OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY

Buildings forthe 21st CenturyBuildings that are moreenergy efficient, comfortable,and affordable...that’s thegoal of DOE’s Office of BuildingTechnology, State andCommunity Programs (BTS).To accelerate the developmentand wide application of energyefficiency measures, BTS:• Conducts R&D on technologies

and concepts for energy efficiency, working closely withthe building industry and withmanufacturers of materials,equipment, and appliances

• Promotes energy/money

saving opportunities to bothbuilders and buyers of homesand commercial buildings

• Works with state and local

regulatory groups to improvebuilding codes, appliance standards, and guidelines for efficient energy use

• Provides support and grants

to states and communitiesfor deployment of energyefficient technologies andpractices

Combustion appliances using natural gas,propane, oil, kerosene, or wood are often amore efficient and cost-effective way toproduce heat than electricity.Examples include

• furnaces• space heaters• fireplaces• wood stoves• water heaters• range tops• ovens• clothes dryers

Combustion applianceshave been used for many years in millions ofhomes. However, careful installation and maintenance of each unit is required to ensure safeand efficient operation, especially in today’senergy-efficient, tightly sealed homes.PROBLEMS POSED BY COMBUSTIONEQUIPMENTCombustion appliances burn fuel by usingoxygen from supply air. They produce exhaustgases that should be directly vented to theoutside to avoid introducing combustionby-products into the house. Exhaust gasesmay be released inside the house eitherknowingly—as in the case of unvented stoves,ovens, fireplaces, or space heaters—orunknowingly from leaky flues, cracked heatexchangers, or backdrafting. Three componentsof exhaust gases are especially troublesomewhen introduced indoors: carbon monoxide,water vapor, and nitrogen oxides.

serious medical problems and is the cause ofhundreds of deaths in U.S. homes each year.CO is produced when insufficient combustionair is supplied to the appliance, the burner isimproperly tuned, and/or the appliance is malfunctioning.Water vapor is present in large amounts inexhaust gases as a result of burning all fuels.When water vapor is introduced into a house, itincreases humidity levels and can lead to condensation on window panes, exterior walls, andinterior surfaces of wall cavities. High humidityand wet surfaces promote mold growth, wooddeterioration, and other health and structuralproblems.Nitrogen oxides are usually present only insmall amounts in exhaust gases, but they stillpresent a health hazard to the inhabitants.

EFFECTS OF CARBON MONOXIDEEXPOSURECO (ppm) Time Symptoms

35 8 hours Maximum exposure

allowed by OSHA in theworkplace over an 8-hourperiod.

200 2-3 hours Mild headache, fatigue,

nausea, and dizziness.

400 1-2 hours Serious headache—other

symptoms intensify. Lifethreatening after 3 hours.

800 45 minutes Dizziness, nausea, and

convulsions. Unconsciouswithin 2 hours. Deathwithin 2-3 hours.

1600 20 minutes Headache, dizziness, and

nausea. Death within1 hour.

L

small jumper duct often in

oor that connects one room to

Foam bafflesdamper sound

ough baffle

Wall cavity

al return register. The pres

ed-off room increases, and

creases in the main part of the

the central return.

ACKDRAFTING

ackdrafting can be reduced by

nces with powered combustion

her than atmospheric vents.

ppliances with atmospheric

ealed combustion closet.

upply and return duct leaks.

turn registers in all rooms with

sters.

 rooms without a return register

 a 1-inch gap under the door

ded only for rooms with one

ter) or a transfer grill to provide

ualization between rooms.

10/30/00, 12:30 PM
ND FIREPLACES

se against unvented space

rating properly, these units

ch as nitrogen oxides and

 present, do not weatherize

ack windows open to

r the units are operating.

oor air quality and

oves and ovens.

g area near the kitchen.

fan to the outside and oper

h all major appliances,

s is recommended).

a space heater.

ess ignition.

nstalled by knowledgeable

urer’s installation instruc

nd local code requirements.

measurements should be

of the units and the safety

d be measured in the com

er heaters before the

after the burner has run

ater than 100 ppm (air free

ents are necessary; levels

chievable. Ovens should be

tting, and range tops

n over the burner. CO levels

acceptable.

Solid (non-louvered) door with weatherstripping

Door closes against solid threshold

Insulatedwater heaterBottom platesealedInsulatedwalls

Seal gas and plumbing penetrations through walls

Vented exhaust pipethrough roof

Low High Screened high and 

low combustion air ducts into closet (extend 6" above insulation in attic)

WATER HEATER CLOSET

Return grill with filter

Seal 

Door closes against solid thresholdSealed return plenum

Seal penetrations and under bottom plate of walls

Air from

house

Weatherstripping

Drywall

Insulated wallsbetween equipmentcloset and home

Warning:

Do not store anything 

in this closet.

Keep door shut.

WARNING

Solid door (non-louvered) must seal tightly against weatherstripping at top, bottom, and sides 

the home by louvered doors, air leaks, and uninsulated walls.A sealed-combustion closet is like a “little piece of the outside

located in the middle of the home.” Fresh air for combustion is

provided from sources not connected with the living space.Isolating the mechanical room from the living area protects thehome against backdrafting and increased heat gains or lossesdue to infiltration or conduction.

A SEALED-COMBUSTION CLOSET I S CONSTRUCTED B Y

FOLLOWING THESE STEPS :

1. Insulate the four walls of the combustion closet.2. Finish the walls and ceiling with drywall.3. Seal all holes and air leakage pathways through the walls,

floor, and ceiling that can connect the closet to the rest ofthe house

—this includes plumbing, gas lines, wiring, electrical boxes, and the bottom plate of the walls.

4. Install a non-louvered door that is weatherstripped and

equipped with a properly adjusted threshold.

5. Install two ducts in the closet, extending to the outside or

to a ventilated attic or crawlspace, to provide outside airfor combustion. Seal the ducts to the ceiling. Check withlocal codes

—the ducts must be sized for the specific

combustion appliances, and usually one duct shouldextend to within 12 inches of the closet floor while theother duct extends to within 12 inches of the ceiling. If theducts are connected to the attic, they should extend6 inches above the insulation level.

6. If a return plenum for a furnace is built below the closet,

completely seal the plenum

—including the plenum walls,

plumbing, and connection of the furnace to the plenum.

7. Seal the ceiling around the flue using sheet metal.

10/30/00, 12:30 PM
ND FIREPLACES

se against unvented space

rating properly, these units

ch as nitrogen oxides and

 present, do not weatherize

ack windows open to

r the units are operating.

oor air quality and

oves and ovens.

g area near the kitchen.

fan to the outside and oper

h all major appliances,

s is recommended).

a space heater.

ess ignition.

nstalled by knowledgeable

urer’s installation instruc

nd local code requirements.

measurements should be

of the units and the safety

d be measured in the com

er heaters before the

after the burner has run

ater than 100 ppm (air free

ents are necessary; levels

chievable. Ovens should be

tting, and range tops

n over the burner. CO levels

acceptable.

Solid (non-louvered) door with weatherstripping

Door closes against solid threshold

Insulatedwater heaterBottom platesealedInsulatedwalls

Seal gas and plumbing penetrations through walls

Vented exhaust pipethrough roof

Low High Screened high and 

low combustion air ducts into closet (extend 6" above insulation in attic)

WATER HEATER CLOSET

Return grill with filter

Seal 

Door closes against solid thresholdSealed return plenum

Seal penetrations and under bottom plate of walls

Air from

house

Weatherstripping

Drywall

Insulated wallsbetween equipmentcloset and home

Warning:

Do not store anything 

in this closet.

Keep door shut.

WARNING

Solid door (non-louvered) must seal tightly against weatherstripping at top, bottom, and sides 

the home by louvered doors, air leaks, and uninsulated walls.A sealed-combustion closet is like a “little piece of the outside

located in the middle of the home.” Fresh air for combustion is

provided from sources not connected with the living space.Isolating the mechanical room from the living area protects thehome against backdrafting and increased heat gains or lossesdue to infiltration or conduction.

A SEALED-COMBUSTION CLOSET I S CONSTRUCTED B Y

FOLLOWING THESE STEPS :

1. Insulate the four walls of the combustion closet.2. Finish the walls and ceiling with drywall.3. Seal all holes and air leakage pathways through the walls,

floor, and ceiling that can connect the closet to the rest ofthe house

—this includes plumbing, gas lines, wiring, electrical boxes, and the bottom plate of the walls.

4. Install a non-louvered door that is weatherstripped and

equipped with a properly adjusted threshold.

5. Install two ducts in the closet, extending to the outside or

to a ventilated attic or crawlspace, to provide outside airfor combustion. Seal the ducts to the ceiling. Check withlocal codes

—the ducts must be sized for the specific

combustion appliances, and usually one duct shouldextend to within 12 inches of the closet floor while theother duct extends to within 12 inches of the ceiling. If theducts are connected to the attic, they should extend6 inches above the insulation level.

6. If a return plenum for a furnace is built below the closet,

completely seal the plenum

—including the plenum walls,

plumbing, and connection of the furnace to the plenum.

7. Seal the ceiling around the flue using sheet metal.

10/30/00, 12:30 PM
OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY

Buildings forthe 21st CenturyBuildings that are moreenergy efficient, comfortable,and affordable...that’s thegoal of DOE’s Office of BuildingTechnology, State andCommunity Programs (BTS).To accelerate the developmentand wide application of energyefficiency measures, BTS:• Conducts R&D on technologies

and concepts for energy efficiency, working closely withthe building industry and withmanufacturers of materials,equipment, and appliances

• Promotes energy/money

saving opportunities to bothbuilders and buyers of homesand commercial buildings

• Works with state and local

regulatory groups to improvebuilding codes, appliance standards, and guidelines for efficient energy use

• Provides support and grants

to states and communitiesfor deployment of energyefficient technologies andpractices

Combustion appliances using natural gas,propane, oil, kerosene, or wood are often amore efficient and cost-effective way toproduce heat than electricity.Examples include

• furnaces• space heaters• fireplaces• wood stoves• water heaters• range tops• ovens• clothes dryers

Combustion applianceshave been used for many years in millions ofhomes. However, careful installation and maintenance of each unit is required to ensure safeand efficient operation, especially in today’senergy-efficient, tightly sealed homes.PROBLEMS POSED BY COMBUSTIONEQUIPMENTCombustion appliances burn fuel by usingoxygen from supply air. They produce exhaustgases that should be directly vented to theoutside to avoid introducing combustionby-products into the house. Exhaust gasesmay be released inside the house eitherknowingly—as in the case of unvented stoves,ovens, fireplaces, or space heaters—orunknowingly from leaky flues, cracked heatexchangers, or backdrafting. Three componentsof exhaust gases are especially troublesomewhen introduced indoors: carbon monoxide,water vapor, and nitrogen oxides.

serious medical problems and is the cause ofhundreds of deaths in U.S. homes each year.CO is produced when insufficient combustionair is supplied to the appliance, the burner isimproperly tuned, and/or the appliance is malfunctioning.Water vapor is present in large amounts inexhaust gases as a result of burning all fuels.When water vapor is introduced into a house, itincreases humidity levels and can lead to condensation on window panes, exterior walls, andinterior surfaces of wall cavities. High humidityand wet surfaces promote mold growth, wooddeterioration, and other health and structuralproblems.Nitrogen oxides are usually present only insmall amounts in exhaust gases, but they stillpresent a health hazard to the inhabitants.

EFFECTS OF CARBON MONOXIDEEXPOSURECO (ppm) Time Symptoms

35 8 hours Maximum exposure

allowed by OSHA in theworkplace over an 8-hourperiod.

200 2-3 hours Mild headache, fatigue,

nausea, and dizziness.

400 1-2 hours Serious headache—other

symptoms intensify. Lifethreatening after 3 hours.

800 45 minutes Dizziness, nausea, and

convulsions. Unconsciouswithin 2 hours. Deathwithin 2-3 hours.

1600 20 minutes Headache, dizziness, and

nausea. Death within1 hour.

L

small jumper duct often in

oor that connects one room to

Foam bafflesdamper sound

ough baffle

Wall cavity

al return register. The pres

ed-off room increases, and

creases in the main part of the

the central return.

ACKDRAFTING

ackdrafting can be reduced by

nces with powered combustion

her than atmospheric vents.

ppliances with atmospheric

ealed combustion closet.

upply and return duct leaks.

turn registers in all rooms with

sters.

 rooms without a return register

 a 1-inch gap under the door

ded only for rooms with one

ter) or a transfer grill to provide

ualization between rooms.

10/30/00, 12:30 PM