Other flame retardants used with polyurethane foam, such as TDCPP and some components of Firemaster 550, are more volatile than the PentaBDE they replaced, so they may be more likely to migrate out of landfills, says Martin Scheringer of ETH Zurich. TDCPP is also at least 1,000 times more soluble in water than BDE-47, a major constituent of PentaBDE.,
Courtney Carignan, then at Boston University’s School of Public Health, was the lead researcher in a project that showed elite gymnasts can be exposed to high levels of flame retardants through their training equipment. For instance, the “foam pits” that gymnasts use to pad their landings during practice are filled with uncovered polyurethane blocks, which may leach flame retardants more quickly than upholstered furniture. Carignan says gymnasts aren’t the only ones who use foam pits—skiers, snowboarders, and other athletes use them, too. The pits are also a popular feature at many of the indoor trampoline parks that are popping up all over the United States.
Foil and plastic facings on rigid polyurethane foam panels can help stabilize the R-value, slowing down thermal drift. Reflective foil, if installed correctly and facing an open air space, can also act as a . Depending upon the size and orientation of the air space, this can add another R-2 to the overall thermal resistance. Panels with foil facings have stabilized R-values of about R-6.5 per inch.
Polyurethane insulation is available as a liquid sprayed foam and rigid foam board. It can also be made into laminated insulation panels with a variety of facings.
Like polyiso foam, the R-value of closed-cell polyurethane insulation can drop over time as some of the low-conductivity gas escapes and air replaces it in a phenomenon known as thermal drift. Most thermal drift occurs within the first two years after the insulation material is manufactured, after which the R-value remains unchanged unless the foam is damaged.
Some manufacturers use polyurethane as the insulating material in structural insulated panels (SIPs). Foam board or liquid foam can be used to manufacture a SIP. Liquid foam can be injected between two wood skins under considerable pressure, and, when hardened, the foam produces a strong bond between the foam and the skins. Wall panels made of polyurethane are typically 3.5 (89 mm) thick. Ceiling panels are up to 7.5 inches (190 mm) thick. These panels, although more expensive, are more fire and water vapor-diffusion resistant than EPS. They also insulate 30% to 40% better per given thickness.
Soy-based, polyurethane liquid spray-foam products are also available. The cured R-value is about R-3.5 per inch. These products can be applied with the same equipment used for petroleum-based polyurethane foam products.
Low-density, open-cell polyurethane foams use air as the blowing agent and about an R-3.6 per inch 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.
Sprayed or foamed-in-place applications of polyurethane insulation are usually cheaper than installing foam boards, and these applications usually perform better because the liquid foam molds itself to all of the surfaces. All closed-cell polyurethane foam insulation made today is produced with a non-HCFC (hydrochlorofluorocarbon) gas as the foaming agent.
UF foam insulation has an R-value of about 4.6 per inch, and uses compressed air as the foaming agent. Nitrogen-based UF foam may take several weeks to cure completely. Unlike polyurethane insulation, UF foam doesn't expand as it cures. Water vapor can easily pass through it, and it breaks down at prolonged temperatures above 190°F (88°C). UF foam contains no fire retardant.
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 and a lower R-value.
Cementitious insulation material is a cement-based foam used as sprayed-foam or foamed-in-placed insulation. One type of cementitious spray foam insulation known as air krete® contains magnesium silicate and has an R-value of about 3.9 per inch. With an initial consistency similar to shaving cream, air krete® is pumped into closed cavities. Cementitious foam costs about as much as polyurethane foam, is nontoxic and nonflammable, and is made from minerals (like magnesium oxide) extracted from seawater.
Polyurethane is a foam insulation material that contains a low-conductivity gas in its cells. The high thermal resistance of the gas gives polyurethane insulation materials an R-value ranging from R-5.5 to R-6.5 per inch.
Other polystyrene insulation materials similar to MEPS are expanded polystyrene (EPS) and extruded polystyrene (XPS). EPS and XPS are both made from polystyrene, but EPS is composed of small plastic beads that are fused together and XPS begins as a molten material that is pressed out of a form into sheets. XPS is most commonly used as foam board insulation. EPS is commonly produced in blocks. Both MEPS and XPS are often used as the insulation for structural insulating panels (SIPs) and insulating concrete forms (ICFs).