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.