Determine CFM based on wattage or room size??

I'm trying to figure out what the minimum cfm rating my venting fan should be. I'm growing in a closet that is about 200 cubic feet and I'm using two 600W lights. The room is soon to be airtight so that I can use CO2 (So I want to keep the temp in the 80's). The lights will be air-cooled with venting that runs from outside the room, through the lights, and back out of the room (about 12-15 ft start to finish). So hopefully the air that's cooling the lights will not move the air inside the room. This makes me think that the grow room volume is irrelevant when determining the proper CFM of ventilation. So, is there a rule of thumb for CFM per watt? Also, am I better off using an intake and exhaust fan with lower CFM ratings, or just an intake with a high CFM rating? The room I'm exhausting into is only 10x14x10 with one window so I will be using a small a/c as well. Thanks for any advice you can offer.

measure the size of your hood and get the CF of it now times by 10 and times by how many lights. hoodcfm*10*#oflights. my opion is to use 1 exhaust and leave the intake open with a dust filter. 2 600 should be about 200cfm ;P good luck and keep on smokin'.

Now I'm not totally 100% sure one this since I've only been able to find a couple sources and they haven't had proof so who knows if they're legitimate or not, but from what I've read if you take your total area in cubed feet and divide that by 5, that's the amount of CFM you'll need on your exhaust. You use the number 5 because in optimal growth conditions you want the entire area to be ventilated out every 5 minutes. Now you say you're going to use supplemental CO2 so maybe you won't need to exchange it quite so much as long as you can keep temps under control. But along with CO2 your plants can handle a little bit higher temps.

And again, not 100% but intake should be twice as much as exhaust(not sure if it's just double CFM or 2 intake fans in different locations for airflow, I'll leave this up to you)

I know those 600 hps's do run pretty hot so I'll leave it up to the more experienced users to help you out. I'm sure there's tons of hps users that have used supplemental CO2 in their rooms, hopefully they drop in and lend a few words of advise as well. Also having that fan just for your lights isn't a bad idea, that could possible alter how much you need to vent out of your main room.

Hopefully this helps though, good luck and let us know what you got and if it's working well etc etc