Growing plants inside wooden cabinet. Questions about ventilation

Discussion in 'Grow Room Design/Setup' started by zizou21, Sep 26, 2010.

  1. I plan to grow inside this thing
    [​IMG]

    Now I am wondering what kind of holes I need to drill in order to allow for proper ventilation. Would a 4-6 inch hole for intake and one for exhaust be sufficient? I don't really understand how a carbon filter works yet, but would attaching a carbon filter to each of these holes eliminate any odor emitting out this cabinet?

    Any tips for a few time grower would be tremondously appreciated :D
     
  2. in order to plan for vents and fans we need to know the Length and width and height of the space in question.....

    ill leave it to you......

    LxWxH=Cubic feet

    Cubic Feet x 3(air movement)=Cubic Feet Per Minute or CFM rating

    X 2 if you add a carbon filter=CFM Rated Fan



    ex: 2feet x 2feet x 2feet = 8 cubic feet

    8 x 3 = 24 CFM rated fan

    X 2= 48 CFM Rated fan

    if you have a four inch computer fan or inline fan pulling air out.. you would need at least one four inch hole to pull air into your grow space... minimum... most would say two four inch holes... but usually its better to play it by ear.... start with one four inch hole and be prepared to drill a second... you want to maximize your pressure with keeping your temps cool at the same time.....
     
  3. LxWxH = 36"x 20"x 60" = 43200

    x2 (since i am using carbon filter) = 86400 CFM Rated fan

    So u think a four inch fan pulling air out and a four inch hole pulling air in, with an carbon filter on the exhaust would probably be good enough?
     
  4. you just did cubic feet and inches together... were looking for feet
     
  5. 3 feet x 2 feet(more or less) x 5 feet =30 Cubic feet in your grow

    30 x 3 = 60 CFM rated fan without carbon scrubber

    120 CFM rated fan with carbon scrubber
     
  6. #6 zizou21, Sep 27, 2010
    Last edited by a moderator: Sep 27, 2010
    oh rofl sorry. so this means I need two 120 CMF rated fans?
     
  7. You just figured out cubic inches, not cubic feet. CFM doesn't really tell the whole story, though. You could have a 12 inch fan pushing 100 cubic feet per minute, and it would hardly feel like a gentle breeze, or you could have a 1 inch fan pushing 100 cubic feet per minute and it would be like a jet engine. The difference in this example is pressure.

    What you really need is a combination of adequate CFM and pressure. Pressure is normally measured in mm of H2O. This is also going to depend on what kind of lights you are planning on running in there. If you're planning on 100 watts of cfls, you won't need much ventilation, but if your going to run a 250w HPS, you're going to need a pretty serious fan to keep it cool. I would guess, however, that you'll need either a 4" vortex style inline fan, or about two really badass 120mm PC fans. If you are going for 120 mm PC fans, you'll need to find some with at least about 10 mm of H2O to both push through a filter, and still push a high enough volume to cool a space of that size. These pc fans are going to sound like a 747 taking off, though, at about 50 decibels or so. I've never used vortex style fans, but I don't really think they'll be any quieter. Here's a bargain 4" fan to get you thinking: High Tech Garden Supply

    This is really the toughest part of setting up a new grow space, and I'm amazed that there isn't more written on the subject.

    Take everything that I just said with a grain of salt, though, as I'm still trying to figure out this whole ventilation conundrum myself.
     

  8. no just one.... or if you wanted to use two fans... two 60 cfm rated fans... but now you need two carbon scrubbers
     
  9. #9 zizou21, Sep 27, 2010
    Last edited by a moderator: Sep 27, 2010

    Well, I had planned on using CFLs for the vegetative phase and HPS for flowering, is there another way to do this?

    I'm a little confused about what you said about the inline fan. This 4" vortex style inline fan would be expelling heat/odors from the grow space (cabinet) into the carbon filter that attaches to it?

    Am I on the right track here :confused:


    Just one? I thought I needed a fan to pull air in, and one to pull air out :|
     
  10. Yeah you're on the right track. An intake fan is not really needed. What most people use is a "passive intake" which is just a hole in the box that lets air in. This is called a "negative pressure" system. With this setup, the air pressure inside your box is lower than the air pressure of the room surrounding it. This way, if it isn't completely sealed, air will suck in to the box through any holes rather than out. If you ran a positive pressure system, you would have your fan on your intake, and your exhaust would be passive, resulting in a higher air pressure inside the box than outside. With this setup, any tiny holes or leaks in your box would allow unfiltered air to escape and you'd soon have a skunky house. For this reason growers almost exclusively use negate pressure systems.

    An intake fan would take some of the burden off of the exhaust fan, and allow you to go with a smaller intake, but you have to be careful because if you go to powerful with your intake fan you'll start to lose your negative pressure, and risk odor leaks. This is why most people go with a passive intake: it takes the guesswork out of it.


    The vortex fan would either push air through a carbon filter and out the box, or it would pull air through a carbon filter and out the box. Either way, all you really need is an exhaust fan.
     
  11. #11 zizou21, Sep 27, 2010
    Last edited by a moderator: Sep 27, 2010
    Ok sounds good. Should I put an intake dust filter into the passive intake hole?
     
  12. That's probably a good idea. I've never done that, and I will find tiny little hairs and shit on my buds sometimes. I think I'm going to do that pretty soon
     
  13. Tell me guys, would a system like this work?
    [​IMG]
     
  14. carbon filter goes on the other side of the light... you will see what im talking about once you look at a couple of pictures of carbon filters... other than that perfect
     
  15. So, something like this?
    [​IMG]

    Or could I plug the carbon filter directly in the light and skip the ducting?
     
  16. your best bet!
     
  17. Thanks ! :smoke:

    so I can't connect the carbon filter directly in the light? I will need to duct the two, correct? Sorry i'm such a newb I just want to make sure I have this right
     
  18. sure you can... thats what pigpen just said.. connect the filter to the light...
     
  19. I am doing this same thing sorta, What if I dont have a "cooling hood"? I just want to pull the air out? I see that you are running the air though something (trapazoid shape) I dont have that.
     

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