S grade vs H grade polystyrene: what is actually different?
I was buying a sheet of polystyrene to sit between a pool table and a plywood workbench top. The listing said “EXPOL 2400 x 1200 x 40mm S Grade Polystyrene ThermaSlab”, and I wondered what the S meant, and whether I should have bought the H instead. The short answer, if that is all you came for: S grade H grade Density 16 kg/m³ 24 kg/m³ Nominal thermal conductivity 0.041 W/m °C 0.038 W/m °C Nominal R-value at 50 mm about 1.2 m² °C/W about 1.3 m² °C/W Colour code on the sheet edge brown green Relative weight a third lighter 50% heavier H grade is denser, stronger, slightly more insulating and more expensive. S grade is the standard board and it is what most people want. ...