Central FL Detached Garage Roof Insulation?

[blk99camaro]

Central FL 24 x 24 stick-built garage.

I have attic trusses that are 2x6 and the soffits are vented.

Currently I do not have drywall on the ceiling so its pretty open. There is no insulation for the roof and it gets pretty warm during the summer so I am looking for the best way to do this.

Initially I was considering foil-faced polyiso nailed to the bottom of the rafters and install gable vents, but 2" foil faced seems hard to find around here.

I happened to find a ton of new 4'x4' GFR (glass reinforced facer) polyiso in 2" thickness. It this acceptable to use? Do I need some sort of vapor barrier between the fiber face and the rafters/roof deck? What if I attached a foil radiant barrier first to the rafters and then the GFR polyiso direct to that? The GFR polyiso is a good deal, so if I can utilize it I will rather than spend 3x the amount on new foil faced (and still have to drive to pick it up).

Let me know your thoughts.

Jon

 

[PoorUB]

Sheet the ceiling with sheet rock or some people prefer USB, and blow in loose insulation in the attic. Make sure you ventilate the attic.

 

[bigdav160]

Air conditioning

 

[cannuck]

the 2" p/u should be great in your area. A vapour barrier is probably required, certainly wise choice. I did this many years ago with foil backed glass fiber, but the tape I used to make vapour barrier failed after 34 or so years and the foil backing itself deteriorated, so the first find out if the glass re-enforced skin is vapour tight and then find some tape to close off the seems. Wait a minute, you are in hot place, not cold. Vapour barrier wants to be on the cold side though, so a 6 mil poly barrier closed by the red tape would probably be what you need, trapped in place with p/u on "celing" and use its existing face for finish.

What are you doing with walls?