Need better ventilation, and a cooltube maybe? Like EC^^ said, depends on intake temperatures a lot, but if the temps are that low then you'd need a heater at night... The ventilation (fan, carbon filter, duct, cooltube, mufflers) with HID's will cost as much if not much more than the lighting setup. I'd say look up some ventilation formulas, there's one in the Noob's Guide to Growroom Design thread by Rhizome. There are others online as well. Figure out the CFM you will need and buy one size larger with a speed controller. :twocents: