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XPS as interior insulation on a plank wall

Joseph Carry| Posted inEnergy Efficiency and Durabilityon

Architect’s plan calls for 2″ of “rigid” on interior side of a plank wall in Williamstown Ma (zone 5). Even if we tape the seams and air seal as best as possible, I am still concerned that moist air will get to the back of the planks and create moisture issues. The exterior is not being touched and I assume that there is no kind of air space between the planks and the siding. The space will be air conditioned in the summers and the 2″ of xps (class II vapor retarder) gives me some drying capacity to the inside. Is that enough? How risky is the assembly?

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Replies

  1. GBA Editor
    Martin Holladay||#1

    Joseph,
    The wall assembly is not risky. Everything on the exterior side of the XPS will dry to the exterior, and everything on the interior side of the XPS is already dry.

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