The light in my cabinet has it's own ventilation system with a 6" duct fan that draws air over the light. The intake/output are the two 4" vents you see on the upper portion of the back of the box. I use a CAP AIR-3DN to control the environment for the grow chamber, which has active intake and exhaust fans. With my garage in the low 30's I can keep the box in the mid 70's. If the ambient temp starts to climb so do the inside temps. I'm in the process of having a whole house back-up generator installed. Once the electrician completes the work, I'm going to put 2 dryer vents in the back of my garage and and hook-up the intake and exhaust to them with the idea that the cooler outside air will help. Bottom line, you'll spend a bunch of $$ on cooling to keep an enclosed space at the right temp for your plants. My other concern is night temperature when I go to flower later in the month. I've ordered a 120v 24" baseboard heater that I'm going to mount in the box. The CAP AIR will control this also. Originally I had a small portable electric with a fan, but I'm out of room with 9 - 12" pots in the cab. I'm sure the population will shrink once I weed out any males, but I didn't want to cook the roots while waiting for flowering..

Hope this helps you!

Farmer Rich