As a custom home builder in Alaska, I’ve seen how poorly conventional wall assemblies perform in extremely cold weather. In Fairbanks, Alaska, where I work, a “typical” wood-frame wall might consist of 2x6 framing with R-19 batt insulation, OSB sheathing, and housewrap on the outside, and a 6-mil poly vapor retarder on the inside.
There are two problems with this construction. The first is that the wall framing members act as heat conductors between the warm interior and the cold outside. There’s nothing to stop the transfer of heat. But the bigger issue is air leakage. It’s nearly impossible to do a perfect job sealing all the penetrations in the vapor retarder, and just...
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