well my flower room is 32 sq feet. and with a 600w HPS, 465cfm squirl fan and a cool tube im still at 80 degreese F with the light on if that helps hehe without the fan on it will get past 100. so yea without vents it will heat up. but you got a little more space and 400s dont get as hot. IMP a cooltube with like a like 200ish cfm fan to exaust and that passive intake will be min to keep the heat down in thier