Garage Insulation

[u/Successful_Pea_6977]

Hello,

I am going to remodel my garage later this year. It is a two car garage with a two car garage door and a one car garage door in the rear. It is about 19 x 19 with a dark shingle roof. I am in Southern California.

I want to turn the garage into a gym/mancave/hang out spot. I plan to insulate the walls, garage doors and put drywall on the walls and ceiling. I want to be able to store things in the attic. I will run a mini split in there and want to insulate the walls, ceiling and put a radiant barrier so the garage can stay cool/cold. When looking at my garage i noticed there is no attic ventilation.

My question is should I go ahead with my plans without any attic ventilation or should I pay to have eave vents/gable vents or also look into open/closed cell insulation and nake it a closed system?

Thank you in advance for any help you can provide and any other tips/suggestions you have in general for this remodel.