Windows are massively important for Passivhaus and sills seem to be disproportionately important for retrofits, especially for woodfibre insulation which needs very careful detailing to avoid water ingress. If water is going to find it’s way in then the sills are the most likely entry point. Sills are Bug aluminium fitted directly to the Purenit packing which Internorm use for transporting the windows but offers good thermal performance and can be fixed to, a special material like Foamglas. Strange ‘Pacman’ butyl corners ensure no driven rain gets past the end caps. The plywood liners are proud of the levelling coat and require blocks to support the the brackets. Silicone between the windows and the tops of the end caps complete the weather tight construction. Quite a lot of work and careful detailing to ensure durability.
