Flash-and-batt for new construction in Climate Zone 5
We are building a house in Ohio, zone 5. 2×4 construction. Builder is recommending flash and batt insulation with 1/2″ of closed cell spray foam, R-13 batt, and 6 mil poly between the fiberglass and sheetrock.
From what I have read on here that seems like a fairly risky way to insulate the house. While it does appear to meet Ohio code for insulation using the “Ohio Homebuilder Association Alternative”, I’m not sure that’s the best approach.
I’m considering requesting 1″ of closed cell and a “smart” membrane like Certainteed Membrain, rather than changing the entirety of the insulation plan like adding exterior foam.
My thought is that, even though the R-13 batt would be further compressed, I’d still maintain the overall R value of the cavity with the increase in foam while reducing my risk for moisture related issues by keeping the inside face of the foam above the dew point. I believe 1″ of foam is sufficient to keep the dew point high enough in Ohio, based on what I’ve read. Would this work as I’m expecting or would it cause additional issues I’m not thinking of?
I’m about a week and half from having to make a decision so any help would be greatly appreciated! First time we’ve built a house and we’re trying to get it right.
Thanks in advance.
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