I have a customer I am working with that did an addition to the house 15 years ago and the shingles are curled up pretty bad. It's a trophy room addition with cathedral ceiling constructed from a 2x8, roof on top side, drywall on bottom side with batts insulation between. It looks like I need to add ventilation to save the new shingles from excessive heat. I can't do that with typical attic venting because the 2x8 cavity is stuffed full of insulation. I was thinking of nailing 1/2"x 1-1/2" furring strips over the existing roof sheathing and then laying new 1/2" sheathing over that leaving a 1/2" void for ventilation. Use a smartvent at the bottom and ridge vent at the top. What do you guys think? Or other ideas?