Field glossary

Vapor barrier

A retarder on the warm, pool side of walls, roof, and floor that stops moist air from condensing inside the assembly

Used across 3 Anvilfield field guides, most in HVAC.

Also defined as

The facing or jacket that keeps room moisture from reaching the cold duct metal, sealed at every seam
The continuous warm-side layer that stops vapor from reaching a cold surface where it would freeze.

Where this shows up