During the late 1970s and early 1980s, I supervised residential insulation projects in central Vermont while working with a couple of regional agencies. Despite our best efforts, we had many problems with blown-in insulation, which was becoming popular at the time.On one occasion, I was doing the final inspection on a newly insulated Victorian - a three-story balloon-framed monster - when I realized I could look down from the attic into empty stud cavities in the exterior walls. Desperate to know how bad the situation really was, we called in a guy with an infrared scanner. The equipment available in...

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