More exhaust or more intake and why??

Discussion in 'Grow Room Design/Setup' started by masterdebater49, Sep 18, 2009.

  1. Could someone please explain to me if you would want more exhaut or more intake and why I cant seem to find a real answer.

    I am trying to figure out the best way to use the 3 computer fans i have..2 80 mm and the other im not sure but its almost twice as big.

    I have a stealth dresser about 2x2.5 with Four 23 watt CFLs
  2. If you're trying to mask the smell, use more exhaust fans. More exhaust fans will pull a vacuum on the box and ensure that the smell exits the box only through the exhaust fan(and then carbon filter), since the vacuum will pull air into the box from small cracks that are sure to exist in your setup.
  3. So pump more air in than out? or More air out than in?
  4. Pump more out
  5. Suck the air air out.

    You want to keep the pressure "negative".

    If it was "positive" air/stink could be forced out of any leaks.
  6. Really you only need exhaust fans.. as long as your maintaining negative pressure then smells shouldnt exit thru your entrance. but remember, you MUST MAINTAIN negative pressure at all times!
  7. I'm on the process of designing my first grow box and I have the same thoughts... More exhaust, more intake or same exhaust as intake?

    I think that having positive pressure in the grow box like in "clean rooms" would be more healthy for the plants because plenty of fresh air will be available to the plants as it would completely fill the grow box before it exits mainly through the exhaust fans and partially from any small holes the grow box might have. I agree with you about the smell issue, but there are solutions for that outside the grow box and I think we should consider the health of the plants more.

    Negative pressure rooms is used in hospitals to keep germs and viruses spread further. That doesn't sound vey healthy for the patients/plants that lie in there, does it? :confused:
  8. #8 jollyrancher1, Sep 18, 2009
    Last edited by a moderator: Sep 18, 2009
    Just because you have "negative pressure" does not mean you don't have air flow.

    Depending on what type of "clean room" your talking about (biological or assembly) some will run at equal pressure.

    The biological run at negative for obvious reasons, they don't want bad bugs getting out.

    Like that, you don't want stink leakage.

    Your not growing cocaine so you don't have to emulate high alttitude.
  9. In the fire service they use to use negative pressure to clear smoke from a house using fans hung in the windows. didn't work very well. today they place a fan at the front door and close all windows and doors except for one and open the window about 6 inches and fire off the fan. This positively pressureizes the house and clears it out much more efficiently. how ever this would work only if your grow box is fairly air tight.
  10. If you want to check your system, I suggest you burn incense in it.

    If you can smell it, it won't be much different then what your grow will emanate.

    The object is to not be able to smell it at all.

    Easy test, and great for finding leaks.
  11. i know this is an old topic but it didn't help me much and im in the same boat. What if your not worried about smell from your vegging box? I need to know whats better for the plants bringing the air in at double the rate its exiting ? or the other way around and why?
  12. You should have twice as much intake as exhaust. There's a Ventilation FAQ at the top of this design forum.
  13. I'd say just go with a passive intake and use the two 80 mm fans for exhaust. Either way is fine as long as you have fresh air coming in and stale air going out.
  14. using 5 120mm PC fans 2 stacked on each other and 1 120mm fan pointed at the plant. 2 for exhaust and 2 for intake. 2 65w CFL warm white and cool daylight and 2 20w warm white  
    the fans on the intake has a filter to keep dirt out. it also helps "push" the air out the 2 exhaust fans.Also im using a PC power supply with fan.
    im not running any carbon filter so the exhaust fan has no restriction. space is 3x2x1 i think. its a cabinet of mine that i converted. i live in a warm humid climate. never had problems with temp in the box. running low to mid 80s
    hope this setup answers your question. Never had issues with the grow as you can see.

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