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干燥胶合板墙背后的潜力

Ryan Lewis - Zone 4A| Posted inGeneral Questionson

I’m opening some walls to install some insulation and some new heat pipes and I discovered that some bays in one room have 3/4” plywood directly behind drywall.

this seems suboptimal for interior drying, is it?

certainly for insulating..

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Replies

  1. Patrick OSullivan||#1

    > this seems suboptimal for interior drying, is it?

    Perhaps not that big of a deal. From an APA website (https://www.performancepanels.com/permeability): "For example, at 50% humidity the water vapor permeance of plywood is approximately 1 perm but the water vapor permeance may be increased by a factor of 10 when the humidity is increased to 90%." So maybe plywood 'does the right thing' when it needs to.

    > certainly for insulating..

    This point I don't understand. It's certainly not worse than drywall directly on the studs. Most conservative estimates of the R value of wood I've seen are around R-1/inch. In reality, this is obviously species dependent. It's not great but it's also not 0. By definition, it's therefore not worse than drywall alone.

  2. Expert Member
    Akos||#2

    Be careful with plywood walls, these could be shear walls, removing them will compromise the structure.

  3. Expert Member
    Kohta Ueno||#3

    I've dealt with some projects where the client requested continuous plywood behind the interior gypsum board finish, so that they could hang their artwork anywhere they wanted. Taking a look at plywood properties (see "The Magic of Plywood and the Modern Residential Wall" in the link below), it actually behaves somewhat close to a smart vapor retarder... relatively vapor closed at low RH, and very open at high RHs. So on the scale of things, not an issue.

    BSI-038: Mind the Gap, Eh!
    https://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh

  4. Ryan Lewis - Zone 4A||#4

    Ok that’s great, thanks everyone.

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