PERM RATING

The permeance of a material. Breather materials have relatively high perm ratings, vapor retarders have relatively low perm ratings, vapor barriers have essentially zero (negligible) perm ratings.


See also: VAPOR RETARDER

SPFA believes that the path to a healthful, safe, high-quality and performing SPF installation travels through the hands of a knowledgeable, trained, experienced, and ideally PCP-certified professional contractor.