The backfill process: the frost walls are built from the footings below the frost line on compacted earth / gravel bed or the bedrock in this site. The house siting design was planned such that no blasting (controlled explosives to remove bedrock) is required. Full basement is located to section of site with minimal bedrock in close proximity to surface. Drainage tubing is integrated at the footing and connected to insure runoff to the lowest level of the site. In the context of cost effective thermal breaks between the frost wall and slab (not yet poured in these images) a three inch layer of R15 XPS is integrated behind the frost wall which will isolate the slab on grade and moderate the ambient temperature of the earth under the main house level.