RH problems

GreenPeace22 said:

I DON'T GET IT! I just cannot understand RH at all, my mind is blowing...
Warm air holds more humidity, right? So if temperature goes up, RH goes up. Then why when lights go off RH goes up by as much as 15%?
Today my RH with lights on was 56%, as soon as lights went off RH went up to 64%, aaaaaaand, aaaand, the moment I put a circulating fan in the tent for air movement RH goes up even further to 73%, what the hell?

Can someone, please, explain me how RH works cause I'm going nuts trying to figure out how to control my RH, especially to lower it.

I'm growing in a 2x2 grow tent, with a 140W light, my intake is more than enough, as my tent walls are sucked in very hard, still my RH won't go lower than 55%. The room where the tent is located (the outside environment) has an RH of 73%. Even if I open the windows during the day the room RH won't go down, because that's the outside conditions as well. (it's fall, and it's rainy) WHAT CAN I DO? I'm in week 3 of flower, If I don't find a way soon, well, we all know what's going to happen...

Also, I wouldn't want to use a dehumidifier, maybe only as a last resort...

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Dr. Who said:

The "why/How" your looking for is based it the fact that the room RH is 73% and your trying to control a tent IN that space and RH...

LOWER/CONTROL THE ROOM'S RH !!! THAT is how to control the tent's basic RH issues...
I suspect that when your tent power goes off. It does not exhaust?

You have to keep moving air in and out off your tent by exhausting regularly/continuously - take your pick.
STILL! It will not get lower then the RH feeding the tent by the area it's in!
UNLESS you control that area's RH!

Dehumidify the ROOM and use the collected water.

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bluemagicman said:

Found this online and just about what i was going to say relating to plant transpiration, not shitting on you but everyone on here should have a basic understanding of how plants operate.

"Plants transpire water at significant rates during the night [8,9]. ... Plants loose water at significant rates during the night through 'night-time transpiration'. Night-time transpirational water loss is most likely the consequence of having respiratory CO2 escape at sufficiently high rates through stomata."

But yeah just drop your RH and get better ventilation.

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Richard Drysift said:

Last resort....you need a dehumidifier. Plants in a small space sweat; that’s growing indoors. Adding a dehumidifier will help but high RH is not as big a problem as high temps. Stop looking so much at your hygrometer and pay closer attention to the thermometer. The only alternative to a dehumidifier is running an a/c.

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GreenPeace22 said:

I DON'T GET IT! I just cannot understand RH at all, my mind is blowing...
Warm air holds more humidity, right? So if temperature goes up, RH goes up. Then why when lights go off RH goes up by as much as 15%?
Today my RH with lights on was 56%, as soon as lights went off RH went up to 64%, aaaaaaand, aaaand, the moment I put a circulating fan in the tent for air movement RH goes up even further to 73%, what the hell?

Can someone, please, explain me how RH works cause I'm going nuts trying to figure out how to control my RH, especially to lower it.

I'm growing in a 2x2 grow tent, with a 140W light, my intake is more than enough, as my tent walls are sucked in very hard, still my RH won't go lower than 55%. The room where the tent is located (the outside environment) has an RH of 73%. Even if I open the windows during the day the room RH won't go down, because that's the outside conditions as well. (it's fall, and it's rainy) WHAT CAN I DO? I'm in week 3 of flower, If I don't find a way soon, well, we all know what's going to happen...

Also, I wouldn't want to use a dehumidifier, maybe only as a last resort...

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GreenPeace22 said:

Temps are 70-85F, night and day, never lower, never higher. The humidity is my concern, I don't want bud rot

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Dougnsalem said:

+1 on the OP, just for the enthusiasm alone! That was an entertaining read. Don't stress too much, and pull a bunch of hair out; or you'll be bald like me..... Lol

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HydroKid239 said:

put an AC in the room the tent is in. Or dehumidifier. Also Only water when the lights come on. Not before lights out. That's asking for it.
My plants ph dropped so I flushed til I got 6.5 out the run off. Down to 330ppm. Unbalanced feeding caused a lockout. Lesson learned.
Had to flush with 3hrs left of daylight. So I have the dehu in the tent and the ac running on low.

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GreenPeace22 said:

I DON'T GET IT! I just cannot understand RH at all, my mind is blowing...
Warm air holds more humidity, right? So if temperature goes up, RH goes up. Then why when lights go off RH goes up by as much as 15%?
Today my RH with lights on was 56%, as soon as lights went off RH went up to 64%, aaaaaaand, aaaand, the moment I put a circulating fan in the tent for air movement RH goes up even further to 73%, what the hell?

Can someone, please, explain me how RH works cause I'm going nuts trying to figure out how to control my RH, especially to lower it.

I'm growing in a 2x2 grow tent, with a 140W light, my intake is more than enough, as my tent walls are sucked in very hard, still my RH won't go lower than 55%. The room where the tent is located (the outside environment) has an RH of 73%. Even if I open the windows during the day the room RH won't go down, because that's the outside conditions as well. (it's fall, and it's rainy) WHAT CAN I DO? I'm in week 3 of flower, If I don't find a way soon, well, we all know what's going to happen...

Also, I wouldn't want to use a dehumidifier, maybe only as a last resort...

Click to expand...

GreenPeace22 said:

Temps are 70-85F, night and day, never lower, never higher. The humidity is my concern, I don't want bud rot

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GreenPeace22 said:

Thanks for the advice, but if I get a better ventilation than I already have my tent will collapse.

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Richard Drysift said:

Nobody does; you will always be fighting things like humidity; it gets better/worse depending upon the weather. Im saying if you can just keep temps pretty much where they are and have good circulation bud rot shouldn’t be a major problem.
If you have mold issues it will happen late in flowering. It has happened to all of us sooner or later but it’s not something that occurs if you are always mitigating against it with prevention like a dehumidifier, fans, and ducted exhaust. Adding an a/c is another option but one that you could employ if needed during a spell of high humidity in your area.
I say this because the last time a plant in our garden got bud rot it was because the power went off for 5 days in August. One plant I had pulled and planned to trim and hang the next day. As it happened I never got back to it until lights were back on. It was elevated on a milk crate but also standing over in a puddle of water due to some basement flooding. We have stone foundation; water can sweat right through if the ground is saturated. Anyway my point is a hurricane caused all of this; not the RH of the grow rooms. It typically is 45-55% on a normal day and higher during summer months. We run a central a/c when it’s real hot but it’s off most of the year. Don’t worry about bud rot so much; you’ll know when it’s too steamy not to try and lower the ambient humidity when/if you can.

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GreenPeace22 said:

Thanks for your positive feedback! Much appreciated! My humidity levels still are in the 60s, but my ventilation is good, hope you are right and mold won't be an issues...

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Bukvičák said:

I think it works like this... It is Relative Humidity and it is just counted of some math form of actual and absolute humidity. When you put these two humidities into other form you can count further and end up with form where RH fluctuation depends only on temperature changing. I can not explain it good in English but the result is like this. You have a room with air which has specific amount of water inside and temperature. RH depends only on temp (when there is same amount of water in the air). When the temp goes higher your RH goes lower but with completely same amount of water in the air. Problem is, when the lights go off and and temperature drops. Than your RH rising high plus that extra water from plant respiration.

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