Insulating a parallel scissor truss roof
The new side of my reno and expand project will have a 8/12 cathedral ceiling with parrallel scissor truss. I am planning R80 so 24″ of batt or blown insulation in the truss space.
My question is…. since this insulation will be applied from the inside (well after the roof sheathing and then shingles are applied) how do I provide a space between the underside of the roof deck and the top of the insulation?
It seems impossible with a sprayed product unless I build a channel or sorts to provide that airspace…like 2×4 laid on their side on either side of the truss with OSB cut and nailed onto the 2X to provide a top limit to the insulation and a 1 1/2″ airspace.
Am I lost or is that the only way?
I don’t want to build a HOT roof as they are not commonly done or understood here (Kenora Ontario Canada zone 7)… how do I build a vented roof…