Quote:
Originally Posted by willcastner
....Insulation to 1ft below grade is the most cost effective way of going about it.
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I think that depends on your definition of "most cost effective." Given that code requires footings to be 48" below grade, to ensure they're being below frost line, the soil can be quite chilly well below the first foot. Also, the concrete conducts heat readily (R nominally only 0.08/inch), so that inside heat absorbed by the concrete well below a short insulated area will be conducted upward to the above ground portion as well as directly outward to chilly ground. If it's deemed worthwhile to insulate part of the foundation wall, it's worth it to insulate all the way down to floor level. Aside from fuel savings, the dramatic improvement in comfort in the basement will be worth it. The floor above the basement ought to feel warmer above also, if uninsulated.