U-Value of 50mm, 75mm, 120mm and 150mm PIR Insulation Compared
Quick answer
PIR at λ 0.022 W/mK has a declared R-value of 2.25 (50mm), 3.40 (75mm), 5.45 (120mm) and 6.80 m²K/W (150mm). The finished U-value depends on the build-up: for example, 75mm in a solid concrete floor gives about 0.20 W/m²K at a perimeter-to-area ratio of 0.4, while 150mm between rafters, with 57.5mm of Kooltherm K118 insulated plasterboard under, gives about 0.13. Our PIR U-value calculator works it out for your own construction. For 100mm, see our guide to the U-value of 100mm PIR.
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