Frost Protected Shallow Foundation

I've been spending many man-hours working on the plan. We spoke with a concrete contractor regarding the footers, and he had some interesting facts to share with us. The first fact was the two foot [24 inch] frost depth required for footers here. I had been thinking about the amount of concrete we'd need to adequately support those big posts, and had settled on 12 inch depth, 36 inch square footers, but to avoid using excess concrete, we were planning on laying each footer on a bed of ruble 12 inches thick. The local code, however, requires a depth of 24 inches for a footer. No matter, we can accommodate that. But I recalled something I had come across before regarding shallow foundations, and frost protection I'd like to share.

A frost-protected shallow foundation system was started in Scandinavia. They use rigid foam insulation set around the outside of the foundation to protect against frost heave. Such shallow foundations reduce costs several ways. First, you have less excavation and backfill. You can use significantly less concrete by not needing to pour footings below the frost line. Since we plan to use in-floor radiant hydronic heating,
it just makes sense to combine the insulation of the surrounding foundation with the slab insulation.