Kooltherm K18 Direcectly onto existing plasterboard?

[gazandwiz]

Hello.
My house is upside down, ie, bedrooms, office and bathrooms downstairs and upstairs is one massive room covering almost all of the groundfloor rooms.
It's cold up there! We have poorly fitted Kingspan/Celotex type foam between the sloping walls/roof joists which lead up to the ceiling and the loft area. The loft has 9 inches of glass wool insulation that I did a few years back and I now want to improve the sloping walls. Can I add Kooltherm K18 straight onto the existing plasterboard or must I remove the old PB before fitting the K18 directly onto the rafters/joists?
The sloping ceiling goes as high as 4.5m from the floor so the less work the better!
Any thoughts?
Happy New Year to all )
Gaz

 

[catlad]

I can see no reason to remove the old plasterboard.

 

[theprinceofdarkness]

I am not sure that its suitable for fixing at an angle. The Kingspan stuff is all about it being used as a wall insulation. I would give them a telephone call.
Frank

 

[gazandwiz]

Thanks to both replies. I appreciate your efforts to do so.

Cheers
Gary