I am redoing my shot through metal front porch roof with an EPDM glued roof. The porch walls are 2×6, tight, on 3 sides, and the house on the 4th. the roof is 8×28 with a 7:1 pitch from the house. The ceiling is a 100 year old bead board beauty…. I want to insulate the ceiling from above while I’m doing the roof. Online Spray foam kits that I see are 4x or 30x expanding closed cell poly for about 650-700 bucks. (my local distributor sells a 600 bd ft kit for $1700! ) I could cover the ceiling and house wall side of the space. This would solve the vapor problem, I think,,, or I could ventilate the roof from the eaves and put down batts. This way wouldn’t be a great vapor prevention method but would be a lot cheaper. I figure the air from the eaves would diminish the vapor problems, but I don’t want to put a vent through the high side of the roof.
Spray or Lay batts? 4X or 30X expansion? Ventilate no matter what or only if I use batts?
Any real world advice?