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Concerns about spray foam off gassing

user-7631443 | Posted in General Questions on

Scenario: I am building a mobile home in climate zone 6. The exterior walls are 2×4″ with 1.5″ of air sealed XPS on the exterior, and 2-3″ of closed cell Polyurethane spray foam on the inside. I am reasonably sure that that spray foam was install correctly, and there is no perceivable foam smell in the house. Still, I am concerned that there may be some in-perceivable toxic off gassing and would like to isolate the foam from gas exchange with the interior air. I am considering installing Certainteed’s Membrain detailed as an air barrier before I install the drywall because as I understand it, it would not prohibit the wall from drying to the inside in the unlikely event that there is a leak or the dew point is ever reached on the interior of the foam. 

Question: Would that do anything to prohibit gas exchange with the foam, or would any gas still permeate through the Membrain into my tightly sealed home?

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  1. Expert Member
    BILL WICHERS | | #1

    If you don’t smell anything, you’re probably fine. That said, I don’t see a problem with membrain, but keep in mind that any volatile compounds (solvents) that you’re concerned about would probably be able to migrate through the membrain “barrier” so you wouldn’t really be accomplishing much.

    If you want to find something that WILL work, cole Palmer has a very good solvent compatibility listing on their website. Pick whatever chemical you’re concerned about (look up the A and B components for whichever spray foam you used), and then see what is listed as having “no effect”. With very thin membranes, you’re still likely to have some penetration though.


  2. user-7631443 | | #2

    Thank you for your response Bill. I will check that out.

  3. DavidfromPNW | | #3

    yeah, if you don't smell anything, you should be good. We had it done in our bonus room. I took all sorts of precautions. I had two zip walls and the entire downstairs sealed off. The next day, there was no smell. Nothing. Not a trace.

    This stuff, when done right, goes inert when cured. If it's not cured, you'll know it from the smell. Typically, curing issues are caused by spraying additional layers before the preceding layer cures. sounds like you don't have those issues. So, I wouldn't worry about it.

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