If 6” of Styrofoam Brand foam is specified for a project, it requires that multiple layers of STYROFOAM™ be used. The 6” thickness can be obtained by combining 2 layers of 3” STYROFOAM™ or a layer of 2” and 4”. Another way to get the 6” of insulation is to use expanded polystyrene. EPS is available in any thickness and in a variety of densities and insulation values.