How FPSF Works

The frost protected shallow foundation technology recognizes the thermal interaction of building foundations with the ground. Heat input to the ground from buildings effectively raises the frost depth at the perimeter of the foundation. This effect and other conditions that regulate frost penetration into the ground are illustrated in Figure 2.

It is important to note that the frost line rises near a foundation if the building is heated. This effect is magnified when insulation is strategically placed around the foundation. The FPSF also works on an unheated building by conserving geothermal heat below the building. Unheated areas of homes such as garages may be constructed in this manner.

Figure 3 illustrates the heat exchange process in an FPSF, which results in a higher frost depth around the building. The insulation around the foundation perimeter conserves and redirects heat loss through the slab toward the soil below the foundation. Geothermal heat from the underlying ground also helps to raise the frost depth around the building.

FPSFs are most suitable for slab-on-grade homes on sites with moderate to low sloping grades. The method may, however, be used effectively with walk-out basements by insulating the foundation on the downhill side of the house, thus eliminating the need for a stepped footing. FPSFs are also useful for remodeling projects in part because they minimize site disturbance. In addition to residential, commercial, and agricultural buildings, the technology has been applied to highways, dams, underground utilities, railroads, and earth embankments.