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Ignition rated Vapor open air barrier for wood foundation insulation

kevinbmn | Posted in Building Code Questions on

CZ6. Reinsulating treated wood crawl space foundation with flash& rockwool batts. Need thermal or ignition listed vapor-open membrane to contain batt fibers. AHJ excludes house wrap.
Insights appreciated.

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  1. Expert Member
    Akos | | #1

    OSB or plywood is about 1 or 2 perm and would also satisfy the ignition barrier requirements. You can also look at perforated radiant barrier.

    I would go for wood, takes abuse and you can use it for mounting shelving.

    P.S. It looks like there is a vapor barrier on the ceiling. That is a bad idea, this crawlspace needs to be sealed and conditioned not separated from the house.

    1. kevinbmn | | #2

      Thanks Akos, appreciate your time & consideration. Photo is unclear- no insul in floor joists, you may have seen rim area.
      Per respect for potential crawl space moisture and to limit mold food, the air (convection) barrier will be 1" unfaced mineral wool board. AHJ happy dance.
      Again, thank you

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