Frost-Protected Shallow Foundation
A frost-protected shallow foundation (FPSF) is a slab-on-grade or stem-wall foundation that uses horizontal "wing" insulation extending outward from the building edge to push the frost line down and outward instead of digging deep. By protecting the soil under and around the foundation from freezing, an FPSF can replace a deep frost-depth footing with a shallow one — saving concrete, excavation, and embodied carbon. FPSFs are common in Scandinavian builds and increasingly popular in North American cold-climate Passive House projects.