Keeping out the air
A new NRCA document provides design guidance for air retarders
In March, NRCA published Guidelines for Air Retarders in Roof Assemblies, a new document that provides an overview of the energy code's air barrier requirements, industry-conducted research and NRCA's recommendations for designers about air retarders in roof assemblies.
The term "air barrier" used in standards and energy codes (and by some in the construction industry) is somewhat of a misnomer. Many construction materials and assemblies have been tested and shown to have low air-permeance values but not zero permeance as the term "barrier" implies. Therefore, NRCA prefers and recommends the term "air retarder" except when specifically quoting code language. NRCA suggests others in the roofing industry also adopt this more accurate terminology. The construction industry has taken a similar stance when referring to vapor retarders, which are known to have low but not zero vapor permeance.
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