Warmed or air-conditioned air mixes with outside air through gaps in your home’s thermal envelope—exterior walls, windows, doors, the roof, and floors. Such air leaks can waste large amounts of energy.
Most experts agree that caulking and weather stripping any gaps will pay for itself within one year in energy savings. Caulking and weather stripping will also alleviate drafts and help your home feel warmer when it’s cold outside. However, these two weatherization techniques can’t replace the need for proper insulation throughout your home.
Because caulk and weatherstripping limit indoor-outdoor air circulation, you should assess your indoor air quality before you
apply them. Some homes contain dust, mold, carbon dioxide, and other indoor air contaminants. Sealing air leaks in these homes, without proper ventilation, can also seal in their indoor air pollutants. There-fore, any plan to tighten the thermal envelope of a home should be accompanied by a look at your home’s ventilation needs.
This series sheet does not cover indoor air quality assessment and ventilation.
You may already know where some air leakage occurs in your home, such as an under-the-door draft that makes you want to put on socks. But you’ll probably need to search to find the less obvious gaps.
Look at areas where different materials meet, like between brick and wood siding, between foundation and walls, and between the chimney and siding. Also inspect around the following for any cracks and gaps that could cause air leaks:
Depressurize your home to help detect leaks. On a cool, very windy day, turn off the furnace. Shut all windows and doors. Turn on all fans that blow air outside, such as bathroom fans or stove vents. Then light an incense stick and pass it around the edges of common leak sites. Wherever the smoke is sucked out of or blown into the room, there’s a draft. Or just turn on all your exhaust fans (don’t need to turn off the furnace) and try one of these methods:
For a more thorough and accurate measurement of air leakage, you can hire a technician to conduct a blower door test in your home. Blower doors are variable-speed fans with a frame and shroud that allows them to fit inside a variety of door frames. Pressure gauges determine airflow through the fan, as well as fan-induced pressure. The leakier a house, the more airflow required to induce a pressure difference. When used as a diagnostic tool, a blower door can also reveal the location of many leaks.