Gentlemen;
I want to insulate my basement, inside, typical concrete formed walls. 85 inches from sill to floor. Two of the walls are backfilled to about 70 inches. I want to insulate the inside with 2″ foam.
I need to let some heat out to prevent the earth backfill from freezing and buckling the walls from the outside. My thought was to insulate the top four feet with the EPS foam with a 6mill plastic down to the floor, stud wall covering the EPS/plastic.
With no insulation on the bottom section of wall it would let some heat out to keep the earth from freezing.
What am I screwing up? I am all ears for a better method.
Replies
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Here and our bldg frost depth is 40 inches, backfilling with stone and proper drainage is the preferred method to prevent buckling walls.
One thing we do see is on a dry summer/fall, the clay shrinking back and then in the late fall/winter, water filling up the void between earth backfill and the foundation. Then, freezing puts pressure on the foundation and can really cause problems.
If your backfill and drainage were done properly, and the crete has the right rebar lacement and mix, there is no need to worry about this idea of letting some heat out.
The way that frost exerts pressure on the wall is if it retains a good deal of moisture. Good backfill material allows water to rain thru to the perimeter drains and away from the foundation. Without that moisture, the soil does not heave when it gets cold