Optimum Humidity?

The real question is how low is too low? I've read some say humidity can't be too low. I think otherwise at the moment. Leaves looking pretty dry, humidity down as low as 9% up to 15% or so. Tossed in a green pad CO2 pad and a humidifier, took the oscillating fan down from 24/7 to 30 min on/off. I still have some ventilation with an inline fan on low, running maybe 100 cfm (low as it goes) plumbed through my hood and intaking at the top of the grow area. Just a 2x2 veg area. Doubt the RH will rise too much, but my temp/rh/co2 monitor does track on a graph and highs and lows, so I will know if I have to adjust. It's been set on about 3/4 power. Pain in the ass to keep filling, but I'm filling with RO water. I'd like to see at least 25-30% if not 40%. These are not old, 3 weeks or so from seed. Leaves feel dry, a few twisted. A little droopy too...not overwatering I don't think, letting it get relatively light before watering. I inspected one root zone, nice and white roots forming.

If just set it and forget it doesn't work, I'll hook up my humidity power switch, but I was hoping to only need one of those for the flower area.

Temps between high 60's and high 70's

co2 levels 550-750

Underground Scientist said:

The real question is how low is too low? I've read some say humidity can't be too low. I think otherwise at the moment. Leaves looking pretty dry, humidity down as low as 9% up to 15% or so. Tossed in a green pad CO2 pad and a humidifier, took the oscillating fan down from 24/7 to 30 min on/off. I still have some ventilation with an inline fan on low, running maybe 100 cfm (low as it goes) plumbed through my hood and intaking at the top of the grow area. Just a 2x2 veg area. Doubt the RH will rise too much, but my temp/rh/co2 monitor does track on a graph and highs and lows, so I will know if I have to adjust. It's been set on about 3/4 power. Pain in the ass to keep filling, but I'm filling with RO water. I'd like to see at least 25-30% if not 40%. These are not old, 3 weeks or so from seed. Leaves feel dry, a few twisted. A little droopy too...not overwatering I don't think, letting it get relatively light before watering. I inspected one root zone, nice and white roots forming.

If just set it and forget it doesn't work, I'll hook up my humidity power switch, but I was hoping to only need one of those for the flower area.

Temps between high 60's and high 70's

co2 levels 550-750

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Personally, In my rooms that have plenty of airflow I can push the temps to 85º + and humidity to 70%. If you are cramming plants in somewhere, then maybe running lower humidity to prevent mold would be a good idea. I have heard of plenty of people growing around 40% humidity, which seems pretty low to me, but they kill it. This make its hard to say anything, maybe it's strain dependent, but idk. Young plants love humidity so if you have the ability to supply them that, do so. What do you mean your humidity power switch? Like a timer with your humidifier plugged into it?

DO some reading on VPD (Vapor Pressure Differential), but don't follow it right away!!!!! I think you are right on thinking of getting your RH up to 40%. Start there and go forward crop after crop. GOod Luck

xmatox said:

Personally, In my rooms that have plenty of airflow I can push the temps to 85º + and humidity to 70%. If you are cramming plants in somewhere, then maybe running lower humidity to prevent mold would be a good idea. I have heard of plenty of people growing around 40% humidity, which seems pretty low to me, but they kill it. This make its hard to say anything, maybe it's strain dependent, but idk. Young plants love humidity so if you have the ability to supply them that, do so. What do you mean your humidity power switch? Like a timer with your humidifier plugged into it?

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I got a programmable power switch for humidity...Like 30 bucks. Set the low boundary, when hit, switch turns on until high boundary achieved, then doesn't turn on again until low boundary crossed again. It has a sensor on a cord you can mount. Pretty cool. I have temp switches that are the same.

Underground Scientist said:

I got a programmable power switch for humidity...Like 30 bucks. Set the low boundary, when hit, switch turns on until high boundary achieved, then doesn't turn on again until low boundary crossed again. It has a sensor on a cord you can mount. Pretty cool. I have temp switches that are the same.

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For sure. I'm fully aware of environmental controls capable of doing that, just didn't know how high-speed you were going.

xmatox said:

For sure. I'm fully aware of environmental controls capable of doing that, just didn't know how high-speed you were going.

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For 30 bucks, whatever. Its pretty cool

Underground Scientist said:

For 30 bucks, whatever. Its pretty cool

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Sounds great... do you have a link to the one you have?? Hope so

The humidity controller is 37.50, the temp is a little under 30. Just search WILLHI humidity controller on Amazon.

There is a temp controller for about $55 that is wifi. So you could adjust it with your smart phone if you have accessible wifi to the controller. I think it gives you the capability to see the temperature in real time and make adjustments. Really cool.

The regular temp is 28.50. I have one for a homemade spot cooler. I have a small box for clone/early veg with a 2 bulb 24" T5. It's in a 1'x2'x3'tall box. I have a small clip fan in there and I zip tied a coil of copper. That coil is connected with plastic flexible pipe to a tiny submersible fountain pump that circulates it through the pipe and heat exchanger and back into the 5 gallon cooler where the pump is. The box has 2 variable speed muffin fans for inside/outside air exchange. I just put 1 frozen gallon of water in the cooler with water and you get a long enough period of cooling when you need to bring it from 82-84 down to 76-78. I could just speed up the muffin fans, but with this method, I can pipe in some fermented co2. It can get warmer in there, I hate wasting light though, and a tiny space only needs a tiny bit of co2, and cane sugar co2 is really cheap to make. I can easily get my levels up if I slow down air exchange for that small space. I have diamond foil on the inside. I get about 15-33,000 lux, evenly spread on 2 square feet. Fine for a small amount of solo cup starters. I love these square based Solo Cups.

Underground Scientist said:

I got a programmable power switch for humidity...Like 30 bucks. Set the low boundary, when hit, switch turns on until high boundary achieved, then doesn't turn on again until low boundary crossed again. It has a sensor on a cord you can mount. Pretty cool. I have temp switches that are the same.

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What brand do you prefer?

Generally its more about keeping the RH low enough. Easy to raise the RH by leaving a bit of water in the trays or by misting them with neem, kelp, dishsoap, and plain water in rotation.

I dont really have a meter anymore, because i can feel and smell the humidity/temperature close enough to know when its fucked in one direction. But in flower, under 30-40 for me. For veg, 50+ but doesnt matter in veg if you mist them sometimes.

growingforfun said:

I dont really have a meter anymore, because i can feel and smell the humidity/temperature close enough to know when its fucked in one direction. But in flower, under 30-40 for me. For veg, 50+ but doesnt matter in veg if you mist them sometimes.

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Is misting enough?

RH of 9%, dry basement in the winter...with water boiler 30' across the room. Stays 64-70 in large room, grows enclosed in custom grow boxes, but real dry. It's kind of a pain filling the humidifier, but I'm getting up to 25% now, which seems good.

Underground Scientist said:

Is misting enough?

RH of 9%, dry basement in the winter...with water boiler 30' across the room. Stays 64-70 in large room, grows enclosed in custom grow boxes, but real dry. It's kind of a pain filling the humidifier, but I'm getting up to 25% now, which seems good.

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Thats what i do. Meh.

Underground Scientist said:

Is misting enough?

RH of 9%, dry basement in the winter...with water boiler 30' across the room. Stays 64-70 in large room, grows enclosed in custom grow boxes, but real dry. It's kind of a pain filling the humidifier, but I'm getting up to 25% now, which seems good.

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Misting very effective in raising hymidity. Do you have a microcontroller or ardiuno?

Judging by the other threads youve made, and your screenname, im assuming you think its a lot more percise than things are in reality.

So also take a deep breath and relax. Many times the best thing you can do for the girls is to take it easy.

How effective have those co2 bags been for you? Especially given a 100cfm flow for a 2x2x? Im asking not being a dick.

SSGrower said:

How effective have those co2 bags been for you? Especially given a 100cfm flow for a 2x2x? Im asking not being a dick.

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Yeah, It's not ideal to have so much flow for a small space, i might try not having the intake in the box, but external.

With the bag, it recommends just spraying with water to activate. If I spray it, my co2 meter will go up 100 - 200 ppm, even with the door off. Looking at the CO2 graph on my monitor, it looks like as it dries it peaks and then fades. So if my humidity was actually stable and I spritzed it, it might work better longer. Running some mild humidification does seem to add 100 to 200 ppm fairly steadily, even with ventilation. So it does work, but I think being fairly sealed is important to get greater results.

I screwed up my first few batches of fermentation. They worked, but not like they should have. I made some foolish mistakes, like not heating the water enough to dissolve the sugar better or properly activating the yeast. Using DADY Distiller's yeast. It is cheap in bulk and can withstand high alcohol content. I can hook a hose from the carboy, into the grow space, and put the airlock in the grow space for co2 release. I'm about ready to start another batch. If honey wasn't so expensive, I would use my Mead runs to fuel my grows. Pretty efficient from a production standpoint. Cane sugar brew costs me about $1 per gallon, Mead costs about $12 a gallon, but I get a nice end product with Mead, and I just dump the sugar brew.