Do I need to keep an air gap between foil faced Polyiso Rigid Foam and 3/4” plywood?
Hello Everyone,
I live in coastal Washington near the Salish Sea
I have recently built a 15’x13’ She Shed with a 6/12 roof with 4×8 rafters that we were going to leave exposed on the inside.
I added a layer of Epilay Peel & Stik to the 3/4” CDX then added 2×6 @ 2’ OC framing to encapsulate 5” of XPS Polyiso taped all the seams filled any gaps with foam.
Enclosed it all with 5/8” CDX plywood to then seal it up with 9” Hydro gap from the 3/4” CDX, 2×6, 5/8” CDX, then laid another layer of Epilay Peel & Stik over the entire roof where I’ll install a metal roof.
I was going to add 1-1/2” foil faced RMAX to the inside of ceiling with 1-1/2” furring strips to attach drywall.
Will it be okay to add a spray foam along the perimeter then attach 2×2’s for the RMax Foam board to be directly attached to the ceiling?
Thank you.
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Replies
Niditobuilder,
Nice shed!
You don't need a gap, although it does no harm. If it were me though, I'd dispense with the interior rigid insulation and just drywall (or given how nice your roof is, fill in between the rafters with t&g or GBS plywood). In the PNW, with 5" of exterior XPS, the extra R-value will not be noticeable from either a comfort or economic standpoint.