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What is minimum humidity for veg/flower? How to keep raised in vented rooms?

Discussion in 'Grow Room Design & Setup' started by NewGrower2011, Jan 11, 2017.


    NewGrower2011 Well-Known Member

    So the house humidity is low... high 20's currently. I know that plants need that humidity to facilitate nutrient uptake, etc through transpiration. Additionally, I'm running LED(s) so the room is actually staying fairly nice in the high 70's...

    What are the minimums during the two phases? I know in cloning/rooting it's high, but plain old veg/flower is what I'm uncertain of for minimum and ideal targets...

    Plus, how can I get this elevated? I have a humidifier (2 gal) but with the room being exhausted through a carbon filter, I don't want all that moisture just to be sucked up/out of the room (shortening the carbon life to boot - right?)...

    How do you all get that humidity in the ideal zone and keep it there, all the while venting the room (6" inline fan)...

    NewGrower2011 Well-Known Member

    I'm also worrying that my night temps are too low, my exhaust fan is a Hyper Fan and I've already been able to dial it down near its lowest point and keep those temps in the 70's - but I need minimum negative pressure to at least ensure odor control is being achieved through the filter and refreshing the CO2...

    ChaosHunter Well-Known Member


    Wilderb Well-Known Member

    Put the exhaust fan on a timer. Have it pull for a couple of min every hour or so. Timers are cheap and easy. The one I have is a digital and has 8on/off timers.
    I grow in a basement and always deal with cooler temps. If i set the timers around every 1 1/2 hours, I have no odor issues.

    NewGrower2011 Well-Known Member

    Not a bad idea on cycling the fan, but what about losing odor control when off (loss of negative pressure).

    I thought about backdraft dampers on my passive intakes but I don't know if the neg pressure is enough to open them (4" intakes x 3 could drop to 2 for more pressure....

    What I'd like is a fan controller where it always maintains a very low minimum and then using a cycle-time behavior for running @ higher speed (or temp controlled)

    ChaosHunter Well-Known Member

    I think an Audrino type controller might be the closest we can come to dialing in the perfect growing atmosphere. Compensating the rise and fall of external temps/humidity means we're constantly manually adjusting.

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