Engineering and Construction

In  shallow frost-protected foundations, extruded polystyrene foam insulation boards can be used in cold climates to construct footings that lie above the normal frost line in the soil, resulting  in lower excavation costs. Continuous  layers of insulation board are placed  around the perimeter of the building  in such a way that heat fl owing into the  soil in winter from the interior of the  building maintains the soil beneath  the footings at a temperature above  freezing (Figure 2.68). Even beneath  unheated buildings, properly installed  thermal insulation can trap enough  geothermal heat around shallow foundations to prevent freezing.

Figure 2.68 A typical detail for a shallow frost- protected footing.