Good Afternoon Mike,
Any particular reason for the 2' below grade ...
Im sure your frost goes deeper than that,... quote]
My building has a concrete /stone foundation that was formed on the inside only with 3 courses of block up to ground level. I raised the building another 3 courses. The only way to use foam more than 2'below grade would be to clean the rough wall & spray foam. My building usually has good snow cover for at least 10' around the house so frost doesn't go very deep unless it's a bare winter. I keep the snowmachines, etc, away from that snow. Going deeper with the foam would be better but there's a diminishing return there somewhere. MikeD74T