Read the thread by Tranoble called 'the sealed room 3 lbs a light'.
With CO2, exhausting room air can waste it. DOES waste it. To cool the lights, run them on closed vent runs with intake and exhaust outside the room, not in contact with room air. You will most lkiely have to cob up a portable a/c with ducts for not only the exhaust, but also for the condenser cooling intake, because you can lose CO2 that way as welll.