Air leaks can raise your home energy bills by as much as 30 percent. Having a “leaky” home causes an exchange of warm and cool air through openings in the building. That means much of your heated or air-conditioned air is being wasted. Air sealing creates a barrier at openings to prevent or minimize air movement, saving energy and increasing comfort. Even if you live in a well-insulated new building, your home may be adequately sealed. Homeowners can correct problems with air leakage in the following ways:

Easy-to-Find Air Leaks

Fix these obvious sources of air leakage yourself, or hire a handyman to take care of them for you.

1. Inspect under any sinks on exterior walls to see whether waste or water pipes are going through holes in the wall much larger than the pipe. If so, use spray foam insulation to seal these spaces.

2. Look for gaps in the framing around windows and doors. Remove moldings and fill gaps with spray foam insulation specifically for doors and windows, which won't warp framing as it expands. After replacing trim, apply acrylic-latex caulk, preferably one that’s paintable, around door and window frames. Use non-glossy clear caulk that won’t showcase mistakes, or buy an inexpensive caulking tool to create a neat profile and minimize stretching and cracking. If necessary, install new weatherstripping, too.  

3. Check for cracks along basement floors or walls, as well as gaps along the sill plate and foundation and at the top and bottom of rim joists. (Rim joists are located at the ends of the building, the final joist that supports the floor/ceiling.) For cracks less than ¼” wide, use acrylic latex caulk to seal. For larger gaps, use spray foam insulation according to manufacturer’s instructions.

4. Insulate outlets and switches on interior and exterior walls. Remove receptacle plates and apply foam sealers to eliminate the flow of air. If there are unsealed gaps around the outlet boxes, use spray foam insulation to fill open areas (do not spray the interior of the box).

Leakage Requiring In-Depth Investigation

Other areas of the home require more in-depth investigation to determine whether they have been properly sealed. It’s safer to hire a professional weatherization contractor if you have the following conditions: Recessed lights (these must be sealed in a specialized manner to prevent a fire hazard), vents exhausting into attic spaces, mold (especially in basements or attics), wet or excessively damp conditions in either the attic or basement, or old wiring.  

5. Check attic insulation for dirt; check exterior for ice dams. Attics and basements are the largest source of air leaks due to “chimney effect,” when cool air is drawn in through the basement and hot air generated by the furnace rises up and into the attic. Pressure is created at the highest and lowest points, causing a drafty home. Dirt on batt insulation in your home is a sure sign of air movement. Finished attics are not immune to air leaks, which can occur in openings in sidewalls and kneewalls.
NOTE:  Extra precautions must be taken in older homes with vermiculite insulation (gray, pea-sized granules) that may contain asbestos. In this case, do not disturb any insulation before consulting a professional.  

Another costly and serious symptom of poor air sealing is ice dams. Ice dams form when there is a temperature difference between the higher parts of the roof and the eaves. In winter, snow melts on the upper portion of the roof and flows down to the edges, re-freezing as temperatures drop, especially at night. This forms a build-up of ice as the freeze-thaw cycle repeats itself. Eliminating the flow of warm air into the attic space is the only permanent solution. Left uncorrected, ice dams will damage a roof and eventually cause water leaks into the home.  

6. Seal supply ducts. They are one of the greatest sources of energy loss as well, mainly due to significant temperature differences between the leaky supply air and the indoor environment, impacting heating and cooling efficiency.  

Updated March 18, 2018.