What size or CFM of fan for my room?

I have a closet that is 4.5'L x 3'W x 8'H. I have a 250 HPS and the balist in the room, no Co2, what size of fan woul be required for this room? and where would the best spot be for it? in the attic on the top of the hole sucking the air out or under it blowing the air out of the room?


I also want to add a carbon filter but not sure what size?

Looking at these two:
GrowBright 4" fan (170 cfm) + Carbon Filter $120.95

Or..

GrowBright 6" fan (424 cfm) + Carbon Filter $185.95

your room is 108 cubic feet the four inch grow bright is more than enough for your size room and along with a 4 '' carbon filter you will be sorted mate.

ideally i would have 2 small fans 1 pulling cool fresh air either from an attic or another room outside your grow room. and 1 exhaust and have your carbon filter inline with the exhaust you can buy 2 fans and a carbon filter here in the uk for around £100.. this is just my opinion happy growing

instead of buying all of those fans, just use your 424 cfm as an exhaust fan, leave an opening for the closet to suck in fresh air from the negative pressure. since that fan is almost four times what you need you should be able to rig it up with just the one fan and maybe one small oscillating fan in your closet

Great info guys, I like the 1 fan idea, Could the intake duct go from my attic(coolside) to the floor of my closet, then the exhast to the other side of the attic out a whrilly bird?

Honkeycorn said:

Great info guys, I like the 1 fan idea, Could the intake duct go from my attic(coolside) to the floor of my closet, then the exhast to the other side of the attic out a whrilly bird?

Click to expand...

just make sure the intake isn't sucking in the exhaust air

http://www.htgsupply.com/Product-GrowBright-4in-Inline-Fan-&-Carbon-Filter-Combo.asp

I have this combo in a 2'x2'x5'4" grow space, and it is awesome. it moves plenty of air and heat out, and draws plenty of fresh air in the tent. I have 1 6" clip fan that i use for extra circulation. And like kbo said, make sure you're drawing fresh intake air, and not just sucking in the heat and exhaust air. Happy Growing..