Frost-Protected Shallow Foundations Save Time, Money

advice, guidance, support, results

“I wouldn’t do a foundation any other way.”

— Judy Fosdick



Nearly a decade ago, an interest in sustainable design and energy efficiency led Judy Fosdick to experiment with insulated foundation techniques. What she discovered changed her business.

She could save money, she discovered, and complete foundations more quickly with a little innovation. A frost protected shallow foundation (FPSF) could protect a concrete slab from frost heave without the need for excavating below the frost line. All of a sudden, the time, labor and equipment invested in deeper excavation disappeared. But for Fosdick–who now installs FPSFs in every home she builds–these advantages were only the beginning.

[IMAGE: Extruded polystyrene insulation being placed at the base of the horizontal wall surface.] “For me, it’s about comfort. The beauty of FPSFs is that they let you take advantage of the heat in the building slab and the surrounding soil to raise the frost depth. With a correctly insulated slab and footings, you don’t lose that heat. You’ve got a warmer home. And you don’t have to worry about frost heave.”

“The energy performance of our very first project with FPSFs was independently monitored by the National Renewable Energy Laboratory (NREL). The results showed that the foundation inside the insulation on the north-facing walls never dipped below 50 degrees during the winter, despite below-freezing temperatures outside. I wouldn’t do a foundation any other way.”

“Construction is similar to conventional foundations, except that you’ve got shallower footing depths and an insulated foundation. FPSFs don’t require any special tools or materials, other than the insulation itself. It’s pretty easy to incorporate it into standard building practices.”


“My company offers both design and general contracting services, so we’re well positioned to recommend new technologies like FPSFs to our clients,” Fosdick says. “Getting their buy-in is easy; getting approval from building department officials is a little more difficult.”

[IMAGE: Field personnel work with the crane operator to line up the perimeter concrete walls.]”Since building officials in Pueblo County were already familiar with FPSFs, approval wasn’t a big issue, but this wasn’t always the case. The first time we proposed using FPSFs, the building official had never heard of them and was inclined to disallow them, so I immediately asked about their appeals process. I got on the appeals board agenda and came in with my engineer and our pile of documentation from the NAHB Research Center. We used two case studies to educate them about the technology and were able to persuade them. The whole process only took a few weeks. NREL studied our first FPSF home. Ever since, I have used the results from their study to obtain approval from other building departments.”

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