Instruments recorded ground, foundation, slab, indoor and outdoor temperatures. The insulated footings kept the soil above freezing even in the coldest weather. 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. The technology has even made some customers reconsider what they want in a house. In Eich's market, everyone used to build full basements, since the footing had to go down 4 feet anyway. Now he finds more people building larger homes on the main level and forgetting about the basement. The NAHB Research Center has prepared a Design Guide for Frost-Protected Shallow Foundations that includes the simplified guidelines referenced by CABO, as well as a more detailed design procedure.