Crawlspace Insulation

Technology Fact Sheet CRAWLSPACE INSULATION

For more information, contact: ARE CRAWLSPACE VENTS NECESSARY? BUILD IN RADON RESISTANCE Most building codes require crawlspace vents Radon is a radioactive gas that occurs in some CRAWLSPACE Energy Efficiency and Renewable Energy to aid in removing moisture from the soils. It can enter a home through the foundation Clearinghouse (EREC) crawlspace. However, many building and floor system. If it occurs in significant INSULATION 1-800-DOE-3732 professionals are now recognizing that an concentrations (greater that 4 pico-curies per Improve comfort and increase durability in the home www.eren.doe.gov unvented crawlspace (or closing crawlspace liter), it may pose a severe health risk to the home Or visit the BTS Web site at vents after the crawlspace has had time to dry occupants. To guard against radon problems: EFFECTIVE CRAWLSPACE INSULATION www.eren.doe.gov/buildings out after construction) is the best option in • Install a sealed, continuous layer of 6-mil A properly sealed, moisture-protected, and WATER-MANAGED CRAWLSPACE homes using proper moisture control and Or refer to the Builder’s Guide polyethylene over the crawlspace floor. insulated crawlspace will increase comfort, FOUNDATION Energy Efficient Building exterior drainage techniques for two reasons. Association, Inc. • Install a plastic tee below the polyethylene save on energy costs, improve the durability of First, ventilation in the winter is undesirable in 2 651-268-7585 that protrudes through the polyethylene. Buildings for the home, and reduce entry of moisture, radon, 1 www.eeba.org order to keep crawlspaces warmer. Second, the 21st Century and other potential irritants or pollutants into • Install a vertical 3-inch plastic pipe from the 4 warm, moist outdoor air brought into the the home. Whichever design is followed, the 5 Written and prepared for foundation to the roof through an interior wall. Buildings that are more

yyy the U.S. Department of crawlspace through foundation vents in the keys to an effective crawlspace are: 6" energy efficient, comfortable, or more Energy by: summer is often unable to dehumidify a • Connect the tee to the vertical 3-inch plastic yyy

and affordable… that’s the Moisture control – using a water-managed 3 yyy crawlspace and, in fact, can lead to increased pipe for passive mitigation. yyy

yyyy Southface Energy Institute goal of DOE’s Office of Building foundation system to drain rainwater and 6 yy y

moisture levels in the crawlspace. 7 yyy • Have an electrician stub-in a junction box in yyyy 404-872-3549 Technology, State and groundwater away from foundations. yyy

www.southface.org yy y For example, a crawlspace kept cool by the the attic. Community Programs (BTS). yyyy 9 8 yyyyyyy Airtight construction – sealing all air leaks yyy

yyyy U.S. Department of ground in the summer may have a temperature To accelerate the development • Test the bottom conditioned room for radon yyyyy yy between the conditioned space and the outside

yyyy Energy’s Oak Ridge and wide application of energy of 65°F and 90% relative humidity (RH)—the with an EPA-listed radon test kit, or hire a yyyyyyy prior to insulation installation. National Laboratory yyyy dew point temperature of the air is 62°F. The qualified technician. If the house has a high efficiency measures, BTS: Buildings Technology Center Complete insulation coverage – properly 5. Install a protective membrane, such as an 423-574-5178 dew point of outdoor air at 90°F and 60% RH is radon concentration, install an active radon • Conducts R&D on technologies installing the correct insulation levels and EPDM-type membrane, to serve as a capillary www.ornl.gov/ORNL/BTC about 74°F. Thus, outdoor air brought into the mitigation system by attaching a small and concepts for energy effi- making sure the insulation coverage is break that reduces wicking of water from the The International Energy crawlspace will actually increase the moisture blower to the plastic pipe in the attic to expel ciency, working closely with continuous and complete. masonry wall. This membrane, in addition to Conservation Code level until water condenses out on cool the gases to the outside. the building industry and with metal flashing, can serve as a termite shield. can be obtained from the crawlspace surfaces such as floor joists, manufacturers of materials, International Code Council • If radon levels are especially high (over 25 pico- WATER-MANAGED FOUNDATION SYSTEM foundation walls, and air-conditioning ducts. equipment, and appliances 6. Dampproof the below-grade portion of the by calling 703-931-4533, curies per liter), consult with local radon experts. A crawlspace is susceptible to moisture and As framing stays moist, mold grows and dry • Promotes energy/money foundation wall to prevent the wall from www.intlcode.org deterioration problems because of contact with rot develops. saving opportunities to both absorbing ground moisture by capillary action. the earth. The best approaches for preventing MECcheck, a companion builders and buyers of homes compliance software RADON RESISTANT these problems will depend on the local climate 7. Install drainage plane material or gravel and commercial buildings package, can be ordered from CONSTRUCTION against the foundation wall to relieve PSYCROMETRIC CHART and style of construction, but the following DOE by calling • Works with state and local 100% general rules apply to most crawlspace designs. hydrostatic pressure and channel water to 1-800-270-CODE Optional blower regulatory groups to improve RH the foundation drain. or downloaded directly 80% (if required) 1. Keep all untreated wood materials away from RH building codes, appliance from the Web at: Electrical junction box standards, and guidelines for the earth. 8. Provide a foundation drainage system at the www.energycodes.org/ efficient energy use bottom of the footing, not on top, when the resid/resid.htm. Dewpoint 2. Provide rain drainage, such as gutters, to 60% 74ûF foundation floor (interior grade) is below the NOTICE: Neither the United RH • Provides support and grants conduct rainwater away from the house. States government nor any to states and communities exterior grade. Surround a perforated 4-inch drain Plastic 3. Slope the earth away from the house for at agency thereof, nor any of their 40% vent stack for deployment of energy- pipe with gravel and cover them with filter fabric. employees, makes any warranty, RH least 5 feet at a minimum 5% grade (3 inches efficient technologies and 9. Install 6-mil polyethylene across the express or implied, or assumes in 5 feet). Establish drainage swales to direct any legal liability or responsibility 50û 60û 70û 80û 90û 100û practices crawlspace floor to prevent soil moisture from for the accuracy, completeness, Degrees Fahrenheit rainwater around the house. migrating into the crawlspace. Overlap and or usefulness of any information, Sealed 4. Add a sill gasket to provide air sealing. apparatus, product, or process polyethylene tape all seams by 12 inches, and seal the disclosed. The views and opin- polyethylene 6 inches up the crawlspace walls. ions of authors expressed herein Printed with a renewable-source ink on paper containing at do not necessarily state or reflect Perforated "T" fitting least 50% wastepaper, including 20% postconsumer waste. those of the United States gov- OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMS December 2000 DOE/GO2000-0774 ernment or any agency thereof. ENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY CRAWLSPACE INSULATION

CRAWLSPACE WALL INSULATION TECHNIQUES • A radon mitigation system will require ventilation of the 5. Locate the crawlspace access inside the home or install an access For years, standard building practice was to insulate underneath crawlspace to the exterior. Not planning for radon-resistant through the perimeter that will remain airtight after repeated use. UNDERFLOOR INSULATION the floor over a ventilated, unconditioned crawlspace. A better ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ construction may necessitate air sealing the floor in order to 6. Select insulation levels in accordance with the International approach is to build a well sealed, unventilated crawlspace (i.e., mitigate the radon through ventilation. Energy Conservation Code or the DOE Insulation Fact Sheet. build the crawlspace like a basement) by sealing and insulating • The crawlspace must be built airtight and the air barrier must The Insulation Fact Sheet (DOE/CE-0180) can be ordered from the foundation walls rather than the subfloor. be maintained. the Energy Efficiency and Renewable Energy Clearinghouse or Advantages to insulating the crawlspace walls are: accessed from the Internet at www.ornl.gov/roofs+walls. • The access door to the crawlspace must be located inside the Metal staves • Problems associated with ventilating the crawlspace are support insulation – home through the subfloor unless an airtight, insulated ac- 7. Install rigid or batt insulation using one of three options engineered I-beams avoided. cess door in the perimeter wall is built and maintained. (exterior foam, interior foam, or interior batt) to achieve com- require a longer stave plete insulation coverage. Insulate the band joist with batt in- • Less insulation is required (around 400 square feet for a Loose-fill insulation fills gaps STEPS FOR INSTALLING CRAWLSPACE WALL 1,000-square-foot crawlspace with 3-foot walls). sulation, and the crawlspace access if it is located in the wall. between trusses and is INSULATION contained by landscape cloth Install a continuous termite shield between the band joist and attached to truss members • Piping and ductwork are within the conditioned volume of the 1. Review plans for this method of foundation insulation with pest masonry foundation wall that covers the wall insulation and house so they do not require insulation for energy efficiency control and local building officials to ensure code compliance. extends completely outside, or leave a 2- to 4-inch insulation yyyyyÀÀÀÀÀ@@@@@yyyÀÀÀ@@@ yyyy or protection against freezing. 2. Eliminate or seal the foundation vents. gap at the top for termite inspection. • Air sealing between the house and crawlspace is less critical. yyyyyyyyÀÀÀÀÀÀÀÀ@@@@@@@@ yyyy 3. Ensure that combustion furnaces and water heaters located in 8. Install a supply outlet in the crawlspace, relying on the

Disadvantages to insulating the crawlspace walls are: yyyyyyyyÀÀÀÀÀÀÀÀ@@@@@@@@ yyyy the crawlspace are sealed-combustion units equipped with a leakiness of the floor to provide the return air path. • The insulation may be damaged by rodents, pests, or water. powered combustion system. InexpensiveyyyyyyyyÀÀÀÀÀÀÀÀ@@@@@@@@ landscape yyyy 4. Seal all air leaks through the exterior wall during and after STEPS FOR INSTALLING UNDERFLOOR cloth stapled to webs INSULATION support insulation construction, including the band joist. 1. During the early phases of construction, meet with the ○○○ INSULATING TRUSS FLOOR SYSTEMS mechanical subcontractors (plumbing, electrical, and heating/ Instead of batt insulation, a better approach is to cooling) to inform them of the importance of keeping the INSULATED CRAWL SPACE WALLS—3 OPTIONS install netting or rigid insulation to the underside space between floor joists as clear as possible. Run drain of the floor trusses and filling the space created lines, electrical wiring, and ductwork below the bottom of the Option 1 between the netting or insulation and subfloor Exterior foam insulation so that a continuous layer of insulation can be insulation with a loose-fill insulation. Protective membrane installed. For protection against freezing, supply plumbing covers exterior rigid Unfaced insulation Unfaced insulation insulation and folds in band joist Option 2 in band joist Option 3 may be located within the insulation. The best approach is to over top course of foundation block Interior foam Interior batt run supply plumbing together in a few joist spaces. The Sill gasket insulation Sill gasket insulation insulation can be split and run around the piping. joist being insulated and slit to fit around wiring and plumbing. yyyy Protective yyyy Protective membrane Insulate the band joist area between air ducts and the floor as membrane overlaps overlaps and extends 2. Seal all air leaks between the conditioned area of the home yyyy and extends down yyyy down underneath space permits. Use insulation hangers (wire staves) spaced every insulation to provide insulation to footing and the crawlspace. High-priority leaks include holes around Protective membrane capillary break Protective membrane covers top course of covers top course of 12-18 inches to hold the floor insulation in place without com- block and provides bathtub drains and other drain lines, plenums for ductwork, Rigid insulation block and provides termite resistance termite resistance pressing the insulation more than 1 inch. (fire-rated) with R-11 to R-19 batt and penetrations for electrical wiring, plumbing, and ductwork joints taped or insulation sealed (including duct boot connections at the floor). 5. The orientation of the vapor barrier depends on the home’s 3. Select insulation levels in accordance with the International location. In most of the country, the vapor barrier should face upward. However, in certain regions of the Gulf states and yyyyyyyyy Energy Conservation Code or the DOE Insulation Fact Sheet. 6-mil poly other areas with mild winters and hot summers, it should face yyyyyyyyyyyyyyyyy 6-mil poly yyyyyy vapor diffusion 4. Insulation batts with an attached vapor barrier are usually used to vapor diffusion retarder downward.

yyyyyyyyyyyyyyyyyyyyy retarder yyyyyyyyyyyyyyy insulate framed floors. Obtain insulation with the proper width for yyyyy yyyyy 6. Insulate all ductwork in the crawlspace.

yyyyy yyyyy the joist spacing of the floor being insulated. Complete coverage

yyyyyyyyyyyyyyyyyyyyy yyyyyyyyyyyyyyy yyyyy yyyyy is essential – leave no insulation voids. The batts should be 7. Insulate all hot and cold water lines in the crawlspace unless yyyyy yyyyy

yyyyyyyyyyyy yyyyyyyyy yyyyy yyyyy installed flush against the subfloor to eliminate any gaps that may they are located within the insulation. Perforated drainage pipe is embedded in gravel, Perforated drainage pipe is embedded in gravel, yyyyyyyyyyyy yyyyyyyyy covered with filter fabric, and located at lower perimeter covered with filter fabric, and located at lower perimeter serve as passageways for cold air to flow between the insulation 8. Close crawlspace vents after making sure the crawlspace is dry of foundation footing to provide drainage. of foundation footing to provide drainage. and the subfloor. The batts should be cut to the full length of the and all construction materials have dried out. CRAWLSPACE INSULATION

Disadvantages to insulating the crawlspace walls are: yyyyyyyyÀÀÀÀÀÀÀÀ@@@@@@@@ yyyy the crawlspace are sealed-combustion units equipped with a leakiness of the floor to provide the return air path. • The insulation may be damaged by rodents, pests, or water. powered combustion system. InexpensiveyyyyyyyyÀÀÀÀÀÀÀÀ@@@@@@@@ landscape yyyy 4. Seal all air leaks through the exterior wall during and after STEPS FOR INSTALLING UNDERFLOOR cloth stapled to webs INSULATION support insulation construction, including the band joist. 1. During the early phases of construction, meet with the ○○○ INSULATING TRUSS FLOOR SYSTEMS mechanical subcontractors (plumbing, electrical, and heating/ Instead of batt insulation, a better approach is to cooling) to inform them of the importance of keeping the INSULATED CRAWL SPACE WALLS— 3 OPTIONS install netting or rigid insulation to the underside space between floor joists as clear as possible. Run drain of the floor trusses and filling the space created lines, electrical wiring, and ductwork below the bottom of the Option 1 between the netting or insulation and subfloor Exterior foam insulation so that a continuous layer of insulation can be insulation with a loose-fill insulation. Protective membrane installed. For protection against freezing, supply plumbing covers exterior rigid Unfaced insulation Unfaced insulation insulation and folds in band joist Option 2 in band joist Option 3 may be located within the insulation. The best approach is to over top course of foundation block Interior foam Interior batt run supply plumbing together in a few joist spaces. The Sill gasket insulation Sill gasket insulation insulation can be split and run around the piping. joist being insulated and slit to fit around wiring and plumbing. yyyy Protective yyyy Protective membrane Insulate the band joist area between air ducts and the floor as membrane overlaps overlaps and extends 2. Seal all air leaks between the conditioned area of the home yyyy and extends down yyyy down underneath space permits. Use insulation hangers (wire staves) spaced every insulation to provide insulation to footing and the crawlspace. High-priority leaks include holes around Protective membrane capillary break Protective membrane covers top course of covers top course of 12-18 inches to hold the floor insulation in place without com- block and provides bathtub drains and other drain lines, plenums for ductwork, Rigid insulation block and provides termite resistance termite resistance pressing the insulation more than 1 inch. (fire-rated) with R-11 to R-19 batt and penetrations for electrical wiring, plumbing, and ductwork joints taped or insulation sealed (including duct boot connections at the floor). 5. The orientation of the vapor barrier depends on the home’s 3. Select insulation levels in accordance with the International location. In most of the country, the vapor barrier should face upward. However, in certain regions of the Gulf states and yyyyyyyyy Energy Conservation Code or the DOE Insulation Fact Sheet. 6-mil poly other areas with mild winters and hot summers, it should face yyyyyyyyyyyyyyyyy 6-mil poly yyyyyy vapor diffusion 4. Insulation batts with an attached vapor barrier are usually used to vapor diffusion retarder downward. yyyyyyyyyyyyyyyyyyyyy retarder yyyyyyyyyyyyyyy insulate framed floors. Obtain insulation with the proper width for yyyyy yyyyy 6. Insulate all ductwork in the crawlspace. yyyyy yyyyy the joist spacing of the floor being insulated. Complete coverage yyyyyyyyyyyyyyyyyyyyy yyyyyyyyyyyyyyy yyyyy yyyyy is essential – leave no insulation voids. The batts should be 7. Insulate all hot and cold water lines in the crawlspace unless yyyyy yyyyy

and affordable… that’s the Moisture control – using a water-managed 3 yyy crawlspace and, in fact, can lead to increased pipe for passive mitigation. yyy

yyyy Southface Energy Institute goal of DOE’s Office of Building foundation system to drain rainwater and 6 yy y

moisture levels in the crawlspace. 7 yyy • Have an electrician stub-in a junction box in yyyy 404-872-3549 Technology, State and groundwater away from foundations. yyy

www.southface.org yy y For example, a crawlspace kept cool by the the attic. Community Programs (BTS). yyyy 9 8 yyyyyyy Airtight construction – sealing all air leaks yyy

yyyy U.S. Department of ground in the summer may have a temperature To accelerate the development • Test the bottom conditioned room for radon yyyyy yy between the conditioned space and the outside