ground will be disconnected. Therefore,

the housing inspector should always check the house

ground to see if it is properly connected.

Figure 11.8 shows a typical grounding scheme at the

service box of a residence. In this figure, only the

grounded neutral wires are shown. The neutral strap is a

conductive bare metal strip that is riveted directly to the

service box. This conductive strip forms a collective

ground that joins the ground wires from the service

entrance, branch circuits, and house ground. 

Follow these key grounding points:

• Use two metal rods driven 8 feet into the ground. 

• Bond around water heaters and filters to assure

grounding.

• If water pipes are used, they must be supplemented with a second ground.

• Ground rod must be driven to full depth.

• If ground rod resistance exceeds 25 ohms, install

two rods at a minimum of 6 feet apart.

• When properly grounded, the metal frame of a

building can be used as a ground point.

• Do not use underground gas lines as a ground.

• Provide external grounds to other systems such as

satellite, telephone, and other services to further

protect the electrical system from surges.

Healthy Housing Reference Manual 11-5

Figure 11.6. Electric Meter

Figure 11.7. Typical Service Entrance [2]
• If the water service pipes to the home are not

metal or if all of the service components in the

home are not metal, then the water system cannot

play a role in grounding.

Bonding is necessary to provide a route for electricity to

flow around isolated elements of a piping system to

ensure electrical potential is minimized for both the

protection of the system from corrosion and to protect

individuals from electrical shock. 

Two- or Three-wire Electric Services

One of the wires in every electrical service installation is

supposed to be grounded. This neutral wire should always

be white. The hot wires are usually black, red, or some

other color, but never white.

The potential difference or voltage between the hot wires

and the ground or neutral wire of a normal residential

electrical system is 115 volts. Thus, where there is a twowire installation (one hot and one neutral), only 115 volts

are available.

When three wires are installed (two hot and one neutral),

either 115 or 230 volts are available. In a three-wire

system, the voltage between the neutral and either of the

hot wires is 115 volts; between the two hot wires, it is

230 (Figure 11.9). The major advantage of a three-wire

system is that it permits the operation of heavy electrical

equipment such as clothes dryers, cooking ranges, and air

conditioners, the majority of which require 230-volt

circuits. In addition, the three-wire system is split at the

service panel into two 115-volt systems to supply power

for small appliances and electric lights. The result is a

doubling of the number of circuits, and, possibly, a

corresponding increase in the number of branch circuits,

with a reduction in the probability of fire caused by

overloading electrical circuits if the electrical demands

exceed the capacity.

Residential Wiring Adequacy

The use of electricity in the home has risen sharply since

the 1930s. Many homeowners have failed to repair or

improve their wiring to keep it safe and up to date. In the

1970s, the code recommended that the main distribution

panel in a home be a minimum of 100 amps. Because the

number of appliances that use electricity has continued to

grow, so has the size of recommended panels. For a

normal house (2,500 to 3,500 square feet), a 200-amp

panel is recommended. The panel must be of the breaker

type with a main breaker for the entire system (Figure 11.4).

Fuse boxes are not recommended for new housing.

This type of service is sufficient in a one-family house or

dwelling unit to provide safe and adequate electricity for

the lighting, refrigerator, iron, and an 8,000-watt cooking

range, plus other appliances requiring a total of up to

10,000 watts.

Some older homes have a 60-ampere, three-wire service

(Figure 11.10). It is recommended that these homes be

rewired for at least the minimum of 200-amperes

recommended in the code. The 60-amp service is safely

capable of supplying current for only lighting and

portable appliances, such as a cooking range and regular

dryer (4,500 watts), or an electric hot water heater

(2,500 watts), and cannot handle additional major

appliances. Other older homes today have only a 30-ampere,

115-volt, two-wire service (Figure 11.11). This system can

safely handle only a limited amount of lighting, a few

minor appliances, and no major appliances. Therefore,

this size service is substandard in terms of the modern

household’s needs for electricity. Furthermore, it is a fire

hazard and a threat to the safety of the home and the

occupants. 

11-6 Electricity

Figure 11.9. Grounding [2]

Figure 11.8. Grounding Scheme [2]
Wire Sizes and Types

Aluminum wiring, used in some homes from the mid

1960s to the early 1970s, is a potential fire hazard [3].

According to the U.S. Consumer Product Safety

Commission (CPSC), fires and even deaths have been

caused by this hazard. Problems due to expansion can

cause overheating at connections between the wire and

devices (switches and outlets) or at splices. CPSC research

shows that homes wired with aluminum wire

manufactured before 1972 are 55 times more likely to

have one or more connections reach fire hazard

conditions than are homes wired with copper. Post-1972 

aluminum wire is also a concern. Introduction of

aluminum wire alloys around 1972 did not solve most of

the connection failure problems. Aluminum wiring is still

permitted and used for certain applications, including

residential service entrance wiring and single-purpose

higher amperage circuits such as 240-volt air conditioning

or electric range circuits. 

Reducing Risk

Only two remedies for aluminum wiring have been

recommended by the CPSC: discontinued use of the

aluminum circuit or the less costly option of adding

copper connecting “pigtail” wires between the aluminum

wire and the wired device (receptacle, switch, or other

device). The pigtail connection must be made using only

a special connector and special crimping tool licensed by

the AMP Corporation. Emergency temporary repairs

necessary to keep an essential circuit in service might be

possible following other procedures described by the

CPSC, and in accordance with local electrical codes [4,5].

Wire Sizes

Electric power actually flows along the surface of the wire.

It flows with relative ease (little resistance) in some materials,

such as copper and aluminum, and with a substantial

amount of resistance in iron. If iron wire were used, it

would have to be 10 times as large as copper wire to be as

effective in conducting electricity. In fine electronics, gold

is the preferred conductor because of the resistance to

corrosion and the very high conductivity.

Electricity is the movement of electrons from an area of

higher potential to one of lower potential. An analogy to

how electricity flows would be the flow of water along the

path of least resistance or down a hill. All it takes to

create the potential for electricity is the collection of

Healthy Housing Reference Manual 11-7

Figure 11.10. Three-wire Service [2] Figure 11.11. Two-wire Service [2]
electrons and a pathway for them to flow to an area of

lesser concentration along a conductor. When a person

walks across a nylon carpet in times of low atmospheric

humidity, his or her body will often collect electrons and

serve as a capacitor (a storage container for electrons).

When that person nears a grounding source, the electrons

will often jump from a finger to the ground, creating a

spark and small shock. 

A number preceded by the letters AWG (American Wire

Gauge) indicates copper wire sizes [6]. As the AWG

number of the wire becomes smaller, the size and current

capacity of the wire increases. AWG 14 is most

commonly found in older residential branch circuits.

AWG 14 wires should be used only in a branch circuit

with a 15-ampere capacity or no more than a 1,500-watt

demand. Wire sizes AWG 16, 18, and 20 are progressively

smaller than AWG 14 and are used for extension wires or

low-voltage systems. Wire of the correct size must be used

for two reasons: current capacity and voltage drop or loss. 

When current flows through a wire, it creates heat. The

greater the amount of flow, the greater the amount of

heat generated. (Doubling the amperes without changing

the wire size increases the amount of heat by four times.)

The heat is electric energy (electrons) that has been

converted into heat energy by the resistance of the wire.

The heat created by the coils in a toaster is an example of

designed resistance to create heat. Most heat developed by

an electrical conductor is wasted; therefore, the electric

energy used to generate it is also wasted. 

If the amount of heat generated by the flow of current

through a wire becomes excessive, a fire may result.

Therefore, the code sets the maximum permissible current

that may flow through a certain type and size wire. The 

blue box provides examples of current capacities for

copper wire of various sizes.

In addition to heat generation, there will be a reduction in

voltage as a result of attempting to force more current

through a wire than it is designed to carry. Certain

appliances, such as induction-type electric motors, may be

damaged if operated at too low a voltage.

Wire Types

All wires must be marked to indicate the maximum

working voltage, the proper type letter or letters for the

type wire specified in the code, the manufacturer’s name

or trademark, and the AWG size or circular-mil area

(Figure 11.12). A variety of wire types can be used for a

wide range of temperature and moisture conditions. The

code should be consulted to determine the proper wire

for specific conditions.

Types of Cable

Nonmetallic sheathed cable consists of wires wrapped in

plastic and then a paper layer, followed by another spiral

layer of paper, and enclosed in a fabric braid, which is

treated with moisture- and fire-resistant compounds.

Figure 11.12 shows this type of cable, which often is

marketed under the name Romex. This type of cable can

be used only indoors and in permanently dry locations.

Romex-type wiring is normally used in residential

construction. However, when cost permits, it is

recommended that a conduit-based system be used.

Armored cable is commonly known as BX or Flexsteel

trade names. Wires are wrapped in a tough paper and

covered with a strong spiral flexible steel armor. This type

of cable is shown in Figure 11.13 and may be used only

in permanently dry indoor locations. Armored cable must

be supported by a strap or staple every 6 feet and within

24 inches of every switch or junction box, except for

concealed runs in old work where it is impossible to

mount straps.

Cables are also available with other outer coatings of metals,

such as copper, bronze, and aluminum for use in a variety of

conditions. 

11-8 Electricity

Figure 11.12. Wire Markings [2]

Size wire (AWG) (larger wire, smaller number) #14 #12 #10 #8

Maximum capacity in amperes 15 20 30 40

Maximum Current Recommended for AWG Wire Size
Flexible Cords

CPSC estimates that about 4,000 injuries associated with

electric extension cords are treated in hospital emergency

rooms each year. About half of the injuries involve

fractures, lacerations, contusions, or sprains from people

tripping over extension cords. Thirteen percent of the

injuries involve children younger than 5 years of age;

electrical burns to the mouth account for half the injuries

to young children [7]. 

CPSC also estimates that about 3,300 residential fires

originate in extension cords each year, killing 50 people

and injuring about 270 others [7]. The most frequent

causes of such fires are short circuits, overloading the

system, and damage to or misuse of extension cords.

The Problem

Following are CPSC investigations of injuries that

illustrate the major injury patterns associated with

extension cords: children putting extension cords in their

mouths, overloaded cords, worn or damaged cords, and

tripping over cords: 

• A 15-month-old girl put an extension cord in her

mouth and suffered an electrical burn. She

required surgery.

• Two young children were injured in a fire caused

by an overloaded extension cord in their family’s

home. A lamp, TV set, and electric heater had

been plugged into a single, light-duty extension

cord.

• A 65-year-old woman was treated for a fractured

ankle after tripping over an extension cord.

The Standards

The code says that many cord-connected appliances

should be equipped with polarized grounding plugs.

Polarized plugs can only be inserted one way into the

outlet because one blade is slightly wider than the other.

Polarization and grounding ensure that certain parts of

appliances that could have a higher risk of electric shock

when they become live are instead connected to the

neutral, or grounded, side of the circuit. Such electrical

products should only be used with polarized or grounded

extension cords. 

Voluntary industry safety standards, including those of

Underwriter’s Laboratory (UL), now require that generaluse extension cords have safety closures, warning labels,

rating information about the electrical current, and other

features for the protection of children and other

consumers.

In addition, UL-listed extension cords now must be

constructed with 16-gauge or larger wire or be equipped

with integral fuses. The 16-gauge wire is rated to carry

13 amperes (up to 1,560 watts), as compared with the

formerly used 18-gauge cords that were rated for

10 amperes (up to 1,200 watts). 

Safety Suggestions

The following are CPSC recommendations [7] for

purchasing and safely using extension cords: 

• Use extension cords only when necessary and only

on a temporary basis.

• Use polarized extension cords with polarize

appliances.

• Make sure cords do not dangle from the counter

or tabletops where they can be pulled down or

tripped over.

• Replace cracked or worn extension cords with

new 16-gauge cords that have the listing of a

nationally recognized testing laboratory, safety

closures, and other safety features.

• With cords lacking safety closures, cover any

unused outlets with electrical tape or with plastic

caps to prevent the chance of a child making

contact with the live circuit.

• Insert plugs fully so that no part of the prongs is

exposed when an extension cord is in use.

• When disconnecting cords, pull the plug rather

than the cord itself.

• Teach children not to play with plugs and outlets.

• Use only three-wire extension cords for appliances

with three-prong plugs. Never remove the third

(round or U-shaped) prong, which is a safety

feature designed to reduce the risk for shock and

electrocution.

Healthy Housing Reference Manual 11-9

Figure 11.13. Armored Cable [2]
• In locations where furniture or beds may be

pushed against an extension cord where the cord

joins the plug, use a special angle extension cord

specifically designed for use in these instances.

• Check the plug and the body of the extension

cord while the cord is in use. Noticeable warming

of these plastic parts is expected when cords are

being used at their maximum rating. If the cord

feels hot or if there is a softening of the plastic,

this is a warning that the plug wires or

connections are failing and that the extension

cord should be discarded and replaced.

• Never use an extension cord while it is coiled or

looped. Never cover any part of an extension cord

with newspapers, clothing, rugs, or any objects

while the cord is in use. Never place an extension

cord where it is likely to be damaged by heavy

furniture or foot traffic.

• Do not use staples or nails to attach extension

cords to a baseboard or to another surface. This

could damage the cord and present a shock or fire

hazard.

• Do not overload extension cords by plugging in

appliances that draw a total of more watts than

the rating of the cord.

• Use special heavy-duty extension cords for highwattage appliances such as air conditioners,

portable electric heaters, and freezers.

• When using outdoor tools and appliances, use

only extension cords labeled for outdoor use.

Wiring

Open Wiring

Open wiring is a wiring method using knobs, nonmetallic

tubes, cleats, and flexible tubing for the protection and

support of insulated conductors in or on buildings and

not concealed by the structure. The term “open wiring”

does not mean exposed, bare wiring. In dry locations,

when not exposed to severe physical damage, conductors

may be separately encased in flexible tubing. Tubing

should be in continuous lengths not exceeding 15 feet

and secured to the surface by straps not more than

41⁄2 feet apart. Tubing should be separated from other

conductors by at least 21⁄2 inches and should have a

permanently maintained airspace between them and any

and all pipes they cross. 

Concealed Knob and Tube Wiring

Concealed knob and tube wiring is a wiring method

using knobs, tubes, and flexible nonmetallic tubing for

the protection and support of insulated wires concealed in

hollow spaces of walls and ceilings of buildings. This

wiring method is similar to open wiring and, like open

wiring, is usually found only in older buildings.

Electric Service Panel

The service switch is a main switch that will disconnect

the entire electrical system at one time. The main fuses or

circuit breakers are usually located within the service

switch box. The branch circuit fuse or circuit breaker may

also be located within this box.

According to the code, the switch must be externally

operable. This condition is fulfilled if the switch can be

operated without the operator being exposed to

electrically active parts. Figure 11.14 shows a 200-amp

service box. Figure 11.15 shows an external “hinged

switch” power shutoff installed on the outside of a home. 

Most of today’s older homes do not have hinged switches.

Instead, the main fuse is mounted on a small insulated

block that can be pulled out of the switch. When this

block is removed, the circuit is broken.

In some installations, the service switch is a “solid

neutral” switch, meaning that the switch or a fuse does

not break the neutral wire in the switch.

When circuit breakers are used in homes instead of fuses,

main circuit breakers may or may not be required. If it

takes more than six movements of the hand to open all

the branch-circuit breakers, a main breaker, switch, or

fuse will be required ahead of the branch-circuit breakers.

Thus, a house with seven or more branch circuits requires

a separate disconnect means or a main circuit breaker

ahead of the branch-circuit breakers. 

Over-current Devices

The amperage (current flow) in any wire is limited to the

maximum permitted by using an over-current device of a

size specified by the code. Four types of over-current

devices are common: circuit breakers, ground fault circuit

interrupters (GFCIs), arc fault circuit interrupters

(AFCIs), and fuses. The over-current device of a specific

size is specified by the code. The over-current device must

be rated at equal or lower capacity than the wire of the

circuit it protects. 

11-10 Electricity
Circuit Breakers (Fuseless Service Panels)

A circuit breaker looks something like an ordinary electric

light switch. Figure 11.14 shows the service box in a 200-

amp fuseless system. Figure 11.15 shows a service switch.

There is a handle that may be used to turn power on or

off. Inside is a simple mechanism that, in case of a circuit

overload, trips the switch and breaks the circuit. The

circuit breaker may be reset by turning the switch to off

and then simply resetting the switch to the on position. A

circuit breaker is capable of taking harmless short-period

overloads (such as the heavy initial current required in the

starting of a washing machine or air conditioner) without

tripping, but protects against prolonged overloads. After

the cause of trouble has been located and corrected, power

is easily restored. Fuseless service panels or breaker boxes are

usually broken up into the following circuits:

• A 100-ampere or larger main circuit breaker that

shuts off all power.

• A 40-ampere circuit for an appliance such as an

electric cooking range.

• A 30-ampere circuit for a clothes dryer, water

heater, heat pump, or central air conditioning.

• A 20-ampere circuit for small appliances and

power tools.

• A 15-ampere circuit for general-purpose lighting,

TVs, VCRs, computers, and vacuum cleaners.

• Space for new circuits to be added if needed for

future use.

Ground Fault Circuit Interrupters 

Unlike circuit breakers and fuses, GFCIs are installed to

protect the user from electrocution. These devices provide

protection against electrical shock and electrocution from

ground faults or contact with live parts by a grounded

individual. They constantly monitor electrical currents

flowing into a product. If the electricity flowing through

the product differs even slightly from that returning, the

GFCI will quickly shut off the current. GFCIs detect

amounts of electricity much smaller than those required

for a fuse or circuit breaker to activate and shut off the

circuit. UL lists three types of GFCIs designed for home

use that are readily available and fairly inexpensive and

simple to install: 

• Wall Receptacle GFCI—This type of GFCI

(Figure 11.16) is used in place of a standard

receptacle found throughout the house. It fits into

a standard outlet box and protects against ground

faults whenever an electrical product is plugged

into the outlet. If strategically located, it will also

provide protection to downstream receptacles. 

• Circuit Breaker GFCI—In homes equipped with

circuit breakers, this type of GFCI may be

installed in a panel box to protect selected circuits.

A circuit breaker GFCI serves a dual purpose: it

shuts off electricity in the event of a ground fault

Figure 11.14. 200-Amp Service Box Figure 11.15. External Power Shutoff and Meter 

Healthy Housing Reference Manual 11-11
and will also trip when a short circuit or an

overload occurs.

• Portable GFCI—A portable GFCI requires no

special knowledge or equipment to install. One

type contains the GFCI circuitry in a selfcontained enclosure with plug blades in the back

and receptacle slots in the front. It can be plugged

into a receptacle, and the electrical product

plugged into the GFCI. Another type of portable

GFCI is an extension cord combined with a

GFCI. It adds flexibility in using receptacles that

are not protected by GFCIs. 

Once a GFCI is installed, it must be checked monthly to

determine that it is operating properly. Pressing the test

button can check units; the GFCI should disconnect the

power to that outlet. Pressing the reset button reconnects

the power. If the GFCI does not disconnect the power,

have it checked by a qualified, certified electrician. 

GFCIs should be installed on circuits in the following

areas: garages, bathrooms, kitchens, crawl spaces,

unfinished basements, hot tubs and spas, pool electronics,

and exterior outlets. However, they are not required on

single outlets that serve major appliances.

Arc-fault Circuit Interrupters 

Arc-fault circuit interrupters are new devices intended to

provide fire protection by opening the circuit if an arcing

fault is detected. An arcing fault is an electric spark or hot

plasma field that extends from the hot wire to a ground.

An arc is a luminous discharge of electricity across an

insulating medium or simply a spark across an air gap.

Arcs occur every day in homes. For example, an arc

occurs inside the switch when a light is turned on. Toy

racecars and trains create arcs. The motors inside hair

dyers and power drills have tiny arcs. All of these are

controlled arcs. It is the

uncontrolled or nondesigned

arc that is a serious fire hazard

in the home. The arc-fault

circuit interrupter looks like

the GFCI unit (Figure 11.17),

but it is not designed to

protect against electric shock.

Because most electrical wiring

in a home is hidden from

view, many arc faults go

undetected and continue

arcing indefinitely. If left in

this arcing state, the potential

for fire increases. It is estimated that about one third of

fires are caused by arcing faults. Normal fuses and circuit

breakers are not capable of detecting arc faults and therefore

will not open the circuit and stop the flow of electricity.

Fused Ampere Service Panel (Fuse Box)

Fuse-type panel boxes are generally found in older homes.

They are as safe and adequate as a circuit breaker of

equivalent capacity, provided fuses of the proper size are used. 

A fuse, like a circuit breaker, is designed to protect a

circuit against overloading and short circuits and does so

in two ways.

When a fuse is blown by a short circuit, the metal strip is

instantly heated to an extremely high temperature, and

this heat causes it to vaporize. A fuse blown by a short

circuit may be easily recognized because the window of

the fuse usually becomes discolored.

In a fuse blown by an overload, the metal strip is melted

at its weakest point, breaking the flow of current to the

load. In this case, the window of the fuse remains clear;

therefore, a blown fuse caused by an overload may also be

easily recognized.

Sometimes, although a fuse has not been blown, the

bottom of the fuse may be severely discolored and pitted.

This indicates a loose connection because the fuse was not

screwed in properly.

It is critical to check that all fuses are properly rated for

the designed amperage. The placing of a fuse with a

higher amperage than recommended presents a significant

fire hazard. 

Generally, all fused panel boxes are wired similarly for

two- and three-wire systems. In a two-wire-circuit panel

box, the black or red hot wire is connected to a terminal

of the main disconnect, and the white or light gray

neutral wire is connected to the neutral strip, which is then

grounded to the pipe on the street side of the water meter.

In a three-wire system, the

black and red hot wires are

connected to separate

terminals of the main

disconnect, and the neutral

wire is grounded the same as

for a two-wire system. Below

each fuse is a terminal to

which a black or red wire is

11-12 Electricity

Figure 11.16. GFCI 

Figure 11.17. Arc Interrupter 
connected. The white or light gray neutral wires are then

connected to the neutral strip. Each fuse indicates a

separate circuit (Figure 11.18).

• Nontamperable fuses—All ordinary plug fuses

have the same diameter and physical appearance,

regardless of their current capacity, whereas

nontamperable fuses are sized by amperage load.

Thus, with regular fuses, if a circuit designed for a

15-ampere fuse is overloaded so that the 15-ampere

fuse blows out, nothing will prevent a person

from replacing the 15-ampere fuse with a 20- or

30-ampere fuse, which may not blow out. If a

circuit wired with 14-gauge wire (current capacity

15 amperes) is fused with a 20- or 30-ampere fuse

and an overload develops, more current than the

14-gauge wire is safely capable of carrying could

pass through the circuit. The result would be a

heating of the wire and potential fire.

• Type-S fuses—Type-S fuses have different lengths

and diameter threads for each amperage capacity.

An adapter is first inserted into the ordinary fuse

holder, which adapts the fuse holder for only one

capacity fuse. Once the adapter is inserted, it

cannot be removed.

• Cartridge fuses—A cartridge fuse protects an

electric circuit in the same manner as an ordinary

plug fuse, already described, protects an electric

circuit. Cartridge fuses are often used as main fuses.

Electric Circuits

An electric circuit in good repair carries electricity

through two or three wires from the source of supply to

an outlet and back to the source. A branch circuit is an

electric circuit that supplies current to a limited number

of outlets and fixtures. A residence generally has many

branch circuits. Each is protected against short circuits

and overloads by a 15- or 20-ampere fuse or circuit breaker.

The number of outlets per branch circuit varies from

building to building. The code requires enough light

circuits so that 3 watts of power will be available for each

square foot of floor area in a house. A circuit wired with

14-gauge wire and protected by a 15 ampere over-current

protection device provides 15×115 (1,725 watts); each

circuit is enough for 1,725 divided by 3 (575 square feet).

Note that 575 is a minimum figure; if future use is

considered, 500 or even 400 square feet per branch circuit

should be used.

Special appliance circuits will provide electric power for

lighting, radio, TV, and small portable appliances.

However, the larger electric appliances usually found in

the kitchen consume more power and must have their

own special circuit.

Section 220-3b of the code requires two special circuits to

serve only appliance outlets in the kitchen, laundry,

pantry, family room, dining room, and breakfast room.

Both circuits must be extended to the kitchen; either one

or both of these circuits may serve the other rooms. No

lighting outlets may be connected to these circuits, and

they must be wired with 12-gauge wire and protected by

a 20-ampere over-current device. Each circuit will have a

capacity of 20×115 (2,300 watts), which is not too much

when toasters often require more than 1,600 watts.

It is customary to provide a circuit for each of the

following appliances: range, water heater, washing

machine, clothes dryer, garbage disposal, dishwasher,

furnace, water pump, air conditioner, heat pump, and air

compressor. These circuits may be either 115 volts or

230 volts, depending on the particular appliance or motor

installed.

Outlet Switches and Junction Boxes

The code requires that every switch, outlet, and joint in

wire or cable be housed in a box. Every fixture must be

mounted on a box. Most boxes are made of plastic or

metal with a galvanized coating. When a cable of any

style is used for wiring, the code requires that it be

securely anchored with a connector to each box it enters.

Grounding Outlets

An electrical appliance may appear to be in good repair,

and yet it might be a danger to the user. Older portable

Healthy Housing Reference Manual 11-13 Figure 11.18. Types of Fuses 
electric drills consist of an electric motor inside a metal

casing. When the switch is depressed, the current flows to

the motor and the drill rotates. As a result of wear,

however, the insulation on the wire inside the drill may

deteriorate and allow the hot side of the power cord to

come in contact with the metal casing. This will not

affect the operation of the drill.

A person fully clothed using the drill in the living room,

which has a dry floor, will not receive a shock, even

though he or she is in contact with the electrified drill

case. The operator’s body is not grounded because of the

dry floor. If standing on a wet basement floor, the

operator’s body might be grounded; and, when the

electrified drill case is touched, current will pass through

the operator’s body.

To protect people from electrocution, the drill case is

usually connected to the system ground by means of a

wire called an appliance ground. In this instance, as the

drill is plugged in, current will flow between the shorted

hot wire and the drill case and cause the over-current

device to break the circuit. Thus, the appliance ground

has protected the human operator. Newer appliances and

tools are equipped with two-prong polarized plugs, as

discussed in the standards section of this manual.

The appliance ground (Figure 11.19) is the third wire

found on many appliances. The appliance ground will be

of no use unless the outlet into which the appliance is

plugged is grounded. Being in physical contact with a

ground outlet box grounds the outlet. Having a third

ground wire, or a grounded conduit, as part of the circuit

wiring grounds the outlet box. 

All new buildings are required to have grounded outlets.

A two-lead circuit tester can be used to test the outlet.

The circuit tester lights when both of its leads are plugged

into the two elongated parallel openings of the outlet. In

addition, the tester lights when one lead is plugged into

the round third opening and the other is plugged into the

hot side of the outlet. Most problems can be resolved

using inexpensive testers resembling a plug with three

leads. These can be purchased in many stores and most

hardware stores for very reasonable prices. 

If the conventional two-opening outlet is used, it may be

grounded if the screw that holds the outlet cover plate is

electrically connected to the third-wire ground. The tester

should light when one lead is in contact with a clean

paint-free metal outlet cover plate screw and the hot side

of the outlet. If the tester does not light, the outlet is not

grounded. If a two-opening outlet is grounded, it may be

adapted for use by a three-wire appliance by using an

adapter. The loose-wire portion or screw tab of the

adapter should be secured behind the metal screw of the

outlet plate cover. Many appliances, such as electric

shavers and some new hand tools, are double insulated

and are safe without having a third ground wire.

Polarized Plugs and Connectors

Plugs are polarized or unpolarized. Polarization helps

reduce the potential for shock. Consumers can easily

identify polarized plugs; one blade-the ground prong-is

wider than the other. Three-conductor plugs are

automatically polarized because they can only be inserted

one way. Polarized plugs are used to connect the mostexposed part of an appliance to the ground wire so that if

you are touching a ground (such as a pipe, bathtub, or

faucet) and the exposed part of an appliance (the case, the

threaded part of a light bulb socket, etc.), you will not get

an electrical shock. Many appliances, such as electric

drills, are doubly insulated so the probability of any

exposed part of the appliance being connected, by a short

or other problem in the appliance, to either wire is very

small. Such devices often use unpolarized plugs where the

two prongs of the plug are identical. 

Common Electrical Violations

The most obvious things that a housing inspector must

check are the power supply; the type, location, and

condition of the wiring; and the number and conditions of

wall outlets or ceiling fixtures required by the local code. In

making an investigation, the following considerations will

serve as useful guides.

11-14 Electricity

Figure 11.19. Appliance Ground and Grounded Plug 
• Power supply—Where is it, is it grounded

properly, and is it at least of the minimum

capacity required to supply current safely for

lighting and the major and minor appliances in

the dwelling?

• Panel box covers or doors—These should be

accessible only from the front and should be

sealed in such a way that they can be operated

safely without the danger of contact with live or

exposed parts of the wiring system.

• Switch, outlets, and junction boxes—These also

must be covered to protect against danger of

electric shock.

• Frayed or bare wires—These are usually the result

of long use and drying out and cracking of the

insulation, which leave the wires exposed, or of

constant friction and rough handling of the wire,

which cause it to fray or become bare. Wiring in

this condition constitutes a safety hazard. Correction

of such defects should be ordered immediately.

• Electric cords under rugs or other floor

coverings—Putting electric cords in locations

such as these is prohibited because of the potential

fire hazard caused by continuing contact over a

period of time between these heat-bearing cords

and the flammable floor coverings. Direct the

occupant to shift the cords to a safe location, explain

why, and make sure it is done before you leave.

• Ground fault circuit interrupter—All bathroom,

kitchen, and workroom outlets-where shock

hazard is great-should have GFCI outlets. Check

for lack of or nonuse of GFCI outlets. 

• Bathroom lighting—Bathrooms should include at

least one permanently installed ceiling or wall

light fixture with a wall switch and plate located

and maintained so that there is no danger of short

circuiting from use of other bathroom facilities or

splashing water. Fixture or cover plates should be

insulated or grounded.

• Lighting of public hallways, stairways, landings,

and foyers—A common standard is sufficient

lighting to illuminate 10 foot-candles on every part

of these areas at all times. Sufficient lighting

means that people can clearly see their feet on all

parts of the stairways and halls. Public halls and

stairways in structures containing less than three

dwelling units may be supplied with conveniently

located light switches controlling an adequate

lighting system that may be turned on when

needed, instead of full-time lighting.

• Habitable room lighting—The standard here

may be two floor convenience outlets (although

floor outlets are dangerous unless protected by

proper dust and water covers) or one convenience

outlet and one wall or ceiling electric light fixture.

This number is an absolute and often inadequate

minimum, given the contemporary widespread

use of electricity in the home. The minimum

should be the number required to provide

adequate lighting and power to accommodate

lighting and appliances normally used in each room.

• Octopus outlets or wiring—This term is applied

to outlets into which plugs have been inserted and

are being used to permit more than two lights or

portable appliances, such as a TV, lamp, or radio,

to be connected to the electrical system. The

condition occurs where the number of outlets is

insufficient to accommodate the normal use of

the room. This practice overloads the circuit and

is a potential source of fire.

• Outlet covers—Every outlet and receptacle must

be covered by a protective plate to prevent contact

of its wiring or terminals with the body,

combustible objects, or water.

Following are six situations that can cause danger and

should also be corrected.

Excessive or Faulty Fusing

The wire’s capacity must not be exceeded by the fuse or

circuit breaker capacity or be left unprotected by faulty

fusing or circuit breakers. Fuses and circuit breakers are

safety devices designed to “blow” to protect against

overloading the electrical system or one or more of its

circuits. Pennies under fuses are there to bypass the fuse.

These are illegal and must be removed. Overfusing is

done for the same reason. The latter can be prevented by

installing modern fusestats, which prevent use of any fuse of a

higher amperage than can be handled by the circuit it serves.

Cords Run Through Walls or Doorways and 

Hanging Cords or Wires

This makeshift installation often is the work of an

unqualified handyman or do-it-yourself occupant. The

Healthy Housing Reference Manual 11-15
inspector should check the local electrical code to

determine the policy regarding this type of installation.

Temporary Wiring

Temporary wiring should not be allowed, with the

exception of extension cords that go directly from

portable lights and electric fixtures to convenience outlets.

Excessively Long Extension Cords

City code standards often limit the length of loose cords

or extension lines to a maximum of 8 feet. This is

necessary because cords that are too long will overheat if

overloaded or if a short circuit develops and, thus, create a

fire hazard. This requirement does not apply to specially

designed extension cords for operating portable tools and

trouble lights.

Dead or Dummy Outlets

These are sometimes installed to deceive the housing

inspector. All outlets must be tested or the occupants

questioned to see if these are live and functioning

properly. A dead outlet cannot be counted to determine

compliance with the code.

Aluminum Wiring Inside the Home

Although aluminum is an excellent conductor, it tends to

oxidize on the conducting surface. The nonconductive

oxidized face of the conductor will arc from the remaining

conductive surfaces, and this arc can result in fire. 

Inspection Steps

The basic tools required by a housing inspector for

making an electrical inspection are fuse and circuit testers

and a flashlight. The first thing to remember is that you

are in a strange house, and the layout is unfamiliar to

you. The second thing to remember is that you are

dealing with electricity-take no chances. Go to the site of

the ground, usually at the water meter, and check the

ground. It should connect to the water line on the street

side of the water meter or be equipped with a jumper

wire. Do not touch any box or wire until you are sure of

the ground. Go to the main fuse box or circuit breaker

box and check all fuses and breakers for operational

integrity (proper amperage range; functional). Note the

condition of the wiring and of the box itself and check

whether it is over-fused. Examine all wiring in the

basement. Make sure you are standing in a dry spot

(concrete poses a particular problem because you cannot

determine its water content from visual examination)

before touching any electrical device. Standing on a dry

piece of wood is far safer than standing on concrete. Do 

not disassemble the fuse box, circuit breaker, or other

devices. Decisions must be made on what you see. If in

doubt, consult your supervisor. 

Note whether any fuse boxes, circuit breakers, or junction

boxes are uncovered. Examine all wiring for frayed or bare

spots; improper splicing; or rotted, worn, or inadequate

insulation. Avoid all careless touching; when in

doubt—DON’T! If you see bare wires, have the owner

call an electrician. Look for wires or cords in use in the

basement. Be certain all switch boxes and outlets are in a

tight, sound condition. Make sure that the emergency

switch for an oil burner is at the top of the basement

stairs, not on top of the unit.

Bathrooms, kitchens, and utility rooms-where electric

shock hazard is great-should have GFCI outlets. 

While inspecting the bathroom, also check for dangerous

items, such as radios that are not made for bathroom use

or portable electric heaters. Have inappropriate items

removed immediately. Such items have killed thousands

of people who touched them after getting out of the

bathtub or shower while still wet or because the appliance

fell into water the person had contact with. 

Electric washer and dryer combinations should have a

240-volt circuit, 30-ampere service connected to a

separate fuse or circuit breaker. Washer and dryer

combinations and other portable appliances should be

served by sufficiently heavy electrical service. If either of

these special lines is not available under the above-stated

conditions, consult your supervisor.

An electric range needs a 50-ampere, 240-volt circuit. A

dishwasher needs a 20-ampere, 120-volt circuit. A

separate three-wire circuit must be installed for an electric

water heater. Continue your inspection systematically

through the house.

To sum up, the housing inspector investigates specified

electrical elements in a house to detect any obvious

evidence of an insufficient power supply, to ensure the

availability of adequate and safe lighting and electrical

facilities, and to discover and correct any obvious hazard.

Because electricity is a technical, complicated field, the

housing inspector, when in doubt, should consult his or

her supervisor. The inspector cannot, however, close the

case until appropriate corrective action has been taken on

all such referrals.

11-16 Electricity
References

1. National Fire Protection Association. National

electrical code handbook 2005. Florence, KY:

Thomson Delmar Learning; 2005.

2. Center for Disease Control. Basic housing

inspection. Atlanta: US Department of Health

and Human Services; 1976.

3. British Columbia Safety Authority. The facts

about aluminum wiring in the home. New

Westminster, British Columbia, Canada: British

Columbia Safety Authority; no date. Available

from URL: http://www.safetyauthority.ca/

services/esp/

The_Facts_About_Aluminum_Wiring_In_The_

Home.pdf.

4. Consumer Product Safety Commission. May is

National Electrical Safety Month: good news for

homeowners-aluminum wiring fix still available.

Washington, DC: Consumer Product Safety

Commission; 2003. Available from URL:

http://www.cpsc.gov/CPSCPUB/PREREL/prhtml

03/03120.html.

5. Consumer Product Safety Commission. CPSC

safety recommendations for aluminum wiring in

homes. Washington, DC: Consumer Product

Safety Commission; 1974. Available from URL:

http://www.cpsc.gov/CPSCPUB/PREREL/prhtml

74/74040.html.

6. AWG American wire gauge/diameter/resistance.

Cologne, Germany: Bernd Noack; no date.

Available from URL:

http://www.bnoack.com/data/wireresistance.html.

7. Consumer Product Safety Commission. Extension

cords fact sheet. Washington, DC: Consumer

Product Safety Commission; no date. CPSC #16.

Available from URL:

http://www.cpsc.gov/CPSCPUB/PUBS/16.html. 

Additional Sources of Information

Croft T, Summers W. American electricians’ handbook.

14th edition, New York: McGraw-Hill Professional; 2002. 

Tuck D, Tuck G, Woodson RD. Electrician’s instant

answers. New York: McGraw-Hill Professional; 2003.

Black and Decker. The complete guide to home wiring: a

comprehensive manual, from basic repairs to advanced

projects (Black & Decker Home Improvement Library;

US edition). Chanhassen, MN: Creative Publishing

International; 2001.

Sunset Publishing. Basic wiring. 3rd edition. Menlo Park,

CA: Sunset Books, 1995.

Hometime.com. Electrical service panel: panel

components, circuit breakers, fuses, electrical glossary.

Hometime.com; no date. Available from URL:

http://www.hometime.com/Howto/ projects/

electric/elec_2.htm.

Vandervort D. How your house works: electric systems.

Glendale, CA: Hometips.com; no date. Available from

URL: http://www.hometips.com/hyhw/

electrical/electric.html.

PNM Resources. Residential subdivisions: electric service

requirements. In: Electric service guide. Albuquerque,

NM: PNM; 2004. Available from URL:

http://www.pnm.com/esg/chapters/56-63.pdf.

Textor K. Extension cord basics. Fine Homebuilding

2000, 129: 84-9. Available from URL:

http://www.taunton.com/finehomebuilding/

pages/h00010.asp.

Consumer Product Safety Commission. Repairing

aluminum wiring. Washington, DC: Consumer Product

Safety Commission; 1994. CPSC #516. Available from

URL: http://www.cpsc.gov/CPSCPUB/PUBS/516.pdf.

Healthy Housing Reference Manual 11-17
11-18 Electricity
Chapter 12—Heating, Air Conditioning, and Ventilating

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-1

Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-4

Standard Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-4

Central Heating Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-7

Space Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-12

Hydronic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Direct Vent Wall Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-15

Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-15

Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-15

Circulation Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Evaporation Coolers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-17

Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-17

Fireplaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-18

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-19

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-19

Figure 12.1. Heat Pump in Cooling Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-5

Figure 12.2. Piping Hookup for Inside Tank Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-6

Figure 12.3. Piping Hookup for Buried Outside Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-6

Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm Air Furnace . . . . . . .12-7

Figure 12.5. Minimum Clearance for Steam or Hot Water Boiler and Mechanical Warm-air Furnace .12-7

Figure 12.6. Heating Ducts Covered With Asbestos Insulation . . . . . . . . . . . . . . . . . . . . . . . . .12-7

Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers . . . . . . . . . . . . . . . . .12-8

Figure 12.8. Cutaway View of Typical High-pressure Gun Burner . . . . . . . . . . . . . . . . . . . . . . .12-9

Figure 12.9. Gas-fired Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-9

Figure 12.10. Typical Gravity One-pipe Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-10

Figure 12.11. One-pipe Gravity Water Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-11

Figure 12.12. Two-pipe Gravity Water Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-11

Figure 12.13. Warm-air Convection Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-11

Figure 12.14. Cross-sectional View of Building Showing Forced-warm-air Heating System . . . . .12-12

Figure 12.15. Perforated-sleeve Burner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-13

Figure 12.16. Condition of Burner Flame With Different Rates of Fuel Flow . . . . . . . . . . . . . . .12-13

Figure 12.17. Wall and Ceiling Clearance Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Figure 12.18. Draft in Relation to Height of Chimney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-14

Figure 12.19. Location and Operation of Typical Backdraft Diverter . . . . . . . . . . . . . . . . . . . . . .12-15

Figure 12.20. Split-system Air Conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Figure 12.21. External Air-conditioning Condenser Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-16

Figure 12.22. Chimney Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-17

Figure 12.23. Fireplace Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-18

Healthy Housing Reference Manual 1

Contents
“Our climate is warming at a faster rate than ever before recorded.” 

D. James Baker 

NOAA Administrator, 1993–2004 

Introduction

The quotes below provide a profound lesson in the need for

housing to provide protection from both the heat and cold. 

“France heat wave death toll set at 14,802: The

death toll in France from August’s blistering heat

wave has reached nearly 15,000, according to a

government-commissioned report released

Thursday, surpassing a prior tally by more than

3,000.” USA Today, September 25, 2003.

“In the study of the 1995 Chicago heat wave, those

at greatest risk of dying from the heat were people

with medical illnesses who were socially isolated

and did not have access to air conditioning.”

Centers for Disease Control and Prevention,

Morbidity and Mortality Weekly Report, July 4, 2003.

“3 Deaths tied to cold . . .The bitter cold that

gripped the Northeast through the weekend and

iced over roads was blamed for at least three deaths,

including that of a Philadelphia man found inside a

home without heat.” Lexington [Kentucky] Herald

Leader, January 12, 2004.

“In many temperate countries, death rates during

the winter season are 10%–25% higher than those

in the summer.” World Health Organization,

Health Evidence Network, November 1, 2004.

This chapter provides a general overview of the heating

and cooling of today’s homes. Heating and cooling are

not merely a matter of comfort, but of survival. Both

very cold and very hot temperatures can threaten health.

Excessive exposure to heat is referred to as heat stress and

excessive exposure to cold is referred to as cold stress.

In a very hot environment, the most serious health risk is

heat stroke. Heat stroke requires immediate medical

attention and can be fatal or leave permanent damage.

Heat stroke fatalities occur every summer. Heat

exhaustion and fainting are less serious types of illnesses.

Typically they are not fatal, but they do interfere with a

person’s ability to work.

At very cold temperatures, the most serious concern is

the risk for hypothermia or dangerous overcooling of the

body. Another serious effect of cold exposure is frostbite

or freezing of exposed extremities, such as fingers, toes,

nose, and ear lobes. Hypothermia can be fatal if

immediate medical attention is not received.

Heat and cold are dangerous because the victims of heat

stroke and hypothermia often do not notice the

Chapter 12: Heating, Air Conditioning, and Ventilating

Healthy Housing Reference Manual 12-1

Air duct—A formed conduit that carries warm or cold air from the furnace or air-conditioner and back again.

Antiflooding Control—A safety control that shuts off fuel and ignition when excessive fuel oil accumulates in the

appliance.

Appliance: 

High heat—A unit that operates with flue entrance temperature of combustion products above 1,500°F (820°C).

Medium heat—Same as high-heat, except above 600°F (320°C).

Low heat—same as high-heat, except below 600°F (320°C).

Boiler:

High pressure—A boiler furnishing pressure at 15 psi or more.

Low pressure (hot water or steam)—A boiler furnishing steam at a pressure less than 15 psi or hot water 

not more than 30 psi.

Burner—A device that mixes fuel, air, and ignition in a combustion chamber.

Definitions of Terms Related to HVAC Systems
symptoms. This means that family, neighbors, and

friends are essential for early recognition of the onset of

the conditions. The affected individual’s survival depends

on others to identify symptoms and to seek medical help.

Family, neighbors, and friends must be particularly

diligent during heat or cold waves to check on

individuals who live alone.

Although symptoms vary from person to person, the

warning signs of heat exhaustion include confusion and

profuse and prolonged sweating. The person should be

removed from the heat, cooled, and heavily hydrated.

Heat stroke signs and symptoms include sudden and

severe fatigue, nausea, dizziness, rapid pulse,

lightheadedness, confusion, unconsciousness, extremely

high temperature, and hot and dry skin surface. An

individual who appears disorientated or confused, seems

euphoric or unaccountably irritable, or suffers from

malaise or flulike symptoms should be moved to a cool

location and medical advice should be sought

immediately.

Carbon monoxide (CO) detector—A device used to detect CO (specific gravity of 0.97 vs. 1.00 for oxygen, a colorless

odorless gas resulting from combustion of fuel). CO detectors should be placed on each floor of the structure at eye level

and should have an audible alarm and, when possible, a digital readout at eye level.

Chimney—A vertical shaft containing one or more passageways.

Factory-built chimney—A tested and accredited flue for venting gas appliances, incinerators and solid or liquid 

fuel-burning appliances.

Masonry chimney—A field-constructed chimney built of masonry and lined with terra cotta flue or firebrick.

Metal chimney—A field-constructed chimney of metal.

Chimney connector—A pipe or breeching that connects the heating appliance to the chimney.

Clearance—The distance separating the appliance, chimney connector, plenum, and flue from the nearest surface of

combustible material.

Central cooling system—An electric or gas-powered system containing an outside compressor, cooling coils, and a

ducting system inside the structure designed to supply cool air uniformly throughout the structure. 

Central heating system—A flue connected boiler or furnace installed as an integral part of the structure and designed to

supply heat adequately for the structure.

Collectors—The key component of active solar systems and are designed to meet the specific temperature requirements

and climate conditions for different end uses. Several types of solar collectors exist: flat-plate collectors, evacuated-tube

collectors, concentrating collectors, and transpired air collectors.

Controls:

High-low limit control—An automatic control that responds to liquid level changes and will shut down if they 

are exceeded. 

Primary safety control—The automatic safety control intended to prevent abnormal discharge of fuel at the burner 

in case of ignition failure or flame failure.

Combustion safety control—A primary safety control that responds to flame properties, sensing the presence 

of flame and causing fuel to be shut off in event of flame failure.

Convector—A radiator that supplies a maximum amount of heat by convection, using many closely spaced metal fins

fitted onto pipes that carry hot water or steam and thereby heat the circulating air.

Conversion—A boiler or furnace, flue connected, originally designed for solid fuel but converted for liquid or gas fuel.

Damper—A valve for regulating draft on coal-fired equipment. Generally located on the exhaust side of the combustion

chamber, usually in the chimney connector. Dampers are not allowed on oil- and gas-fired equipment. 

Draft hood—-A device placed in and made a part of the vent connector (chimney connector or smoke pipe) from an

appliance, or in the appliance itself. The hood is designed to a) ensure the ready escape of the products of combustion in

the event of no draft, back draft, or stoppage beyond the draft hood; b) prevent backdraft from entering the appliance;

and c) neutralize the effect of stack action of the chimney flue upon appliance operation.

Definitions of Terms Related to HVAC Systems

12-2 Heating, Air Conditioning, and Ventilating
Healthy Housing Reference Manual 12-3

Warning signs of hypothermia include nausea, fatigue,

dizziness, irritability, or euphoria. Individuals also

experience pain in their extremities (e.g., hands, feet,

ears) and severe shivering. People who exhibit these

symptoms, particularly the elderly and young, should be

moved to a heated shelter and medical advice should be

sought when appropriate.

The function of a heating, ventilation, and air

conditioning (HVAC) system is to provide for more than

human health and comfort. The HVAC system produces

heat, cool air, and ventilation, and helps control dust and

moisture, which can lead to adverse health effects. The

variables to be controlled are temperature, air quality, air

motion, and relative humidity. Temperature must be

maintained uniformly throughout the heated/cooled

area. There is a 6°F to 10°F (-14°C to -12°C) variation

in room temperature from floor to ceiling. The adequacy

of the HVAC system and the air-tightness of the

structure or room determine the degree of personal safety

and comfort within the dwelling.

Draft regulator—A device that functions to maintain a desired draft in oil-fired appliances by automatically reducing the

chimney draft to the desired value. Sometimes this device is referred to in the field as air-balance, air-stat, or flue velocity

control or barometer damper. 

Fuel oil—A liquid mixture or compound derived from petroleum that does not emit flammable vapor below a

temperature of 125°F (52°C).

Heat—The warming of a building, apartment, or room by a furnace or electrical stove.

Heating plant—The furnace, boiler, or the other heating devices used to generate steam, hot water, or hot air, which

then is circulated through a distribution system. It typically uses coal, gas, oil or wood as its source of heat.

Limit control—A thermostatic device installed in the duct system to shut off the supply of heat at a predetermined

temperature of the circulated air.

Oil burner—A device for burning oil in heating appliances such as boilers, furnaces, water heaters, and ranges. A burner

of this type may be a pressure-atomizing gun type, a horizontal or vertical rotary type, or a mechanical or natural draftvaporizing type.

Oil stove—A flue-connected, self-contained, self-supporting oil-burning range or room heater equipped with an integral

tank not exceeding 10 gallons; it may be designed to be connected to a separate oil tank.

Plenum chamber—An air compartment to which one or more distributing air ducts are connected.

Pump, automatic oil—A device that automatically pumps oil from the supply tank and delivers it in specific quantities

to an oil-burning appliance. The pump or device is designed to stop pumping automatically if the oil supply line breaks.

Radiant heat—A method of heating a building by means of electric coils, hot water, or steam pipes installed in the

floors, walls, or ceilings.

Register—A grille-covered opening in a floor, ceiling, or wall through which hot or cold air can be introduced into a

room. It may or may not be arranged to permit closing the grille.

Room heater—A self-contained, freestanding heating appliance (space heater) intended for installation in the space

being heated and not intended for duct connection.

Smoke detector—A device installed in several rooms of the structure to warn of the presence of smoke. It should provide

an audible alarm. It can be battery powered or electric, or both. If the unit is battery powered, the batteries should be

tested or checked on a routine basis and changed once per year. If the unit is equipped with a 10-year battery, it is not

necessary to replace the battery every year. 

Tank—A separate tank connected, directly or by pump, to an oil-burning appliance.

Thimble—A metal or terra cotta lining for a chimney or furnace pipe.

Valve (main shut-off valve)—A manually operated valve in an oil line used to turn the oil supply to the burner on or off.

Vent system—The gas vent or chimney and vent connector, if used, assembled to form a continuous, unobstructed

passageway from the gas appliance to the outside atmosphere to remove vent gases. 

Definitions of Terms Related to HVAC Systems
Gas, electricity, oil, coal, wood, and solar energy are the

main energy sources for home heating and cooling. Heating

systems commonly used are steam, hot water and hot air.

A housing inspector should have knowledge of the various

heating fuels and systems to be able to determine their

adequacy and safety in operation. To cover fully all

aspects of the heating and cooling system, the entire area

and physical components of the system must be considered.

Heating

Fifty-one percent of the homes in the United States are

heated with natural gas, 30% are heated with electricity,

and 9% with fuel oil. The remaining 11% are heated with

bottled fuel, wood, coal, solar, geothermal, wind, or solar

energy [1]. Any home using combustion as a source of

heating, cooling, or cooking or that has an attached

garage should have appropriately located and maintained

carbon monoxide (CO) gas detectors. According to the

U.S. Consumer Product Safety Commission (CPSC),

from data collected in 2000, CO kills 200 people and

sends more than 10,000 to the hospital each year. 

The standard fuels for heating are discussed below.

Standard Fuels

Gas

More than 50% of American homes use gas fuel. Gas

fuels are colorless gases. Some have a characteristic pungent

odor; others are odorless and cannot be detected by smell.

Although gas fuels are easily handled in heating equipment,

their presence in air in appreciable quantities becomes a

serious health hazard. Gases diffuse readily in the air,

making explosive mixtures possible. A proportion of

combustible gas and air that is ignited burns with such a

high velocity that an explosive force is created. Because of

these characteristics of gas fuels, precautions must be

taken to prevent leaks, and care must be exercised when

gas-fired equipment is lit. 

Gas is broadly classified as natural or manufactured. 

• Natural gas—This gas is a mixture of several

combustible and inert gases. It is one of the richest

gases and is obtained from wells ordinarily located

in petroleum-producing areas. The heat content

may vary from 700 to 1,300 British thermal units

(BTUs) per cubic foot, with a generally accepted

average figure of 1,000 BTUs per cubic foot.

Natural gases are distributed through pipelines to the

point of use and are often mixed with manufactured

gas to maintain a guaranteed BTU content. 

• Manufactured gas—This gas, as distributed, is

usually a combination of certain proportions of

gases produced from coke, coal, and petroleum.

Its BTU value per cubic foot is generally closely

regulated, and costs are determined on a guaranteed

BTU basis, usually 520 to 540 BTUs per cubic foot.

• Liquefied petroleum gas—Principal products of

liquefied petroleum gas are butane and propane.

Butane and propane are derived from natural gas

or petroleum refinery gas and are chemically

classified as hydrocarbon gases. Specifically,

butane and propane are on the borderline

between a liquid and a gaseous state. At ordinary

atmospheric pressure, butane is a gas above 33°F

(0.6°C) and propane a gas at -42°F (-41°C).

These gases are mixed to produce commercial gas

suitable for various climatic conditions. Butane

and propane are heavier than air. The heat content of

butane is 3,274 BTUs per cubic foot, whereas that

of propane is 2,519 BTUs per cubic foot. 

Gas burners should be equipped with an automatic

shutoff in case the flame fails. Shutoff valves should be

located within 1 foot of the burner connection and on the

output side of the meter.

Caution: Liquefied petroleum gas is heavier than air;

therefore, the gas will accumulate at the bottom of

confined areas. If a leak develops, care should be taken to

ventilate the appliance before lighting it.

Electricity

Electricity has gained popularity for heating in many

regions, particularly where costs are competitive with

other sources of heat energy, with usage increasing from

2% in 1960 to 30% in 2000. With an electric system, the

housing inspector should rely mainly on the electrical

inspector to determine proper installation. There are a few

items, however, to be concerned with to ensure safe use of

the equipment. Check to see that the units are approved

by an accredited testing agency and installed according to

the manufacturer’s specifications. Most convector-type

units must be installed at least 2 inches above the floor

level, not only to ensure that proper convection currents

are established through the unit, but also to allow

sufficient air insulation from any combustible flooring

material. The housing inspector should check for curtains

that extend too close to the unit or loose, long-pile rugs

that are too close. A distance of 6 inches on the floor and

12 inches on the walls should separate rugs or curtains

from the appliance.

12-4 Heating, Air Conditioning, and Ventilating
Heat pumps are air conditioners that contain a valve that

allows switching between air conditioner and heater.

When the valve is switched one way, the heat pump acts

like an air conditioner; when it is switched the other way,

it reverses the flow of refrigerants and acts like a heater.

Cold is the absence of energy or calories of heat. To cool

something, the heat must be removed; to warm

something, energy or calories of heat must be provided.

Heat pumps do both.

A heat pump has a few additions beyond the typical air

conditioner: a reversing valve, two thermal expansion valves,

and two bypass valves. The reversing valve allows the unit

to provide both cooling and heating. Figure 12.1 shows a

heat pump in cooling mode. The unit operates as follows: 

• The compressor compacts the refrigerant vapor

and pumps it to the reversing valve. 

• The reversing valve directs the compressed vapor

to flow to the outside heat exchanger (condenser),

where the refrigerant is cooled and condensed to a

liquid. 

• The air blowing through the condenser coil

removes heat from the refrigerant. 

• The liquid refrigerant bypasses the first thermal

expansion valve and flows to the second thermal

expansion valve at the inside heat exchanger

(evaporator) where it expands into the evaporator

and becomes vapor. 

• The refrigerant picks up heat energy from the air

blowing across the evaporator coil and cool air

comes out at the other side of the coil. The cool

air is ducted to the occupied space as airconditioned air.

• The refrigerant vapor then goes back to the

reversing valve to be directed to the compressor to

start the refrigeration cycle all over again. 

Heat pumps [3] are quite efficient in their use of energy.

However, heat pumps often freeze up; that is, the coils in

the outside air collect ice. The heat pump has to melt this

ice periodically, so it switches itself back to air conditioner

mode to heat up the coils. To avoid pumping cold air into

the house in air conditioner mode, the heat pump also

uses electric strip heaters to heat the cold air that the air

conditioner is pumping out. Once the ice is melted, the

heat pump switches back to heating mode and turns off

the burners.

Radiant heat warms objects directly with longwave

electromagnetic energy. The heating panels diffuse heating

energy rays in a 160° arc, distributing warmth evenly. The

goal is to achieve no more than a 4°F (-16°C) difference

in temperature between floor level and ceiling level.

When properly installed, radiant heat warms a room

sooner and at lower temperature settings than do other

kinds of heat. Extreme care must be taken to protect

against fire hazards from objects in close proximity to the

infrared radiation reflectors. Inspectors dealing with this

heat source should have specialized training. Radiant

heating is plastered into the ceiling or wall in some homes

or in the brick or ceramic floors of bathrooms. If wires are

bare in the plaster, they should be treated as open and

exposed wiring. The inspector should be knowledgeable

about these systems, which are technical and relatively new.

Fuel Oil

Fuel oils are derived from petroleum, which consists

primarily of compounds of hydrogen and carbon

(hydrocarbons) and smaller amounts of nitrogen and

sulfur. Domestic fuel oils are controlled by rigid

specifications. Six grades of fuel oil—numbered 1

through 6—are generally used in heating systems; the

lighter two grades are used primarily for domestic heating: 

• Grade Number 1—a volatile, distillate oil for use

in burners that prepare fuel for burning solely by

vaporization (oil-fired space heaters).

• Grade Number 2—a moderate weight, volatile,

distillate oil used for burners that prepare oil for

burning by a combination of vaporization and

atomization. This grade of oil is commonly used

in domestic heating furnaces.

Healthy Housing Reference Manual 12-5

Figure 12.1. Heat Pump in Cooling Mode [2]
Heating values of oil vary from approximately 152,000 BTU

per gallon for number 6 oil to 136,000 BTU per gallon for

number 1 oil. Oil is more widely used today than coal

and provides a more automatic source of heat and

comfort. It also requires more complicated systems and

controls. If the oil supply is in the basement or cellar area,

certain code regulations must be followed (Figure 12.2)

[4–7]. No more than two 275-gallon tanks may be

installed above ground in the lowest story of any one

building. The IRC recommends a maximum fuel oil

storage of 660 gallons. The tank shall not be closer than

7 feet horizontally to any boiler, furnace, stove, or

exposed flame(s). 

Fuel oil lines should be embedded in a concrete or

cement floor or protected against damage if they run

across the floor. Each tank must have a shutoff valve that

will stop the flow if a leak develops in the line to or in the

burner itself. A leak-tight liner or pan should be installed

under tanks and lines located above the floor. They

contain potential leaks so the oil does not spread over the

floor, creating a fire hazard.

The tank or tanks must be vented to the outside, and a

gauge showing the quantity of oil in the tank or tanks

must be tight and operative. Steel tanks constructed

before 1985 had a life expectancy of 12–20 years. Tanks

must be off the floor and on a stable base to prevent

settlement or movement that may rupture the

connections. Figure 12.3 shows a buried outside tank

installation. In 1985, federal legislation was passed

requiring that the exterior components of underground

storage tanks (USTs) installed after 1985 resist the effects

of pressure, vibration, and movement. Federal regulations

for USTs exclude the following: farm and residential tanks

of 1,100 gallons (420 liters) or less capacity; tanks storing

heating oil used on the premises; tanks on or above the

floor of basements; septic tanks; flow-through process

tanks; all tanks with capacity of 110 gallons or less; and

emergency spill and overfill tanks [8]. A review of local

and state regulations should be completed before

installing underground tanks because many jurisdictions

do not allow burial of gas or oil tanks. 

Coal

The four types of coal are anthracite, bituminous, subbituminous, and lignite. Coal is prepared in many sizes

and combinations of sizes. The combustible portions of

the coal are fixed carbons, volatile matter (hydrocarbons),

and small amounts of sulfur. In combination with these

are noncombustible elements composed of moisture and

impurities that form ash. The various types differ in heat

content. Heat content is determined by analysis and is

expressed in British thermal units per pound.

Improper coal furnace operation can result in an

extremely hazardous and unhealthy home. Ventilation of

the area surrounding the furnace is very important to

prevent heat buildup and to supply air for combustion.

Solar Energy

Solar energy has gained popularity in the last 25 years as

the cost of installation of solar panels and battery storage

has decreased. Improved technology with panels,

installation of panels, piping, and batteries has created a

much larger market. Solar energy largely has been used to

heat water. Today, there are more than a million solar

water-heating systems in the United States. Solar water

heaters use direct sun to heat either water or a heattransfer fluid in collectors [3]. That water is then stored

for use as needed, with a conventional system providing

any necessary additional heating. A typical system will

reduce the need for conventional water heating by about

two-thirds, minimizing the cost of electricity or the use of

fossil fuel and thus the environmental impact associated

12-6 Heating, Air Conditioning, and Ventilating

Figure 12.2. Piping Hookup for Inside Tank Installation [4] Figure 12.3. Piping Hookup for Buried Outside Tank [4]
with their use. The U.S. Department of Housing and

Urban Development and the U.S. Department of Energy

(DOE) have instituted initiatives to deploy new solar

technologies in the next generation of American housing

[3]. For example, DOE has the Million Solar Roofs

Initiative begun in 1997 to install solar energy systems in

more than 1 million U.S. buildings by 2010.

Central Heating Units

The boiler should be placed in a separate room whenever

possible, which is usually required in new construction.

In most housing inspections, however, the inspector is

dealing with existing conditions and must adapt the

situation as closely as possible to acceptable safety

standards. In many old buildings, the furnace is located in

the center of the cellar or basement. This location does

not lend itself to practical conversion to a boiler room.

Consider the physical requirements for a boiler or

furnace.

• Ventilation—More circulating air is required for

the boiler room than for a habitable room, to

reduce the heat buildup caused by the boiler or

furnace and to supply oxygen for combustion.

• Fire protection rating—As specified by various

codes (fire code, building code, and insurance

underwriters), the fire regulations must be strictly

adhered to in areas surrounding the boiler or

furnace. This minimum clearance for a boiler or

furnace from a wall or ceiling is shown in

Figures 12.4 and 12.5. 

Asbestos was used in numerous places on furnaces to

protect buildings from fire and to prevent lost heat.

Figure 12.6 shows asbestos-coated heating ducts, for

example. Where asbestos insulation is found, it must be

handled with care (breathing protection and protective

clothing) and care must be taken to prevent or contain

release into the air [10]. 

The furnace or boiler makes it difficult to supply air and

ventilation for the room. Where codes and local authority

permit, it may be more practical to place the furnace or

boiler in an open area. The ceiling above the furnace

should be protected to a distance of 3 feet beyond all

furnace or boiler appurtenances, and this area should be

free of all storage material. The furnace or boiler should

be on a firm foundation of concrete if located in the cellar

or basement. If codes permit furnace installations on the

first floor, then they must be consulted for proper setting

and location.

Heating Boilers

The term boiler is applied to the single heat source that

can supply either steam or hot water (a boiler is often

called a heater).

Healthy Housing Reference Manual 12-7

Figure 12.5. Minimum Clearance for Steam or Hot Water Boiler and

Mechanical Warm-air Furnace [4]

Figure 12.6. Heating Ducts Covered With Asbestos Insulation

Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm Air

Furnace [4]
Boilers may be classified according to several kinds of

characteristics. They are typically made from cast iron or

steel. Their construction design may be sectional,

portable, fire-tube, water-tube, or special. Domestic

heating boilers are generally of low-pressure type with a

maximum working pressure of 15 pounds per square inch

(psi) for steam and 30 psi for hot water. All boilers have a

combustion chamber for burning fuel. Automatic fuelfiring devices help supply the fuel and control the

combustion. Hand firing is accomplished by the provision of

a grate, ash pit, and controllable drafts to admit air under

the fuel bed and over it through slots in the firing door. A

check draft is required at the smoke pipe connection to

control chimney draft. The gas passes from the

combustion chamber to the flue passages (smoke pipe)

designed for maximum possible transfer of heat from the

gas. Provisions must be made for cleaning flue passages.

Cast-iron boilers are usually shipped in sections and

assembled at the site. They are generally classified as 

• square or rectangular boilers with vertical

sections; and

• round, square, or rectangular boilers with

horizontal pancake sections.

Most steel boilers are assembled units with welded steel

construction and are called portable boilers. Large boilers

are installed in refractory brick settings on the site. Above

the combustion chamber, a group of tubes is suspended,

usually horizontally, between two headers. If flue gases

pass through the tubes and water surrounds them, the

boiler is designated as the fire-tube type. When water

flows through the tubes, it is termed water-tube. Fire-tube

is the predominant type.

Heating Furnaces

Heating furnaces are the heat sources used when air is the

heat-carrying medium. When air circulates because of the

different densities of the heated and cooled air, the

furnace is a gravity type. A fan may be included for the

air circulation; this type is called a mechanical warm-air

furnace. Furnaces may be of cast iron or steel and burn

various types of fuel.

Some new furnaces are as fuel efficient as 95%. Furnaces

with an efficiency of 90% or greater use two heat

exchangers instead of one. Energy savings come not only

from the increased efficiency, but also from improved

comfort at lower thermostat settings.

Fuel-burning Furnaces

Some localities throughout the United States still use coal

as a heating fuel, including residences, schools, colleges

and universities, small manufacturing facilities, and other

facilities located near coal sources.

In many older furnaces, the coal is stoked or fed into the

firebox by hand. The single-retort, underfeed-type

bituminous coal stoker is the most commonly used

domestic automatic-stoking steam or hot-water boiler

(Figure 12.7). The stoker consists of a coal hopper, a

screw for conveying coal from hopper to retort, a fan that

supplies air for combustion, a transmission for driving

coal feed and fan, and an electric motor for supplying

power. The air for combustion is admitted to the fuel

through tuyeres (air inlets) at the top of the retort. The

stoker feeds coal to the furnace intermittently in

accordance with temperature or pressure demands. 

Oil burners are broadly designated as distillate, domestic,

and commercial or industrial. Distillate burners are

usually found in oil-fired space heaters. Domestic oil

burners are usually power driven and are used in domestic

heating plants. Commercial or industrial burners are used

in larger central-heating plants for steam or power

generation.

Domestic oil burners vaporize and atomize the oil and

deliver a predetermined quantity of oil and air to the

combustion chambers. Domestic oil burners operate

automatically to maintain a desired temperature.

Gun-type burners atomize the oil either by oil pressure or

by low-pressure air forced through a nozzle. The oil

system pressure-atomizing burner consists of a strainer,

pump, pressure-regulating valve, shutoff valve and

atomizing nozzle. The air system consists of a powerdriven fan and an air tube that surrounds the nozzle and

electrode assembly.

12-8 Heating, Air Conditioning, and Ventilating

Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers [4]
The fan and oil pump are generally connected directly to the

motor. Oil pressures normally used are about 100 psi, but

pressures considerably in excess of this are sometimes used.

The form and parts of low-pressure, air-atomizing burners

are similar to high-pressure atomizing (gun) burners

(Figure 12.8) except for addition of a small air pump and

a different way of delivering air and oil to the nozzle or orifice. 

The atomizing type burner, sometimes known as a

radiant or suspended flame burner, atomizes oil by

throwing it from the circumference of a rapidly rotating

motor-driven cup. The burner is installed so that the

driving parts are protected from the heat of the flame by a

hearth of refractory material at about the grate elevation.

Oil is fed by pump or gravity; the draft is mechanical or a

combination of natural and mechanical.

Horizontal rotary burners were originally designed for

commercial and industrial use but are available in sizes

suitable for domestic use. In this burner, fuel oil being

thrown in a conical spray from a rapidly rotating cup is

atomized. Horizontal rotary burners use electric gas or

gas-pilot ignition and operate with a wide range of fuels,

primarily Numbers 1 and 2 fuel oil. Primary safety

controls for burner operation are necessary. An

antiflooding device must be a part of the system to stop

oil flow if ignition in the burner should fail. Likewise, a

stack control is necessary to shut off the burner if the

stack temperatures are exceeded, thus cutting off all power

to the burner. This button must be reset before starting

can be attempted. The newer models now use electric eyetype control on the burner itself.

On the basis of the method used to ignite fuels, burners

are divided into five groups:

• Electric—A high-voltage electric spark in the path

of an oil and air mixture causes ignition. This

electric spark may be continuous or may operate

only long enough to ignite the oil. Electric

ignition is almost universally used. Electrodes are

located near the nozzles, but not in the path of

the oil spray.

• Gas pilot—A small gas pilot light that burns

continuously is frequently used. Gas pilots usually

have expanded gas valves that automatically

increase flame size when a motor circuit starts.

After a fixed interval, the flame reverts to normal

size (Figure 12.9). 

• Electric gas—An electric spark ignites a gas jet,

which in turn ignites the oil-air mixture.

• Oil pilot—A small oil flame is used.

• Manual—A burning wick or torch is placed in

the combustion space through peepholes and thus

ignites the charge. The operator should stand to

one side of the fire door to guard against injury

from chance explosion.

The refractory lining or material should be an insulating

fireproof bricklike substance, never ordinary firebrick.

The insulating brick should be set on end to build a

21⁄2-inch-thick wall from furnace to furnace. The size and

shape of the refractory pot vary from furnace to furnace.

Healthy Housing Reference Manual 12-9

Figure 12.8. Cutaway View of Typical High-pressure Gun Burner [4] Figure 12.9. Gas-fired Boiler

Source: HUD
The shape can be either round or square, whichever is

more convenient to build. It is more important to use a

special cement having properties similar to that of the

insulating refractory-type brick.

Steam Heating Systems

Steam heating systems are classified according to the pipe

arrangement, accessories used, method of returning the

condensate to the boiler, method of expelling air from the

system, or the type of control used. The successful

operation of a steam heating system consists of generating

steam in sufficient quantity to equalize building heat loss

at maximum efficiency, expelling entrapped air, and

returning all condensate to the boiler rapidly. Steam

cannot enter a space filled with air or water at pressure

equal to the steam pressure. It is important, therefore, to

eliminate air and remove water from the distribution

system. All hot pipelines exposed to contact by residents

must be properly insulated or guarded. Steam heating

systems use the following methods to return the

condensate to the boiler:

• Gravity one-pipe air-vent system—One of the

earliest types used, this method returns

condensate to the boiler by gravity. This system is

generally found in one-building-type heating

systems. The steam is supplied by the boiler and

carried through a single system or pipe to

radiators, as shown in Figure 12.10. Return of the

condensate is dependent on hydrostatic head.

Therefore, the end of the stream main, where it

attaches to the boiler, must be full of water

(termed a wet return) for a distance above the

boiler line to create a pressure drop balance

between the boiler and the stream main.

Radiators are equipped with an inlet valve and an

air valve. The air valve permits venting of air from

the radiator and its displacement by steam.

Condensate is drained from the radiator through

the same pipe that supplies steam.

• Two-pipe steam vapor system with return trap—

The two-pipe vapor system with boiler return trap

and air eliminator is an improvement of the onepipe system. The return connection of the radiator

has a thermostatic trap that permits flow of

condensate and air only from the radiator and

prevents steam from leaving the radiator. Because

the return main is at atmospheric pressure or less,

a boiler return trap is installed to equalize

condensate return pressure with boiler pressure.

Water Heating Systems

All water heating systems are similar in design and

operating principle. The one-pipe gravity water heating

system is the most elementary of the gravity systems and

is shown in Figure 12.10. Water is heated at the lowest

point in the system. It rises through a single main because

of a difference in density between hot and cold water. The

supply rise or radiator branch takes off from the top of

the main to supply water to the radiators. After the water

gives up heat in the radiator, it goes back to the same

main through return piping from the radiator. This cooler

return water mixes with water in the supply main and

causes the water to cool a little. As a result, the next

radiator on the system has a lower emission rate and must

be larger.

Note in Figure 12.11 that the high points of the hot

water system are vented and the low points are drained.

In this case, the radiators are the high points and the

heater is the low point. 

• One-pipe forced-feed system—If a pump or

circulator is introduced in the main near the heater

of the one-pipe system, it becomes a forced

system that can be used for much larger

applications than can the gravity type. This system

can operate at higher water temperatures than the

gravity system can. When the water is moving

faster and at higher temperatures, it makes a more

responsive system, with smaller temperature drops

and smaller radiators for the same heating load.

• Two-pipe gravity system—A one-pipe gravity

system may become a two-pipe system if the return

radiator branch connects to a second main that

returns water to the heater (Figure 12.12). Water

temperature is practically the same in the entire

radiator.

12-10 Heating, Air Conditioning, and Ventilating

Figure 12.10. Typical Gravity One-pipe Heating System [4]
• Two-pipe forced-circulation system—This system

is similar to a one-pipe forced-circulation system

except that it uses the same piping arrangement

found in the two-pipe gravity system.

• Expansion tanks—When water is heated, it tends

to expand. Therefore, an expansion tank is necessary

in a hot water system. The expansion tank, either

open or closed, must be of sufficient size to

permit a change in water volume within the

heating system. If the expansion tank is open, it

must be placed at least 3 feet above the highest

point of the system. It will require a vent and an

overflow. The open tank is usually in an attic, where

it needs protection from freezing.

The closed expansion tank is found in modern

installations. An air cushion in the tank compresses

and expands according to the change of volume

and pressure in the system. Closed tanks are

usually at the low point in the system and close to

the heater. They can, however, be placed at almost

any location within the heating system. 

Air Heating Systems

Gravity Warm-air Heating Systems. These operate

because of the difference in specific gravity of warm air

and cold air. Warm air is lighter than cold air and rises if

cold air is available to replace it (Figure 12.13).

• Operation—Satisfactory operation of a gravity

warm-air heating system depends on three factors:

size of warm air and cold air ducts, heat loss of

the building, and heat available from the furnace.

• Heat distribution—The most common source of

trouble in these systems is insufficient pipe area,

usually in the return or cold air duct. The total

cross-section area of the cold duct or ducts must

be at least equal to the total cross-section area of

all warm ducts.

• Pipeless furnaces—The pipeless hot-air furnace is

the simplest type of hot-air furnace and is suitable

for small homes where all rooms can be grouped

about a single large register. Other pipeless gravity

furnaces are often installed at floor level. These are

really oversized jacketed space heaters. The most

common difficulty experienced with this type of

furnace is supplying a return air opening of

sufficient size on the floor. 

Forced-Warm-Air Heating Systems. The mechanical

warm-air furnace is the most modern type of warm-air

equipment (Figures 12.13 and 12.14). It is the safest type

because it operates at low temperatures. The principle of a

Healthy Housing Reference Manual 12-11

Figure 12.11. One-pipe Gravity Water Heating System [4]

Figure 12.12. Two-pipe Gravity Water Heating System [4]

Figure 12.13. Warm-air Convection Furnace [4]
forced-warm-air heating system is very similar to that of

the gravity system, except that a fan or blower is added to

increase air movement. Because of the assistance of the

fan or blower, the pitch of the ducts or leaders can be

disregarded; therefore, it is practical to deliver heated air

in the most convenient places. 

• Operation—In a forced-air system, operation of

the fan or blower must be controlled by air

temperature in a bonnet or by a blower control

furnace stat. The blower control starts the fan or

blower when the temperature reaches a certain

point and turns the fan or blower off when the

temperature drops to a predetermined point.

• Heat distribution—Dampers in the various

warm-air ducts control distribution of warm air

either at the branch takeoff or at the warm-air

outlet. Humidifiers are often mounted in the

supply bonnet to regulate the humidity within the

residence.

Space Heaters

Space heaters are the least desirable type of heating from

the viewpoint of fire safety and housing inspection. A

space heater is a self-contained, free-standing air-heating

appliance intended for installation in the space being

heated and not intended for duct connection. According

to the CPSC, consumers are not using care when

purchasing and using space heaters. Approximately

21,800 residential fires are caused by space heaters a year,

and 300 people die in these fires. An estimated 6,000

persons receive hospital emergency room care for burn

injuries associated with contacting hot surfaces of space

heaters, mostly in nonfire situations. 

Individuals using space heaters should use the heaters in

accordance with the following precautions:

• Read and follow the manufacturer’s operating

instructions. A good practice is to read aloud the

instructions and warning labels to all members of

the household to be certain that everyone

understands how to operate the heater safely.

Keep the owner’s manual in a convenient place to

refer to when needed.

• Choose a space heater that has been tested and

certified by a nationally recognized testing

laboratory. These heaters meet specific safety

standards.

• Buy a heater that is the correct size for the area

you want to heat. The wrong size heater could

produce more pollutants and may not be an

efficient use of energy.

• Choose models that have automatic safety

switches that turn off the unit if it is tipped over

accidentally.

• Select a space heater with a guard around the

flame area or heating element. Place the heater on

a level, hard, nonflammable surface, not on rugs

or carpets or near bedding or drapes. Keep the

heater at least 3 feet from bedding, drapes,

furniture, or other flammable materials.

• Keep doors open to the rest of the house if you

are using an unvented fuel-burning space heater.

This helps prevent pollutant build-up and

promotes proper combustion. Follow the

manufacturer’s instructions for oil heaters to

provide sufficient combustion air to prevent CO

production. 

• Never leave a space heater on when you go to

sleep. Never place a space heater close to any

sleeping person.

• Turn the space heater off if you leave the area.

Keep children and pets away from space heaters.

Children should not be permitted to either adjust

the controls or move the heater.

• Keep any portable heater as least 3 feet away from

curtains, newspapers, or anything that might burn.

• Have a smoke detector with fresh batteries on

each level of the house and a CO detector outside

the sleeping area. Install a CO monitor near oil

space heaters at the height recommended by the

manufacturer.

12-12 Heating, Air Conditioning, and Ventilating

Figure 12.14. Cross-sectional View of Building Showing Forced warm-air

Heating System [4]
• Be aware that mobile homes require specially

designed heating equipment. Only electric or

vented fuel-fired heaters should be used.

• Have gas and kerosene space heaters inspected

annually.

• Do not hang items to dry above or on the heater.

• Keep all heaters out of exit and high-traffic areas.

• Keep portable electric heaters away from sinks,

tubs, and other wet or damp places to avoid

deadly electric shocks.

• Never use or store flammable liquids (such as

gasoline) around a space heater. The flammable

vapors can flow from one part of the room to

another and be ignited by the open flame or by an

electrical spark. 

Coal-fired Space Heaters (Cannon Stove)

A coal stove is made entirely of cast iron. Coal on the

grates receives primary air for combustion through the

grates from the ash-door draft intake. Combustible gases

driven from the coal by heat burn in the barrel of the

stove, where they receive additional or secondary air

through the feed door. The side and top of the stove

absorb the heat of combustion and radiate it to the

surrounding space. Coal stoves must be vented to the flue.

Oil-fired Space Heaters

Oil-fired space heaters

have atmospheric

vaporizing-type

burners. The burners

require a light grade of

fuel oil that vaporizes

easily and in

comparatively low

temperatures. In

addition, the oil must

be such that it leaves

only a small amount of

carbon residue and ash

within the heater. Oil

stoves must be vented.

The burner of an oilfired space heater

consists essentially of a bowl, 8 to 13 inches in diameter,

with perforations in the side that admit air for

combustion. The upper part of the bowl has a flame ring

or collar. Figure 12.15 shows a perforated-sleeve burner.

When several space heaters are installed in a building, an

oil supply from an outside tank to all heaters is often

desirable. Figure 12.16 shows the condition of a burner

flame with different rates of fuel flow and indicates the

ideal flame height.

Electric Space Heaters

Electric space heaters do not need to be vented.

Gas-fired Space Heaters

The three types of gas-fired space heaters (natural,

manufactured, and liquefied petroleum gas) have a similar

construction. All gas-fired space heaters must be vented to

prevent a dangerous buildup of poisonous gases. Each

unit console consists of an enamel steel cabinet with top

and bottom circulating grilles or openings, gas burners,

heating elements, gas pilot, and a gas valve. The heating

element or combustion chamber is usually cast iron.

Caution: All gas-fired space heaters and their connections

must be approved by the American Gas Association

(AGA). They must be installed in accordance with the

recommendations of that organization or the local code.

Venting

Use of proper venting materials and correct installation of

venting for gas-fired space heaters is necessary to

minimize harmful effects of condensation and to ensure

that combustion products are carried off. (Approximately

12 gallons of water are produced in the burning of

Healthy Housing Reference Manual 12-13

Figure 12.15. Perforated-sleeve Burner 

Figure 12.16. Condition of Burner Flame with Different Rates of Fuel Flow [4]
1,000 cubic feet of natural gas. The inner surface of the

vent must therefore be heated above the dew point of the

combustion products to prevent water from forming in

the flue.) A horizontal vent must be given an upward

pitch of at least 1 inch per foot of horizontal distance.

When the smoke pipe extends through floors or walls, the

metal pipe must be insulated from the floor or wall

system by an air space (Figure 12.17). Sharp bends should

be avoided. A 9° vent elbow has a resistance to flow

equivalent to that of a straight section of pipe with a

length 10 times the elbow diameter. Be sure that vents are

of rigid construction and resistant to corrosion by flue gas

products. Several types of venting material are available

such as B-vent and other ceramic-type materials. A

chimney lined with firebrick type of terra cotta must be

relined with an acceptable vent material if it is to be used

for venting gas-fired appliances.

The same size vent pipe should be used throughout its

length. A vent should never be smaller than the heater

outlet except when two or more vents converge from

separate heaters. To determine the size of vents beyond

the point of convergence, one-half the area of each vent

should be added to the area of the largest heater’s vent.

Vents should be installed with male ends of inner liner

down to ensure condensate is kept within pipes on a cold

start. The vertical length of each vent or stack should be

at least 2 feet greater than the length between horizontal

connection and stack. Remember that the more

conductive the unit, the lower the temperature of

combustion and the more byproducts of combustion are

likely to be produced. These by-products are sometimes

referred to as soot and creosote. These by-products will

build up in vents, stacks, and chimneys. They are extremely

flammable and can result in fire in these units that is hot

enough to penetrate the heat shielding and throw burning

material onto the roof of the home. 

The vent should be run at least 3 feet above any

projection within 20 feet of the building to place it above

a possible pressure zone due to wind currents (Figure 12.18).

A weather cap should prevent entrance of rain and snow.

Gas-fired space heaters, as well as gas furnaces and water

heaters, must be equipped with a backdraft diverter

(Figure 12.19) to protect heaters against downdrafts and

excessive updrafts. Only draft diverters approved by the AGA

should be used.

The combustion chamber or firebox must be insulated

from the floor, usually with airspace of 15 to 18 inches.

The firebox is sometimes insulated within the unit and

thus allows for lesser clearance firebox combustibles.

Floors should be protected where coal space heaters are

located. The floor protection allows hot coals and ashes to

cool off if dropped while being removed from the ash

chamber. Noncombustible walls and materials should be

used when they are exposed to heated surfaces. For space

heaters, a top or ceiling clearance of 36 inches, a wall

clearance of 18 inches, and a smoke pipe clearance of

18 inches are recommended.

Hydronic Systems

Hydronic (circulating water) systems involving traditional

baseboards can be single-pipe or two-pipe. Radiant

systems are also an option. All hydronic systems require

an expansion tank to compensate for the increase in water

volume when it is heated (i.e., the volume of 50°F [10°C]

water increases almost 4% when it is heated to 200°F

[93°C]). Single-pipe hydronic systems are most

commonly used in residences. They use a single pipe with

hot water flowing in a series loop from radiator to

radiator. Massachusetts has a prototype set of hydronic

systems requirements [11].

12-14 Heating, Air Conditioning, and Ventilating

Figure 12.17. Wall and Ceiling Clearance Reduction [4] Figure 12.18. Draft Relation to Height of Chimney [4]
The drawback to this arrangement is that the temperature

of the water decreases as it moves through each radiator.

Thus, larger radiators are needed for those locations

downstream in the loop. A common solution to this is

multiple loops or zones. Each zone has its own

temperature control with circulation provided by a small

pump or zone valve in each loop. Two-pipe hydronic

systems use a pipe for supplying hot water to the radiators

and a second pipe for returning the water from the

radiators to the boiler.

There are also direct- and reverse-return arrangements.

The direct-return system can be difficult to balance

because the pressure drop through the nearest radiator

piping can be significantly less than for the farthest

radiator. Reverse-return systems take care of the balancing

problem, but require the expense of additional piping.

Orifice plates at radiator inlets or balancing valves at

radiator outlets can also be used to balance the pressure

drops in a direct-return system.

Direct Vent Wall Furnaces

Direct vent wall furnaces are specifically designed for

areas where flues or chimneys are not available or cannot

be used. The furnace is directly vented to the outside and

external air is used to support combustion. The air on the

inside is warmed as it recirculates around a sealed chamber.

Cooling

Air Conditioning

Many old homes relied on passive cooling-opening windows

and doors and using shading devices-during the summer

months. Homes were designed with windows on opposite

walls to encourage cross ventilation and large shade trees

reduced solar heat gains. This approach is still viable, and

improved thermal performance (insulating value)

windows are available that allow for larger window areas

to let in more air in the summer without the heat loss

penalty in the winter. However, increased outdoor noise

levels, pollution, and security issues make relying on open

windows a less attractive option in some locations today.

An air conditioning system of some kind may be installed

in the home. It may be a window air conditioner or

through-the-wall unit for cooling one or two rooms, or a

central split-system air conditioner or heat pump. In any

event, the performance of these systems, in terms of

providing adequate comfort without excessive energy use,

should be investigated. The age of the equipment alone

will provide some indication. If the existing system is

more than 10 years old, replacement should be considered

because it is much less efficient than today’s systems and

nearing the end of its useful life.

The refrigerant commonly used in today’s residential air

conditioners is R-22. Because of the suspicion that R-22

depletes the ozone layer, manufacturers will be prohibited

from producing units with R-22 in 2010. The leading

replacements for R-22 are R-134A and R-410A, and new

products are now available with these nonozone-depleting

refrigerants.

The performance measure for electric air conditioners

with capacities less than 65,000 BTU is the seasonal

energy efficiency ratio (SEER). SEER is a rating of

cooling performance based on representative residential

loads. It is reported in units of BTU of cooling per watt

per hour of electric energy consumption. It includes

energy used by the unit’s compressor, fans, and controls.

The higher the SEER, the more efficient the system.

However, the highest SEER unit may not provide the

most comfort. In humid climates, some of the highest

SEER units exhibit poor dehumidification capability

because they operate at higher evaporator temperatures to

attain the higher efficiency. A SEER of at least 10 is

required by the National Appliance Energy Conservation

Act of 1987 for conventional central split-system aircooled systems. The Department of Energy announced a

SEER of 13 effective January 2006.

Cooling system options vary widely, depending on the

level of control and comfort desired by the homeowner.

Fans can increase circulation and reduce cooling loads,

but they may be unsatisfactory in hot climates because

their cooling capability is directly limited by outdoor

conditions. Radiant barriers can reduce cooling loads in

very hot climates. Evaporative coolers can be a relatively

inexpensive and effective method of cooling in dry

climates, such as the Southwest. Electric air conditioning

maintains a comfortable indoor temperature and

humidity even under the most severe outdoor conditions.

Healthy Housing Reference Manual 12-15

Figure 12.19. Location and Operation of Typical Backdraft Diverter [4]
More than 75% of new homes in the United States are

equipped with some form of central air conditioning:

50% of the homes in the Northeast, 75% in the Midwest,

95% in the South, and approximately 60% in the West.

Electric air conditioning removes moisture from the air

and reduces its temperature. It can be a good investment

because, in most parts of the country, the payback is

significant when the house is sold.

Electric air conditioners that use the vapor-compression,

refrigeration cycle are available in a variety of sizes and

configurations, ranging from small window units to large

central systems. The most common form of central air

conditioning is a split-system with a warm air furnace

(Figure 12.20). The same ductwork is used for distributing

conditioned air during the heating and cooling seasons.

Supply air is cooled and dehumidified as it passes over an

A-shaped evaporator coil. The liquid refrigerant

evaporates inside the coil as it absorbs heat from the air.

The refrigerant gas then travels through refrigerant piping

to the outdoor unit, where it is pressurized in an

electrically driven compressor, raising its temperature and

pressure, and returned to a liquid state in the condenser

as it releases, or dumps, the heat to the outdoors. A fan

draws outdoor air in over the condenser coil. The use of

two-speed indoor fans can be advantageous in this type of

system because the cooling load often requires higher

airflows than the heating load. The lower speed can be

used for the heating season and for improved

dehumidification performance during the cooling season.

The condenser unit for a house air conditioner is shown

in Figure 12.21.

Circulation Fans

Air movement can make a person feel comfortable even

when dry-bulb temperatures are elevated. A circulation

fan (ceiling or portable) that creates an airspeed of 150 to

200 feet per minute can compensate for a 4°F (-16°C)

increase in temperature.

Ceiling circulation fans also can be beneficial in the

heating season by redistributing warm air that collects

along the ceiling, but they can be noisy. 

Evaporation Coolers

In dry climates, as in the southwestern United States, an

evaporative cooler or “swamp” cooler may provide

sufficient cooling. This system cools an airstream by

evaporating water into it; the airstream’s relative humidity

increases while the dry-bulb temperature decreases. A

95°F (35°C), 15% relative humidity airstream can be

conditioned to 75°F (24°C), 50% relative humidity. The

simplest direct systems are centrally located and use a

pump to supply water to a saturated pad over which the

supply air is blown. Indirect systems use a heat exchanger

between the airstream that is cooled by evaporating water

and the supply airstream. The moisture level of the supply

airstream is not affected as it is cooled.

Evaporation coolers have lower installation and operating

costs than electric air conditioning. No ozone-depleting

refrigerant is involved. They provide high levels of

ventilation because they typically condition and supply

100% outside air.

The disadvantages are that bacterial contamination can

result if not properly maintained and they are only

appropriate for dry, hot climates.

12-16 Heating, Air Conditioning, and Ventilating

Figure 12.20. Split-system Air Conditioner Figure 12.21. External Air-conditioning Condenser Unit 
Safety

Cooling homes with window air conditioners requires

attention to the maintenance requirements of the unit.

The filter must be cleaned or replaced as recommended

by the manufacturer, and the drip pan should be checked

to ensure that proper drainage from the unit is occurring.

The pans should be rinsed and disinfected as

recommended by the manufacturer. Both bacteria and

fungi can establish themselves in these areas and present

serious health hazards.

Condensation forms on the cooling coils of central air

units inside and outside the home. These units should

have a properly installed drip pan and should be drained

according to the manufacturer’s instructions. They also

should receive routine maintenance, flushing, and

disinfection. In the spring, before starting the air

conditioner, the unit should be checked by a professional

or someone familiar with the operation of the system.

This is a good time to check drip line(s) for conditions

such as plugs, cracks, or bacterial contamination because

many of these lines are plastic. The drip pan should be

cleaned thoroughly and disinfected if necessary or

replaced. A plugged drip line can cause water damage by

overflow from the drip pan. In the fall, the heat unit also

should be checked before starting the system. Care should

be taken with both window air conditioning units and

central air systems to use quality air filters that are

designed for the specific units and meet the specifications

required by the system’s manufacturer.

The housing inspector should be on the alert for unvented,

open flame heaters. Coil-type, wall-mounted water

heaters that do not have safety relief valves are not

permitted. Kerosene (portable) units for cooking or

heating should be prohibited. Generally, open-flame

portable units are not allowed under fire safety regulations.

In oil heating units, other than integral tank units, the oil

must be filled and vented outside the building. Filling oil

within buildings is prohibited. Cutoff switches should be

close to the entry but outside of a boiler room. 

Chimneys 

Chimneys (Figure 12.22) are often an integral part of a

building. Masonry chimneys must be tight and sound;

flues should be terra cotta-lined; and, where no linings are

installed, the brick should be tight to permit proper draft

and elimination of combustion gases.

Chimneys that act as flues for gas-fired equipment must

be lined with either B vent or terra cotta. When a portion

of the chimney above the roof either loses insulation or

the insulation peels back, it indicates potential poisonous

gas release or water leakage problems and a need for

rebuilding. Exterior deterioration of the chimney, if

neglected too long, will permit erosion from within the

flues and eventually block the flue opening.

Rusted flashing at the roof level will also contribute to the

chimney’s deterioration. Efflorescence on the inside wall

of the chimney below the roof and on the outside of the

chimney, if exposed, will show salt accumulations—a

telltale sign of water penetration and flue gas escape and a

sign of chimney deterioration. During rainy seasons, if

terra cotta chimneys leak, dark areas show the number of

flues inside the masonry chimney so they can actually be

counted. When this condition occurs, it usually requires

2 or 3 months to dry out. After drying out, the mortar

joints are discolored (brown). After a few years of this

type of deterioration, the joints can be distinguished

whether the chimney is wet or dry. These conditions

usually develop when coal is used and become more

pronounced 2 to 5 years after conversion to oil or gas.

An unlined chimney can be checked for deterioration

below the roofline by looking for residue deposited at the

base of the chimney, usually accessible through a cleanout

(door or plug) or breaching. Red granular or fine powder

showing through coal or oil soot will generally indicate, if

in quantity (a handful), that deterioration is excessive and

repairs are needed.

Unlined chimneys with attached gas units will be devoid

of soot, but will usually show similar telltale brick powder

and deterioration. Manufactured gas has a greater

tendency to dehydrate and decompose brick in chimney

flues than does natural gas. For gas installations in older

Healthy Housing Reference Manual 12-17

Figure 12.22. Chimney Plan [4]
homes, utility companies usually specify chimney

requirements before installlation; therefore, older

chimneys may require the installation of terra cotta liners,

nonlead-lined copper liners, stainless steel liners, or transit

pipe. Black carbon deposits around the top of the

chimney usually indicate an oil burner operation using a

low air ratio and high oil consumption. Prolonged

operation in this burner setting results in long carbon

water deposits down the chimney for 4 to 6 feet or more

and should indicate to the inspector a possibility of poor

burner maintenance. This will accent the need to be more

thorough on the next inspection. This type of condition

can result from other causes, such as improper chimney

height, or exterior obstructions, such as trees or buildings,

that will cause downdrafts or insufficient draft or

contribute to a faulty heating operation. Rust spots and sootmold usually occur on deteriorated galvanized smoke pipe.

Fireplaces

Careful attention should be given to construction of the

fireplace (Figure 12.23). Improperly built fireplaces are a

serious safety and fire hazard. The most common causes of

fireplace fires are thin walls, combustible materials such as

studding or trim against sides and back of the fireplace,

wood mantels, and unsafe hearths.

Fireplace walls should be no less than 8 inches thick; if

built of stone or hollow masonry units, they should be no

less than 12 inches thick. The faces of all walls exposed to

fire should be lined with firebrick or other suitable fireresistant material. When the lining consists of 4 inches of

firebrick, such lining thickness may be included in the

required minimum thickness of the wall.

The fireplace hearth should be constructed of brick,

stone, tile, or similar incombustible material and should

be supported on a fireproof slab or on a brick arch. The

hearth should extend at least 20 inches beyond the

chimney breast and no less than 12 inches beyond each side

of the fireplace opening along the chimney breast. The

combined thickness of the hearth and its supporting

construction should be no less than 6 inches at any point. 

It is important that all wooden beams, joists, and studs

are set off from the fireplace and chimney so that there is

no less than 2 inches of clearance between the wood

members and the sidewalls of the fireplace or chimney

and no less than 4 inches of clearance between wood

members and the back wall of the fireplace.

A gas-log set is primarily a decorative appliance. It

includes a grate holding ceramic logs, simulated embers, a

gas burner, and a variable flame controller. These sets can

be installed in most existing fireplaces. There are two

principal types: vented and unvented. Vented types

require a chimney flue for exhausting the gases. They are

only 20% to 30% efficient; and most codes require that

the flue be welded open, which results in an easy exit path

for heated room air. Unvented types operate like the

burner on a gas stove and the combustion products are

emitted into the room. They are more efficient because

no heat is lost up the flue and most are equipped with

oxygen-depletion sensors. However, unvented types are

banned in some states, including Massachusetts and

California. Gas fireplaces incorporate a gas-log set into a

complete firebox unit with a glass door. Some have builtin dampers, smoke shelves, and heat-circulating features

that allow them to provide both radiant and convective

heat. Units can have push-button ignition, remote

control, variable heat controls, and thermostats. Gas

fireplaces are more efficient than gas logs, with efficiencies

of 60% to 80%. Many draw combustion air in from the

outside and are direct vented, eliminating the need for a

chimney. Some of these units are wall-furnace rated.

There are also electric fireplaces that provide the

ambience of a fire and, if desired, a small amount of

resistance heat. These units have no venting requirements.

The advantages are that there are no ashes or flying sparks

that occur with wood-burning fireplaces. They are not

12-18 Heating, Air Conditioning, and Ventilating

Figure 12.23. Fireplace Construction [4]
affected by wood-burning bans imposed in some areas

when air quality standards are not met. Direct-vented gas

or electric models eliminate the need for a chimney.

The disadvantages are that the cost for equipment and

running the gas line can be high. 

References

1. US Census Bureau. Rooms, number of bedrooms,

and house heating fuel: 2000. Census 2000

Summary File 4 (SF4). Washington, DC: US

Census Bureau; 2000. Available from URL:

http://factfinder.census.gov [select Data Sets, then

select Census 2000 Summary File 4 (SF 4) -

Sample Data].

2. National Energy Efficiency Committee. Building:

heat pumps; application of heat pumps in

Singapore. Singapore: National Environment

Agency; 2003. Available from URL:

http://www.neec.gov.sg/building/

heat_pump.shtm.

3. National Energy Efficiency Committee.

Renewables: solar energy. Singapore: National

Environment Agency; no date. Available from

URL: http://www.neec.gov.sg/

renewables/solar.shtm.

4. Center for Disease Control. Basic housing

inspection. Atlanta: US Department of Health

and Human Services; 1976. 

5. Fairfax County. Fuel storage tanks. Fairfax, VA:

Fairfax County; 2004. Available from URL:

http://www.co.fairfax.va.us/dpwes/construction/

fuel_tanks.htm.

6. Wisconsin Department of Commerce.

Environmental services—residential fuel oil and

gasoline storage tanks. Madison, WI: Wisconsin

Department of Commerce; 2004. Available from

URL: http://www.commerce.state.wi.us/ER/ERBST-ResTk.html.

7. Michigan Department of Environmental Quality.

FAQ: Home heating oil tanks, Lansing, MI:

Michigan Department of Environmental Quality;

no date. Available from URL:

http://www.michigan.gov/deq/

0,1607,7-135-3311_4115_4238-9379--,00.html.

8. US Environmental Protection Agency. Overview

of the federal underground storage tank program.

Washington, DC: U.S. Environmental Protection

Agency; no date. Available from URL:

http://www.epa.gov/swerust1/overview.htm.

9. US Department of Housing and Urban

Development. Initiatives Programs. Washington,

DC: US Department of Housing and Urban

Development; 2004. Available from URL:

http://www.hud.gov/offices/cpd/energyenviron/

energy/initiatives.

10. US Environmental Protection Agency. Sources of

indoor air pollution—asbestos. Washington, DC:

U.S. Environmental Protection Agency; no date.

Available from URL: http://www.epa.gov/

iaq/asbestos.html.

11. The Commonwealth of Massachusetts Board of

Building Regulations and Standards (BBRS).

Hydronic system requirements. Boston: The

Commonwealth of Massachusetts Board of

Building Regulations and Standards (BBRS); no

date. Available from URL: http://www.mass.gov/

bbrs/commntry/cmpxhydr.htm.

Additional Sources of Information

McQuiston FC, Parker JD, Spitler JD. Heating,

ventilation, and air conditioning: analysis and design. 5th

ed. Hoboken, NJ: John Wiley and Sons, Inc.; 2000.

Kittle JL. Home heating and air conditioning systems.

New York: McGraw-Hill; 1990.

Pita EG. Air conditioning principles and systems: an

energy approach. 4th ed. New York: Prentice Hall; 2001. 

Healthy Housing Reference Manual 12-19
12-20 Heating, Air Conditioning, and Ventilating
Chapter 13—Energy Efficiency

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

Energy Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

R-values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-2

Ridge Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Fan-powered Attic Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

White Roof Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Wall Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Floor Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Hot Water Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Caulking and Weather-stripping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Replacing Window Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Tinted Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Reducing Heat Loss and Condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Layering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Other Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Active Solar Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Passive Solar Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-10

Conducting an Energy Audit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-11

Figure 13.1. Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Figure 13.2. Potential Effects of Radiant Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Figure 13.3. Common Floor Insulation Flaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Figure 13.4. Insulation Cavity Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-6

Figure 13.5. Solar Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Table 13.1. Cost-effective Insulation R-values for Existing Homes . . . . . . . . . . . . . . . . . . . . . .13-2

Table 13.2. R-values of Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Table 13.3. Floor Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Healthy Housing Reference Manual 1

Contents
“Engineering is the science of economy, of conserving the

energy, kinetic and potential, provided and stored up by

nature for the use of man. It is the business of engineering to

utilize this energy to the best advantage, so that there may

be the least possible waste.”

William A. Smith

1908

Introduction

Using energy efficiently can reduce the cost of heating,

ventilating, and air-conditioning, which account for a

significant part of the overall cost of housing. Energy

costs recur month-to-month and are hard to reduce after

a home has been designed and built. The development of

an energy-efficient home or building must be thought

through using a systems approach. Planning for energy

efficiency involves considering where the air is coming

from, how it is treated, and where it is desired in the

home. Improper use or installation of sealing and

insulating materials may lead to moisture saturation or

retention, encouraging the growth of mold, bacteria, and

viruses. In addition, toxic chemicals may be created or

contained within the living environment. These building

errors may result in major health hazards. The major

issues that must be balanced in using a systems approach

to energy efficiency are energy cost and availability, longterm affordability and sustainability, comfort and

efficiency, and health and safety. 

Energy Systems

Making sound decisions in designing, constructing, or

updating dwellings will ensure not only greater use and

enjoyment of the space, but also can significantly lower

energy bills and help residents avoid adverse health

effects. Systematic planning for energy efficiency also can

assist prospective homeowners in qualifying for

mortgages because lower fuel bills translate into lower

total housing and utility payments. Some banks and

credit unions take this into account when qualifying

prospective homeowners for mortgages. “Energyefficient” mortgages provide buyers with special benefits

when purchasing an energy-efficient home.

Energy use and efficiency should be addressed in the

context of selection of fuel types and appliances, location

of the equipment, equipment sizing and backup systems,

and programmed use when making decisions on space

heating, water heating, space cooling, window glazing,

and lighting. Usage variables, such as taking excessively

long showers, turning off lights when leaving rooms, or

using appliances at full or near-full capacity, may increase

or decrease energy use, depending on occupancy. Many

of these demands can be optimized in the design stage of

housing for new construction. However, when

remodeling dwellings, making modifications to improve

energy efficiency is often difficult. Preconstruction

consultations with architects and energy specialists can

produce tradeoffs that retain the aesthetics and special

aspects of a dwelling, while making appropriate

investments in energy efficiency. 

A price is paid for poor design and lack of proper

insulation of dwellings, both in dollars for utility bills

and in comfort of the occupants. The layout of rooms

and overall tightness of a house in terms of air exchange

affect energy requirements. In addition, home occupants

and owners often are called on to make relatively minor

decisions affecting total energy consumption, such as

selecting lighting fixtures and bulbs and selecting settings

for thermostats. Buying energy-efficient appliances can

save energy, but the largest reduction in energy use can

be derived from major decisions, such as considering the

R-value of roof systems, insulation, and windows.

R-values

Thermal resistance (a material’s resistance to heat flow) is

rated by R-value. Higher R values mean greater

insulating power, which means greater household energy

savings and commensurate cost savings. Table 13.1 is a

guideline for choosing R-values that are right for a

particular home based on the climate, household heating

system, and area in which it is located.

Another way of understanding R-value is to see it as the

resistance to heat losses from a warmer inside

temperature to the outside temperature through a

material or building envelope (wall, ceiling or roof

assembly, or window). Total heat loss is a function of the

thermal conductivity of materials, area, time, and

construction in a house.

The R-value of thermal insulation depends on the type

of material, its thickness, and its density. In calculating

the R-value of a multilayered installation, the R-values of

the individual layers are added. Installing more insulation

increases R-value and the resistance to heat flow. 

The effectiveness of an insulated wall or ceiling also

Chapter 13: Energy Efficiency

Healthy Housing Reference Manual 13-1
depends on how and where the insulation is installed. For

example, insulation that is compressed will not provide its

full rated R-value. Also, the overall R-value of a wall or

ceiling will be somewhat different from the R-value of the

insulation itself because some heat flows around the

insulation through the studs and joists. That is, the

overall R-value of a wall with insulation between wood

studs is less than the R-value of the insulation itself

because the wood provides a thermal short-circuit around

the insulation. The short-circuiting through metal

framing is much greater than that through wood-framed

walls; sometimes the metal wall’s overall R-value can be as

low as half the insulation’s R-value. With careful design,

this short-circuiting can be reduced.

Roofs

Roofs are composite structures, with composite R-values.

The total R-value for the roof components shown in

Figure 13.1 is 14.54 (Table 13.2). In general, a composite

structure with a composite R-value of more than R-38

provides a substantial barrier to heat loss. Of course, in

the winter the outside air temperature would vary

significantly between locations such as Pensacola, Florida,

and Fairbanks, Alaska, and would affect the cost13-2 Energy Efficiency

Table 13.1. Cost-effective Insulation R-values for Existing Homes [a;1]
effectiveness of additional insulation and construction

using various roofing components (Table 13.2).

The location of a house is usually a fixed variable in

calculating R-values once the lot is purchased. However,

the homeowner should consider the value of additional

insulation by comparing its cost with the savings resulting

from the increase in energy efficiency. Roof construction,

including components such as ridge vents and insulating

materials, is quite important and is often one of the more

cost-effective ways to lower energy costs. 

Ridge Vents

Ridge vents are important to roofs for at least three

reasons. First, ridge vents help lower the temperature in

the roof structure and, consequently, in the attic and in

the habitable space below. Second, ridge vents and

rotating turbine vents help prolong the life of the roofing

materials, particularly asphalt shingles and plywood

sheathing. Third, ridge vents assist in air circulation and

help avoid problems with excessive moisture. 

Fan-powered Attic Ventilation

Attic ventilators are small fans that remove hot air and

reduce attic temperature. Adequate inlet vents are

important. Typically these vents are located under the

eaves of the house. The fan should be located near the

peak of the roof for best performance.

White Roof Surface

White roof surfaces combined with any of the measures

listed above will improve their performance significantly.

The white surface reflects much of the sun’s heat and

keeps the roof much cooler than a typical roof.

Insulation

Insulation forms a barrier to the outside elements. It can

help ensure that occupants are comfortable and that the

home is energy-efficient. Ceiling insulation improves

comfort and cuts electricity or natural gas costs for

heating and cooling. For instance, the use of R-19

insulation in houses in Hawaii [3] could have the

following results: 

• Reduce indoor air temperature by 4°F (-16°C) in

the afternoon. 

• Lower the ceiling temperature, perhaps by more

than 15°F (-9.4°C). Insulation [radiant barrier]

can reduce ceiling temperatures from 101°F

(38°C) in bright sun on Oahu to 83°F (28°C).

(Figure 13.2).

• Reduce or eliminate the need for an airconditioner. 

Energy savings, of course, will vary depending on energy

prices. The payback afforded by additional insulation or

investment in energy conservation measures is the average

amount of time it will require for the initial capital cost

to be recovered as a result of the savings in energy bills. A

payback of 3 to 5 years might be economic, because the

average homeowner stays in a home that long. However,

payback criteria can vary by individual, and renters, for

example, often face the dilemma of not wanting to make

improvements for which they may not be able to fully

realize the benefits. Described below are a few insulation

alternatives.

To achieve maximum effect, the method of installation

and type of insulation are of considerable importance.

The proper placement of moisture barriers is essential. If

insulation becomes moisture-saturated, its resistance to

energy loss is significantly reduced. Barriers to moisture

should be installed toward the living area because

significant moisture is generated in the home through

respiration, cooking, and the combustion of heating fuels.

Cellulose or fiberglass insulation is the most cost-effective

insulation. Blown-in cellulose or fiberglass and fiberglass

batts are similar in cost and performance. Recycled cellulose

Healthy Housing Reference Manual 13-3

Figure 13.1. Roof Components [2]

Table 13.2. Potential Effects of Radiant Barriers [3]
insulation may be available. For the best performance,

insulation should be 5 to 6 inches thick. It can be installed

in attics of new and existing homes. It is typically the best

choice for framed ceilings in new homes, but can be costly

to install in existing framed ceilings. It is very important

that this type of insulation be treated for fire resistance.

Foamboard (R-10, 1.5 to 2 inches) provides more insulation

per inch than does cellulose or fiberglass, but is also more

expensive. It is best where other insulation cannot be

used, such as open-beam ceilings. It is applicable for new

construction or when roofing is replaced on an existing

home. Two common materials are polystyrene and

polyisocyanurate. Polystyrene is better in moist conditions,

and polyisocyanurate has a higher R-value per inch

(millimeter). However, some of these insulations present

serious fire spread hazards. They should be evaluated to

ensure that they are covered with fire-retardant materials

and meet local fire and building codes.

Radiant barrier insulation is a reflective foil sheet

installed under the roof deck like regular roof sheathing.

The effectiveness of a radiant barrier (Figure 13.2)

depends on its emissivity (the relative power of the surface

to emit heat by radiation). In general, the shinier the foil

the better. Radiant barrier insulation cuts the amount of

heat radiated from the hot roof to the ceiling below. It

may be draped over the rafters before the roof is installed

or stapled to the underside of the rafters. The shiny side

should face downward for best performance. Some

manufacturers claim that the radiant barrier prevents up to

97% of the sun’s heat from entering the attic.

Wall Insulation

As shown in Table 13.1, it makes sense to insulate to high

R-values in the ceiling. Insulation in walls should range

from R-11 in relatively mild climate zones to R-38 in

New England, the northern Midwest, the Great Lakes,

and the Rocky Mountain states of Colorado and Wyoming.

Insulation requirements vary within climate zones in these

states and areas as well (for instance, mountainous areas

and areas farther north may have more heating-degree

days). The same logic of installing insulation applies to

both ceilings and walls: the insulation should provide a

barrier for heat and moisture transfer and buildup from

inside the dwelling, where temperatures will generally be

in the 68°F to 72°F (20°C to 22°C) range, compared

with the much colder or hotter temperatures outside. The

key to heat loss is the difference in temperatures and the

time that the heat transfer takes place over a given area or

surface. The choice of heating system, from gas/oil or heat

pump, to electric resistance, will also affect the payback of

additional wall insulation due to variation in energy fuel

prices. For regions identified as “cold,” careful attention

should be made in selecting energy fuel type; in

particular, a heat pump may not be a practical option.

A homeowner exploring designs and construction methods

should examine the value of using structural insulated

panels. The incorporation of high levels of insulation

directly from the factory on building wall and ceiling

components makes them outstanding barriers to heat and

moisture. These integrated systems, if appropriately used,

can save substantial amounts of energy when compared

with traditional stick-built systems using 2×4 or 2×6

lumber. Also, building energy-efficient features (as well as

electrical, plumbing, and other elements) directly into the

building envelope at the factory can result in labor cost

savings over the more traditional methods of construction.

Floor Insulation

Warm air expands and rises above surrounding cooler air.

This process of heat transfer is called convection. Warm

air, which is lighter, rises and, as it cools, falls, creating a

convection current of air. The two other processes of heat

transfer are conduction (kinetic energy transferred from

particle to particle, such as in a water- or electrically

heated floor) and radiation (radiant energy emitted in the

form of waves or particles such as in a fireplace or hot

glowing heating element). Floor insulation limits all three

modes of heat loss. A warmer floor reduces the temperature

difference that drives convection. Floor insulation also

directly impedes conduction and radiation to the colder

air below the floor.

Batt Insulation 

The advantage of floor insulation lies in adding extra

R-value without a significant increase in cost. It is cheaper to

13-4 Energy Efficiency

Figure 13.2. Potential Effects of Radiant Barriers [3]
put more insulation under the floor than to add foam

sheathing or change the type of wall construction to

accommodate greater insulation levels. 

Like walls, floor cavities should be completely filled with

insulation-without gaps, missing insulation, or cavity

voids. Floor insulation must contact the subfloor and

both joists. In many cases, it is worth the extra cost to

buy enough insulation to fill the entire cavity.

The amount of floor insulation required by some codes

can be less than the space available. For example, an R-19

fiberglass batt is 61⁄4 inches thick. A floor framed with

2×8s is about 71⁄2 inches deep, while a 2×10 floor is

91⁄2 inches deep. A builder following a code’s minimum

insulation level will leave extra space that will allow for

greater heat loss. To avoid this situation, the batt must be

pushed up into the cavity. With the proper support, this

can be done. Springy metal rods are commonly used to

hold insulation up in the top of the floor cavity. Another

viable option is the use of plastic straps. Figure 13.3

shows batt insulation improperly applied to the floor

above a crawl space or a basement.

The thickness of typical fiberglass batts can assist the

designer and the builder in creating a floor system that

works for the occupants. Table 13.3 shows a list of R-values,

along with the associated batt thickness. Individual

brands can vary by as much as 1 inch. 

Cavity Fill 

According to Oikos, a commercial Web site devoted to

serving professionals whose work promotes sustainable

design and construction, “Buying a thicker batt may be a

better option than trying to lift a thinner batt into the

proper position. Material costs will climb slightly but labor

should be the same. Attaching the insulation support to the

bottom of the floor joist will be easier. It could also lead to a

higher quality job because there is less chance for

compression or gaps” (Figure 13.4) [4]. 

In some areas, it’s common to hang plastic mesh over

floor joists. Installers drop the insulation onto the mesh

before the subfloor is

installed. However,

hanging the mesh

creates sagging bellies.

Insulation compresses

near the framing and

sags in the middle. Mesh

should be attached to the

bottom of the floor

framing [4]. 

Each stage of increased

floor insulation, from

R-19 to R-30 or R-30 to

R-38, can save energy over

the life of the house. This energy translates into energy

savings that are multiples of the initial installation costs.

Floor insulation will generate the greatest savings in

colder climates; in moderate climates, the target

insulation level should depend on economics.

Blow-In Insulation

A blown-in insulation system allows the builder or

insulator to fill the entire cavity completely, even around

pipes, wires and other appurtenances. Using well-trained

installers will pay dividends in quality workmanship.

Doors

Today there is an endless variety of doors, ranging from

metal doors with or without insulation to hollow core to

solid wood. When properly installed into fitted frames,

doors serve as a heat barrier to maintain indoor temperatures.

Quality metal doors with insulation are best if they have a

thermal break between the interior and exterior metal

surfaces; this keeps heat from being transferred from one

side to the other. 

Standard Doors

Because doors take up a small percentage of a wall,

insulating them is not as high a priority as is insulating

walls and ceilings. That said, heat loss follows the path of

least resistance; therefore, doors should be selected that

Healthy Housing Reference Manual 13-5

Figure 13.3. Common Floor Insulation Flaws [4.] Two common flaws in floor

insulation are gaps above the batt and compression of the batt in the cavity.

Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc.,

publisher of Oikos.com.

Table 13.3. Floor Insulation [5]
are functional and add to the energy-efficiency of the

house. Doors usually have lower R-values than the

surrounding wall.

Storm doors can add R-1 to R-2 to the existing door’s Rvalue. They are a valuable addition to doors that are

frequently used and those that are exposed to cold winds,

snow, and other weather. Screens allow natural breezes to

circulate air from outside, rather than totally relying on

air-conditioning, which can be energy intensive.

When considering replacement doors, select insulated,

metal foam-core doors. Besides insulation, metal doors

provide good security, seal more tightly, tend to warp less.

Metal doors also are more soundproof than conventional

wood doors. 

Sliding Glass Doors

Although sliding glass doors have aesthetic appeal, they

have very low R-values and hence are minimally energy

efficient. To improve the energy efficiency of existing

sliding glass doors, the homeowner should ensure that

they seal tightly and are properly weather-stripped.

Additionally, heavy insulated drapes with weights, which

impede the airflow, can cut down on heat loss through

sliding glass doors.

13-6 Energy Efficiency

Figure 13.4a. Insulation Cavity Fill [4]. 

Lath provides a sturdy support for insulation.

Figure 13.4b. Insulation Cavity Fill [4]. 

Metal rods are available through insulation distributors. They are easy to use,

but insulation has to be compressed in the middle.

Figure 13.4c. Insulation Cavity Fill [4]. 

Mesh should be attached to the bottom of the framing. Draping the mesh over

the joists leads to compression that reduces insulating value.

Figure 13.4d. Insulation Cavity Fill [4]. 

Polypropylene twine resists rot, mildew, rodents, and other dangers. It is to be

stapled every 12 to 18 inches.

Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc., publisher of Oikos.com.
Door Installation

Doors must be installed as recommended by the

manufacturer. Care must be taken to be sure that doors

are installed in a manner that does not trap moisture or

allow unintended introduction of air. Numerous types of

sealing materials are available that range from foam to

plastic, to metal flanging and magnetic strips.

Hot Water Systems

The hot water tank can be insulated to make it more

efficient, unless the heat loss is used within the space

where it is located. Special insulation is available for this

type of appliance, and insulating it will reduce the energy

required to deliver the hot water needed by the occupants

of the dwelling. Of course, any pipe that is subject to

extreme temperatures also should be insulated to decrease

heat loss.

Windows

Windows by nature are transparent. They allow occupants

of a dwelling to see outside and bring in sunlight and

heat from the sun. They make space more pleasant and

often provide lighting for tasks undertaken in the space.

Especially in the winter, these desirable characteristics

offset the heat loss. Heat gain in the summer through

windows can be undesirable.

Rather than give them up, it is important to use windows

prudently and to keep energy considerations in mind in

their design and their insulating characteristics (air, glass,

plastic, or gas filler). Good design takes advantage of day

lighting. Weather-stripping and sealing leaks around

windows can enhance comfort and energy savings. Energy

Star windows are highly recommended. Housekeeping

measures can improve the efficiency of retaining heat.

Heat loss follows the path of least resistance: caulking,

weather-stripped framing, and films can help. These

measures are relatively labor intensive, low to very low in

cost, and can be quite satisfying to the homeowner if

accomplished correctly. On the other hand, it is not easy

finding the perfect materials or even replacement parts for

old windows.

When working with older windows, remember that there

is the risk for leaded paint and the dispersion of toxic lead

dust into the work area. Please refer to the lead section of

Chapter 5, Indoor Air Pollutants and Toxic Materials.

Caulking and Weather-Stripping 

According to the U.S. Department of Energy, caulking

and weather-stripping have substantial housekeeping 

benefits in preventing energy loss or unwanted heat gain.

Caulking

Caulks are airtight compounds (usually latex or silicone)

that fill cracks and holes. Before applying new caulk, old

caulk or paint residue remaining around a window should

be removed using a putty knife, stiff brush, or special

solvent. After old caulk is removed, new caulk can then

be applied to all joints in the window frame and the joint

between the frame and the wall. The best time to apply

caulk is during dry weather when the outdoor

temperature is above 45°F (7.2°C). Low humidity is

important during application to prevent cracks from

swelling with moisture. Warm temperatures are also

necessary so the caulk will set properly and adhere to the

surface [5].

Weather-stripping

Weather-stripped frames are narrow pieces of metal, vinyl,

rubber, felt, or foam that seal the contact area between

the fixed and movable sections of a window joint. They

should be applied between the sash and the frame, but

should not interfere with the operation of the window [6].

Replacing Window Frames 

The heat-loss characteristics and the air tightness of a window

vary with the type and quality of the window frame. The

types of available window frames are fixed-pane,

casement, double- and single-hung, horizontal sliding,

hopper, and awning. Each type varies in energy efficiency. 

Correctly installed fixed-pane windows are the most

airtight and inexpensive choice, but are not suited to

places that require ventilation. The air infiltration

properties of casement windows (which open sideways

with hand cranks), awning windows (which are similar to

casement windows but have hinges at the top), and

hopper windows (inverted awning windows with hinges

at the bottom) are moderate. Double-hung windows,

which have top and bottom sashes (the part of the

window that can slide), tend to be leaky. The advantage

of the single-hung window over the double-hung is that it

tends to restrict air leakage because there is only one

moving part. Horizontal sliding windows, though suitable

for small, narrow spaces, provide minimal ventilation and

are the least airtight. 

In buildings with large older windows, there are often

weight cavity areas that hide counter balances that make

it easy to raise and lower heavy windows. These areas

should be insulated to reduce energy loss.

Healthy Housing Reference Manual 13-7
Tinted Windows

Another way to conserve energy is the installation of

tinted windows. Window tinting can be installed that will

both conserve energy and also prevent damaging ultraviolet

light from entering the room and potentially fading wood

surfaces, fabrics, and carpeting. Low-emissivity coatings,

called low-e coatings, are also available. These coatings are

designed for specific geographic regions. 

Reducing Heat Loss and Condensation 

The energy efficiency of windows is measured in terms of

their U-values (measure of the conductance of heat) or

their R-values. Besides a few highly energy-efficient

exceptions, window R-values range from 0.9 to 3.0.

When comparing different windows, it is advisable to

focus on the following guidance for R- and U-values:

• R- and U-values are based on standards set by the

American Society of Heating, Refrigerating, and

Air-Conditioning Engineers [7].

• R- and U-values are calculated for the entire

window, which includes the frame.

• R- and U-values represent the same style and size

of windows.

The R-value of a window in an actual house is affected by

the type of glazing material, the number of layers of glass,

the amount of space between layers and the nature of the

gas filling them, the heat-conducting properties of the frame

and spacer materials, and the airtightness associated with

manufacturing. 

For windows, rating and approval by the National Fenestration

Rating Council or equivalent rating and approval is

strongly recommended [8].

Please refer to the window section of Chapter 6, Housing

Structure. 

Glazing

Glazing refers to cutting and fitting windowpanes into

frames. Glass has been traditionally the material of choice

for windowpanes, but that is changing. Several new

materials are available that can increase the energy

efficiency of windows. These include the following:

• Low-emissivity (low-e) glass uses a surface coating

to minimize transmission of heat through the

window by reflecting 40% to 70% of incident

heat while letting full light pass through the pane.

• Heat-absorbing glass is specially tinted to absorb

approximately 45% of the incoming solar energy;

some of this energy passes through the pane.

• Reflective glass has a reflective film that reduces heat

gain by reflecting most of the incident solar radiation.

• Plastic glazing materials such as acrylic,

polycarbonate, polyester, polyvinyl fluoride, and

polyethylene are stronger, lighter, cheaper, and

easier to cut than glass. However, they are less

durable and tend to be affected by the weather

more than glass is. 

• Storm windows can improve the energy efficiency

of single-pane windows. The simplest example of

storm windows would be plastic film, available in

prepackaged kits, taped to the inside of the

window frame. Because this can affect visibility

and be easily damaged, a better choice would be

to attach rigid or semirigid plastic sheets such as

plexiglass, acrylic, polycarbonate, or fiberreinforced polyester directly to the window frame

or mounting it in channels around the frame on

the outside of the building. Care should be taken

in installation to avoid ripples or blemishes that

will affect visibility.

Layering

The insulating capacity of single-pane windows is minimal,

around R-1. Multiple layers of glass can be used to increase

the energy efficiency of windows. Double- or triple-pane

windows have air-filled or gas-filled spaces, coupled with

multiple panes that resist heat flow. The space between

the panes is critical because the air spaces that are too

wide (more than 5/8 inch) or too narrow (less than 1⁄2 inch)

allow excessive heat transfer. Modern windows use inert

gases, such as argon and krypton, to fill the spaces

between panes because these gases are much more

resistant to heat flow than air is. These gas-filled windows

are more expensive than regular double-pane windows. 

• Frame and spacer materials may be aluminum,

wood, vinyl, fiberglass, or a combination of these

materials, such as vinyl- or aluminum-clad wood. 

• Aluminum frames are strong and are ideal for

customized window design, but they conduct heat

and are prone to condensation. The deterioration

of these frames can be avoided by anodizing or

coating. Their thermal resistance can be boosted 

13-8 Energy Efficiency
using continuous strips of plastic between the

interior and exterior of the frame. 

• Wood frames are superior to aluminum frames in

having higher R-values, tolerance to temperature

extremes, and resistance to condensation. On the

other hand, wood frames require considerable

maintenance in the form of painting or staining.

Improper maintenance can lead to rot or warping.

• Vinyl window frames made from polyvinyl

chloride are available in a wide range of styles and

shapes, can be easily customized, have moderate

R-values, and can be competitively priced. Large

windows made of vinyl frames are reinforced

using aluminum or steel bars. Vinyl windows

should be selected only after consideration of the

concerns surrounding the use of vinyl materials

and their off-gassing characteristics.

• Fiberglass frames have the highest R-values and

are not given to warping, shrinking, swelling,

rotting, or corroding. Fiberglass is not weatherresistant, so it should also be painted. Some

fiberglass frames are hollow; others are filled with

fiberglass insulation.

• Spacers separating multiple windowpanes in a

window use aluminum to separate glass in

multipane windows, but it conducts heat. In

addition, in cold weather, the thermal resistance

around the edge of such a window is lower than

that in the center, allowing heat to escape and

condensation to occur along the edges. 

• Polyvinyl chloride foam separators placed along

the edges of the frame reduce heat loss and

condensation. Window manufacturers use foam

separators, nylon spacers, and insulation materials

such as polystyrene and rock wool insulation

between the glass panes inside windows.

Other Options

Shades, shutters, and drapes used on windows inside the

house reduce heat loss in the winter and heat gain in the

summer. The heat gain during summer can also be minimized

by the use of awnings, exterior shutters, or screens. These

cost-effective window treatments should be considered before

deciding on window replacement. By considering orientation,

day lighting, storage of or reflection of energy from

sunshine, and materials used within the house and on the

building envelope, heat loss and gain can be decreased.

Solar Energy

Solar energy is a form of renewable energy available to

homeowners for heating, cooling, and lighting. The more

energy-efficient new structures are designed to store solar

energy. Remodeled structures may be retrofitted to increase

energy efficiency by improving insulation characteristics,

improving airflow and airtightness of the structure, and

enhancing the ability to use solar energy. Solar energy

systems are active and passive. Whereas active solar systems use

some type of mechanical power to collect, store, and

distribute the sun’s energy, passive systems use the

materials and design elements in the structure itself. 

Active Solar Systems

Active solar systems use devices to collect, convert, and

deliver solar energy. Solar collectors on roofs or other

south-facing surfaces can be used to heat water and air

and generate electricity. Active solar systems can be

installed in new or existing buildings and periodically

need to be inspected and maintained. Active solar energy

equipment consists of collectors, a storage tank, piping or

ductwork, fans, motors, and other hardware. Flat panel

collectors (Figure 13.5) can be placed on the roof or on

walls. Typically, the collector will be a sandwich of one or

two sheets of glass or plastic and another air space above a

metal absorber plate, which is painted black to enhance

heat absorption. After collection, when the sun’s energy is

converted to heat, a transfer is made to a liquid storage

tank. The heated liquid travels through coils in the hot

water tank, and the heat is transferred to the water and

perhaps the heating system. Most hot water systems use a

liquid collector system because it is more efficient and less

costly than an air-type system.

In the southwest United States, solar roof ponds have

become popular for solar cooling. Evaporative cooling

systems depend on water vaporization to lower the

temperature of the air. These have been shown to be more

effective in dry climates than in areas with extremely high

relative humidity.

In certain climates, like those in the Hawaiian Islands,

using solar energy is cost-effective for providing hot water.

Figure 13.5. Solar Panels

Healthy Housing Reference Manual 13-9
Some builders even include it as a standard feature in

their homes. The total cost to the homeowner of solar

energy systems consists of the capital, operational, and

maintenance costs. The real cost of capital may be

lowered by the availability of tax credits offered at the

federal (to lower federal income taxes) and state levels. 

Homeowners and builders can benefit from tax credits

because they lower the total upfront investment cost of

installing active solar systems. This is the major portion of

the total cost of using solar energy, because operation and

maintenance costs are small in comparison to initial

system costs.

Passive Solar Systems

Buildings designed to use passive solar energy have

features incorporated into their design that absorb and

slowly release the sun’s heat. In cold climates, the design

allows the light and heat of the sun to be stored in the

structure, while insulating against the cold. In warm

climates, the best effect is achieved by admitting light

while rejecting heat. A building using passive solar

systems may have the following features in the floor plan:

• Large south-facing windows

• Small windows in other directions, particularly on

the north side of the structure

• Designs that allow daylight and solar heat to

permeate the main living areas

• Special glass to block ultraviolet radiation

• Building materials that absorb and slowly

reradiate the solar heat

• Structural features such as overhangs, baffles, and

summer shading to eliminate summer

overheating.

Passive design can be a direct-gain system when the sun

shines directly into the building, thereby heating it and

storing this heat in the building materials (concrete, stone

floor slabs, and masonry partitions). Alternatively, it may

be an indirect gain system where the thermal mass is

located between the sun and the living space. Isolated

gain is yet another type of system that is separated from

the main living area (such as a sunroom or a solar

greenhouse), with convective loops for space conditioning

into the living space.

Energy Star is a program supported and promoted by the

U.S. Environmental Protection Agency (EPA) that helps

individuals protect the environment through superior

energy efficiency. For the individual in his or her home,

energy-efficient choices can save families about one third

on their energy bill, with similar savings of greenhouse

gas emissions, without sacrificing features, style, or

comfort. When replacing household products, look for

ones that have earned the Energy Star; these products

meet strict energy-efficiency guidelines set by EPA and

the U.S. Department of Energy. When looking for a new

home, look for one that has earned the Energy Star

approval. If you are planning to make larger

improvements to your home, EPA offers tools and

resources to help you plan and undertake projects to

reduce your energy bills and improve home comfort [9].

In 2004 alone, Americans, with the help of Energy Star,

saved enough energy to power 24 million homes and

avoid greenhouse gas emissions equivalent to those from

20 million cars-all while saving $10 billion.

Conducting an Energy Audit

Energy audits can help identify areas where energy

investments can be made, thereby reducing energy used in

lighting, heating, cooling, or meeting other demands of

housing occupants. An inspection can evaluate the

worthiness or compliance with codes of energy-saving

measures, including accepted or written standards. For

example, if a new addition requires the equivalent of R-19

insulation in the ceilings, this can be validated in the

inspection process. Whereas an audit is generally

informational, an inspection should validate that

materials and workmanship have yielded a structure that

protects the occupants from the elements, such as rain,

snow, wind, cold, and heat. Potentially hazardous

situations within a structure should be evaluated in an

inspection. The overall goal of a housing inspection in the

case of energy efficiency is to identify potential hazardous

conditions and help to create conditions under which the

health and welfare of the occupants can be enhanced,

rather than put at risk.

The housing inspector should be aware that there is

variation (sometimes quite significant differences) in

heating degree days or cooling loads and in relative

humidity conditions within given regions. Local and

regional topography, as well as site conditions, can affect

temperatures and moisture.

Numerous Web sites listed in this chapter’s Additional

Sources of Information section discuss the procedures for

conducting energy audits. Local and regional utilities

13-10 Energy Efficiency
often offer audit services and assist with selecting costeffective conservation measures for given areas of the

United States.

References

1. Lawrence Berkeley National Laboratory. Energy

star insulation project: R-value guidelines.

Berkeley, CA: Lawrence Berkeley National

Laboratory; 2004. Available from URL:

http://enduse.lbl.gov/Projects/Rvalue.html.

2. RoofHelp.com. R-value. Fort Worth, TX:

RoofHelp; 1999. Available from URL:

http://www.roofhelp.com/Rvalue.htm.

3. State of Hawaii, Department of Business,

Economic Development, and Tourism, Energy

Resources and Technology Division. Ceiling

insulation. Honolulu, HI: State of Hawaii,

Department of Business, Economic Development,

and Tourism; no date. Available from

URL:http://www.hawaii.gov/dbedt/

ert/rf_insul.html. 

4. Oikos. Filling a floor with batt insulation. Energy

Source Builder 1995 [Apr]; 38. Available from

URL: http://oikos.com/esb/38/

floorinsulation.html.

5. US Department of Energy. Energy savers: fact

sheets. Washington, DC: US Department of

Energy; no date. Available from URL:

http://www.eere.energy.gov/consumerinfo/

factsheets.html.

6. US Department of Energy. Advances in glazing

materials for windows. Washington, DC: US

Department of Energy; 1994. 

7. American Society of Heating, Refrigerating and

Air-Conditioning Engineers (ASHRAE).

Standards; no date. Atlanta: American Society of

Heating, Refrigerating and Air-Conditioning

Engineers. Available from URL:

http://www.ashrae.org.

8. National Fenestration Rating Council. Search for

energy performance ratings. Silver Spring, MD:

National Fenestration Rating Council; no date.

Available from URL: http://www.nfrc.org/

windowshop/surveybegin.aspx.

9. US Environmental Protection Agency. What is

Energy Star? Washington, DC: US Environmental

Protection Agency; no date. Available from URL:

http://www.energystar.gov/

index.cfm?c=about.ab_index.

Additional Sources of Information

Alliance to Save Energy. Save energy at home. Available

from URL: http://www.ase.org/section/

_audience/educators/edsavhome/.

Christian J, Kosnay J. Home Calculating whole wall Rvalues on the Net. Energy Magazine Online,

November/December 1999. 

Energy Information Administration. Available from URL:

http://www.eia.doe.gov.

Environmental Solar Systems. Available from URL:

http://www.environmentalsolarsystems.com/systems/.

Enviro$en$e: Common sense solutions to environmental

problems. Available from URL: http://es.epa.gov/.

Florida Power and Light. Building shell: insulation.

Available from URL: http://www.fpl.com/savings/

energy_advisor/PA_45.html.

Florida Power and Light. Online home energy survey.

Available from URL:

http://www.fpl.com/home/ohes/contents/

online_home_energy_survey.shtml.

Hawaii Department of Business, Economic Development

and Tourism. Ceiling insulation. Available from URL:

http://www.state.hi.us/dbedt/ert/rf_insul.html.

National Association of State Energy Officials. Available

from URL: http://www.naseo.org.

Nexus Energyguide. Available from URL:

http://www.energyguide.com/default.asp.

Oak Ridge National Laboratory Buildings Technology

Center. Available from URL:

http://www.ornl.gov/ORNL/BTC.

Oak Ridge National Laboratory. Whole-wall thermal

calculator performance. Available from URL:

http://www.ornl.gov/roofs+walls/

whole_wall/wall-a30.html.

Healthy Housing Reference Manual 13-11
Oikos. Whole wall R-value ratings. Energy Source Builder

#47; October 1996. Available from URL:

http://oikos.com/esb/47/wholewall.html.

RoofHelp.com. R-value. Available from URL:

http://www.roofhelp.com/Rvalue.htm.

Senate Committee on Energy and Natural Resources.

Highlights of the Energy Policy Act of 2003 and the

Energy Tax Incentives Act of 2003. Available from URL:

http://energy.senate.gov/news/rep_release.cfm?id=203374.

Trandt J. Americans want energy efficiency. Available

from URL: http://healthandenergy.com/

energy_efficiency.htm.

US Department of Energy, Energy Efficiency and

Renewable Energy. Building envelope. Available from

URL: http://www.eere.energy.gov/

EE/buildings_envelope.html.

US Department of Energy, Energy Information

Administration. Available from URL: http://eia.doe.gov/.

US Environmental Protection Agency. Available from

URL: http://www.epa.gov.

US Environmental Protection Agency, Energy Star.

Available from URL: http://www.energystar.gov.

Wilson A. Thermal mass and R-value: making sense of a

confusing issue. EBN 1998 7(4). Available from URL:

http://www.buildinggreen.com/features/tm/thermal.cfm.

World Energy Efficiency Association. Available from

URL: http://www.weea.org/.

13-12 Energy Efficiency
Chapter 14—Residential Swimming Pools and Spas

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-1

Child-proofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-1

Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-2

Public Health Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-2

Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-3

Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-3

Water Testing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-3

Disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-4

Content Turnover Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-4

Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

High-rate Sand Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Cartridge Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Diatomaceous Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Filter Loading Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Disinfectants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Effect of pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-6

Chlorine Disinfectants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-6

Pool Water Hardness and Alkalinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-8

Liquid Chemical Feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-9

Positive Displacement Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-9

Erosion and Flow-through Disinfectant Feeders . . . . . . . . . . . . . . . . . . . . . .14-10

Spas and Hot Tubs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-11

Figure 14.1. Pool Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-2

Figure 14.2. Typical Home Pool Equipment System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-5

Table 14.1. Pool Water Quality Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-7

Table 14.2. pH Effect on Chlorine Disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-8

Table 14.3. Chlorine Use in Swimming Pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-8

Table 14.4. Swimming Pool Operating Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-9

Table 14.5. Spa and Hot Tub Operating Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-11

Healthy Housing Reference Manual 1

Contents
Chapter 14: Residential Swimming Pools and Spas

“Most people assume if their young child falls into the pool,

there will be lots of splashing and screaming, and plenty of

time to react. In reality, a child slips into the water and

often goes under the surface. These drownings can happen

quickly and silently-without warning.”

Hal Stratton, Chair 

U.S. Consumer Product Safety Commission,

2002–Present

Introduction

Swimming is one of the best forms of exercise available

and having a residential swimming pool also can provide

much pleasure. Nevertheless, it takes a great deal of work

and expense to make and keep the pool water clean and

free of floating debris. Without a doubt, a properly

maintained and operated pool is quite rewarding. Home

pools, however, are sometimes referred to as attractive

nuisances or hazards. It is essential to be able to evaluate

the risks associated with a pool. A regulatory agent or

consultant must understand the total engineered pool

system and be capable of identifying all equipment,

valves, and piping systems. The piping system for a pool

should be color-coded to assist the pool operator or the

owner to determine the correct way to operate the

swimming pool. The specific goal is to protect the

owners, their families, and others who may be attracted

to a residential pool. 

Residential pools and spas should provide clean, clear water;

water free of disease agents; and a safe recreational

environment. In addition, residential pools and spas

should have effective, properly operating equipment and

effective maintenance and operation.

Childproofing 

Although it seems obvious, close supervision of young

children is vital for families with a residential pool. A

common scenario is a young child leaving the house without

the parent or caregiver realizing it. Children are drawn to

water, and they can drown even if they know how to swim.

All children should be supervised at all times while in

and around a pool. 

The key to preventing pool tragedies is to provide layers

of protection. These layers include limiting pool access, using

pool alarms, closely supervising children, and being prepared

in case of an emergency. The U.S. Consumer Product Safety

Commission (CPSC) offers these tips to prevent drowning: 

• Fences and walls should be at least 4 feet high

and installed completely around the pool. The

fence should be no more than 2 inches above

grade. Openings in the fence should be a

maximum of 4 inches. A fence should be difficult

to climb over. 

• Fence gates should be self-closing and selflatching. The latch should be out of a small

child’s reach. The gate should open away from

the pool; the latch should face the pool.

• Any doors with direct pool access should have an

audible alarm that sounds for 30 seconds. The

alarm control must be a minimum of 54 inches

high and reset automatically. 

• If the house forms one side of the barrier to the

pool, then doors leading from the house to the

pool should be protected with alarms that

produce a sound when a door is opened.

• Young children who have taken swimming

lessons should not be considered “drown proof”;

young children should always be watched

carefully while swimming.

• A power safety cover-a motor-powered barrier

that can be placed over the water area-can be

used when the pool is not in use.

• Rescue equipment and a telephone should be

kept by the pool; emergency numbers should be

posted. Knowing cardiopulmonary resuscitation

(CPR) can be a lifesaver.

• For aboveground pools, steps and ladders should

be secured and locked or removed when the pool

is not in use.

• Babysitters should be instructed about potential

hazards to young children in and around

swimming pools and their need for constant

supervision.

• If a child is missing, the pool should always be

checked first. Seconds count in preventing death

or disability.

Healthy Housing Reference Manual 14-1
• Pool alarms can be used as an added precaution.

Underwater pool alarms can be used in

conjunction with power safety covers. CPSC

advises consumers to use remote alarm receivers so

the alarm can be heard inside the house or in

other places away from the pool area.

• Toys and flotation devices should be used in pools

only under supervision; they should not be used

in place of supervision.

• Well-maintained rescue equipment (including a

ring buoy with an attached line and/or a

shepherd’s crook rescue pole should be kept by the

pool.

• Emergency procedures should be clearly written

and posted in the pool area.

• All caregivers must know how to swim, know how

to get emergency help, and know CPR.

• Children should be taught to swim (swimming

classes are not recommended for children under

the age of 4 years) and should always swim with a

buddy.

• Alcohol should not be consumed during or just

before swimming or while supervising children.

• To prevent choking, chewing gum and eating

should be avoided while swimming, diving, or

playing in water.

• Water depth should be checked before entering a

pool. The American Red Cross recommends 9 feet

as a minimum depth for diving and jumping.

• Rules should be posted in easily seen areas. Rules

should state “no running,” “no pushing,” no

drinking,” and “never swim alone.” Be sure to

enforce the rules.

• Tables, chairs, and other objects should be placed

well away from the pool fence to prevent children

from using them to climb into the pool area.

• When the pool is not in use, all toys should be

removed to prevent children from playing with or

reaching for them and unintentionally falling into

the water.

• A clear view of the pool from the house should be

ensured by removing vegetation and other

obstacles that block the view.

Hazards 

Numerous issues need to be considered before building

residential pools: location of overhead power lines,

installation and maintenance of ground fault circuit

interruptors, electrical system grounding, electrical wiring

sizing, location of the pool, and type of vegetation near

the pool. The commonly used solar covers that rest on the

surface of the pool and amplify sunlight do an excellent

job of increasing the pool temperature, and they also

increase the risk for drowning. If children or pets fall in

and sink below the cover, it can be nearly impenetrable if

they attempt to surface under it. 

Winterizing the pool also can be hazardous. The pool

water in most belowground pools is seldom drained

because of groundwater pressure that can damage the

structure of the pool. Therefore, water in most home

pools is only lowered below the frost line for winter

protection. In these cases, a pool cover is installed to keep

debris and leaves from filling the pool in the winter

months. The pool cover becomes an excellent mosquitobreeding area before the pool is reopened in the spring

because of the decomposing vegetation that is on the pool

cover, the rain that accumulates on the top of the pool

cover during the winter, and the eggs laid on the pool

cover in early fall and early spring. The cover also

provides ideal conditions for mosquitoes to breed:

stagnant water, protection from wind that can sink

floating eggs, the near absence of predators, and warm

water created by the pool cover collecting heat just below

the surface (Figure 14.1).

Public Health Issues 

Current epidemiologic evidence indicates that correctly

constructed and operated swimming pools are not a

14-2 Residential Swimming Pools and Spas

Figure 14.1. Pool Cover
major public health problem. They are preferable to

bathing beaches because of the engineered controls

designed into pools. Poorly designed or operated pools,

however, can be major public health hazards. Data from

CDC between 1999 and 2000 show that 59 disease

outbreaks from 23 states were attributed to recreational

water exposure and affected an estimated 2,093 people.

Of the 59 recreational outbreaks, 44 (74.6%) were of

known infectious etiology. Of the 36 outbreaks involving

gastroenteritis, 17 (47.2%) were caused by parasites;

9 (25.0%) by bacteria; 3 (8.3%) by viruses; 1 (2.8%) by a

combination of parasites and bacteria, and the remaining

6 (16.7%) were of unknown cause. Of the

23 nongastroenteritis-related recreational outbreaks, seven

were attributed to Pseudomonas aeruginosa, four to freeliving amoebae, one to Leptospira species, one to

Legionella species, and one to bromide. Sixteen of the

17 parasitic recreational water outbreaks involving

gastroenteritis; nine (24.3%) were outbreaks of dermatitis;

and six (16.2%) were caused by Cryptosporidium parvum.

The seventeenth outbreak was caused by Giardia lamblia

(intestinalis). In 1999, an outbreak of Campylobacter

jejuni was associated with a private pool that did not have

continuous chlorine disinfection and reportedly had

ducks swimming in the pool [1].

Diseases

• Intestinal diseases: Escherichia coli O157:H7,

typhoid fever, paratyphoid fever, amoebic dysentery,

leptospirosis, cryptosporidiosis (highly chlorine

resistant), and bacillary dysentery can be a

problem where water is polluted by domestic or

animal sewage or waste. Swimming pools have

also been implicated in outbreaks of leptospirosis.

• Respiratory diseases: Colds, sinusitis, and septic

sore throat can spread more readily in swimming

areas as a result of close contact, or improperly

treated pool water, coupled with lowered

resistance because of exertion.

• Eye, ear, nose, throat, and skin infections: The

exposure of delicate mucous membranes, the

movement of harmful organisms into ear and

nasal passages, the excessive use of watertreatment chemicals, and the presence of harmful

agents in water can contribute to eye, ear, nose,

throat, and skin infections. Close physical contact

and the presence of fomites (such as towels) also

help to spread athlete’s foot, impetigo, and dermatitis.

Injuries

Injuries and drowning deaths are by far the greatest problem

at swimming pools. Lack of bather supervision is a prime

cause, as is the improper construction, use, and maintenance

of equipment. Injuries include evisceration, electrocution,

entrapment, and entanglement. Some particular problem

areas include the following:

• lose or poorly located diving board,

• slippery decks or pool bottoms,

• poorly designed or located water slides,

• projecting or ungrated pipes and drains that can

catch hair or body parts,

• drain grates of inadequate size,

• improperly installed or maintained electrical

equipment, and 

• improperly vented chlorinators and mishandled

chlorine materials.

Water Testing Equipment

It is essential that correct equipment be used and maintained

for assessing the water quality of both swimming pools

and spas. The operators of pool and spas need to monitor

a wide range of chemicals that influence pool operations

and water quality. Their equipment should test for chlorine,

bromine, pH, alkalinity, hardness, and cyanuric acid build

up. The chlorine should be measurable at a range of 0 to

10 parts per million (ppm). Water pH levels should be

accurately measured with an acid or base test. A kit to

check pool chemical levels usually includes N,N-diethylp-phenylene-diamine (DPD) tablet tests for free and total

chlorine, and other one-step tablet tests for pH, total

alkalinity, calcium hardness, and cyanuric acids. The

homeowner should determine acid or base demand using

an already reacted pH sample in dropper bottles. Paper

test strips with multiple tests (including chlorine, bromine,

and pH) are also available, but the reliability of these tests

varies greatly. If used, they should be kept fresh, protected

from heat and moisture, and checked against other test

systems periodically if water quality problems persist.

Swimming pools are engineered systems, with demanding

safety and sanitary requirements that result in rather

sophisticated design standards and water treatment

systems. The size, shape, and operating system of the pool

is based on the following considerations:

Healthy Housing Reference Manual 14-3
• the intended use of the pool and the maximum

expected bather loading;

• the selection of skimmers, scuppers, or gutters,

depending on the purpose, size, and shape of the

pool; 

• the recirculation pump, whose horsepower and

impeller configuration are based on the distance,

volume, and height of the water to be pumped; 

• the filters, which are sized on the volume of water

to be treated and the maximum gallons (liters) of

water per minute that can be delivered by the

pump and the type of filter media selected; and 

• the chemical feeder sizes and types, which are

based on the chemicals used, total quantity of the

water in the system, expected use rates, and

external environmental factors, such as quantity of

sunlight and wind that affect the system.

Disinfection 

The length of time it takes to disinfect a pool depends,

for example, on the type of fecal accident and the

chlorine levels chosen to disinfect the pool. If a fecal

accident is a formed stool, the faollowing chlorine levels

will determine the times needed to inactivate Giardia:

Chlorine Levels (ppm) Disinfection Time

1.0 45 minutes

2.0 25 minutes

3.0 19 minutes

These times are based on a 99.9% inactivation of Giardia

cysts by chlorine, pH 7.5, and 77°F (25°C). The times

were derived from the EPA LT1ESWTR Disinfection

Profiling and Benchmarking Technical Guidance Manual

[2]. These times do not take into account “dead spots”

and other areas of poor pool water mixing.

If the fecal accident is diarrhea, the following chlorine

levels will determine the times needed to inactivate

Cryptosporidia:

Chlorine Levels (ppm) Disinfection Time

1.0 6.7 days 

10.0 16 hours

20.0 8 hours

A CT value is the concentration (C) of free available

chlorine in parts per million (ppm) multiplied by the

time (T) in minutes (CT value = C×T ). The CT value

for Giardia is 45 and the value for Cryptosporidia is 9,600. If

a different chlorine concentration or inactivation time is

used, CT values must remain the same. For example, to

determine the length of time needed to disinfect a pool at

15 ppm after a diarrheal accident, the following formula

is used: C×T = 9,600. Solve for time: T= 9,600÷15 ppm

= 10.7 hours. It would, thus, take 10.7 hours to inactivate

Cryptosporidia at 15 ppm. You can do the same for

Giardia by using the CT of 45.

CDC has Web sites that contain excellent information

about safe swimming recommendations, recreational

water diseases, and disinfection procedures for fecal

accidents [3,4].

Content Turnover Rate

The number of times a pool’s contents can be filtered

though its filtration equipment in a 24-hour period is the

turnover rate of the pool. Because the filtered water is

diluted with the nonfiltered water of the pool, the

turbidity continually decreases. Once the pool water has

reached equilibrium with the sources of contamination, a

6-hour turnover rate will result in 98% clarification if the

pool is properly designed. A typical-use pool should have

a pump and filtration system capable of pumping the

entire contents of the pool though the filters every 6 hours. To

determine compliance with this 6-hour turnover standard,

the following formula is used:

Turnover rate = pool volume (gallons)/

flow rate×60 (minutes in hour)

Following is a sample calculation of the pool content

turnover rate using the rate of flow reading from the flow

meter:

Turnover rate = 90,000 (gallons in pool)/

180 gallons per minute×60 (minutes in hour)

8.3-hour turnover rate = 90,000 (pool volume in

gallons)/10,800

The above pool would not meet the required turnover

rate of 6 hours. The cause could be improperly sized

piping or restrictions in the piping, an undersized pump,

or undersized or clogged filters. This turnover rate would

probably result in cloudy water if the pool is used at the

normal bather load. The decreased circulation would also

make it difficult for the disinfecting equipment to meet

the required levels.

14-4 Residential Swimming Pools and Spas
Filters

Pool filters are not designed to remove bacteria, but to

make the water in the pool clear. Normal tap water looks

quite dingy if used to fill a pool and, in some cases, the

bottom of the pool is not visible. The maximum turbidity

level of a pool should be less than 0.5 nephelometric

turbidity units. Pool filters should be sized to ensure that

the complete contents of the pool pass through the filter

once every 6 hours. Home pools typically use one of three

types of filters.

High-rate Sand Filters 

High-rate sand filters were introduced more than 30 years

ago and reduced the size of the conventional sand filter by

80%. The sand filter is the most popular filter on the

market. High-rate sand filters use a silica sand that has

been strained to give it a uniform size. It is referred to as

pool-grade sand #20 silica. The sand is normally

0.45 millimeters (mm) to 0.55 mm in diameter. As water

passes through the filter, the sharp edges of the sand trap

the dirt from the pool water. When the backpressure of

the filter increases to 3 to 5 psi, the filter needs to be

cleaned. This is usually accomplished by reversing the

flow of the water through the filter and flushing the dirt

out the waste pipe until the water being discharged

appears clear. These filters perform best when used at

pressure levels below 15 to 20 gallons per minute,

depending on the manufacturer of the filter.

Cartridge Filters

Cartridge filters have been around for many years, but

only recently have gained in popularity in the pool

industry. They are similar to the filter on a car engine.

The water is passed through the cartridge and returned to

the pool. When the pressure of a cartridge filter increases

approximately 5 psi, the pump is turned off; and the top

of the filter is removed. The cartridge is removed and

either discarded and replaced or, in some cases, washed.

Diatomaceous Earth 

Diatomaceous earth (DE) is a porous powder made from

the skeletons of billions of microscopic animals that were

buried millions of years ago. There are two primary types

of DE filters, but they both work the same way. Water

comes into the filter, passes through the DE, and is

returned to the pool. If properly sized and operated, DE

filters are considered by some to provide the highest

quality of water. They are capable of filtering the smallest

particle size of all the filter types. It is usually adequate to

change the DE once every 30 days. However, if your pool

water is very dirty, it is not uncommon to change it

3–4 times a day until the water is clear. The frequency of

backwashing will depend on many factors, including the

size of your filter, flow rate of your plumbing, and the

bather load in your pool. When the pressure reading on

the filter reaches the level set by the manufacturer’s

manual, it will be ready for backwashing. 

Filter Loading Rates

The specification plate on the side of approved residential

or commercial swimming pool filters contains such

information as the manufacturer, type of filter, serial

number, surface area, and designed loading rate. Knowing

the surface area of the filter permits calculation of the

number of gallons flowing through the filter per minute.

An excessive flow rate can push the media into the pool

or force pool solids and materials thought the media,

resulting in turbid water. Figure 14.2 shows a typical

home pool treatment system. Regulations typically specify

how much water can be filtered through the various types

of pool filtration systems. 

Disinfectants

Many disinfectants are used in pools and spas around the

world, including halogen-based compounds (chlorine,

bromine, iodine), ozone, and ultraviolet light with

hydrogen peroxide. Those used most often are chlorine,

bromine, and iodine, and each has advantages and limitations.

Healthy Housing Reference Manual 14-5

Figure 14.2. Typical Home Pool Equipment System
Chlorine—Pools can be disinfected with chlorinereleasing compounds, including hypochlorite salt

compounds. Calcium hypochlorite is inexpensive and

popular for cold-water pools, but not suitable for hot

pools and spas because it will promote scaling on heat

exchangers and piping. Chlorine levels can be rapidly

reduced with high use and regular checks should be made

to ensure maintenance of disinfection. Some adjustment

of pH is required for most forms of chlorine disinfection.

When chlorine gas is used, a fairly high alkalinity needs

to be maintained to remove the acid formed during

dosing [5]. Sodium hypochlorite is a liquid chlorine, and

has a pH of 13, causing a slight increase in the pH of the

pool water, which should be adjusted with an acidic

mixture. The sun’s rays will degrade sodium hypochlorite.

Chlorinated isocyanate is available in three formsgranular, tablet, and stick. The granular form contains

55%–62% available chlorine and the stick and tablet

form contain 89% available chlorine [6].

Bromine—Bromine needs to be used at levels twice those

of chlorine to achieve similar disinfection. Bromine is

available as the sodium or potassium salts. In the presence

of ammonia, bromine rapidly forms relatively unstable

ammonia bromamines that possess disinfection

efficiencies comparable to that of free bromine. It is also

unnecessary to destroy ammonia bromamines because

they do not produce irritating odors [5].

Iodine—Potassium iodide is a white, crystal chemical.

This chemical needs an oxidizer, such as hypochlorite, to

react with organic debris and bacteria. Iodine does not

react with ammonia, hair, or bathing suits, or cause eye

irritation, but it can react with metals, producing greenishcolored pool water [6].

Ozone—Ozone is a very powerful oxidant and is effective

against viruses. It can only be generated at the point of

use and commercial generation units are safe for use.

Ozone dosing is only practical where there is water

circulating off-pool because adequate ozone-water mixing

is essential for maximum oxidation. Ozone generators

may be of the ultraviolet lamp or corona discharge type.

The ultraviolet lamp efficiency reduces with time and the

lamp and associated activated charcoal filter will need

replacement [5].

Ultraviolet Light—Ultraviolet light, like ozone, is

sometimes used for off-pool water disinfection.

Ultraviolet light has no effect on pH or color and has

little effect on the chemical composition of the water.

However, color, turbidity, and chemical composition of

the water can interfere with ultraviolet light transmission.

The water must be adequately treated before ultraviolet

light exposure. Hydrogen peroxide is often used for this

purpose as it is relatively safe in low concentrations, is

nonflammable, and produces oxygen and water as end

products. For the ultraviolet light plus hydrogen peroxide

system to be effective, it must operate 24 hours a day.

Ultraviolet light disinfection is not pH dependent, but

the addition of hydrogen peroxide results in slightly acidic

conditions [5].

Silver-copper Ionization—Sanitizing can be

accomplished by using an ionizing unit that introduces

silver and copper ions into the water by electrolysis, or by

passing an electric current through a silver and copper

electrode. The limiting factors in using this system in the

pool and spa are cost, slow bactericidal action, and

potentially high contaminant levels caused by bather

loads. Also, black spots can form on pool surfaces if the

proper parameters of water chemistry are not maintained.

An approved chemical disinfectant must be used with an

ionizing unit [6].

The effective use of halogen disinfectants is based on the

pH, hardness, and alkalinity of the water. Improper pH,

hardness, and alkalinity levels in the pool can render high

levels of disinfectant useless in killing disease-causing

organisms. Table 14.1 summarizes water-quality problems

that affect pools and suggests corrective actions. 

Effect of pH 

The ideal pH to avoid eye irritation is 7.3. Bacteria- or

algae-killing effectiveness is improved with an even lower

pH. National standards typically recommend a range of

7.2 to 7.6, which is cost-effective. Table 14.2

demonstrates the loss of disinfection as pH increases:

Chlorine Disinfectants

The options for selecting the form of chlorine disinfectant

to use in pools are quite varied, and the choices are

complex. Table 14.3 gives the properties of each form.

Gas chlorine costs the least, and the relative cost of each

form of chlorine increases as you move right across the

table. The cost of the disinfectant tends to be less the

higher the concentration of available chlorine. The safety

issues are more complex than they might appear. The

hazards of gas chlorine are well known. The solid forms of

chlorine, such as calcium hypochlorite, are quite reactive.

When exposed to organic compounds, they can generate

a great deal of heat and are potentially explosive. Because

solid chlorine seems inert to the untrained worker, it is

often stored beside motor oil or gasoline or left in where

14-6 Residential Swimming Pools and Spas
Table 14.1. Pool Water Quality Problem Solving [7]

Healthy Housing Reference Manual 14-7
moisture can start a chemical reaction. Even a pencil with

a graphite core that drops from a shirt pocket into a

container of calcium hypochlorite could result in a

chemical reaction leading to a fire that would release free

chlorine gas [7].

The following chemical reactions produce chlorine byproducts that reduce the effectiveness of chlorine and

cause most eye irritation.

Cl2 + H2O = HCl + HOCl

Chlorine + Water = Hydrochloric Acid +

Hypochlorous Acid

HOCl + NH3 = H2O + NH2Cl

Hypochlorous Acid + Ammonia = Water +

Monochloramine

HOCl + NH2Cl = H2O + NHCl2

Hypochlorous Acid + Monochloramine = Water +

Dichloramine

HOCl + NHCl2 = H2O + NCl3

Hypochlorous Acid + Dichloramine = Water +

Nitrogen Trichloride

Tables 14.1–14.4 serve as a quick problem-solving

reference for the home pool owner and operator. The

CDC Web site (www.cdc.gov/healthyswimming) provides

a great deal of useful information for both the inspector

and the homeowner.

Pool Water Hardness and Alkalinity 

The ideal range of water hardness for a plaster pool is

200 to 275 ppm. The ideal range for a vinyl, painted, or

fiberglass surface is 175 to 225 ppm. Excess hardness causes

scaling, discoloration, and filter inefficiency. Less than

recommended hardness results in corrosion of most

contact surfaces.

Alkalinity should be 80 to 120 ppm. High alkaline levels cause

scale and high chlorine demand. Low levels cause unstable

pH. Sodium bicarbonate will raise the alkalinity level. The

pool water will be cloudy if alkalinity is over 200 ppm. 

Table 14.2. pH Effect on Chlorine Disinfection [7]

Table 14.3. Chlorine Use in Swimming Pools

14-8 Residential Swimming Pools and Spas
Table 14.4. Swimming Pool Operating Parameters [7]

Liquid Chemical Feeders

Positive Displacement Pump

A positive displacement pump is preferable to erosion

disinfectant feeders. Positive displacement pumps can be

set to administer varied and specific chemical dosage rates

to ensure that a pool does not become contaminated with

harmful microorganisms. A positive displacement pump

does need routine cleaning, descaling, and servicing.

Running a weak muratic acid or vinegar solution through

the pump weekly can minimize most major servicing of the

pump. Most service on the pump involves one of four areas:

1. the check valves are scaled, their springs are weak,

or valves are no longer flexible;

2. the diaphragm is cracked, leaking, or not flexible;

3. the drive cam needs replacement or requires

adjustment; or

4. the motor requires replacement.

Healthy Housing Reference Manual 14-9
Erosion and Flow-through Disinfectant Feeders

These feeders work by the action of water moving around

a solid cake of chlorine and eroding the cake. The feeders

work quite well for smaller pools, but require

considerable care and maintenance. The variables that

affect the effectiveness of erosion feeders are

1. solubility of the chlorine cake or tablet;

2. surface area of the cake or tablet;

3. amount of water flowing around the cake or

tablet;

4. concentration of chlorine in the cake or

tablet; and 

5. number of cakes or tablets in the feeder.

Note: For safety reasons, the disinfectant cake must not

be accessible.

Spas and Hot Tubs

Hot tubs (large tubs filled with hot water for one or more

people) or spas (a tub with aerating or swirling water) are

used for pleasure and are increasingly being

recommended for therapy. The complexity of these

devices increases with each new model manufactured.

Newer models often have both ozone and ultraviolet light

emitters for enhanced disinfection (see Disinfectants

section earlier in this chapter). However, the environment

of the spa and hot tub, if not cleaned and operated

correctly, can become a culture medium for

microorganisms. Because the warm water is at the ideal

temperature for growth of microorganisms, good

disinfection is critical. Table 14.5 provides suggested hot

tub and spa operating parameters. It is essential that all

equipment works properly and that the units are cleaned

and disinfected on a routine basis. Monitoring the water

temperature is very important and, depending on the

health of the user, can be a matter of life and death. Time

in the heated water should be limited, and the

temperature for pregnant users should be below 103°F

(39°C) to protect the unborn baby. 

References

1. Lee HL, Levy DA, Craun GF, Beach MJ,

Calderon RL. Surveillance for waterborne-disease

outbreaks—United States, 1999–2000. MMWR

2002; 51(SS08):1–28. Available from URL:

http://www.cdc.gov/mmwr/preview/mmwrhtml/

ss5108a1.htm.

2. US Environmental Protection Agency.

LT1ESWTR Disinfection profiling and

benchmarking: technical guidance manual.

Washington, DC: US Environmental Protection

Agency; 2003. Available from URL:

http://www.epa.gov/safewater/mdbp/pdf/

profile/lt1profiling.pdf.

3. Centers for Disease Control and Prevention.

Healthy swimming. Atlanta: US Department of

Health and Human Services; no date. Available

from URL:

http://www.cdc.gov/healthyswimming/. 

4. Centers for Disease Control and Prevention. Fecal

accidents response recommendations for aquatics

staff. Atlanta: US Department of Health and

Human Services; no date. Available from URL:

http://www.cdc.gov/healthyswimming/fecalacc.htm.

5. Broadbent C. Guidance on water quality for

heated spas. Rundle Mall, South Australia,

Australia: Public Environmental Health Service;

1996. Available from URL:

http://www.dh.sa.gov.au/pehs/publications/

monograph-heated-spas.pdf.

6. Michigan State University Pesticide Education

Program. Swimming pool pest management:

category 5A, a training guide for commercial

pesticide applicators and swimming pool

operators. Chapter 3: pool disinfectants and pH.

East Lansing, MI: Michigan State University; no

date. Available from URL:

http://www.pested.msu.edu/BullSlideNews/

bulletins/pdf/2621/E2621chap3.pdf.

7. National Swimming Pool Foundation. Certified

pool-spa operator handbook, 2004. Colorado

Springs, CO: National Swimming Pool

Foundation; 2004. Available from URL:

http://nspf.org.

Additional Sources of Information

American Academy of Pediatrics. Available from URL:

www.aap.org.

American National Standards Institute. Available from

URL: http://www.ansi.org.

American Red Cross. Available from URL:

www.redcross.org.

14-10 Residential Swimming Pools and Spas
American Trauma Society. Available from URL:

www.amtrauma.org.

Association of Pool and Spa Professionals. Available from

URL: http://www.nspi.org/.

Centers for Disease Control and Prevention, National

Center for Injury Prevention and Control. Available from

URL: www.cdc.gov/ncipc/factsheets/drown.htm. 

For more information about the CDC fecal accident

recommendations, go to URL:

http://www.cdc.gov/healthyswimming/

fecal_response.htm. 

For additional information about cryptosporidiosis,

go to URL: http://www.cdc.gov/healthyswimming/

cryptofacts.htm.

See also Web-based Injury Statistics Query and

Reporting System (WISQARS) [Online]. (2002).

National Center for Injury Prevention and Control,

Centers for Disease Control and Prevention. Available

from URL: www.cdc.gov/ncipc/wisqars. 

Children’s Safety Network. Available from URL:

http://www.childrenssafetynetwork.org.

Healthy Housing Reference Manual 14-11

Table 14.5. Spa and Hot Tub Operating Parameters [7]
Chlorine Institute, Inc. Available from URL:

http://www.cl2.com.

National Safe Kids Campaign. Available from URL:

http://www.safekids.org.

National Safety Council. Available from URL:

http://www.nsc.org/.

National Swimming Pool Foundation. Available from

URL: http://www.nspf.com/.

Think First National Injury Foundation. Available from

URL: http://www.thinkfirst.org.

US Consumer Product Safety Commission. Available

from URL: http://www.cpsc.gov.

14-12 Residential Swimming Pools and Spas