Sprayed-Foam Polyurethane Insulation

Sprayed or foamed-in-place applications of polyurethane insulation are usually cheaper than installing foam boards. These applications also usually perform better since the liquid foam molds itself to all of the surfaces.

All closed-cell polyurethane foam insulation made today is produced with a non-CFC (chlorofluorocarbon) gas as the foaming agent. Some polyurethane foam combines with a HCFC gas. These foams have an aged R-6 per inch thickness. Their density is generally 2.0 lb/ft3 (32.0 kilograms per cubic meter [kg/m3]).
Low-density, open-cell polyurethane foams (0.5 lb/ft3 [8 kg/m3]) have an R-value of about R-3.6, which doesn’t change over time. These foams are similar to conventional polyurethane foams, but are more flexible. Some low-density varieties use carbon dioxide (CO2) as the foaming agent.

Low-density foams are sprayed into open wall cavities and rapidly expand to seal and fill the cavity. A slow-expanding foam is also available, which is intended for cavities in existing homes. The liquid foam expands very slowly, reducing the chance of damaging the wall from overexpansion. The foam is water-vapor permeable, remains flexible, and is resistant to wicking of moisture. It provides good air sealing and yields about R-3.6 per inch of thickness. It is also fire resistant and won’t sustain a flame.

Polyurethane Insulation Materials

Polyurethane is a foam insulation material that contains a low-conductivity gas in its cells—usually a hydrocarbon or hydrochlorofluorocarbon (HCFC). The high thermal resistance of the gas gives polyurethane insulation materials an R-value typically around R-5.5 to R-6.5 per inch.

Polyurethane foam insulation is available in closed-cell and open-cell formulas. With closed-cell foam, the high-density cells are closed and filled with a gas that helps the foam expand to fill the spaces around it. Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture.