I have a bonus room to insulate- my concern is the roofdeck- I have 2 x 8 rafters to deal with on a new construction- I am assuming it needs to be vented? Any ideas would be greatly appreciated.

Thanks

I agree that it needs to be vented. You don't have a lot of space there to work with so every bt of technical edge will help. Here's a way to maximize insulation results. install perforated foil 1" below the plywood; use spacers and staples to accomplish this. This 1" space must be vented. Add insulation to the remaining space. Cover bottom of joists with a vapor barier foil. Tape and secure all seem so that there is zero air leak through this barrier. Add furing strips, then drywall. The two foil surfaces will kick back huge amounts of radiant heat from the summer sun, and from the heated space in the winter. If you really want to kick the values up, add foil face dowward 1/2" foam board under the rafters, then furing strips to get the 3/4" reflective air space, then drywall. Again, all seams must be completely sealed. Use tape. I did a system like this in Quebec. The results were extremely effective.

Where & when & how vapor barriers & radiant barriers should be applied vary considerably with climate. What makes great sense in Quebec can be a disaster in Florida (and conversely.)

Where is this house located?