All Hytherm Products are manufactured to BS3837 and without the use of CFC’s or HCFC’s. EPS cells contain air and not gas, therefore the performance of the preoducts will remain constant throughout the life of the building Physical Property Grade   Unit SD HD EHD UHD Max thermal conductivity @ 10º Celsius W/m2K 0.037 0.034 0.033 0.032 Compressive strength or compressive Stress @ 10% strain kPa 70 110 150 190 Min cross breaking strength kPa 140 170 205 275 Dimensional stability @ 80º Celsius max Percentage linear change   1.0 1.0 1.0 1.0 Max water vapour permeability @ 38º Celsius Ng/(Pa.s.m) 6.9 5.0 4.2 4.2