In need of input on venting a colset grow set up

Hey,
I'm planning an indoor grow, a closet grow to be specific, and could use some input on proper venting and air recycling issues. The dimensions of the closet are 5' long x 2.5' deepx8' tall. I have a 400w MH light with a Lumecool reflector;It being vented as instructed. My question is whether or not i should invest in a blower fan or something to bring outside air into the space. what do yall think?

Nah, passive intakes will suffice. My closet set up is going to be very similar....at about 80 cu ft all u need is a 256cfm fan, even with a carbon filter...and u will be replacing the air 2 to 3 times a minute in that area. The bigger problem in my case is having sufficient passive intakes....I think i'm just going to lay some elbow pipes on the floor and cut around them or something with my poly plastic lightproof "door". Also keep in mind that with only a 256cfm fan and a 400watter in that same space, you'll probably run about 5 or 7 degrees higher than the temperate of the room you are taking air FROM (and thats if you have a properly vented light [sealed hood]).

Bigbud,
thanks for the help. I'm not to sure i understand how the passive intake you're describing would work but im looking into them. ive found one i think would suit my needs. Its a bite indiscreet and obtrusive but non-the-less its manageable. check it out.
Diy Light Baffle - UK420

That's interesting. With my closet, I have a folding door that rolls to the left on a track at the top of the door frame. My 2x4 planter is wedged into the room a bit. I'm attempting to use black poly (white side inside, black side outside) in front of the door to make a light proof barrier, and then cutting a big piece out and then velcro it as a door. I'm thinkin that I'll just lay 3 or 4 pvc elbows EvergreenSprinklers.com ::... on the ground and have the poly just lay on top of it. But I might try that method. It's a bit complicated, but basically I have to keep the swinging doors because its a bedroom closet (stealth) but i also need to make it light proof behind it (with little room).

It might be better to buy a new bi-fold door and modify it to suit your needs. Thats what im doing with my closet door.

What kind of growing medium are you using?

If its an aircooled hood and the hot air is being exhausted somewhere outside the closet then all you need to do is not have any intake ducting and it will create a negative pressure in the closet that will create passive intake.

The real issue for your closet will be getting enough outside air into the room where the closet is located, unless you decide to run ducting from the window to the closet.

I would suggest a simple, cheap $30 fan that fits into the window, flip it so its taking air in, problem solved.

Good luck.

tjgob22: Buying a new door is not an option for me....and I'm using Rockwool and Hydroton

BCtrippin: I would have to somehow incorporate an intake fan with black poly as lightproof "door" (behind the original closet door). I don't know if thats a feasible option, so I might just try some pvc elbows at the bottom...should allow enough passive intake/co2/fresh air replishment u think (with closet exhausted).