Advcie for render and construction of new external wall

[totoisacat]

Have bought a place to renovate. An annex to the side of the house is like a cold box and i wish to insulate and rconstruct it.
One thing i am going to do is take out 4 large windows (single glazed) and make stud walls based on existing window construction, which is fine.
Questions are: what board to use outside to render directly onto.
Also i have rendered before with 4:1 mix and used sharpsand. This was fine but would like to know if any other possibilities. Finishes?
I have seen sponge flaots-what finish do they give?
Any advice appreciated. Can upload photos if it helps.

 

[plstering]

http://www.netweber.co.uk/
iv used this stuff in the past and id use it agen and agen

 

[totoisacat]

Thanks for that.
I note that it is designed for houses with solid brick single walls.
The annex i have has been constructed with a double wall from concrete blocks so i guess that i could simply fill the void to achieve less heat loss.
It seems that the system you point to is designed for larger projects and consists of expanded polystyrene fixed to the outside wall and then renedered. I had seen some houses being built in Dorset and bing on the main road witnessed their progression. It appears they used this or a very similar system. I am not sure whether my project warrants this and being double wall may not be necessary.
Many thanks

 

[AbnerWright]

My vote is also with that material. I also used it and have not faced any difficulty till now. I think go for it again.