The party wall where the chimney has been removed was in a terrible state (as expected!) with holes visible into the neighbour’s chimney flues so a brick skin (shown partially complete) has been added to strengthen the structure and give a basic level of airtightness.  Additionally both party walls are being plastered in lime which will allow any existing and future moisture from the brickwork to migrate into the void between the new stud wall and escape through the roof (details to follow) and to further improve airtightness.  There is also a strip of Perinsul blocks (black on the photo) above the steel to reduce cold bridging and the second photo shows how this integrates with a Purenit sleeve to form a continuous thermal envelope around the steels (in grey) in this tricky configuration.  Note there is also a Spacetherm blanket around the back of the steel which can be seen in an earlier blog.  These hi-tech materials are rarely used in traditional buildings but are tools of the trade for high performance buildings and while they are expensive both in material and labor costs there is a significant reduction in heat loss, improved thermal comfort and additional safeguarding of the building fabric, and I would expect a payback over the lifetime of the building.