As custom home builders and remodelers, and owners of a spray-foam insulation business, we would like to commend Mr. Morshead on his article "Insulating Unvented Attics With Spray Foam" (3/07). He addressed several misconceptions that we deal with frequently in our work with architects, homeowners, and other builders.

There is one point, though, that needs clarification. Mr. Morshead discusses the fact that spray-foam insulation (both closed-cell and open-cell) is an extremely effective insulation and air barrier all in one. He writes that in his climate zone, "it's important to avoid excessive vapor diffusion," and he thinks "the best way to...

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