Vapor Barrier Inspection

Vapor barrier must be on the warm side of insulation (interior in cold climates, exterior in hot-humid climates). Continuous with sealed seams.

1. Verify vapor barrier is on the correct side (warm-in-winter side in heating climates)

2. Check for continuity — no gaps, holes, or tears

3. Verify seams are overlapped minimum 6" and taped

4. Check around penetrations (pipes, wires, boxes) — sealed with tape or caulk

5. In crawl spaces: verify 6-mil minimum poly covers entire ground surface

6. Under slabs: verify 10-mil minimum poly under entire slab area

7. Check that vapor barrier does not trap moisture in wrong location

8. Verify compatibility with insulation type (some insulation has built-in vapor barrier)

- Vapor barrier on wrong side (traps moisture in wall — rot and mold)

- Gaps or tears in barrier (moisture bypasses)

- Unsealed seams (moisture pathway)

- Penetrations not sealed

- Two vapor barriers (both sides) — traps moisture with no escape

- No vapor barrier in crawl space (moisture from soil enters house)

- Undersized for application (less than recommended mil thickness)