Insulated Footings-- Thermal Break for Monolithic Domes
by David B. South
Cold from outside goes through the top of the footing, which is generally the top of the floor. The colder air cools off the inside surface of the floor and the area heated just above the floor of the dome.
Total heat loss is nothing to worry about at all. The problem is that it (the cold air) lowers the surface temperature of the floor. This can cause condensation. Condensation makes a place for mold to grow. In much of the United States this is not a problem if the internal humidity is kept low. However, in some areas, the drop in interior surface temperatures will promote mold growth.
The best way to insulate footings is to spray foam on the exterior of the footing after the dome is built. Spray polyurethane foam two to three inches up onto the exterior of the dome and down over the concrete at least eight to ten inches into the ground. The foam will have to be coated to be protected from sunshine.
The insulation does not need to be coated below dirt level. The foam stands up very well to back fill. There is not enough heat loss to ever consider paying for insulating the outside of the footing, but the perplexity of fighting the mold may make it feasible.
Insulating the foundation keeps the concrete on the inside the same temperature as the air inside and prevents condensation.
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