Hi, I'm after a bit of advice on how to insulate the roof of my summerhouse. What I'd like to do is to insulate and then plasterboard over it leaving about 25-30mm of the purlins showing which I could then paint them. It does get very cold in there, just above freezing so some decent insulation (and I'll look at doing the floor during the warmer months) would be nice. However I'm not sure on the best way to go with it. I was thinking of PIR with an air gap and put some vents in between the purlins front and back of the summer house and then plasterboard (with a vapour barrier) over this. I've attached some images showing the roof of the summer house. Had it up 2 years but not done much with it since it was built. Roof is 18mm ply with a layer of felt followed by a layer of shingles, no issues with leaking. Purlins are 120mm width

 

Cheers

Hi there, you could insulate above the roof section using Kingspan TR27 or Celotex Crown-Up of crown-Fix or similar. Use a good  Phenolic insulation like Kingspan K110 or Kingspan TP10 maybe. Both of which will give decent U-values.