Normally a basements walls are restrained against earth pressure by the slab at the bottom and the floor above at the top. Concrete is a miserable insulator! Between the slab and footings high strength XPS (which shouldn't be loaded above 20 PSI to avoid creep issues) appears to be applicable. But around the slab edge there is only a relatively small area (4"slab) a higher strength material is needed. It seems Foamglass doesn't have creep issues and is available in strengths up to 300+ PSI Has anyone used it? There is a similar problem at the top of the walls as well & it seems Foamglass could be useful there as well.