There's too much badly installed insulation


Q. We’re colder than usual this winter and want to insulate, since our 1952 splanch probably has very little. Is there a way to insulate from the outside so we don’t damage our walls? Our attic isn’t completely accessible. One contractor told us about blowing insulation through small holes outside, but another said it won’t work. Can we do this?

A. The most important thing to remember about insulation is continuity. If insulation isn’t continuous and there’s no continuous vapor barrier right against the back side of your wall, the results are limited. I use the example, when doing walk-throughs with the contractor and owner, that openings in insulation the size of a quarter are like leaving a window open all winter long. Even though this is true, I return to each job after seeing gaps only to find multiple gaps where cold air can still blow freely through.

What humors me is when I hear a contractor or their employee say that “one small gap doesn’t make that much difference.” The same guy who said that last had just told the owner and me about his love of engine design and the cars he’s built. I wonder what one small hole in his gas tank, brake lines, engine block, or radiator would mean.

Is there really a difference between a great street machine and a building system? Your home could be insulated using blown-in fibers or foam, but you still may not have a continuous vapor barrier. This can lead to moisture buildup and mold. Another homeowner finally believed me when we opened his wall this winter and, just as I predicted, found a layer of ice on the back side of the sheetrock where the vapor barrier was never installed. He had been wondering why he felt a chill every time he sat in his favorite chair watching TV.

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