Open-cell foam and airtightness
bradrh
| Posted in Green Products and Materials on
I’ve seen reports from the foam manufacturers touting how much better the foam is than fiberglass of the same R value. They’re essentially using the improved airtightness of the foam to show better performance compared to fiberglass with no air barrier. I can see it’s mostly BS. I am wondering if you have a proper air barrier if open cell foam can measurably increase the air tightness of the structure?
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Replies
With a well installed air barrier, I don't see how any foam in walls will make enough difference in air tightness to matter much. For our Pretty Good House, we took a lot of care with taping all seams. Without any foam, except canned foam around windows, we ended up at PH level of air tightness.
IMO their claim is probably valid when compared against a "typical" code-built house. IMO I think of tract homes as being "typical". Of course one can build better or build worse with or without spray foam.
Brad,
You don't need spray foam to achieve a very low rate of air leakage.
For more information on this issue, see It’s OK to Skimp On Insulation, Icynene Says.