Air Sealing

Energy experts look at your home as an “envelope” that seals the inside environment against the outside environment. Air will leak through a building envelope that is not well sealed. This leakage of air decreases the comfort of a residency by allowing moisture, cold drafts, and unwanted noise to enter and may lower indoor air quality by allowing in dust and airborne pollutants. In addition, air leakage accounts for between 25 percent and 40 percent of the energy used for heating and cooling in a typical residence. Getting a low cost home energy audit though the Switch It Provo program is a great way to learn how efficient your home is, and what improvements you could make to save money.

The amount of air leakage in a house depends on two factors. The first is the number and size of air leakage paths through the building envelope. As shown in the illustration below, these paths include joints between building materials, gaps around doors and windows, and penetrations for piping, wiring, and ducts.

The second factor is the difference in air pressure between the inside and outside. Pressure differences are caused by wind, indoor and outdoor temperature differences (stack effect), chimney and flue exhaust fans, equipment with exhaust fans (dryers, central vacuums) and ventilation fans (bath, kitchen). To prevent air leakage, it is important to seal the building envelope during construction prior to installation of the drywall. Once covered, many air leakage paths cannot be accessed and properly sealed. There are many products available for air sealing including caulks, foams, weatherstripping, gaskets, and door sweeps. Air sealing the building envelope is one of the most critical features of an energy efficient home. Look for the results of a “blower door” test (typically included with a Home Energy Rating) to ensure that your ENERGY STAR labeled home had all air leakage paths identified and sealed using appropriate materials. Once a house is tightly sealed, you will want to make sure there is adequate fresh air for ventilation. It is better to use controlled or active ventilation than to rely on air leakage. In many ENERGY STAR labeled homes, an active ventilation system is installed along with air sealing to ensure that fresh air is provided.

Learn more about air sealing your home with this free brochure, available as a PDF download from the U.S. Department of Energy.