Wall insulation question

[Tris123]

I've recently moved into a house that has solid brick walls with no cavity. The previous owner has insulated two of the external walls and as a result the third is getting condensation issues. Im wanting to continue the insulation onto the third wall but I have a question about how the previous owner did the first two.

They put a green vapour barrier sheet over the old plaster, put 25mm celotex board on it and then put 12.5mm plasterboard on that. Is this an ok procedure to insulate the wall or should the old plaster have been removed before putting up the vapour barrier? And what is the best method of attaching the vapour barrier to the plaster if that is the case.

Also, how would you attach celotex to a vapour barrier sheet as I'm assuming dot and dab wont stick to the sheet?

 

[Doggit]

If you talk to Celotex or Kingspan, they'll tell you to batten the walls at 450 centres, and around the edges 25mm deep, then put on 72mm of insulated plasterboard. I've never heard of putting a vapour barrier on the wall, nor of not having an air gap. Taking the plaster off helps mitigate the thickness of the insulation, that's all.

 

[Tris123]

Why 72mm of insulated plasterboard? I did find it strange that there was a vapour barrier sheet and then foil backed insulation.

 

[John D v2.0]

72mm I guess is the typical amount needed to meet building regs u values for retrofit on a solid wall. 60+12