Quagmire

hey i read somewhere that to determine the right amount of cfm you need from an exhaust fan in your grow room, you divide the cubic feet by 5. is this true?

Ex. a grow room the size of 240 cubic feet would need an exhaust fan of 48 CFM.

Supposedly you only need the air to refresh every 5 minutes

If I'm wrong please correct me - what do u think??????

my grow room is about 240 cubic feet and I was thinking about getting a 70 cfm bathroom exhaust fan from home depot and rigging it up to a window in the room.

gary420

that sounds a little low to me, for over 200sq feet with 70cfm.. im runnin about 30 square foot, an dim gonna put in 2 50cfm fans, and see how that does me..

im no expert or any thing, but i think that youd need more than that. check the growguide, i think it said you want it to cl ear out once a minute or something as such.

Quagmire

yeah i was hoping to go with that 70 cfm bathroom exhaust fan from home depot because it has a vent on it. There is a window in the room and it looks like I can rig that vent up to the window.

Otherwise what kind of 260 cfm fan do you think i can get and where can i find it? The home depot won't have it.

Europa

Five minutes refresh rate is not too bad. How many watts will you have in there?

Quagmire

1000 watt switchable mh/hps... BUT keep in mind there is a window in the small room. (10' X 4' X 6') 250 cf

i'd like to have the 70 cfm fan run on half the window sucking the air out of the room and a window fan on the other half of the window bringing fresh air in.

right now the temp outside is gonna be between 20 and 30 until our last month of growing, by then the temp will rise to 85 at the absolute most

jayda

my grow room will be much much less.. like 3 foot X 2 ... im using 4 105CFM fans.. and only 250W.. maybe i dont need the 4.

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gary420

damn!! 4 fans at 105cfm each!?!?!.. thats gonna kill your humidity man.. id take out 2 at least, and more than likely 3..

p.s., where did you get 105 cfm?? how much??

jayda

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i hope that they will be suitable
their is a 100,000 hour one for a little more i would probably just get that.

so you think too much venting will not be good?

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jayda

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230CFM... may put on after the carbon filter, to draw it hard and expell it from the box

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realpplsuck

for my grow box, im putting in 4 120mm computer fans with an old 200 was at psu. the fans im getting are 190cfm each, but im running them at 7v instead of 12v (so i will get approx. 70cfm each) it cost me $40 total. they are pretty loud at 12v tho.