I imagine a good fan around the plant will be well, make sure it does go to exceeding temperatures, even ninety I see as fine from what I have read the plant tends to take in more light and sprayed nutrients at higher temperatures due to the left pores being more open. I know human skin pores open more in hot water so I imagine it to be the same.
cut a few vent holes in the roof ,,,should help a lot, be sure the seal around vents ,the vents will let alot of the heat out but also the smell as they get older ,,fans also will be needed (you can get a portable a.c unit about 300$ covers about 250sq feet ,needs to be vented to the out side ,small hole in the side of building )anyway good luck,be carefull ,PEACE,LOVE ,RASTAFARI
Yup, portable AC or take from the main unit if there is one, venting will go a long way but if you are sucking nothing but hot air in for ventilation you'll only get so much. If it's 95 outside in the summer, the intake/exhaust won't help as much. How hot is hot?
He could build a smaller grow room area within the garage and plumb a small intake fan from within the house to pull the a/c into the box and back into the house. He could put an inline carbon scrubber in to evade the odor problem. It would be the least expencive method of using the garage space.
After a crop or two, he could use his extra money to insulate the entire garage and put a split, ductless a/c unit in it. They work real damn good. You can get one up to 4 ton I think.