15mm xtratherm insulation board range is a high performance foil faced Polyisocyanurate (PIR) insulation with a certified thermal conductivity as Low as 0.022 W/mK. Thin-R Pitched Roof XT/PR on sloped roofs (ventilated, hybrid or warm) provides the most efficient U-Values with minimal intrusion into valuable living space. The roof construction is a critical element in the building fabric and is an area at high risk of heat loss. Using XT/PR will reduce heat loss while also delivering excellent thermal bridging details.