We had wanted to use the pavatherm woodfibre board for the external wall insulation at the back of the house as well as internally. However, we were unable to find a system (render + insulation +fixing) that was guaranteed. Unfortunately we therefore decided to use a more tried and tested system using 70mm of PIR (poly isocyuranate) insulation with a coloured render. The external insulation went on without any problems and the rain stayed away until the render had been applied and dried. We did have to extend the flue for the boiler so that it protruded from the external insulation. The photo shows the finished render.