Timber frame wall with a rigid sheathing board made water and air tight by the self-adhered vapour permeable ProctorPassive Wraptite SA, externally insulated with a thermoset rigid DCT PIR insulation, protected by a lightweight cladding on battens. The insulation is mechanically fixed to the sheathing board with minimal thermal bridging, to form a continuous external insulation layer. Additional insulation within the frame would only be considered having assessed condensation risk.