by Denny » Thu 17 Aug 2006, 23:16:37
It is immaterial whether the concrete is insulated on the outside or the inside from the standpint of physics. But, practically, its much easier to insulate the inside, even during construction, as the compressive forces of the soil mess up the air pockets which insulation uses to be effective.
Most homes built in the last thirty years or so, at least around here, have insulation starting 0.7 m. below grade in the basement, up to the main floor joists. And, with a vapor barrier to preclude condensate causing mold and mildew. (At least that is the objective, but I found my basement vapor barrier was not so good when I renovated it and I replaced the barrier and the old insulation too, and the studding anchored to the basement wall.)
I am not sure if its a good thing to insulate all the way down the wall, at least its not called for in building standards, but am not sure why. My experience is that the lower part of the basement wall does not seem to feel so cold even in mid-winter.