Exterior foundation insulation and basement windows
New build, CZ 6A (Ottawa ON)
I would like to insulate the above-grade portion of my basement walls to at least a foot below grade, in addition to the code required interior insulation (R20 with no thermal bridging), most likely a layer of EPS foam board with a framed 2×4 wall and cellulose or fiberglass.
Assuming an 8″ thick foundation wall, how do you suggest approaching the insulation details around basement windows? Can the exterior insulation wrap inside the rough opening and connect with the interior insulation? If so, how is the window installed onto the insulation?
My concern is, leaving the foundation wall exposed around the outside of the window will effectively bypass the exterior foundation insulation for quite a ways around the window opening, as well as perhaps offer a path for water to get behind the exterior insulation.