One of our current projects is a renovation/residential conversion of a 1950's Hop-picker's Barracks. This is a long narrow building, with solid gable ends and long sides of repeated doors and windows. It has a single brick thickness shell wall, of common brick. We want to bring this up to AECB Silver Standard.
We plan to line it with 100mm medium density block work. NHBC specifies an air gap between outer shell and insulation, but would it be satisfactory to completely fill the cavity with 100mm of polyisocyanurate (Celotex GA3000z), as this will be much easier for the Self-Builder to install? Exterior cladding on the long walls will be vertical cedar, and brick slips below windows. The gable ends could be clad with better quality brick, with or without an air gap between these and existing brickwork. Attention will be paid to cold bridging.
So, can we have a fully filled 100mm cavity, and still meet Silver Standard?
Advice will be welcomed!