Polyurethane insulation is a synthetic material with a high degree of heat transfer resistance. It is designated as a closed-cell type of insulation since its cell pockets are inflated with a non-chlorofluorocarbon gas, which gives the material a higher density and more rigid structure than soft, open-cell types of insulation material. In general, the benefits of using polyurethane insulation over other materials include reduced infiltration of outside air pollutants and allergens, as well as resisting water vapors and the formation of mold and mildew. There are three basic types of polyurethane insulation available: Molded expanded polystyrene foam board (MEPS), extruded expanded polystyrene (XEPS), and liquid foam.
MEPS foam blocks or panels are also known in the industry as beadboard. This is because the material contains beads that hold polystyrene, a thermoplastic, and a liquid hydrocarbon called pentane. When combined with a chemical blowing agent and subjected to heat, the beads expand. The material is then injected into a mold and heated a second time. Depending on the type of beads, blowing agents, and molds used, the resulting blocks or panels will possess different degrees of density.
XEPS is very similar to MEPS, but is more expensive since it undergoes a slightly different process. Instead of being heated and molded, the polystyrene beads are placed in an extruder where they are mixed with chemical catalysts to melt them. When the blowing agent is introduced, the mixture releases gas and a thick, foaming liquid is produced. This liquid is then fed through a die, from which it exits and continues to expand to its maximum capacity. Once cooled, the material is then cut to specification.
Both MEPS and XEPS types of polyurethane insulation can be laminated with a variety of facings to provide further radiant value, as well as additional moisture and flame resistance. The type of facing used, which ranges from kraft paper to heavy-duty aluminum foil and vinyl, depends on its application. In addition, while these types of rigid foam insulation are commonly used in construction, they are also used to line picnic coolers, refrigerators, freezers, and refrigerated trucks.
Liquid foam polyurethane insulation typically has a lower density than molded or extruded insulation. However, its coverage capacity is a distinct advantage. Once this material is introduced into an open space it quickly expands and spreads, which enables it to seep into the smallest of cracks and crevices. Polyurethane foam insulation also has exceptional moisture-repelling properties in addition to being highly flame retardant.