Will this keep moisture off my fiberglass batts?
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Neilc1
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Will this 1″ XPS board keep moisture off my fiberglass batts in the stud bays in my basement?
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Should be more informative,I got enough of this 1" Xps roofing board for free and have put it up against all my poured concrete walls,now I am ready to stud the walls and then Sheetrock,I know it's not the best but the price was right and I talked with Owens Corning and they feel I should be ok with it but wanted a other opinion,I actually got enough to double it up on some walls to make 2",so minimal 1" plus 4" of batting should give me a descent r value
Neil,
I think you forgot to tell us your location or climate zone.
Massachusetts zone 5 I believe
Tape the seams and can-foam the edges, and yes, R5 XPS is sufficient for dew point control on the above-grade portion for up to 2x4/R15 without interior vapor retarders in zone 5. The ~1-1.5 perm vapor retardency is a sufficient vapor retarder against ground moisture for the below grade portion, assuming it's a reasonably dry foundation wall (no history of bulk water leakage of that wall.)
And, 1" XPS + 2x4/R13 would meet the IRC code-min performance equivalent to R10 continuous insulation for basements in zone 5.
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm
In MA there are multiple vendors of reclaimed roofing foam. It may be cheaper to go with 2-2.5" everywhere than to use batts in the studwalls. Nationwide Foam in Framingham and Green Insulation Group in Worcester are probably the biggest, but there are others.