Atlanta Inspection News! Consumer information: Frost-Protected Shallow Foundations (FPSF)/FindmeanInspector.com

Frost-Protected Shallow Foundations (FPSF) provides protection against frost damage without the need for excavating below the frost line. An FPSF has insulation placed strategically around the outside walls to direct heat loss from the building toward the foundation, and also to use the earth's natural geothermal energy.
Traditionally, foundations are protected from frost-heaving damage by placing the footing below the frost line.

Because FPSF are protected from freezing by thermal insulation, the bottoms of footings can be just 12 to 16 inches below grade. This reduces excavation costs, making it an economical alternative for protecting foundations against frost damage.

Insulated footings have been used as early as the 1930s by Frank Lloyd Wright in the Chicago area. There are now over one million homes in Norway, Sweden, and Finland with insulated shallow footings, recognized by their building codes as standard practice. It is estimated that there are over 5,000 buildings in the United States that have successfully used frost protected shallow foundations.

FPSFs are similar to conventional foundations except in insulation placement and footing depth. Bottoms of FPSF footings are placed about 12 to 16 inches below grade. FPSF have vertical insulation placed at the outside edge of the foundation extending from above grade to the bottom of the footing.

When required in colder climates, "wing" insulation extends outward horizontally from the footing. The colder the climate, the further the wing insulation is extended. Wing insulation is unnecessary in moderate climates.

The insulation used in FPSF is commonly rigid expanded or extruded polystyrene foam suitable for below grade application, and it must be in compliance with ASTM C 578 Standard. FPSF can be used for both heated and unheated portions of a building.