Products > Therma > Therma TR31 > Overview Therma TR31 Structural insulation / FSC certified plywood composite for flat roofs waterproofed with partially bonded built-up felt Kingspan Therma TR31 Properties Download PDF Thermal conductivity 0.022 W/m.K (insulant) 0.14 W/m.K (plywood component) Compressive strength at 10% compression 150 kPa Upper facing 6 mm FSC certified WBP exterior grade plywood Core High performance rigid thermoset polyisocyanurate (PIR) insulant manufactured with a blowing agent that has zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP). Lower facing Composite foil Board size 1.2 x 2.4 m