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

, 

p

component of the building envelope toinsulate, air seal, and control moisture.The keys to an effective wall are:• Airtight construction—all air leaks

sealed in the wall during constructionand prior to insulation installation.

• Moisture control—exterior rain drainage system, continuous air barrier, and

vapor barrier located on the PREVENT RAIN PENETRATION

Causes of rain leaks through exterior wallsinclude improper installation of sidingmaterials; poor-quality flashing,weatherstripping, or caulking around joints inthe building exterior (such as windows, doors,and bottom plates); and wind-driven rain thatpenetrates the exterior finish. To enhance protection against rain penetration, create a drainage plane within the wall system of the home.CONTROL MOISTURE I N WALLSAll climates require these steps:• Install a polyethylene ground cover on

the earth floor of houses with crawlspaces and slope the ground away fromthe foundations of all houses.

• Install a continuous vapor barrier that has a

Perm rating of less than one (see page 3).

• Place a termite shield, sill gaskets, or

other vapor-impermeable membrane onthe top of the foundation wall. Thisaction will prevent moisture from wickinginto the framed wall from the concretefoundation wall by capillary action.

connected to downspouts that drain water away from the house

Tape joints in foam sheathing

Extend sheathing below bottom plateand seal

Siding primed on all six faces (front, back, edges) to improve durability

1⁄2" Sheathing

Siding

1⁄2" x 2" Strips

1⁄2" Gap behind siding

Studs and insulation

appropriate side of the wall.

• Complete insulation coverage—advanced

framing to maximize insulation coverage andreduce thermal bridging, no gaps orcompressed insulation, and continuousinsulated sheathing.

AIR SEALINGAir sealing reduces heat flow from air movement (convection) and prevents water vapor inthe air from entering the wall. In a 100-squarefoot wall, one cup of water can diffuse throughdrywall without a vapor barrier in a year, but 50cups can enter through a 1⁄2-inch, round hole.In fact, sealing air leaks is 10 to 100 times asimportant as installing a vapor barrier.MOISTURE CONTROLAir sealing and moisture control make insulationmore effective. It is a myth that installing vaporbarriers is the most important step for controlling moisture in walls. Vapor barriers only retardmoisture due to diffusion, while most moistureenters walls either through fluid capillary actionor as water vapor through air leaks.

rage of batt or blown wall

batt insulation to fit snugly

rd stud spaces and to com

.

on to fit around the back and

ctrical wiring and plumbing

ssing or tearing the

sulation around electrical boxes

o insulate behind the box.

r drywall is in place, seal all

h durable caulking.

with drywall clips

Subfloor

Caulk bottom plate

or use sill gasket

Floor joist

air seal

a

s

 Insulation

R-value Cost

(¢/sq.ft.)

11 12-16

13 15-20

15 (high density) 34-40

19 27-34

21 (high density)33-39

25 37-45

30 (high density) 45-49

30 (standard)39-43

38 55-60

arison only. Determine actual

d cost from manufacturer or local

10/30/00, 11:10 AM
 be spaced on 24-inch

used for 2x4’s. The advan

centers are:

m for R-19 or R-21 wall

studs is reduced due to the

ud area in the wall.

around piping, wiring, and

on is favorable primarily in

mes in which windows and

e total wall area. Walls

a may require almost as

each opening can add extra

oor jambs must be wider,

nder that increases costs

 less expensive way to

struction, especially in

g

g nailed to studs

abor cost of 1x4

d

brace

ow 

ner

1x4 let-in brace notchedinto wall studs

Sheet for R-value recommendations for your climate and building type. The DOE Insulation Fact Sheet (DOE/CE-0180) can beordered from the Energy Efficiency and Renewable EnergyClearinghouse or accessed from the Internet at www.ornl.gov/roofs+walls.• Fiberglass and rock wool batts— 2x4 walls can hold R-13 or

R-15 batts; 2x6 walls can have R-19 or R-21 products.Generally, batt insulation is the least expensive wall insulationmaterial but requires careful installation for effectiveperformance (see page 4).

• Cellulose insulation, made from recycled newsprint, comes primarily in loose-fill form. It can be installed in walls using a

dry-pack process or a moist-spray technique. It generally costsmore than batt insulation, but it offers reduced air leakagethrough the wall cavity plus improved sound deadening.

• Fiberglass and rock wool loose-fill insulation provide full

coverage with a “Blow-in Blanket” System (BIBS) that involves

blowing insulation into open stud cavities behind a net.

• Rigid foam insulation has a higher R-value per inch

than fiberglass or cellulose and stops air leaks, but it isconsiderably more expensive. It is manufactured insheet-good dimensions and is often used as the outer layer ofinsulation.

Sheathing thicker than 1⁄2 inch will yield even higher R-values.Foam sheathing has these advantages:• The continuous layer of insulation reduces thermal bridging

through wood studs, saving energy and improving comfort.

• It is easier to cut and install than heavier weight sheathing

products.

• It protects against condensation on the inside wall by keeping

the interior of the wall warmer.

• It usually costs less than plywood or oriented strand board

(OSB).

Ensure that the sheathing completely covers, and is sealed to,the top plate and band joist at the floor. Most sheathing products come in 8-, 9-, or 10-foot lengths to allow complete coverage of the wall. Once it is installed, patch all holes, penetrations,and seams with caulk or housewrap tape.Because of its insulation advantages over plywood and OSB,foam sheathing is best when used continuously in combinationwith let-in bracing, which provides structural support similar tothat offered by plywood or OSB. Some builders use two layers ofsheathing— plywood or OSB for structural support and a seamstaggered layer of rigid foam for insulation. When the total depthof the sheathing material exceeds 1⁄2 inch, make certain thewindow and door jambs are adjusted for the total wall thickness.Some flanged windows are readily adaptable to this approach.

Interior

Exterior or no vapor barrier

Omit vapor barrier

VAPOR BARRIER PLACEMENT BY GEOGRAPHICAL LOCATIONIn most cold climates, vapor barriers should be placed on the interior(warm-in-winter) side of walls. However, the map shows that in somesouthern climates, the vaporbarrier should be omitted, while inhot and humid climates, such asalong the Gulf coast and in Florida,the vapor barrier should be placedon the exterior of the wall.

Perm Ratings of Different Materials

(Rating of 1 or less qualifies as a vapor barrier)

Asphalt-coated paper backing on insulation 0.40Polyethylene plastic (6 mil) 0.06Plywood with exterior glue 0.70Plastic-coated insulated foam sheathing 0.4 to 1.2Aluminum foil (.35 mil) 0.05Vapor barrier paint or primer 0.45Drywall (unpainted)50Drywall (painted - latex paint)2-3

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10/30/00, 11:10 AM
 be spaced on 24-inch

used for 2x4’s. The advan

centers are:

m for R-19 or R-21 wall

studs is reduced due to the

ud area in the wall.

around piping, wiring, and

on is favorable primarily in

mes in which windows and

e total wall area. Walls

a may require almost as

each opening can add extra

oor jambs must be wider,

nder that increases costs

 less expensive way to

struction, especially in

g

g nailed to studs

abor cost of 1x4

d

brace

ow 

ner

1x4 let-in brace notchedinto wall studs

Sheet for R-value recommendations for your climate and building type. The DOE Insulation Fact Sheet (DOE/CE-0180) can beordered from the Energy Efficiency and Renewable EnergyClearinghouse or accessed from the Internet at www.ornl.gov/roofs+walls.• Fiberglass and rock wool batts—2x4 walls can hold R-13 or

R-15 batts; 2x6 walls can have R-19 or R-21 products.Generally, batt insulation is the least expensive wall insulationmaterial but requires careful installation for effectiveperformance (see page 4).

• Cellulose insulation, made from recycled newsprint, comes primarily in loose-fill form. It can be installed in walls using a

dry-pack process or a moist-spray technique. It generally costsmore than batt insulation, but it offers reduced air leakagethrough the wall cavity plus improved sound deadening.

• Fiberglass and rock wool loose-fill insulation provide full

coverage with a “Blow-in Blanket” System (BIBS) that involves

blowing insulation into open stud cavities behind a net.

• Rigid foam insulation has a higher R-value per inch

than fiberglass or cellulose and stops air leaks, but it isconsiderably more expensive. It is manufactured insheet-good dimensions and is often used as the outer layer ofinsulation.

Sheathing thicker than 1⁄2 inch will yield even higher R-values.Foam sheathing has these advantages:• The continuous layer of insulation reduces thermal bridging

through wood studs, saving energy and improving comfort.

• It is easier to cut and install than heavier weight sheathing

products.

• It protects against condensation on the inside wall by keeping

the interior of the wall warmer.

• It usually costs less than plywood or oriented strand board

(OSB).

Ensure that the sheathing completely covers, and is sealed to,the top plate and band joist at the floor. Most sheathing products come in 8-, 9-, or 10-foot lengths to allow complete coverage of the wall. Once it is installed, patch all holes, penetrations,and seams with caulk or housewrap tape.Because of its insulation advantages over plywood and OSB,foam sheathing is best when used continuously in combinationwith let-in bracing, which provides structural support similar tothat offered by plywood or OSB. Some builders use two layers ofsheathing—plywood or OSB for structural support and a seamstaggered layer of rigid foam for insulation. When the total depthof the sheathing material exceeds 1⁄2 inch, make certain thewindow and door jambs are adjusted for the total wall thickness.Some flanged windows are readily adaptable to this approach.

Interior

Exterior or no vapor barrier

Omit vapor barrier

VAPOR BARRIER PLACEMENT BY GEOGRAPHICAL LOCATIONIn most cold climates, vapor barriers should be placed on the interior(warm-in-winter) side of walls. However, the map shows that in somesouthern climates, the vaporbarrier should be omitted, while inhot and humid climates, such asalong the Gulf coast and in Florida,the vapor barrier should be placedon the exterior of the wall.

Perm Ratings of Different Materials

(Rating of 1 or less qualifies as a vapor barrier)

Asphalt-coated paper backing on insulation 0.40Polyethylene plastic (6 mil) 0.06Plywood with exterior glue 0.70Plastic-coated insulated foam sheathing 0.4 to 1.2Aluminum foil (.35 mil) 0.05Vapor barrier paint or primer 0.45Drywall (unpainted)50Drywall (painted - latex paint)2-3

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10/30/00, 11:10 AM
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

, 

p

component of the building envelope toinsulate, air seal, and control moisture.The keys to an effective wall are:• Airtight construction—all air leaks

sealed in the wall during constructionand prior to insulation installation.

• Moisture control—exterior rain drainage system, continuous air barrier, and

vapor barrier located on the PREVENT RAIN PENETRATION

Causes of rain leaks through exterior wallsinclude improper installation of sidingmaterials; poor-quality flashing,weatherstripping, or caulking around joints inthe building exterior (such as windows, doors,and bottom plates); and wind-driven rain thatpenetrates the exterior finish. To enhance protection against rain penetration, create a drainage plane within the wall system of the home.CONTROL MOISTURE I N WALLSAll climates require these steps:• Install a polyethylene ground cover on

the earth floor of houses with crawlspaces and slope the ground away fromthe foundations of all houses.

• Install a continuous vapor barrier that has a

Perm rating of less than one (see page 3).

• Place a termite shield, sill gaskets, or

other vapor-impermeable membrane onthe top of the foundation wall. Thisaction will prevent moisture from wickinginto the framed wall from the concretefoundation wall by capillary action.

connected to downspouts that drain water away from the house

Tape joints in foam sheathing

Extend sheathing below bottom plateand seal

Siding primed on all six faces (front, back, edges) to improve durability

1⁄2" Sheathing

Siding

1⁄2" x 2" Strips

1⁄2" Gap behind siding

Studs and insulation

appropriate side of the wall.

• Complete insulation coverage— advanced

framing to maximize insulation coverage andreduce thermal bridging, no gaps orcompressed insulation, and continuousinsulated sheathing.

AIR SEALINGAir sealing reduces heat flow from air movement (convection) and prevents water vapor inthe air from entering the wall. In a 100-squarefoot wall, one cup of water can diffuse throughdrywall without a vapor barrier in a year, but 50cups can enter through a 1⁄2-inch, round hole.In fact, sealing air leaks is 10 to 100 times asimportant as installing a vapor barrier.MOISTURE CONTROLAir sealing and moisture control make insulationmore effective. It is a myth that installing vaporbarriers is the most important step for controlling moisture in walls. Vapor barriers only retardmoisture due to diffusion, while most moistureenters walls either through fluid capillary actionor as water vapor through air leaks.

rage of batt or blown wall

batt insulation to fit snugly

rd stud spaces and to com

.

on to fit around the back and

ctrical wiring and plumbing

ssing or tearing the

sulation around electrical boxes

o insulate behind the box.

r drywall is in place, seal all

h durable caulking.

with drywall clips

Subfloor

Caulk bottom plate

or use sill gasket

Floor joist

air seal

a

s

 Insulation

R-value Cost

(¢/sq.ft.)

11 12-16

13 15-20

15 (high density) 34-40

19 27-34

21 (high density)33-39

25 37-45

30 (high density) 45-49

30 (standard)39-43

38 55-60

arison only. Determine actual

d cost from manufacturer or local

10/30/00, 11:10 AM