Polyurethane insulation can increase a house's energy efficiency, but may need to be replaced more frequently than other kinds. In spray form it expands slowly, providing better insulation without damaging walls or ceiling boards. The insulation is easy for a do-it-yourselfer to apply. It's also water-vapour permeable, doesn't collect moisture and is flame-resistant.
Polyurethane insulation is a closed-cell foam that contains a low-conductivity gas in its cells. The gas is usually hydrochlorofluorocarbons (HCFC). Polyurethane insulation comes in spray foam and rigid foam board.
R-value per Inch
Polyurethane insulation has a relatively high R-value per inch. Generally, it averages around R-7 or R-8 per inch.
As polyurethane insulation ages, however, the R-value drops, because the gas escapes from the cells. The insulation can drop as much as two R-values in two years before stabilising.
While hydrochlorofluorocarbons are not as bad for the ozone layer as chlorofluorocarbons, they still do damage it. Alternative chemicals, such as carbon dioxide, also damage the ozone when released, impacting the climate.
Spray polyurethane insulation is more cost-effective than foam board or batt insulation because a little goes a long way. Spray insulation can go around pipes and into cracks and other hard-to-reach places.