How to Find and Fix Air Leaks in Your Home

In an older home, air sealing can reduce your heating costs in winter and keep you comfortable by keeping the warm air in and the cold air out! It can be as simple as a few 'do-it-yourself' upgrades, or more extensive work performed by contractors during an energy efficiency retrofit. Air leaks are no fun. Here, we provide some tips on finding and dealing with air leakage from the excellent Natural Resources Canada publication 'Keeping the Heat In.'

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By Rise

Apr 11, 2025 · 3 min read

Common Sources of Air Leaks in Your Home

Attic hatch
Ceiling penetrations into attic, such as ceiling light fixtures
Door
Exhaust vent
Mail slot
Foundation sill and header
Service entry
Floor drain
Foundation crack
Electrical outlet
Window
Chimney

Finding Air Leaks With Low-Cost Air Leak Detection Methods

You can detect air leakage yourself on a cold and windy day using incense sticks. Think of this as your first step in the air leakage testing journey. Just light a couple of incense sticks and walk around with them. Then, hold them near places you think might be drafty, like electrical outlets, window frames, doors, and attic hatches. Air leaks will cause the smoke to dissipate and the tips of the incense to glow. The same technique can be used during a home energy assessment, while a 'blower door test' is being conducted. In this test, an energy advisor uses a large fan to blow air out of the house so that outdoor air will enter air leakage locations.

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Air Sealing Materials for Your House

Materials for air sealing can be purchased at any local building supply store. These supplies include caulking for air sealing trim and joints, spray foam for more significant gaps behind door and window trim, foam gaskets for electrical outlets, and weather-stripping for doors, windows, and hatches. With a little preparation and knowledge, these can be 'do-it-yourself' projects. If not, there are many renovation contractors experienced at these tasks.

When doing a renovation that involves removing the wallboards, you can decrease your home's air leakage by installing or repairing air and vapor barriers in exterior walls. These barriers are often made of polyethylene sheets or house wrap to reduce airflow into the wall. Air and vapor barriers should be as continuous as possible and sealed with acoustical sealant and construction tape.

Don't Make Your House Too Airtight! Homes Needs Ventilation

It is necessary to be aware that as you make your house more airtight, condensation and moisture problems can arise. If your home doesn't have a ventilation system, you may need to limit the amount of air sealing you do. Since the house relies on natural ventilation, it is possible to make it too airtight. Signs that a home is too airtight include mold or condensation on your ceilings, outer walls, and windows.

This becomes particularly important if you have fuel-burning combustion devices such as gas ranges or furnaces. The dangerous exhaust gases may enter your house rather than exit through the flue. In these situations, it is essential to install a carbon monoxide detector to alert you if gas levels reach dangerous concentrations.

Most older homes suffer from cold air leakage, and normal air-sealing activities, as described above, will help improve the situation without making them too airtight. However, if you are planning a significant, ambitious, and comprehensive air-sealing renovation, getting a home energy audit with a Certified Energy Advisor is recommended. The advisor will conduct blower-door testing before and after the renovation to measure how airtight the building is and will advise on a ventilation strategy. As a rule of thumb, if the measured airtightness is less than three air changes per hour, you might need to install a heat-recovery ventilation system.

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