Exterior insulation in MN attic
I have two walls of a bedroom that are adjacent to my garage attic. I am hoping to beef up the insulation on the outside of the wall in the attic. I am worried about a few things – cost, installation, and moisture issues.
I have a 2x6wall , FG batts, with vapor barrier on the inside – so wouldn’t be in for something that is too vapor resistive on the outside (i think?). Currently the wall on the exterior is sheathed with vapor permeable fiber sheathing (Brace-rite,28perms). I was under the impression that xps or polyiso wouldn’t be advisable…
what about at only 1″ thickness on the xps? seems to me that through reading about basement insulation – at 1.5″-2″ is when the perms gets to near 1..?
Otherwise would EPS be do able in the 1-2″ range (3 perms at 1″)? EPS has a nice cost/R
Thinking rigid board would be easiest to install. Can’t find a easy source for mineral wool board… and strapping/attaching fiberglass batts (cheap) doesn’t seem like it would be very effective.
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