Insulation novice

Mella

Help please! I am insulating a part of the house that is half concrete blocks and half old stone. It was built on to a two hundred year old house. I was thinking of using the holmflex for the roof insulation. Should I use a breathable film/vapour check on roof and walls and then put up ordinary plasterboard? Or is the plasterboard with vapour barrier already on it ok? I know the stone walls need to breathe. And then the walls - dry line and rockwool? Should there be ventilation from outside into the gap between wall and plasterboard. There is no ventilation in any of the three rooms even in the new concrete walls. I can't this information anywhere.

muffler

There are several options and Im sure you will get good feedback here shortly

Viking House

Mella wrote:

Help please! I am insulating a part of the house that is half concrete blocks and half old stone. It was built on to a two hundred year old house. I was thinking of using the holmflex for the roof insulation. Should I use a breathable film/vapour check on roof and walls and then put up ordinary plasterboard? Or is the plasterboard with vapour barrier already on it ok? I know the stone walls need to breathe. And then the walls - dry line and rockwool? Should there be ventilation from outside into the gap between wall and plasterboard. There is no ventilation in any of the three rooms even in the new concrete walls.

I would say you are better off going with the Vapour Control layer as it is continious, the foil back plasterboard lets in moisture at the joints. You don't need the vapour check on the walls
Best practice would be to put a ventilation gap between the insulation and the wall. But better than that would be to use a Hydroscopic drylining like Softboard that doesn't need a vent gap or insulate on the outside of the complete house.

Mella

Thankyou Viking King! Do you think that I should do the whole roof with the vapour control or just the bathroom and kitchen?