Pretty Good House in Iowa
I am planning on building a “pretty good house” in the MidWest (Des Moines). After throwing around ideas on different wall structures (double stud, 2×6 with wet blown cellulose and rigid foam exterior), I’m curious what the prevailing thoughts are on building a 2×4 wall (16″ o.c.) with 1/2″ exterior plywood sheathing. 2″ rigid EPS would go exterior, with WRB being Tyvek, then furring strips and hardi-plank siding.
My questions truly relates to interior cavity insulation. I desire to fill the cavity with closed-cell spray foam for high R-vale and air sealing qualities. Many articles on this site state to refrain from having a vapor barrier (the closed cell, in this case) in the wall cavity. However, I note that most building examples include foil-faced polyiso instead of EPS. I ran across a comment stating spray foam would be acceptable in the cavity if rigid foam was not foil-faced or greater than 3″.
In this case would closed cell foam be acceptable as moisture would still be allowed to permeate the semi-permeable EPS with exterior vapor barrier?
Thank your for your responses.
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