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Community and Q&A

Condensation on inside surface of sheathing

kpklein | Posted in Energy Efficiency and Durability on

I’m planning a house in climate zone 3, inland Southern California (De Luz near Temecula), and respectfully ask for a definitive answer to the question of whether or not the problem of condensation forming on the interior side of the sheathing (Plan A layers will be plywood sheathing, Tyvek Commercial D, two layers of Super JumboTex 60, then conventional three coat stucco) is something I need to worry about. Walls will be 2×6 with conventional fiberglass batts or maybe Rockwool. A Plan B possibility is to substitute Zip-R for the plywood and Tyvek layer. Should I stick with Plan A? Zip is not common here (and neither is Rockwool). Thank you…

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  1. GBA Editor
    Martin Holladay | | #1

    Condensation on the interior side of wall sheathing happens during cold weather, and southern California doesn't have any cold weather. So don't worry.

    That said, the main reason (other than cold weather) for the problem is air leakage. So plan for airtight walls, and you'll be good.

    1. kpklein | | #2

      Thank you Martin!

    2. Expert Member
      Dana Dorsett | | #3

      >"Condensation on the interior side of wall sheathing happens during cold weather..."

      Not really, unless it's been so cold for so long that the sheathing is fully saturated.

      The cold sheathing will take up considerable moisture as adsorb LONG before condensation will form on the surface of the sheathing.

      This is definitely NOT something to be concerned about in SoCal, until perhaps hell begins to freeze over(?) :-)

      1. GBA Editor
        Martin Holladay | | #4

        Shorthand, as I'm sure you know. Kurt asked about condensation, so I used Kurt's term for clarity.

        So you're right, of course -- we're talking about moisture accumulation, not condensation. As I noted in one of my articles from 2010, "Thin [exterior rigid] foam is dangerous, because it reduces the ability of the wall to dry to the exterior without warming the sheathing enough to prevent moisture accumulation (a phenomenon that is usually but incorrectly called 'condensation')."

      2. kpklein | | #5

        Thank you Dana

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