A.Corresponding editor Paul Fisette responds: In a heating climate, you should include a vapor barrier on the warm, wide side of the insulation, even if the home has plastic housewrap.

Housewraps and poly vapor barriers are different materials that perform different functions in a wall. Housewraps are installed on the outside surface of the exterior wall sheathing. Housewrap manufacturers often tout them as a barrier to air leakage. While there have been some reports that housewraps do help minimize air leakage, the...

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