PIR is typically produced as a foam and used as rigid thermal insulation. Its thermal conductivity has a typical value of 0.16 BTU·in/(hr·ft2·°F) (0.023 W/(m·K)) depending on the perimeter:area ratio. PIR foam panels laminated with pure embossed aluminium foil are used for fabrication of pre-insulated duct that is used for heating, ventilation and air conditioning systems. Prefabricated PIR sandwich panels are manufactured with corrosion-protected, corrugated steel facings bonded to a core of PIR foam and used extensively as roofing insulation and vertical walls (e.g. for warehousing, factories, office buildings etc.). Other typical uses for PIR foams include industrial and commercial pipe insulation, and carving/machining media (competing with expanded polystyrene and rigid polyurethane foams).