Can spray foam be used as a WRB?
We are building a ~6000 square foot, 2 story above ground house with a 3000 sqft basement. The house is located in Montreal. The weather here can go from -25C (-13F) in the winter to very hot and humid 32C (90F) in the summer.
The proposed wall assembly from exterior to interior is as follows
5″ of stone
1″ air space
2″ closed cell spray foam
2×6 , 16″ OC filled with blown in cellulose dense pack or blown in fiberglass
Membrain by certainteed (Everyone freaks out at the thought of not having poly, so this was the compromise)
1) Besides the cost of spray foam , is there any reason NOT to use it a WRB? Every new house going up in Montreal is using closed cell 1″ on the outside of the house to air seal the structure.
2) Where can I find details how to flash the windows to the spray foam, as the windows will likely be installed before the foam is applied?
3) Most people on this site seem to prefer foam board instead of spray foam for the exterior – is this because of cost or some other reason?
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