Tanking to Walls
Because we were going well beyond the Passiv Haus German building standards and because we were not building a traditional cavity wall construction we needed to produce external structural walls being totally waterproof and air tight. So the dense 150mm concrete walls that support all our 7m long 200mm thick floor slabs are first painted with a RIW tough seal paint, then a further 2mm thick Fosroc Proofex 3000 rubber waterproof skin is applied to all wall sections – having the effect of creating an entire wetsuit around the building. This membrane was then tied into all our door and window reveals to eliminate air leakage and cold bridging details.
We used extruded polystyrene from URSA their URSA HR E, incredibly high compressive strength (we drove a 7 ½ tonne Manitou telescopic handler) over a sheet without any damage at all, it also 99.9% water proof, almost 100% closed cell – Knauf have a similar product called XPS and Dow Corning have the blue Styrofoam.