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Weatherization Assistance Program

Air Sealing

Photo of a worker applying sealer around electrical outlet in a wall.

A weatherization service provider applies a seal around an electrical outlet in a home he is weatherizing in northern Alabama.
Credit: Community Action and Community Development Agency of Northern Alabama

Air sealing reduces the flow of outside air into the house and is the common energy efficiency measure under weatherization.

The purpose of air sealing is to reduce the leakage of cold outside air into the house in winter or hot outside air into the house in the summer. Typically, weatherization work crews add caulking and weatherstripping around windows and doors to reduce drafts. Old, drafty homes are not only uncomfortable, but they are also very costly to heat and cool. See stack-effect infiltration in a two-story house to see how this process works.

DOE researchers have discovered, however, that tests using blower doors reveal more precisely the holes in the building envelope where outside air infiltrates into the house. Such holes often occur near the base of the building and near the roof and are unobservable to the naked eye. This DOE research has been largely responsible for the widespread adoption of blower doors as a key diagnostic tool in home energy building science.

Information for Homeowners Receiving Weatherization Services

The following documents provide some background on what weatherization crews are trying to accomplish during air sealing:

  • Home Sealing—Do It Yourself

    ENERGY STAR® publishes this short Web page for homeowners about how to reduce air infiltration into the home and save energy.

Information for Weatherization Service Providers and Energy Professionals

DOE publishes several fact sheets and a wealth of research on air sealing and the related issue of providing fresh air for ventilation:

  • Spot Ventilation: Source Control to Improve Indoor Air Quality

    (PDF 255 KB) Download Adobe Reader.
    DOE's Building Technologies Program publishes this fact sheet as part of its "Building Technologies" series; 4 pp.; December 2002.

  • Whole-House Ventilation Systems: Improved Control of Air Quality

    (PDF 399 KB) Download Adobe Reader.
    DOE's Building Technologies Program publishes this fact sheet as part of its "Building Technology" series; 6 pp.; December 2002.