Common air leak locations
Critical itemAir leaks account for 25-40% of heating/cooling costs. Seal all penetrations, gaps at rim joist, attic bypasses, and around windows and doors.
Standard
Air leaks account for 25-40% of heating/cooling costs. Seal all penetrations, gaps at rim joist, attic bypasses, and around windows and doors.
How to check
1. Check rim joist area in basement — should be sealed with spray foam or caulk
2. Check attic: look for bypasses around chimneys, plumbing vents, wiring, recessed lights
3. Check weatherstripping on all exterior doors — should seal tightly
4. Check caulking around windows — interior and exterior
5. Check electrical outlets and switches on exterior walls — feel for drafts
6. Inspect plumbing and electrical penetrations through exterior walls
7. Check attic access/hatch — should be insulated and weatherstripped
8. Seal around dryer vent, exhaust fan, and range hood penetrations
9. If available: request blower door test results (under 3 ACH50 is good)
Common problems
- Unsealed rim joist (biggest hidden air leak in most homes)
- Attic bypasses around chimneys and plumbing (warm air escapes to attic)
- Poor door weatherstripping (visible daylight around doors)
- Unsealed penetrations through exterior walls
- Attic hatch not sealed (equivalent of leaving a window open)
- Recessed lights without IC/AT rating (air leaks into attic)
- No blower door test to verify sealing effectiveness