Glossary

Glossary of Basement & Crawl Space Related Terms

Vapor retarder

A material which retards the transmission of water vapor. It is rated in perms ("permeance"). The smaller the perm rating, the better the water vapor resistance. A good vapor barrier should have a perm rating no greater than 1.0. NOTE: Vapor retarders are often mistakenly referred to as "vapor barriers."

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