Insulation on 2x4 wall


Old 06-12-07, 04:09 PM
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Join Date: Apr 2007
Posts: 2
Insulation on 2x4 wall

I am redoing a house and taking off the siding. Underneath the siding is 1" of thermo ply rigid foam board and then the 2x4 studs. I would like to put 1/2 osb on top the rigid foam (for better shear bracing) board and then another 1 inch of rigid insulation over the osb, then a vapor barrier over the top of that. I would rather not take off the 1 inch rigid insulation next to the outside framing. Has any body tried this sandwich combo? I am thinking that this will cause condensation on the osb and would turn it to mush in a few years. Anybody got any thoughts on this?
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Old 06-12-07, 04:45 PM
Join Date: Mar 2005
Location: USA
Posts: 6,126
Insulation on 2x4 wall

Your vapor barrier belongs on the inside or warm side of the insulation, not on the exterior of the wall.

You should have either a house wrap (roll or spray) or a building paper on the outside prior to adding the siding or brick veneer.

The OSB will not add that much shear resistance over the foam (long nails) compared to direct attachment to the studs. You will have to do a real job of nailing to get it effective.


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