A house looses about 20% of it’s heat energy through the basement. So to build a high efficiencies house you have to start with the foundation. There are a number of ways to add insulation to the foundation.
- The outside: you can attach XPS panels on the out side walls. This didn’t make much sense to me, because I didn’t see how this would keep the concrete wall from trying to get to the ground temperature.
- The inside: putting insulation on the inside wall is better than the outside, but there are a number of choices. Sprayed open-cell foam. A good solution if your finishing the basement, I wasn’t . Another is attaching XPS to the inside wall, there are a couple of ways.
- Both sides: ICFs (Insulated Concrete Forms) are another choice. But I saw issues and looked for a better solution
- In the middle: Thermomass CIP system. Four inches of concrete, four inches of XPS (R-20) and four inches of concrete. The exterior wall adjusts to the ground temperature (apx. 55 degrees; the inside wall is a big mass that adjusts to the basement temperature (65 degrees); nd the four inches of XPF keeps them apart. Plus blocks moisture from migrating through the wall. That very large thermos mass of the inside concrete wall will hold the basement temperature.
So the Thermomass CIP solution made the most sense to me. I met with the local Thermomass rep, Gary Pascoe, and I was sold. A Deptford concrete company Manone Construction gave me a quote. The XPS panels have non-conducting stand-off the center them in the forms, concrete is poured on either side of the XPS. See photos of the insulation panels being installed.