So, my single skin (painted inside & out) garage build is almost complete, it has a felt on OSB roof with 200mm joists, currently no insulation. I've moved in now with bikes, tools, stuff stored on shelfs. No leaks.
During fitting i cut 50mm off the top section of the noggins to allow for air movement once insulated and boarded.
After a dip in temperatures, this morning anything with a metal surface has a layer of condensation on it and paper stuff is damp.
So i presume i need to insulate the roof to stop this condensation forming? It feels chilly in the garage whilst warm outside thus producing what i call the beer out of the fridge condensation problem.
It is only a garage and i'd like to keep this as simple as possible and keep costs down, whilst doing the job properly.
So, am i correct in thinking that 100/150mm Rockwool type insulation between the rafters, held in place with stapled garden netting, then finished off with some kind of boarding (plaster/ply?), and it seems the board requires taping?
OR... could i get away with just stapling some Kontrol R1.9 to the underside of the rafters and be done with it?
Also i believe that the void above the insulation needs venting to the exterior, yes or no?