What exterior foam insulation on retrofit?
My dilemma in my retrofit is this: many years ago, before I was better informed as to where the vapor forms in my exterior walls in my home in Maine, I installed 1 inch of ISO over my dense-packed cellulose walls. I have now been educated to the dramatic thermal inefficiencies in walls stemming from bridging.
I am planning on retrofitting the exterior. I keep coming back to the same prescription: never use two vapor retarders on opposite sides of the walls. The one-inch iso is .03 I believe, and I have been eyeing 2-inch XPS on the exterior, giving an R-10 bump with a perm of .55.
I have also read that there can be an applicable rule of, five times more perm on the exterior than the interior. Will this hold true for a home in Maine?
Posted Feb 14, 2013 4:27 PM ET
Edited Feb 15, 2013 8:05 AM ET
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