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..