XPS Between Studs and Plywood Sheathing
I live in zone 4C and am preparing for a build next spring. One wall assembly that I don’t hear about is putting the rigid foam (XPS) between the plywood sheathing and the studs, instead of on the outside. Also doing a house wrap, rain screen, and siding…probably Hardie, maybe metal. As far as the green concern on XPS, the blower agents have been radically brought down in recent years, and that trend will continue. So, the advantage of having the foam on the inside, is thermal break of course, but there is also a seismic advantage! In testing this wall style, some of the building scene folks in Portland have concluded it improves seismic resilience by 400%…which sounds too good to be true, but that’s the real number. See:
Thermal Break Shear Wall at Sage Green and Plywood over Foam Martha Wall @ BuildingInnovations.org (Building Envelope category)
Living in the PNW, seismic strength and fitting in with common building assembly style, as Martha says, is a win/win.
I am a huge fan of so many of the conversations on this site…any thoughts?
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