I insulated my garage by blowing cellulose into the walls and laying
rolls of fiberglass down over the ceiling. I insulated the door with
styrofoam garage door insulation panels from Home Depot. I also
installed a 24000 BTU mini split A/C. I can now cool my garage down
into the 70s very fast no matter how hot it is outside. Today it got up
to 96 degrees. When I got home from work my garage was 82 deg. I
turned on my A/C and it was 74 in about 30 minutes. I used to have a
portable A/C in my garage. It would run all day and would not drop the
temperature below 80 no matter what the temp was outside.