where to inspect air leaks

Many air leaks and drafts are easy to notice and to feel — like those under the doors or around the windows. But there are some hidden or less visible openings that are major sources of air leaking.

Attic, Basement and Crawlspaces

Openings and cracks in the basements, crawlspaces or in the living space are a source of air leaking into the house, while openings and cracks in the attic cause air leaking out of the house. These different air leakage locations, at different heights, cause leakage flows (since warm air tends to rise and cool air to fall).

Air Leaking SourcesThe attic is the ideal place to stop many air paths and to solve some important leakage problems.

See: Air Sealing Attic Penetrations

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. On the contrary.

See: Around Windows and Doors Air Sealing and Weatherstripping basics

Strategic places to Examine

The image shows the main and most common sources of air leakage, and the places to inspect.

Pay attention to:

- Plumbing penetrations: see Bath Tubs and Plumbing Penetrations Sealing.
- Wiring penetrations and electrical outlets and switches: see Air Sealing Electrical and Ventilation Openings
 - Chimney penetrations: see Fireplaces and Chimney Openings Sealing
- Fireplaces: dampers and openings (see Fireplaces and Chimney Openings Sealing).
- Walls: see missing sheathing and the tops of interior partition walls, where they intersect with the attic space;
- Foundation walls: see along their tops, where they encounter the sill plates and band joists.
- Floor cavities: namely if the floors extend beyond foundation walls.
- Attic: see Air Sealing Attic Penetrations (especially at access doors or built-in cabinets)
- Ceilings: see recessed lights and fans, even if the ceilings are insulated.
- Soffits (dropped ceilings): especially above bathtubs and cabinets. See: Air Sealing Soffits/Dropping Ceilings
- Ducts.

Construction flaws

The larger openings, responsible for most air leakage in common wood and steel frame homes, are related with construction flaws. The image is a good illustration of that very fact.

The image also stresses the importance of the building envelope (smaller square): the red-orange strong line that surrounds the outer walls and the ceiling and floors should involve a strong and continuous air-barrier, often missing in most buildings.

See also: