60% humidity in tents - and airflow

[Rama777]

Anybody else sitting at 55-60% humidity in a tent throughout flowering?

What kind of settings do you use on your intake and exhaust fans?

I have a 3x3 with a 6” intake and exhaust, plus two oscillating fans above the plants. The osci fans don’t point directly at the canopy, and are set at around 5 or 6 out of 10.

I keep the in-line fans at 8 and 9 almost 24/7

I’d love to turn those down for a few reasons but I’m afraid to.

Is that overly paranoid?

 

[Bdubs]

No you’re not paranoid. I’ve been there. To achieve lower exhaust fan speeds and environment dumping, use of a dehumidifier in the tent is the ticket. To keep temps down with humidity removal, find a way to exhaust the dehumidifier exhaust, to a hose that exits the tent. Or you’ll increase temps when the dehumidifier is running in the tent. Even a small dehumidifier you have to dump every morning will help nighttime humidity.

The other way to do it, is to control the rooms humidity in the room it sits in. The lung room. Use a dehumidifier in the lung room and drop that humidity out there low, then your incoming air has way less humidity and you can lower fan speeds.

 

[Bdubs]

My 6” 4x4 tent fan speed never went above level1 or I’d see the tent walls suck in. Too much negative pressure imo. Fans never help my humidity no matter what I do, unless the outside room humidity is substantially lower than the tent or I am forcing low humidity with a dehumidifier in the tent.

 

[Bdubs]

My flower room is the whole room, setup like a tent but the “tent” being a room. If it’s humid Outside, I use my dehumidifier to control. If it’s low humidity Outside, increasing exhaust fans to pull fresh air can do the trick, environment dump. I only like to dump environment when necessary though, as at night they release CO2 and I want to keep that CO2 into the morning light hours to help her perform better photosynthesis. Continual air dump reduces CO2 and tents are great at holding CO2 if environment dump is minimal. So you trying to achieve less fan speeds is desirable.

 

[figolus]

I open the windows in the room where i have my tent And from 57% I go to i have 37% humidity in flow

 

[Rama777]

Opening my window just raises humidity!! Gets to 80% here most every night.

I do run a dehumidifier in the lung room. No room for one in the tent. I have it set so that the flowering tent is always between 55-60%

I could lower that even further with the dehu, and in turn lower the settings in the exhaust and intake. But that will cost more electricity money. I can’t think of any justification for that. Can anyone one else? The only thing that really bugs me about it, aside from the volume of the fans, is the potential for messing up my terpenes with the intense airflow? Is that a thing?

I suppose it will get better as it gets warmer outside and I have to run the central AC.

 

[Gmix]

Anybody else sitting at 55-60% humidity in a tent throughout flowering?

What kind of settings do you use on your intake and exhaust fans?

I have a 3x3 with a 6” intake and exhaust, plus two oscillating fans above the plants. The osci fans don’t point directly at the canopy, and are set at around 5 or 6 out of 10.

I keep the in-line fans at 8 and 9 almost 24/7

I’d love to turn those down for a few reasons but I’m afraid to.

Is that overly paranoid?

Yeah I had 60f last year wasn’t worried as mold grows at 70f as long as you got air flow your fine at 60f.

 

[LoveGrowingIt]

Before I assembled my first tent, I had no idea how much the ambient environment could/would affect the inside of the tent. It sure does, though. Where I live, I deal with relatively low ambient humidity, usually 50% or lower, so I run humidifiers in my tents. I have a dehumidifier in my not-quite lung room, and use it after watering for a day or so. There are two tents in the room and both are in flowering mode. At the moment, the lights are off, the temperature in tent #1 is 74º, the RH is 56% and the VPD is 1.10. In the room, CO2=443 ppm, temperature=75º, RH=51%. The door to the room is closed and there's no heat or ventilation for the room. The lights will turn on in about two hours.

Now that I have three tents and I don't recall how many grows, I think the best approach is to keep tweaking the controllers, and if that doesn't work, add the equipment necessary to make it work.

 

[Rama777]

Before I assembled my first tent, I had no idea how much the ambient environment could/would affect the inside of the tent. It sure does, though. Where I live, I deal with relatively low ambient humidity, usually 50% or lower, so I run humidifiers in my tents. I have a dehumidifier in my not-quite lung room, and use it after watering for a day or so. There are two tents in the room and both are in flowering mode. At the moment, the lights are off, the temperature in tent #1 is 74º, the RH is 56% and the VPD is 1.10. In the room, CO2=443 ppm, temperature=75º, RH=51%. The door to the room is closed and there's no heat or ventilation for the room. The lights will turn on in about two hours.

Now that I have three tents and I don't recall how many grows, I think the best approach is to keep tweaking the controllers, and if that doesn't work, add the equipment necessary to make it work.

Thanks, that’s about where I’m at, though my temps don’t often drop during lights out. I’m at 77 flat almost always.

So when you are also at 56% and 1.1 VPD or so, what settings are your fans on? You have both intake and exhaust as well?

Currently lights off, I’m at 77/58 which is a 1.36VPD

 

[figolus]

Opening my window just raises humidity!! Gets to 80% here most every night.

It's very humid where you live

 

[Rama777]

It's very humid where you live

Yeah it kind of sucks, but the trade off is that I am able to irrigate my entire farm with spring water that I store in 2500 gallon tanks. When the shit hits the fan, I’ll take 30” of annual rainfall with 80% humidity all day..

 

[LoveGrowingIt]

Thanks, that’s about where I’m at, though my temps don’t often drop during lights out. I’m at 77 flat almost always.

My heater is set to 75. I let the light warm the tent during the plant's day. So, the heater only runs during lights out to make sure they don't get too cold. I've been thinking about lowering the lights-off temperature, though.

So when you are also at 56% and 1.1 VPD or so, what settings are your fans on? You have both intake and exhaust as well?

The VPD will rise when the lights come on and heat the tent. I only use an exhaust fan at the top of the tent, so far. It triggers on at 79º. I sometimes trigger it on high humidity, but not now. I don't have trouble with high humidity. It seems like I should when considering I live in a wet climate, but I don't.

I've never fully resolved the matter of controlling the environment in the tent and then venting it out. I don't like how the two practices are working against each other. It seems dumb. A lung room seems to be a workable solution, but I don't have the capability to do it completely. There are computers in the room and some storage. I'm working on a better way to do it, though.

Currently lights off, I’m at 77/58 which is a 1.36VPD

I keep the VPD below 1.3. That depends on whether the plants are vegetating or flowering, of course. I haven't yet advanced to the skill of triggering based on VPD. I'll probably try it soon, though. For now, I mostly look at the RH before I look at the VPD. I have a new tent going in soon and some clones ready to grow in it. So, that'll give me an opportunity to try some new things as well as apply some new learning.

 

[Rama777]

As for running my intake and exhaust so high, I really need to look into the major causes of powdery mildew and budrot, in terms of VPD versus looking at the humidity level alone.

 

[Bdubs]

“So, the heater only runs during lights out to make sure they don't get too cold.”

You have to hit 59 degrees before she stops working. If I hit 65 at night I am gracious. For me it allows my next 2-3 days day temps to be in the 70s before I see 80 peaks and my humidity stays more in check with a gradual increase as well. And less opening the outside door keeps everything more stable. If I am rocking 72-75 during lights on, that’s perfect with a 65 low. Typically it’s 75-80 during flower though. If I only get 70-71 as a low after an 80 peak day, I know I’ll be turning up the cold air intake for the last 3-4 hours of lights on period just to maintain and then pray for 65.

 

[hippyt]

No you’re not paranoid. I’ve been there. To achieve lower exhaust fan speeds and environment dumping, use of a dehumidifier in the tent is the ticket. To keep temps down with humidity removal, find a way to exhaust the dehumidifier exhaust, to a hose that exits the tent. Or you’ll increase temps when the dehumidifier is running in the tent. Even a small dehumidifier you have to dump every morni

ng will help nighttime humidity.

The other way to do it, is to control the rooms humidity in the room it sits in. The lung room. Use a dehumidifier in the lung room and drop that humidity out there low, then your incoming air has way less humidity and you can lower fan speeds.

Yes I absolutely last 3 weeks or so get that humidity as low as possible it really does increase resin production

 

[cannafarmer420]

Anybody else sitting at 55-60% humidity in a tent throughout flowering?

What kind of settings do you use on your intake and exhaust fans?

I have a 3x3 with a 6” intake and exhaust, plus two oscillating fans above the plants. The osci fans don’t point directly at the canopy, and are set at around 5 or 6 out of 10.

I keep the in-line fans at 8 and 9 almost 24/7

I’d love to turn those down for a few reasons but I’m afraid to.

Is that overly paranoid?

I slowly work my way down to 30%, if it's that high then i quote @Captspaulding "make sure you have them fans kicking like Chunk Boris"

 

[LoveGrowingIt]

As for running my intake and exhaust so high, I really need to look into the major causes of powdery mildew and budrot, in terms of VPD versus looking at the humidity level alone.

I've never had mildew or bud rot. AFAIK, they like high humidity. So, I've kept my RH in the 50s.

VPD is a numeric indicator of the plant's transpiration rate. The higher the VPD, the higher the transpiration rate. The optimal rate depends on the life stage of the plant. The older the plant, the higher the VPD it can sustain. The higher the VPD, the higher the growth rate, up to a maximum level. This is how VPD charts are helpful. Basically, VPD helps the grower manage the plant's growth rate, because it describes the rate at which water and nutrients are moving up from the roots to the leaves.

Transpiration is the process by which moisture is pulled through plants. Water and nutrition travels from the smallest root hairs to the underside of leaves, where small pores (called stomata) regulate the release of saturated (100% humid) vapour to the less humid air. Since the external atmosphere has less vapour, it exerts a pulling force (a pressure) on the saturated air when these pores are open. Hence Vapour Pressure Deficit.

Vapour Pressure Deficit dictates how efficiently a plant might balance its internal energy with that of the wider environment. Thus translating into just how well a plant can pick up or lose water, pump nutrients throughout, remain turgid and upright, essentially grow. VPD directly influences a plants’ hydraulic capacity and this, in turn, impacts rates of growth and overall plant health.

Plants are high in moisture content (they process up to 95% more water than they use for growth) and the gases in all healthy plants are always fully saturated. Since the air in the growing space is almost never fully 100% saturated, there is a difference in the pressure of the vapour in the air and the vapour in the leaf.

It seems natural that a healthy leaf should constantly be drying and so be cooler than the surrounding atmosphere, but this is not always the case.

On the one hand, if the air is cold and/or damp, less moisture is pulled from the plant, meaning fewer nutrients go into the plant and the plant might develop deficiencies and mould or freeze and die.

But if the air is hot and/or dry, the Vapour Pressure difference can be too great and can cause plants to become stressed under rapid transpiration. This can result in nutrient toxicity due to excessive uptake of nutrients (even if fed with just water). One of these nutrient overloads may be calcium, which can lead to chlorosis and stunted growth.

If the air is too hot and/or dry, the plant stops growing to save water and closes the cells that release moisture and enable photosynthesis (located on the underside of the leaf, called the stomata cells).

Source: What Is and How to Calculate Vapour Pressure Deficit (VPD)?

 

[Newty]

When do you water your plants?
If I water my plants toward the last part of the day, humidity will be high the next day but if I water at lights on, the humidity is much lower throughout the day and the day after.

 

[hippyt]

you need it during the day sunlight is how the plants suck the water up

 

[hippyt]

you need it during the day sunlight is how the plants suck the water up fwi co2 levels naturally raise at night they plants are u can take advantage of that peace