I'm planning to insulate my attic rafters above a living space. several sources show the use of iso board or other sheathing with canned spray foam for joints and other fill-in requirements, in the attached picture for basement rim joists. I am contemplating using this for rafter insulation.
Experimenting with the board, it seems extremely easy to cut and fit, and it appears it would be much cheaper than a full spray foam installation. It might be a little more labor, but other than that what other reasons could there be to use a full spray like tiger foam?
The panel method could also allow us to easily build in a ventilation channel if we want the 'cold roof' option.