I had some atlas board left over from a project. It's a reflective insulated vapor barrier and goes for almost $20 a sheet. I built a 2' x 2' x 30" cabinet from it and put a 150W HPS to start plants in before putting them into the vegetation room. Right now it's about 110* F with four 4x6 exhaust holes on the top and a small fan pushing air in. Once I receive the power cable I ordered capable of running enough juice to my new fan I will be able to push 38 cfm minus whatever restriction I have from the home made carbon filters. I worried that it won't cool the cabinet enough. Is there anything I could try to bring the temperature down further? I've heard you can run slightly higher temperatures with CO2 but I think I'll have too much air flow for that to be feasible. What makes it possible to grow plants outdoors in such high heat?