Concrete block insulation is typically installed for new home construction or in homes undergoing major renovation. Since installation involves masonry skills, it’s best to have a certified cement mason do it.
When using masonry blocks for a foundation wall, filling the block cores with high-pressure foam works better than most poured-in insulations, like polystyrene beads or vermiculite or perlite pellets.
Note that even though filling the block cavities and special block designs improve a block wall’s thermal characteristics, it doesn’t reduce heat movement very much when compared to insulation installed over the surface of the blocks either on the exterior or interior of the foundation walls. Field studies and computer simulations have shown that core-filling of any type offers little fuel savings since the majority of heat is conducted through the solid parts of the walls such as block webs and mortar joints.
Source: U.S. Department of Energy – Energy Efficiency and Renewable Energy