A substance formed by trapping pockets of gas in a liquid or solid. Solid foams can be divided into closed-cell foams (where each pocket is separated) and open-cell foams (where the pockets connect with each other). Foams have many possible uses in building. A common use is as an insulator.

Related terms: ccSPF, Expanded Polystyrene Insulation, Insulation, ocSPF, PIC, Extruded Polystyrene Insulation