Hi all,
We are in the process of rebuilding the outer shell of our conservatory / extension which is currently split (partition) as a bathroom and small storage area. At present, the structure of the building consists of thin wooden Victorian walls and a lean-to felt rood. It is in a very bad state and the room is always extremely cold. We would like to replace the walls with a more solid structure, that is well insulated and would allow heavy fixtures (wall units). We were thinking of using the brick - gap (for insulation) - concrete block approach for the bottom of the walls with windows across the top 2/3 rds (not the bathroom section) but this would eat up on the very limited interior space . Are there any alternative cost effective approaches that would produce a well insulated space that is thin as possible, can handle fixtures and can cope with a lean-to tiled roof?

Thanks in advance.

I'm just replacing a conservatory with a sun room extension. I have tried to maximise internal space by building the walls in single skin solid 100mm concrete blocks set on the edge of the slab and externally insulating with polystryrene between batons finshed with a timber rainscreen. I'm putting 50mm between batons at 600 mm centres then putting batons the other way with another 50mm between them.