It is familiar as the yellow foam used in trays for fresh cuts of meat at the supermarket. Cement-foam composites are not actually a pure foam, but a mixture of Portland cement and loose EPS beads. Most ICF manufacturers mold their form units out of the foam they judge best for the job. But in several ICF systems the formwork is assembled from standard flat sheets of foam, available from building suppliers. With these systems the buyer may have a choice of different types of foam.
Evidence indicates that all of the foams used in ICFs produce excellent houses.
However, each has its own unique profile of properties. Note also that any one of these foam materials may vary. By changing manufacturing, producers can get somewhat different properties with the same plastic, so any numbers given here for a type of foam are approximate. Consult specific ICF manufacturers for exact specifications. It also insulates well, is resistant to air and moisture infiltration, and moderately strong.