finding home air leaks

Many air leaks and drafts - like those under the doors or around the windows - are easy to notice and to feel. But there are also hidden or less noticeable openings that are very important sources of air leakage, often more important than more visible ones.

Attic, Basement and Crawlspaces

We should consider two different types of air leaks. Those located in the basement and crawlspaces or in the living space, involving cold air leaking into the house; and those located in the attic, where warm air leaks out...

This distinction is relevant because these different air leakage sources, located at different heights, drive the leakage flows (based on a natural law: warm air tends to rise and cool air to sink) and make Air Leaking Sources the attic the ideal place to stop many air paths and to solve some important leakage problems.

Small cracks and openings

Small openings and cracks in windows and doors and in plenty of other locations, should be fixed. Small gaps do not mean small energy losses...

See: Around Windows and Doors Air Sealing and Weatherstripping basics

Strategic places to Examine

The image (from Nrel.gov) shows the main and most common sources of air leakage, and the places to inspect.

Look at areas where different materials meet, like between wood and brick siding, and inspect...

- the basement, namely the air leaks associated with the sill plates and the rim joist.
- the tubs: see Sealing Bathtub Plumbing
- plumbing, wiring and electrical penetrations: see Caulking Electric
- attic: see Attic Air Leaks Sealing.
- penetrations in exterior walls: see Sealing Exterior Walls
- penetrations associated to the chimney and fireplaces: see: Chimney and Fireplace Caulking
- dropped ceilings
- windows and door openings: sealing air leaks around windows and doors

Construction flaws

In wood and steel frame homes, the most important air leaks are connected to construction flaws, namely those associated with the home's envelope (shown by the red-orange strong line surrounding the outer walls and the ceiling and floors in the smaller square in the image on top of this page).

In wood and steel frame homes the envelope needs a strong and continuous air-barrier (and also a vapor barrier/retarder, on freezing climates).

Without them, homes will not withstand the wind and other elements and will always be prone to air leakage, even if small gaps and openings associated to plumbing and electrical elements, or to windows and doors are well caulked and weatherstripped. The caulking and weatherstripping may stop some heat leaking out through the cracks, but structural flaws will forestall any attempt to get an airtight home and all strategies that can be based on such approach...

See: Air and vapor barriers and Airtight Homes