Is there a thin high insulation factor wall material for a uPVC conservatory?

[tonyjeffs]

I intend to build a uPVC conservatory onto the back of the rear of our semi. It needs planning permission because it is 4m deep.

One side wall of the conservatory will be adjacant to the 7' high party-wall wall that runs the length of the garden, so it won't get any sun and if I use a standard uPVC panel it will lose a lot of heat. I could build a cavity brick/block wall instead, which would solve the insulation problem, but it would make the conservatory considerably narrower.

Is there a thin walling material, maybe 3" thick, that has high insulation properties, and that might satisfy planning, that I could use instead?

Thanks

Tony

[dennis]

Assuming you are allowed(1) to use the party wall as part of the structure then foam backed plaster board should do the trick.

1: You would have to attach the roof and put flashing along it to make the joint weather proof.