Lies our fathers told us humidity

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Aqua Man

Aqua Man

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This is another old thread but to revive it, unless your running co2, there would be no reason to have humidity levels at 70% to even 75% during flowering. The reason humidity levels are run higher with CO2 is because the temps run higher up to 95 degrees with LED. And to keep your VPD in a good range you have to run RH around 70-75%..

I run LED lights and the leaf surface temps runs .5 - 1.8 degrees Fahrenheit COOLER then ambient air temperature due to all the air movement needed to move the CO2 around the room and also to keep pests and mold in check. Because my leaf surface runs cooler then ambient air I run my flower rooms at 90-95 degrees with RH at 65-72% as my AC kicks on and cools it down to 90, my RH also decreases to about 65% when the AC kicks off and as the heat builds back up the RH also does with all the biomass... When the lights go out the room cools to 75 and my RH slides down to 55% with lights out. After week 6 co2 is down to 800ppm for week 7 and 600ppm for weeks 8 and 9. When I ramp down co2, I also lower temps..the last 3 weeks it’s 78 degrees lights on and 65 degrees lights off..the humidity only goes down as low as 50% I also run a hybrid setup that exhausts room air every 6 hours.

to grow with with both LED and CO2 really requires you to run hotter which in turn requires more humidity, to do it you need a sealed room and very good air movement both below canopy and above and all around. It’s high maintenance teetering on the razors edge. This type of operation isn’t your typical tent grow you have to have the equipment in place to DOMINATE your growing environment and have backup ventilation system in case something goes array.
I agree and disagree with supplemented co2... you need to run lower humidity and higher temps than what's usually calculated under VPD... co2 slows transpiration rates because the plant photosynthesizes more efficiently and thats how you combat it.

Now there is a whole can of worms that plays into this and no one size fits all.
 
XxTheWolfxX

XxTheWolfxX

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I agree and disagree with supplemented co2... you need to run lower humidity and higher temps than what's usually calculated under VPD... co2 slows transpiration rates because the plant photosynthesizes more efficiently and thats how you combat it.

Now there is a whole can of worms that plays into this and no one size fits all.
Every grower has valid things to contribute, no one knows it all. It’s been my experience with my setup that the plants are eating and drinking ALOT more then when I grew without supplementing co2. How I’ve always gauged that is with how much water my dehew pulls out of the air on a daily. It may not be the most scientific way. I’ve played around with different ratios and what I found works best for my equipment and plants is what I do. I’m always eager to to learn a thing or two though, it’s exciting when you find something new that works amazing.
 
Aqua Man

Aqua Man

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Every grower has valid things to contribute, no one knows it all. It’s been my experience with my setup that the plants are eating and drinking ALOT more then when I grew without supplementing co2. How I’ve always gauged that is with how much water my dehew pulls out of the air on a daily. It may not be the most scientific way. I’ve played around with different ratios and what I found works best for my equipment and plants is what I do. I’m always eager to to learn a thing or two though, it’s exciting when you find something new that works amazing.
Definitely, like I say a whole nother can of worms to it... you may not notice the need for a bit lower humidity if you have really good airflow... that increase to forced evaporation can easily make up for the difference... 100%agree with you there are many ways that work... each grow is its own beast
 
sosincere

sosincere

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To those that feel they cant get away with 60% RH and up, whether veg or bloom, it means ur grow lacks ventilation. Ventilation is the most underrated part of growing if you ask me, and the plant doesn't know the difference between lowering RH and increasing ventilation. Its better to increase ventilation then to decrease humidity, because bugs know the difference and decreasing humidity encourages spider mites. I have found that the sweet spot for veg IN MY SETUP is 67-68% RH and 65% in bloom. Bad Mites have a hard time gaining a good foothold in these conditions as long as temps are kept under 85F. Good mites love and thrive in these conditions (Persimilis etc). My setup is so well ventilated that plants will not grow if humidity is less than 50%. Growing was a headache untill i raised my humidity from the 50's to the 60's. THIS IS MY EXPERIENCE. RESULTS MAY VARY FROM SETUP TO SETUP!
 
XxTheWolfxX

XxTheWolfxX

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To those that feel they cant get away with 60% RH and up, whether veg or bloom, it means ur grow lacks ventilation. Ventilation is the most underrated part of growing if you ask me, and the plant doesn't know the difference between lowering RH and increasing ventilation. Its better to increase ventilation then to decrease humidity, because bugs know the difference and decreasing humidity encourages spider mites. I have found that the sweet spot for veg IN MY SETUP is 67-68% RH and 65% in bloom. Bad Mites have a hard time gaining a good foothold in these conditions as long as temps are kept under 85F. Good mites love and thrive in these conditions (Persimilis etc). My setup is so well ventilated that plants will not grow if humidity is less than 50%. Growing was a headache untill i raised my humidity from the 50's to the 60's. THIS IS MY EXPERIENCE. RESULTS MAY VARY FROM SETUP TO SETUP!
Good air movement and ventilation is definitely important..what you are explaining is you are forcing your plants to transpire more by aggressive air movement and to compensate you raise humidity. Each grow is its own beast. For dense nugs if you can get your humidity down to at least 50-55 percent that is one component that really helps. Of course there’s a genetic component to dense nugs and heat also is the enemy with dense nugs.
 
XxTheWolfxX

XxTheWolfxX

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Define “ventilation “ please.
That is the exchange of air, intake, exhaust which I think is important even in “sealed rooms” I run a hybrid system that exchanges the air 4 times every 24hours, I time it around my co2..if your not running a sealed room you definitely want to be more aggressive with it to keep ambient levels of co2 in the room/ tent..once you have a lot of biomass those plants really deplete available co2 very quickly.
 
Grapefruitroop

Grapefruitroop

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Hey guys, im dooing several experiments on clones and high humidity during flower ....i totally agree that my plants really look great, vigorous and prayn to the light when i raise the humidity above reccomended levels...sealed environment here, Leds and Co2
Last run i went till the first weeks of flower with high humidity then lowered to the reccomended range, but the plants stopped to be so vigorous and perky..
This time i decided im gona go all the way in high humidity....mainly because my bigass dehum puts out sooo much heat and also draws a lot of juice....
Now im in 4th week of flo....68-73 ° at ...uhmmm....yes....85-88 RH....😃
I reduced the watering frequency but didnt notice any delay in the speed of growth....so im also saving on nutrients togheter with power....
wish me luck...hopefullyis not gona turn ina mycelium ball!! ha!
I seriously think, doh, that mold issues comes mainly from microcondensation of water due to rapid temperature swings in vented growrooms and not so much from the sporeload of the room or the Rh.....will see......more tests to come!!
 
XxTheWolfxX

XxTheWolfxX

55
18
Hey guys, im dooing several experiments on clones and high humidity during flower ....i totally agree that my plants really look great, vigorous and prayn to the light when i raise the humidity above reccomended levels...sealed environment here, Leds and Co2
Last run i went till the first weeks of flower with high humidity then lowered to the reccomended range, but the plants stopped to be so vigorous and perky..
This time i decided im gona go all the way in high humidity....mainly because my bigass dehum puts out sooo much heat and also draws a lot of juice....
Now im in 4th week of flo....68-73 ° at ...uhmmm....yes....85-88 RH....😃
I reduced the watering frequency but didnt notice any delay in the speed of growth....so im also saving on nutrients togheter with power....
wish me luck...hopefullyis not gona turn ina mycelium ball!! ha!
I seriously think, doh, that mold issues comes mainly from microcondensation of water due to rapid temperature swings in vented growrooms and not so much from the sporeload of the room or the Rh.....will see......more tests to come!!
80s and above is too high…you’ll definitely run into mildew, mold or both…good luck.
 
goofy81

goofy81

10
3
Wow amazing that this thread is resurrected.
The reason for higher humidity is bigger stomata aperture.
When it's dryer, there's too much transpiration, the plant can't handle it so it closes the stomata to prevent water loss.
There's a study where a certain wind speed can increase transpiration by 60%+ and that same windspeed with co2 110%+.

Good air circulation and ventilation works to alleviate the problems of the imbalance of high humidity as well as increase transpiration!
 
XxTheWolfxX

XxTheWolfxX

55
18
Wow amazing that this thread is resurrected.
The reason for higher humidity is bigger stomata aperture.
When it's dryer, there's too much transpiration, the plant can't handle it so it closes the stomata to prevent water loss.
There's a study where a certain wind speed can increase transpiration by 60%+ and that same windspeed with co2 110%+.

Good air circulation and ventilation works to alleviate the problems of the imbalance of high humidity as well as increase transpiration!
What study is this? I would like to read it.
 
elduderito

elduderito

351
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I also am currently running at around 55-65% humidity and not seeing any problems so far... I have an extractor on my intake puling outside air into my tent to manage temperatures - and outside humidity is around 60% - sometimes higher when it rains... I've got 3 fans (16sqf) going all the all the time for air movement in the tent
 
Grapefruitroop

Grapefruitroop

483
93
DSCN1304yup

DSCN1303yup1

It turned out very well!! Not even a tiny bit of mold....The wettest garden in the world!!! HA haaa.....Rh 85 -88...sealed room
The main reason i did this is bacause i wanted to avoid overheating the room with the dehum, that btw was pulling 900w....i saved about 100$ on the bill
Its just a temporary thing till i will find a better and clever setup for the dehum....i was thinking to put it out of the room and run a duct to the room...

The plants have been always very vigorous and perky.....happy....i run the same clone since several runs and i took note of the bud development in the previous run on lower humidity...around 65-70....and didnt notice any slowth in the grow...even if i was watering every 3 days!!!
The yield was even better this time but i dont think has to deal with the humidity but more of the heavy pruning i did....

I got some black mold growing on the walls doh....and the bamboo sticks molded too!!...
 
sosincere

sosincere

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The plants can handle up to 80% RH with strong lights. The catch is the night cycle. You must keep below 70% RH for this if you have coke can or bigger colas. You def need good circulation and ventilation, but that goes for any plant. Plants outdoors receive unlimited fresh air and circulation, and we should be replicating mother nature.
 
Aaflexy

Aaflexy

346
43
How
View attachment 1157329
View attachment 1157333
It turned out very well!! Not even a tiny bit of mold....The wettest garden in the world!!! HA haaa.....Rh 85 -88...sealed room
The main reason i did this is bacause i wanted to avoid overheating the room with the dehum, that btw was pulling 900w....i saved about 100$ on the bill
Its just a temporary thing till i will find a better and clever setup for the dehum....i was thinking to put it out of the room and run a duct to the room...

The plants have been always very vigorous and perky.....happy....i run the same clone since several runs and i took note of the bud development in the previous run on lower humidity...around 65-70....and didnt notice any slowth in the grow...even if i was watering every 3 days!!!
The yield was even better this time but i dont think has to deal with the humidity but more of the heavy pruning i did....

I got some black mold growing on the walls doh....and the bamboo sticks molded too!!...
How did the cut down process go did you notice any mold afterwards?
 
Grapefruitroop

Grapefruitroop

483
93
Nope, zero mold ! i wrote that post after everything had been trimmed !!
The area i live in is very prone to molds....some weeds outside have PM too...
But the bamboo stick yes they got very colorful funks growing all over...i wasnt afraid cause the look of the leaves was so radiant and tending to the light that was obvious that the VPD , whatever it was, was perfectly spot on..
 
mikeross

mikeross

444
43
To those that feel they cant get away with 60% RH and up, whether veg or bloom, it means ur grow lacks ventilation. Ventilation is the most underrated part of growing if you ask me, and the plant doesn't know the difference between lowering RH and increasing ventilation. Its better to increase ventilation then to decrease humidity, because bugs know the difference and decreasing humidity encourages spider mites. I have found that the sweet spot for veg IN MY SETUP is 67-68% RH and 65% in bloom. Bad Mites have a hard time gaining a good foothold in these conditions as long as temps are kept under 85F. Good mites love and thrive in these conditions (Persimilis etc). My setup is so well ventilated that plants will not grow if humidity is less than 50%. Growing was a headache untill i raised my humidity from the 50's to the 60's. THIS IS MY EXPERIENCE. RESULTS MAY VARY FROM SETUP TO SETUP!

Do you run 65 percent humidity right up to harvest. I see better results with high humidity following VPD charts as best as I could. I also lower the humidity last 10-14 days but wondering if I should let it roll at 65 percent all the way to harvest. I've never had PM either since increase my humidity, sometimes as high as 70 percent in early-mid flower.
 
Aaflexy

Aaflexy

346
43
Nope, zero mold ! i wrote that post after everything had been trimmed !!
The area i live in is very prone to molds....some weeds outside have PM too...
But the bamboo stick yes they got very colorful funks growing all over...i wasnt afraid cause the look of the leaves was so radiant and tending to the light that was obvious that the VPD , whatever it was, was perfectly spot on..
Hey my bad for the late reply but this is amazing how you didn’t get mold at all on your buds and they look dense!
 
Grapefruitroop

Grapefruitroop

483
93
Hey i did it also for another run and that time due to heavy lollipop ing i harvested pretty big colas and i crashed my record of 1.56 Grams x Watts....85% RH ALL THE WAY with lots of ventilation..
I did found a hint of Aspergillum on very few buds doh....prolly 5 or 6 that grew inside the cola but i scaped off with the scissors no biggie....
Now with the winter coming i had to go back to the 60s cause i need the extra heat of the Dehum.....but in the summer ill be back on High RH cause it made me save lots of money on electric and the results were BoooomB
 

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