BlowinKK said:

Having a humidity issue in my bedroom/grow tent.
Ambient temperatures 75, inside the tent is around 80-86 on full power.
Ambient humidity fluxuates beteen 57-63, inside the tent is between 65-75.
AC infinity t6 exhaust, and a t8 intake, running the t8 intake on medium, and exhaust settings on 3.
1 6 inch fan above canopy(adding 2 more fans).

So my question is, if i am aiming for 40-50% humidity in the tent would it be better to get a portable AC rather than a dehumidifer if i'm aiming to drop RH.
From what i have read a dehumidifer would raise the room temps between 5-8°F. I don't want to add any more heat to the tent, i would rather drop my temps dow. some to drop humidity levels.

Main goal is to lower my humidity levels 30-35 percent without raising temps to high or dropping to low.

Currently day 2 of flower.

Many thanks, keep blazin

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I'd get the AC. Cooler tent temps and dehumidifies the ambient air in the bedroom, lower RH in the tent. Win win for your sleeping comfort and the tent environment.

OldSmokie76 said:

I'd get the AC. Cooler tent temps and dehumidifies the ambient air in the bedroom, lower RH in the tent. Win win for your sleeping comfort and the tent environment.

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I'm thinking about getting the portable ac aswell, i'll spend 500 ona good one that will last me years if i have to.

But i am curious, will it drop my RH to the optimal levels? I am really trying to prevent any type of mold i can as this is cannahis will be used for medicinal purposes.

Why on earth would you want a humidity of 30-35%?

BlowinKK said:

I'm thinking about getting the portable ac aswell, i'll spend 500 ona good one that will last me years if i have to.

But i am curious, will it drop my RH to the optimal levels? I am really trying to prevent any type of mold i can as this is cannahis will be used for medicinal purposes.

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I'm not familiar with the abilities of the portable ac, but if you lower the temp and rh of the lung room (your bedroom) the tent numbers should go down also.

OldSmokie76 said:

I'm not familiar with the abilities of the portable ac, but if you lower the temp and rh of the lung room (your bedroom) the tent numbers should go down also.

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Yep... Or he can turn up the exhaust fan.

Aqua Man said:

Yep... Or he can turn up the exhaust fan.

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Exhaust fan is on 3, had it it all the way up at one point, didn't do much. I just ordered a small dehumidifyer and will buy a 5000 btu window unit to drop my temps later. Gonna need it for drying anyways.

Aqua Man said:

Why on earth would you want a humidity of 30-35%?

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Op said they want to lower their humidity from 65-70% by 30-35% to 40-50%

BlowinKK said:

Exhaust fan is on 3, had it it all the way up at one point, didn't do much. I just ordered a small dehumidifyer and will buy a 5000 btu window unit to drop my temps later. Gonna need it for drying anyways.

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Good plan on the window unit. I would avoid any of the portable ac's, I tried several and returned them all, they were pretty useless.

So guys i ended up buying a 30 pint dehumdifier setup outside the tent, ive managed to get my room to 50 RH and 53% inside the tent, would this be acceptable all throughout flower, or should i continue to aim for 40-45? If so, i guess i can try adding some charcoal inside the tent?
If i can save myself from buying an AC unit i would preferr to.

BlowinKK said:

So guys i ended up buying a 30 pint dehumdifier setup outside the tent, ive managed to get my room to 50 RH and 53% inside the tent, would this be acceptable all throughout flower, or should i continue to aim for 40-45? If so, i guess i can try adding some charcoal inside the tent?
If i can save myself from buying an AC unit i would preferr to.

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50% RH is absolutely fine

BlowinKK said:

So guys i ended up buying a 30 pint dehumdifier setup outside the tent, ive managed to get my room to 50 RH and 53% inside the tent, would this be acceptable all throughout flower, or should i continue to aim for 40-45? If so, i guess i can try adding some charcoal inside the tent?
If i can save myself from buying an AC unit i would preferr to.

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Aqua Man said:

50% RH is absolutely fine

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If the rh is above 50% late in flower you will need to make sure there is space between the plants and enough airflow to keep moisture from ever forming on their leaves. It can be done but I have had trouble in the past in flower at 50% rh when there wasnt some serious air movement. Id get a couple fans on the floor pointing up and a couple blowing across the top of the canopy, if the whole plants look like they are always dancing from the breeze youll probably be good.

Aqua Man said:

50% RH is absolutely fine

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FourthCity said:

If the rh is above 50% late in flower you will need to make sure there is space between the plants and enough airflow to keep moisture from ever forming on their leaves. It can be done but I have had trouble in the past in flower at 50% rh when there wasnt some serious air movement. Id get a couple fans on the floor pointing up and a couple blowing across the top of the canopy, if the whole plants look like they are always dancing from the breeze youll probably be good.

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If i put the dehumidifier inside the tent i can get it to 40-45 for sure but it just gets too hot, maybe i can makeshift something to redirect the hot air that comes through the top of the dehumidier outside the tent?

FourthCity said:

If the rh is above 50% late in flower you will need to make sure there is space between the plants and enough airflow to keep moisture from ever forming on their leaves. It can be done but I have had trouble in the past in flower at 50% rh when there wasnt some serious air movement. Id get a couple fans on the floor pointing up and a couple blowing across the top of the canopy, if the whole plants look like they are always dancing from the breeze youll probably be good.

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10% won't make any difference if leaves are laying on eachother.

I have to disagree with the 40-45% in flower. Imo it's old myth stuff. I run 55-60% even late flower. The issue is when the lights go out and then humidity spikes to dew point.

I'm not gonna go into it because I feel like a broken record but low humidity is worse for the plants and actually can increase the production of spores in the room. I know spores exist everywhere but imo this extremely low humidity of 40% is really old broscience. The studies are out there if ppl wanna look.

Airflow is key and keeping plants properly pruned. Humidity at lights out needs to be controlled but humidity during lights on there is no issue even at 60%.

In short the best conditions for PM is low humidity during the day and high humidity at night. Avoid that and no issues

Aqua Man said:

10% won't make any difference if leaves are laying on eachother.

I have to disagree with the 40-45% in flower. Imo it's old myth stuff. I run 55-60% even late flower. The issue is when the lights go out and then humidity spikes to dew point.

I'm not gonna go into it because I feel like a broken record but low humidity is worse for the plants and actually can increase the production of spores in the room. I know spores exist everywhere but imo this extremely low humidity of 40% is really old broscience. The studies are out there if ppl wanna look.

Airflow is key and keeping plants properly pruned. Humidity at lights out needs to be controlled but humidity during lights on there is no issue even at 60%.

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Ill definetly be clearing out all the stuff on the bottoms, if what you say is true i will add some more fans in there to help miminize the risk.

Aqua Man said:

In short the best conditions for PM is low humidity during the day and high humidity at night. Avoid that and no issues

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Ill be leaving the dehumidifier to run through the whole flowrring periid since the area i live in is extremely humid all year

Have a read. There is lots out there you just need to look past the mountain of old info. The reason ppl think 40% o think is due to not understanding how significant that humidity spike can be at lights out. This is why VPD got a bad rap from those ppl with the same view. That and it was largely used improperly.

By Mark June-Wells, Ph.D.
What Can Happen When Humidity Is Unbalanced?

Plants acquire carbon dioxide from the atmosphere in which they are growing; this requires that the plants open their stomata and capture carbon dioxide. Opening the stomata also causes water to be drawn up through the plant from roots to shoots to the leaves and, ultimately, the atmosphere. This process causes the plant to acquire water from the soil medium, which is laden with nutrients. Therefore, the following can occur if humidity is not balanced correctly:

1. With very low humidity, the plant is drawing water from the soil at a very high rate, and if the humidity is too low, the plant is unable to draw water at a rate equal to loss through the stomatal openings. The result is that the plants close their stomata, which slows the photosynthetic process (due to carbon limitations) and leads to stress, slow growth and compromised yield. Under severely low humidity, the plant will wilt and die because even its protective mechanisms cannot offset the water stress imposed by the lack of atmospheric water.

2. When humidity is too high, the rate at which plants draw water from the soil is reduced because transpiration is slowed by the smaller-than-normal water gradient between the plant and the atmosphere. This can result in diminished nutrient uptake efficiency, which can lead to nutrient deficiencies. This phenomenon is particularly evident in the uptake of calcium.

Additionally, saturated media pH has a tendency to climb over time, which can also result in many nutrients (e.g., metals, phosphorus and calcium) becoming unavailable to the plant because of altered chemical interactions under elevated pH conditions.

What Are Optimal Humidity Levels?

While cannabis cultivation research is a growing field, scientific evidence characterizing optimal growing conditions has not been fully explored. Fortunately, a vast body of research exists in the areas of indoor and greenhouse cultivation of many food species. Some of these food crops are suitable surrogates for determining potential cannabis cultivation conditions because of similarities in natural, physiological and environmental requirements.

The general humidity range for indoor cultivation appears to exist between 60% and 75% for all growth stages. When humidity surpasses 80%, particularly during the lights-off phase, a higher risk of fungal, bacterial and viral infections exists. Conversely, if humidity drops much below 50%, crop photosynthetic efficiency may be affected and yield will suffer.

Based on peer-reviewed research in the field of indoor/greenhouse produce cultivation, the following relative humidity (RH) conditions would be suitable for indoor/greenhouse cannabis cultivation.

Cloning: 70%-75% RH
Vegetation: 65%-70% RH
Flower: 60%-65% RH
Night phase of flower: 55%-60% RH
Tips: Always be sure to avoid stagnant air during all light and dark phases and swap air to reduce humidity/carbon dioxide levels during light-dark-phase transitions. Finally, be sure your temperatures are suitable for optimal plant growth during light-phases (75°-80°F) and slightly cooler temperatures during dark-phases (~70°F).

Mark June-Wells is laboratory director for Connecticut Pharmaceutical Solutions (CPS), one of four licensed medical cannabis producers in the state. Dr. June-Wells holds a Ph.D. in botany/plant ecology from Rutgers University, and has engineered CPS’ cannabinoid extraction efficiency and tracking programs, developed one of the largest production databases in the United States, and created efficient and repeatable production methods informed by rigorous data collection and statistical model building.

Aqua Man said:

10% won't make any difference if leaves are laying on eachother.

I have to disagree with the 40-45% in flower. Imo it's old myth stuff. I run 55-60% even late flower. The issue is when the lights go out and then humidity spikes to dew point.

I'm not gonna go into it because I feel like a broken record but low humidity is worse for the plants and actually can increase the production of spores in the room. I know spores exist everywhere but imo this extremely low humidity of 40% is really old broscience. The studies are out there if ppl wanna look.

Airflow is key and keeping plants properly pruned. Humidity at lights out needs to be controlled but humidity during lights on there is no issue even at 60%.

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Saying I had trouble with high humidity late in flower isnt bro science it anecdotal evidence. I was only sharing my experience not making any scientific claims and only suggested it needed to be low for late flower, not the whole grow.

Here are some science bros for you though:

Mary Hausbeck and Blair Harlan Michigan State University Extension said:

Recommendations for Botrytis fungicides for 2020

Research results for greenhouse ornamentals.

www.canr.msu.edu

The greenhouse environment provides ideal growing conditions for both plants and plant pathogens. The high relative humidity and lack of air circulation often found beneath the plant canopy are especially ideal for the pathogen Botrytis cinerea, commonly called gray mold. This pathogen infects many greenhouse ornamentals and is considered the second most important plant pathogen in the world.

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University of Massachusetts Amherst Center for Agriculture said:

Botrytis Blight of Greenhouse Crops : Greenhouse & Floriculture : Center for Agriculture, Food, and the Environment (CAFE) at UMass Amherst

Botrytis blight (“moho gris” or “pudrición gris” in Spanish) is one of the most common fungal diseases of greenhouse crops. The disease is often referred to as gray mold because it produces abundant fuzzy gray spores on the surfaces of infected tissues.

ag.umass.edu

Like other fungi, Botrytis has a specific range of temperature and relative humidity that is necessary for spore germination, infection, and disease development. Germination of spores and infection of the host is dependent on a film of moisture for 8 to 12 hours, relative humidity 85% or greater, and temperatures 55 - 75°F. Colonization of plant tissue takes place at a wide range of temperatures, but 60-75°F is optimum. Botrytis blight is more prevalent in the spring and fall months. Spores are easily disseminated by air currents and splashing water. The fungus may also produce chlamydospores and/or microsclerotia, both of which can survive in soil for extended periods of time. Given the common occurrence of Botrytis in greenhouses and the relative ease with which it spreads, greenhouse managers must avoid conditions that are conducive to disease development.

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Bottom line is it doesn't really matter, we both agree that the key is proper airflow.

I also did a write up on VPD. Here if you want to take it up a notch. Key is at night the plants don't transpire so humidity can be 10-15% lower. Of you have a controller that allows you to program setpoints it would be most ideal.

FourthCity said:

Saying I had trouble with high humidity late in flower isnt bro science it anecdotal evidence. I was only sharing my experience not making any scientific claims and only suggested it needed to be low for late flower, not the whole grow.

Here are some science bros for you though:




Bottom line is it doesn't really matter, we both agree that the key is proper airflow.

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I wasn't meaning to say you were giving broscience I'm bad with text. I agree with what your saying. And airflow is always key no matter the humidity.

I was referring to many growers that say you need to be 40-45% or you will have issues. I would definitely agree that at night 40-45% is absolutely ideal. But lights on 60%ish is ideal IMO. I feel day and night humidity should both be addressed and not just lumped together and called humidity.

Didn't mean to come off rude. Just trying to point out the difference.