Foam insulation cost is influenced by quantity, labor, type and region. As of 2014, closed cell foam insulation is estimated to cost $1.75 per square foot on average. Open cell foam insulation is estimated at $1.15 per square foot for wall cavities and $1.50 per square foot for roof lines.
Foam insulation is usually applied by spraying it on walls, roofs and contoured surfaces. Spray polyurethane foam resists heat transfer and stops air from coming through cracks, seams and joints. High density spray polyurethane foam is used for exterior and roofing applications. Medium density spray polyurethane foam is used to insulate, fill interior cavities and unvented attic applications. Low density spray polyurethane foam can also be used for filling interior cavities and unvented attic applications, but not insulation.