THERMAL BRIDGING

As the build races ahead, we can look back at the dozens of different techniques and tricks we have used to eliminate thermal bridging throughout the build. The Foamglas structural insulation we use has played no small part, as can be seen from the photos - it is the black brick-like stuff.

Take the kitchen for example - to extend the kitchen outwards we installed a steel frame to support the old wall. This “warm” frame sits inside the thermal envelope, so foamglas was used to insulate it from the cold brickwork above and the ground below.

Next, our first layer of insulation (130mm thick) was mounted on battens and a small membrane used to ensure the integrity of the airtight layer.

This left the insulation standing 20mm (or one batten’s width) away from the foanglas, so be sure of closing off the bridge we filled the bottom of the cavity with polystyrene beads. This keeps the thermal skin around the building completely unbroken.

In a different area, we insulated over the top of a suspended floor (which we lowered specifically for this purpose). This meant that any stud walls resting on this suspended floor had to sit on top of a foamglas plinth, which in turn had to be sealed to the OSB with special tape to keep the integrity of the airtight layer.

With a loft extension, kitchen extension, bay windows and a floor that is part basement, part suspended floor and part slab, this build does not have the geometrical simplicity that most Passivhaus designs espouse. This has meant literally dozens of highly complex details must be prepared to cut off thermal bridges and potential air leakages at every single junction, interconnection and corner in the house…

It makes for a lot of work!