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The Difference Between Permeance and Permeability

Green Building

The Difference Between Permeance and Permeability

Originally published on April 18, 2016 by BNP Media through the Architectural Roofing & Waterproofing Blog. All information presented in imperial (I-P) units. Water vapor transmission is a rather confusing issue. The difference in vapor pressure between two sides of a building envelope assembly is the driving force behind vapor transmission. (Although by comparison, gaps in the envelope account for vastly greater amounts moisture migration due to vapor-laden air infiltration.) Vapor = Latent Heat; Air Temperature = Sensible Heat The….

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