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 of a foundation to direct heat loss from the building toward the foundation, and also to use the earth's natural geothermal energy.
Frost-protected shallow foundations are similar to conventional foundations except for 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.
Insulation is only half the equation. The other half is drainage and moisture control. To keep surface water from soaking in around the foundation, all roof runoff must be directed away from the house. This means putting effective gutters all around the building and sloping the final grade away from the foundation at least 5 inches in the first 10 feet. (That's 1/2 inch per foot.) To protect the footing from subterranean water, it must bear on at least 4 inches of a non frost-susceptible material such as washed gravel or rock.
An FPSF can benefit both builder and homeowner. Shallow foundation ditches are easier to work around. The FPSF uses less concrete than a 4-foot deep stemwall. Smaller ditches require less backfill material and the backfill settles less over time. Since a shallow ditch is less likely to disturb root systems, you can leave shade trees closer to the house.
45.2 % of US homes have basements
26% enclosed crawlspaces
7.5% crawlspaces open to outside
31.3 concrete slabs
60 percent of U.S. homes have wet basements, and 38 percent run the risk of basement mold.
The American Society of Home Inspectors