Natural Resources Canada - Basements & Concrete Insulation
Contrary to popular opinion, earth is a poor insulator. Basements and concrete slabs account for up to 20 percent of a buildings total heat loss. This is due to the large, uninsulated surface area both above and below grade level. Some authorities have expressed concern about the possibility of frost action and structural damage when foundations are insulated from the inside. The concern is that frost will penetrate deeper down the outside of the foundation wall. Research has found that this is rarely a problem.