I will build a Japanese style garden outbuilding with a curved roof. The plans come from S. California but the build is in the Northeast. The ceiling will be exposed knpotty pine or spruce
To extend its use into the cooler seasons I will use an electric heater. But would like to put something with insulating value on the exterior of the roof below shingles. It needs to be flexible to follow the roof curve.
All suggests appreciated.
It would help is you added your location to your profile.
It would be great if somehow you could post the web site or something so we could get an idea on what this is going to look like.
One way I've seen it done was with 1-1/2 X 6" T&G then they used SIP roofing panels for added insulation and a nailing surface for the roofing. http://www.raycore.com/roof-panels.php
The panels I saw used were only 1-1/2 thick. And were held down with special scews with large washers.
Wood only has an R value of only 1.25 per inch I believe.