The article “Retrofitting an Insulated Cold Roof” (11/08) does a good job of identifying the problems of condensation, heat loss, thermal breaks, and ice dams associated with this type of structure. I’ve used the same technique successfully for a couple of decades. However, times change, and I have discontinued this practice because it’s too slow, too expensive, and — most important — not the most effective method.
Today, I use a so-called “hot-roof” approach, applying high-density spray urethane foam from the inside. In addition to having a high R-value, this closed-cell foam is a moisture barrier. It’s also quite strong and adds rigidity to the roof structure. We haven’t had any problems with this approach. If the client insists on a “cold” roof, I...
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