Polyisocyanurate Foam

Polyisocyanurate foam (PIR), usually blown with HCFCs is available in two grades: PIR1 and PIR2. It is used as a roof insulation material since it is more heat-resistant than other organic insulation foams, which cannot be directly hot-bitumen bonded. Polyisocyanurate is also appropriate for use in wall and floor insulation. PIR is combustible (BS 476 Part 4) with a Class 1 Surface Spread of Flame (BS 476 Part 7) but is more fire-resistant than polyurethane foam. Polyisocyanurate tends to be rather friable and brittle. Certain proprietary systems for insulated cavity closers use PVC-U-coated polyisocyanurate insulation. Such systems offer a damp-proof barrier and can assist in the elimination of cold bridging, which sometimes causes condensation and mould growth around door and window openings. (The thermal conductivity of polyisocyanurate foam is usually in the range 0.023-0.025 W/m K.)

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