CavityTherm is a high performance composite board. It has a thermal conductivity of 0.021W/mk. They have gas tight facings with one face being bonded to a profiled HIPS skin, this provides a drainage plane. Xtratherms Cavitytherm can achieve U-values in a 100mm cavity that meet the TFEES of 0.18W/m2k (Target Fabric Energy Effieciency Standard)
For more information, please visit https://www.xtratherm.com/products/ct-pir/