Debating cavity insulation
I’m starting a house build in New Brunswick (Climate Zone 6A). My planned assembly has 3″ of EPS foam on the exterior (3″ Silverboard XS). I’ve already bought the Silverboard, so there’s no going back now.
To please the local code officials, I will be installing Membrain on the interior.
I’m debating installing open cell spray foam in the cavity for improved air sealing. However, local spray foam contractors felt I should install closed cell even with the 3″ of exterior foam so that I wouldn’t need the Membrain. I have concerns about a ‘foam sandwich’ if I installed closed cell sprayfoam with 3″ of exterior EPS, as my sheathing would have no way to dry. Is my concern with closed cell valid?
Would open cell foam in my cavity with 3″ of EPS on the exterior be a safe wall, even with the Membrain on the inside, or should I stick with a fluffy insulation, like blown fiberglass?
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