wall construction for garden annexe

[OliverMaxwell]

I am about to start my build of a 46 meter squared garden annex. Given all the issues with supply chain and material costs I am looking at various options in terms of materials.

Please could someone help me understand what insulation I would need to meet regs if I was to build the external walls out of 215 Thermalite blocks (no cavity) with cedral cladding on the outside?

many guidance would be greatly appreciated?

 

[phatboy]

I think it's 90mm of external insulation, when using Thermalite. I'll hopefully be extending in a few months with those same blocks.

the 215s are only available in 4Kn Party Wall, and 7.3Kn High Strength, but for a garden annex, 3.6Kn should be fine....