Dorma cavity

[Piestuff]

Hi,
I have a triangular shaped cavity running the whole length of my dorma style house. At the minute is has 30 year old 'insulation' laying on the floor and up the sides of the bedroom walls. Someone has nailed polystyrene to the roof section aswell which seems to do absolutly nothiing.

Anyway my question is what is the best way to insulate this space Do I insulate the inside wall and floor or all 3 sides (inside bedroom wall, floor and roof rafters?)
This is not in the loft, it is the unusable bit in dorma houses that extend above the downstairs rooms

Cheers

 

[freddiemercurystwin]

Two or three layers of quilt insulation on the floor and some Kingspan or Celotex between the vertical studs behiind the boards will be ok. Maybe add a thin layer (say 25mm) of King or Cel behind the studs for good measure. No need to do the rafters too.