Is 1″ enough?
We are constructing a home in far western SD (Climate Zone 6b)….There is a lot of bedrock here so we have opted to build a post frame (pole barn) style structure. From the outside in, our wall ‘sandwich’ will be
1-pole barn style tin wall covering
3- 1″ Tongue and Groove XPS foam
4-Half inch OSB attached to the girts
5- 7″ of cellulose filling the curtain walls
6- OSB on the shop walls and Drywall in the house.
The house is 27′ by 50′ and the shop is attached via a shared 27′ wall and is 36 by 48′ . for about 3000 sq foot under roof. The Black Hills of SD is Arizona dry (average of 17″ of precip per year with much of that being snow) and at times Canada cold but lots of sunshine. We have been through many recipes for a suitable wall, and have decided on this one for many reasons, but I’m worried about condensation on the OSB. My contractor/friend….said that if it were his, this is what he would do and assume that any moisture that may work its way into the wall will be able to dry “inward” without causing mold and moisture problems when things warm up. There are only 2 of us living in the house and we don’t have tons of plants or humidity producing habits. We plan to have an HRV.
Is the 1″ of foam enough? Or is it to big of a gamble to take? Not taking into consideration the post, girts and studs the will will be R31 with only R5 of that on the outside of the OSB. We really want an efficient home but marvel at the number of ways to ‘skin the cat’ and the difficulty in getting solid local knowledge on projects that are outside of ‘normal’ from area builders. Thank you.
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