upgrade, How many CFM do i need for my exhaust...

trying to upgrade my light from a 250 hps/mh to a 400 hps. i am pretty sure the ventilation i have is not going to cover the switch as it only covers it now if i keep it cold in my house (like 65 degrees cold).

was wondering how many CFM would cover something like this. it is a 64sq. ft. room. i have passive intake in the bottom left of the room and want the active outtake into the attic.

i went to home depot and saw 4 inch, 80 CfM exhaust fans...and then they have 8 inch, 500 CFM....didnt see anything in the middle but i was stoned and wandering.

i also want to pass it through a carbon filter...ideas?

anyone with similar space?

Ya need to change the air every 5 minutes in the grow room.

so 80 cfm should be fine? right?

If your growing in a closet. 80 cfm. That's 80 cubic feet. To find the cubic feet of a room multiply its width by it length. Then multiply that number by its height. Every five minutes is the minimum. Good ventilation requires changing the air every 3 to 5 minutes. So an 80 cfm fan would work well for a room that was 6 feet by 5 feet by 8 feet. Basically a walk-in closet. Your best bet is to buy an in-line fan from a grow shop. Unfortunately they are expensive, at least 100 dollars, and they are relatively loud.

you can buy one or make one. i seen a homemade coffee can filter on here, did'nt think much about it till i seen a canister of activated carbon for like $5 at wal-mart, then realized how easy and cheap it would be to make. you should check FAQ or do a search, fuck i'm stoned...

nice. i am going to try to swing by the hydro shop this weekend and check it out. ill let you guys know how it goes. my last grow i had my lamp maxed out. ended up with 8z's on the 250. i wasnt able to get light to the corners of the room though so really only utilized 2x2.5 at conopy height. i am thinking with the 400 i can get one more row of pots in and also veg a little longer to spread the canopy out.

The Home DEPOT Suncourt inline DUCT boosters are rated way higher than they actually pull under load.

Also there is a middle one rated for 250cfm thats 6 inches.

When you apply load to them there cfm output drops DRAMTICALLY.

I would get the 500cfm 8 inch, and it probally will still not be enough and will burn out the motor within a year.

If you really want a good vent setup you can spend a little extra and get something along these lines that is designed to handle load.

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