fan ? and inside grow room?

Discussion in 'First Time Marijuana Growers' started by korno, Jan 1, 2009.

  1. first off what will be better inside my grow room foil or flat white paint. grow room size is 4'x28"x28"

    the fan question is the exhaust fan duct in my bathroom goes right by my grow box. now could i take that duct put it into my box and bring another duct outside and use that as my fan knowing it will be on all the time or just stick with a seperate fan all together?
  2. never use foil so I'd go with the white paint. Foil creates uneven light distribution which can burn your plants.

    so would the air coming in be from the bathroom? If so, you may not want that since there is warm air with steam when ppl shower. Not the kinda air you want pumped into your grow. If the duct would pull air from both your room and the b-room, sounds like it could work. I;m just a lil unclear on your situation. any further explanation would help.

  3. you answered it i was just wondering if it would be safe and i didnt think the air from the bathroom would be good.

    the duct coming from the exhaust fan goes from the fan to the outside. i was going to take the end going outside and stick it in the box. then take a piece of duct from the ox to the outside. is latex paint flat white ok? thanks for the help i just cant find threads on some questions i want to get it everything right before i start
  4. latex is fineee. and it was np, I'm glad I could help. Best wishes on the grow:eek:
  5. I'd just use a separate fan. Maybe duct your exhaust duct into the duct of the bathroom fan, so you have 2 ducts joining into 1, which empties outside? Without pics I'm still not sure what you're gettin at
  6. #6 LaughingJim, Jan 1, 2009
    Last edited by a moderator: Jan 1, 2009
    Stay away from the bathroom fan...

    Heat rises, and shit sticks... Guess what is inside your bathroom fan's exhaust line? Pure ass fungus!

    Use a 12v wall-wart, and computer fan. Unless you are trying to exhaust 1000w of heat, you should be fine. Too large of a fan, and you are just wasting electricity. Not to mention, you will be wasting a lot of water, as your humidity drops from the high volume of air moving through your box.

    If your box is 120 cubic feet, 4.5 x 4.5 x 5.0, you can go as low as 2CFM, and should be less than 12CFM. (A 60 CFM fan will empty that box's air volume 30 times every hour. A 12 CFM fan will empty the box 6 times in an hour.)

    CF / CFM = Minutes to empty
    60 / MTE = Exchanges per hour

    CF = Cubic feet
    CFM = Cubic feet per minute
    EPH = Exchange per hour
    EPLD = Exchange per light/day

    On a 12/12, if that was constant on... in the light cycle... @ 120 CF
    60 CFM = 30 EPH = 260 EPLD
    12 CFM = 6 EPH = 72 EPLD
    2 CFM = 1 EPH = 12 EPLD

    If you separate the light, and draw out only the light air, 12-24 CFM would be fine for up to 1000w of heat. (The light is only 1 CF of area, so 12-24 CFM is 720-1440 EPH or 8640-17280 EPLD.)

    NOTE: Only a blower-fan, or squirrel-cage fan has a true CFM rating. Open-blade fans are rated on open-air CFM. Open-blade fans do not have much static pressure, and will not pump the rated volume through a constricted 4" or 5" or 6" line. You would need a 12" or larger line, without a grate, to get that CFM flow. EG, Wasted electricity, and additional heat to exhaust from the fan itself.

    A "Quiet" squirrel-cage or blower-fan has a high static pressure, and so you can go with less CFM, and it will be true to the printed CFM rate on the box. You will get 4x the flow, or the same true flow, at 1/4 the power consumed. Lower wattage, higher true flow.

    Open-blade fan, Static rating 60CFM open duct, 10CFM @ 3" duct.
    10 CFM @ 120v @ 0.57a = 68.4w

    Squirrel-cage fan, Static rating 60CFM open duct, 43CFM @ 3" duct.
    43 CFM @ 120v @ 0.98a = 117.6w
    *NOTE: Extra wattage here is due to oversized CFM in undersized vent.
    (Note, this fan is noisy, due to improper design. It is too large for the duct, but it is also 4x more powerful than the open-blade fan that it replaced.)

    Squirrel-cage fan, Static rating 10CFM open duct, 10CFM @ 3" duct.
    10 CFM @ 120v @ 0.15a = 18.0w
    *NOTE: This is the equivalent of the 60CFM open-blade, with that same duct.
    (The fan is correctly matched, and quiet as a toaster! )


    Also, personal experience with high-temp removal, overclocking, lighting, cooking, convection, absorption, and kilning.

Share This Page