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Community and Q&A

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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  1. STEPHEN SHEEHY | | #1

    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.

  2. JC72 | | #2

    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.

  3. GBA Editor
    Martin Holladay | | #3

    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.

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