Im building a new home In Eastern Canada on a concrete slab with infloor heating. On my walls,is where im confused..My exterior walls will be built out of 2" x 6" with 1/2 " OSB ,,I was wanting to install 2" Sm Blue Styrofoam to the exterior and then put regular R-20 on the interior betweeen the studding then with vapor barrier. Is this a good system or am I missing something or is it a bad way!!Thanks for any responses..

You would end up with a double vapour barrier - not good. in your climate, the foam is better placed on the inside of the wall studs

Google up the building science site. Joe has several articles and white papers to detail all you need to understand.

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