A good foam sandwich?
I’m In the very early planning stages of a new home construction near Green Bay Wi (climate zone 6). The house will have a full basement.
I would like this house to be extremely well insulated, but all fairly conventional to build. I want this house to be retirement friendly, so looking to use exterior cladding that will require minimal future maintenance. One problem with using brick or stone siding is the brick ledge requires a thick, and expensive foundation wall. This is compounded when using thick exterior foam, and also makes brick the attachment more difficult. I thought of a wall concept that I haven’t seen before, which seems very easy to build.
wall assembly from outside in.
1. Brick or stone exterior
3. 2×4 structural wood stud wall 16” or 24” oc framing insulated with rock wool batts (no exterior sheathing)
4. 1/2” plywood “interior sheathing” with Zip taped seams detailed as primary air barrier
5. 4” of salvaged EPS foam taped or spray foam at seams (complete thermal break foam sandwich) (secondary air barrier)
6. 2×4 non structural wood stud wall framed 16” oc insulated with BIBs or wet blown cellulose
7. 1/2” gypsum board
Total wall thickness 12”.
-easy to build
-east to air seal
-complete thermal break
-quick to dry in, can air seal
-bulk water leaks in WRB could drain through rock wool
-easy to integrate with brick ledge and easy to attach masonry
-bugs or rodents could make it into rock wool?
-fairly thick to the interior, which would eat up some finished space
-shear strength not as strong?
Thoughts on overall wall? Sheathing wouldn’t be as warm as an external foam wall, but would the rock wool help?
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