cathedral ceiling in garage
i live in southern california, have a cathedral ceiling in the garage. the garage is attached with 2 walls common to the house. all the walls are insulated and covered with fire code drywall. i would like to insulate the ceiling to reduce the heat in summer. the joists are 2x6. the roof sheeting is faced with a reflective barrier. there are no soffit vents and nothing installed to vent air in the spaces. i want to insulate but would rather not have to cover it. i do not plan on heating the space ever. the only doors to the garage are the big door and a 28" entry door into the house at the back of the garage.
i thought about using kraft faced batts, r-19 or 21, or rigid iso board. if i have to put in vents and cover it, i may not do it. anyone have any thoughts?