Works have started back on site and the airtightness layer is now complete. Above ground the taped OSB forms the airtightness layer including airtight boxes to house the lighting in the ceiling and battens to the wall to provide a service void and safeguard the airtightness layer. It was impossible to extend the airtightness on the ground floor with the airtightness on the first floor (i.e. through the intermediate floor) due to complicated structure and steelwork so instead, each room (on the ground and the first floors) are separate airtight ‘boxes’ but it does make detailing complicated! Below ground (in the basement) the foil face of the wall insulation acts as the air and vapour control layer and is taped to the Foamglas to the ceiling. The wall insulation is mechanically restrained by simple timber offcuts to prevent the insulation moving and straining the airtightness tapes.
Photos by Edward Bishop (www.edwardbishop.me)