Wall assembly strategy using Dow structural insulated sheathing
I live in MD, climate zone 4 and want to use the DOW SIS 1" with blown in high density insulation. I can use a 2x4 wall to achieve R20 in the wall. Please help me settle a disagreement with my architect. He is concerned with using the DOW SIS product because the product has such a low perm rating that it will act as a vapor barrier and the wall won't dry to the exterior. He has traditionally used an interior poly so the wall needs to dry to the exterior. I say leave off the interior poly so the wall dries to interior.
He doesn't believe that the wall will dry to the interior, particularly in the bathroom where you have tile. He is concerned that it will produce mold and will be liable for damages. I say I will sign something to remove him from liability.
I have spoke with the product manufacture (no longer DOW) for guidance but not sure how helpful they will be.
Separately, can I use a 2x6 wall for added R value? Concerned that with 1" sheathing, the dew point will remain in the wall. From reading posts by Martin, in my climate zone this should not be a problem.
Posted Jan 19, 2013 10:39 AM ET
Edited Jan 19, 2013 11:57 AM ET
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