Insulating Cavity Block Garage Renovation

[mickf9]

Hi all,
I am doing a detached garage conversion and trying to find wall insulation requirements.
It is a single leaf cavity block wall, rendered inside and out.
The general advice I can find is if it's single leaf, to create frame on inside creating cavity between wall and insulation.
My question is, is cavity block treated the same as solid block.
Would it be sufficient to dryline straight onto in side wall or batten it out and insulate between battens and then over.
I'm hoping not to lose space by needing to create cavity between wall and insulation.
Mick

 

[robinbanks]

If you don't want to lose internal space, consider external wall insulation. You should, ideally, be planning on adding around 100mm of king span type insulation for adequate performance and meeting regs; if going internal I'd be considering battens to pinch the kingspan against the wall(fix through the batten and insulation, into the wall) and then you have a service void the depth of the batten for wires, pipes, socket backboxes etc and you have an air gap to allow the silvering of the kingspan to do its designed-for job. If you want a cavity you're looking at building a stud work inside that you insulate between (and over depending on the size of the stud and desired cavity).

 

[mickf9]

If you don't want to lose internal space, consider external wall insulation. You should, ideally, be planning on adding around 100mm of king span type insulation for adequate performance and meeting regs; if going internal I'd be considering battens to pinch the kingspan against the wall(fix through the batten and insulation, into the wall) and then you have a service void the depth of the batten for wires, pipes, socket backboxes etc and you have an air gap to allow the silvering of the kingspan to do its designed-for job. If you want a cavity you're looking at building a stud work inside that you insulate between (and over depending on the size of the stud and desired cavity).

Thanks Robinbanks,
Internal is preferred, I hadn't thought of using the batten depth for a small void, loss of space there would be minimal and handy to run services as you say.
Would there be any requirement to vapour barrier the wall or just foil back kingspan straight on the battens and battens straight on wall.

 

[robinbanks]

In the scenario where you can foil tape the kingspan joints together I've always regarded that as adequate vapour barrier without an additional sheet

 

[^woody^]

You don't need a cavity, and block has a relatively low insulation value compared to any alternative.

You can directly line a single skin wall, but will need to consider and deal with any potential moisture that can soak through the outer leaf.