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Humidity issue i can't correct!!!

Kalidaze

Kalidaze

New member
Hello farmers,

So, I'm growing 4 plants in a 4x4x7 tent in a 10x12x10 sealed room. They are day 12 seedlings. I live a couple hundred feet from the beach, so humidity is HIGH! It stands at around 70% during the day, and 80-85% at night. Temperature stays between 75-85 degrees in tent. I'm using DWC, and all 4 seedlings are currently in 1 reservoir (5 gallons of water). I have an iPower 6" inline exhaust (442 CFM) and passive intake (Five 6" ducts with insect screens). Running 600W MH at 75% power several feet above seedlings. There is negative air pressure. 2 oscillating fans above and below canopy

The problem I'm having is I can't seem to get the humidity lower than 70% RH (sometimes rises to 80% RH)!

In this stage, I'm not so worried, but I know this will be a problem come flower.

What I've done:
1) installed window A/C--- ran on "dry" setting but still didn't bring humidity down in tent.
2) tried 50-pint dehumidifier---brought humidity in room down to 45%, but TENT stays at around 70% RH in tent.
3) installed fan in room to circulate
4) tried putting dehumidifier in tent---no help
5) tried leaving door to tent wide open during light period with dehumidifier running in room---no change
6) tried exhausting into room instead of outside room---no change
7) took glass out of air-cooled hood---no change

This really is getting quite expensive, and if possible, I'd like to avoid any other big purchases (considered intake fan).

PLEASE HELP! I've been searching for a week and no forums or websites have been able to answer my question. It's usually, "get a dehumidifier." Even this website says it. Maybe DWC isn't the best choice for coastal regions? All I can think is that the 5 gallons of water in the tent is keeping my RH high, despite air pump and air stones.

Any GOOD advice!? Nebula!? Sirius!? I'm modeling my grow after Sirius' 600W grow journal. PLEEEEEASE HELP!

Thanks,
Kalidaze
 
My background is construction/engineering more than grow skills but here is my 2 cents.

It may be that your ambient humidity is so high since you live by a beach that even the best measures seem to do little.
Sometimes there is no way to force an environment to work because nature eventually trumps all.

Ventilating to outside is like opening a window on a submarine, there is no way to push enough humidity out because the surrounding area is saturated.
Dehumidifiers create more heat which makes more problems and it will make your hydro into more humidity.

You might need to switch to coco, even then you will fight humidity.
 
With your environment, you may be better off growing autos. I realize that doesn't help for this grow. But they go from seed to harvest is less time (up to month or more less time). You can leave your lights on up to 24/0 if you want to. Can leave tent flaps open continuously for better air flow. Seems like a hydro grow isn't the best choice. !2 day old seedlings.....seems you could change to another grow medium if you choose to.
 
Thanks for your comment Weedgrodamus. To clarify, are you suggesting I vent inside? I have tried that. Slightly raised temps, and despite 45% RH in room, didn't help inside the tent.
 
Thanks insomniaczzz. I will definitely consider autos for my next grow, and look into transplanting to a different medium.
 
Hi Kalidaze

Right now in the grow you don't have to worry about the humidity when you are vegging. I'm in a basement that was 70 plus humidity and I couldn't bring it down with my dehumidifier running 24/7 I had it in the tent . Just have a good exhaust fan and run it 24/7 4 plants in that tent, I can't see the plants but if they are bushy they make humidity. I run a oscillating fan on the roof pointing across the top and one in a corner blowing up the wall just for better circulation and no mold from high humidity
 
Hi Karlee. Thanks for your input. You are correct, my conditions are ideal for vegging. I'm trying to look forward for when they do flower and humidity should be lower. I've played with it just to see if I could lower RH but no success. Plants are not bushy yet, just started on 2nd set of serrated leaves. I worry about mold in the flowering stage with a RH of 70-80%. Similarly, I have 2 small oscillating fans, one blowing beneath the plant, one above. I run the exhaust fan 24/7. I'm trying to figure out how to lower the humidity now, so that when flowering time comes, RH isn't a big issue.
 
If you learn about the characteristics of relative humidity it might help you understand what you could do. Relative humidity is the ratio of how much water is held in the air compared to how much can be held at that specific temperature. The amount of water than can be held is increased with higher temperatures.
For example, air at 60ºF (~16ºC) can hold over five times as much water as the same air at 20ºF (~ –7ºC)
So for different temperatures with the same RH you have a different total amount of suspended water.

Venting out humid air is thought to lower humidity, but it can only lower it with respect to outside air, as air has to be pulled from somewhere new. So unless your pulling in air from a less humid micro enviroment, the result will be no better than outside air (excluding the temperature and pressure aspect of course). Usually venting is most beneficial where a source of humidity is created internally. Such as bathrooms, greenhouses, living occupents etc.
Greenhouse climate control displays the best efforts at enviroment conditioning. Its basically HVAC used in homes.
Heating venting and air conditioning is used to control nearly all aspects of enviroment control.
Heating increases temperature but is also used to control humidity by warming the air and reducing RH. Venting is used to control heat by venting out warm air and pulling in cooler outside air (remember nothing can be removed without being replaced). Venting is also used to reduce humidity. Air conditioning is used to cool air but also has an effect on lowering humidity (through condensing not from lowering temperature).

With your situation you may want to try one of these things or a combination of all. The higher RH in your grow box compared to the outside room even with dehimid devices could be because of temperature differences or perhaps transpiration from the plants.
 
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South Sierra Dude said:
Can I see a picture of your hygrometer, in place, don't move it.
Click to expand...

Hi South Sierra Dude. Here's the placement of my thermo-hydrometer. Back corner, off the ground, not directly under the lights. Not raining today to RH is "slightly" lower than normal (barely).
 

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I have nothing else construction to add, but I do hope things work out for and you can get a nice harvest avoiding bud rot. Sending good growing vibes your way.
 
Hello Danofdanger. Thanks for your comment. Ummmm, well.......I'm wondering if you read my thread. I have tried all of these things. I installed a window A/C......didn't lower humidity in the tent, though helped control temperature (which isn't an issue anyway). I used a dehumidifier to lower the RH in the room my tent is in (sealed room) to 45% RH......tent RH STAYED at 70% RH after several hours. Air that was being pulled into tent was 45% RH, so, I was pulling in air from a less humid environment. If you wouldn't mind, could you take another look at my thread and maybe suggest something I haven't already tried.

Also, I'm a little confused where you wrote ,"The amount of water than can be held is increased with higher temperatures." Later, you wrote, "Heating increases temperature but is also used to control humidity by warming the air and reducing RH." So, higher temps can increase the water in the air, thus higher RH, yet higher heat (thus higher temp) can REDUCE humidity? Can you help me better understand this? It seems contradictory.
 
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