Rigid foam minimum for 2×8 stud wall
Zone 5 – helping with a wall design. They are using 2x8s for studs to fit in R-30 mineral wool. I am suggesting rigid foam, EPS or XPS, but I have only read that 2×6 wall needs R-7.5 But, this is a 2×8 wall, and I don’t think R30 is traditional. So Will 2″ of XPS or EPS be sufficient? Don’t really want to have to go with two sheets and achieve 2.5″ of rigid foam if 2″ is sufficient with R30 mineral wool on the interior.
Is there any way to make 2″ work? Such as a smart membrane installed before drywall?
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