In the May Q&A, a reader from North Carolina questions whether a polyethylene vapor retarder is required on the interior side of an insulated wall. The North Carolina 2006 Residential Building Code, Section R318.1, requires moisture vapor retarders in only five of the state’s 100 counties: Alleghany, Avery, Mitchell, Watauga, and Yancey. These five counties are in climate zone 2 — mountain elevations that are prone to colder temperatures.

Dan Tingen Chairman, N.C. Building Code Council Raleigh, N.C.

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