Q: As part of the gut remodel of a 1940 house near Houston, Texas, we installed 3/4-inch rigid foam over the exterior wall sheathing, followed by vinyl siding. On the interior, we exposed the 2x4 studs and installed fiberglass batts. Then we installed 1/2-inch foil-faced rigid foam followed by drywall. In that climate, will these “foam sandwich” walls trap moisture?
After an air space gets to a certain size, it stops working as insulation and starts working as a convective loop.
Q: I’m considering installing wood siding over a rain screen, but I’m unsure whether the potential benefits justify the extra expense. What is the real benefit of an air space behind wood siding?
Q: What are the risks of installing cedar siding directly over foil-faced rigid foam insulation? Should tar paper or housewrap be used as well?
Q: Should you put a vapor barrier in an insulated ceiling or not? I build in a cold climate, where many longtime builders swear that you shouldn’t put a ceiling vapor barrier in. The reasons go something like, "Because you have to let the moisture escape," or "Because the house has to breathe out the top." What do the experts say?
