A.Bruce Harley, technical director of Conservation Services Group in Westboro, Mass., and the author of Insulate and Weatherize, responds: Your building inspector was mistaken. The New York code calls for a "... vapor retarder having a maximum permeance rating of 1.0 perm. ... The vapor retarder shall be installed on the warm-in-winter side of the thermal insulation."
A lot of people call this a "vapor barrier" requirement, and believe polyethylene is required by the code, but kraft facing on batt insulation (which has a permeance of about 0.4) meets this code requirement all by itself.
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