Insulating roof of scout hut

[Landscaptv]

Whats the best way to insulate this roof. It's just wooden boards with nailed and battened tiles on the other side. The floor is insulated and the rockwool is sloping away from us on the upstand, being the kitchen ceiling on the other underside. I have read about condensation and want to know what product would be best to fix to the roof side in both the kitchen, currently uninsulated on the roof side and in the main roof from where the photo is taken to get good insulation. There is no gap in the top of the roof where it meets the apex so do I need to put a vent of some sort where the rockwool meets the current roof and in the apex or is it unnecessary.
regards

Nick

 

[Deluks]

Look like 4" (100mm) joists to me???

If so you could use maximum 50mm rigid insulation flush with the underside of the rafters, then cover with polythene/plasterboard or just foil backed plasterboard. You will need vents at the top 50mm of the wall. The circular soffit vents will do it.

You could also warm roof it. which means insulation on the top side of the roof boards, then felting over the top of that (A few vents will still be needed at the top of the wall)

Worth considering if the current roof covering is on the way out, as you could use thicker insulation.

Ps, Rockwool is green, that looks like Knauf