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Can you get your intake air from somewhere else? You're going to need to seal off that door when you flower. During the dark period it's suppose to be completely dark--no light leaks. If light leaks in they'll be reluctant to start flowering and they could even turn into hermaphrodites (so I'm told).
In my situation I build a cabinet that houses my grow. And the cabinet sits in a closet. It would have been easier to just use the closet itself as the grow space but I didn't have a good way to seal it from light leaks AND keep it looking like a normal closet. It was fine as-is for vegging but I needed the cab for flowering.
FWIW, I'm using a 6" 440cfm fan (with an extraordinary long duct run--about 50 feet of mostly rigid duct), an air cooled hood, a DIY carbon scrubber, and a 250w HID. I believe I've lost at least half the rated cfm of my fan (hard to judge). I also have a cheapy humidifier blowing directly into the grow area through some ducting. That helped bring temps down and raise my humidity to 35-40% (dry climate). My temps are 2.5deg above ambient (typically 80 minus 77.5 but the spread holds at slightly lower temps) ~8" below the bulb . Without the humidifier I believe my temp spread was more like 4, perhaps 5 degrees. My cab is actually a functional prototype that needs some tweaking so I think the final setup will improve the temp spreads. The final version will be a complete rebuild out of permanent materials, a real door instead of a sliding piece of cardboard, etc.
The first pic doesn't really show the whole current setup but might give you an idea of what I'm working with. The second and third pics are from before I got the cab prototype installed. With the pre-cab arrangement my temps where 1 degree or less above ambient. Also, that filter you see lasted about a week before it had to go. I've got a different one now that's more substantial (and restrictive).
My goal is to have enough cooling capacity to accommodate a 400w with no more than a 3 degree temp spread. And I'd like to accomplish that without needing the humidifier when the lights are on. I think I can do that but it's likely going to take the addition of another 6" fan. Dual exhaust fans where part of the original plan (even though I've only got one right now) so I'm ok with that. So much fan probably wouldn't be necessary for most but my exhaust fan(s) are really far away up in the attic (stealth!). Long runs means loss in cfm. Sorry for rambling but your situation reminds me a bit of mine.
Last edited by Hawk; 06-10-2008 at 01:18 PM..
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