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how to lower RH?

T

tyler_ hobbyist

New member
How can I lower my Relitive Humidity in my grow room? Without buying a dehumidifyer? I have a window fan that has 3 fans blowing the air into a bigger room I also have a air purifyer blowing air from my grow room into another room
 
id say air conditioning unit like mini split its the best way to go. Controled temperature and humidity around 50% But its expensive to run it 24/7
 
What's your temp atm? You could raise the temp to the upper part of the recomended scale and the humidity would drop a bit
 
Hang a couple of wet bath towels and keep them wet. They will raise the humidity by 5-10% in a small space if you have a small fan blowing on them.
 
Yes you can raise temps to lower humidity, but you are forgetting about the night cycle when the temps drop 10-degrees and then the RH spikes plenty high for the onsets of mold, bud rot and all the other unpleasant things which come from RH swings by trying to use heat to remove the issue. There are really two ways to really deal with humidity, the first is to bring in dry air and well it has always been my personal experience that its like putting a bandaid on the problem, yes it works MOST of the time, except when its humid outside like when its going to rain or gets overcast, or you live in a humid area, etc... The other way is to flat out remove the moisture from the air, aka a dehumidifier whether you buy one or make one yourself. I have never enjoyed a dehumidifier because of the excess heat they put off, so when I learned they are now using a chiller (DIY Chiller) and either buying or making a DIY Liquid Cooled Dehumidifier I was most curious to learn more. The short of it is they are taking an old dehumidifier and cutting the lines to the oversized heater core, I've also read and see guys use a car radiator or even a heater core to pump chilled water through it which then allows the humidity to condense and be removed from the air, just like a cold glass with iced liquid on a hot summer's day. Well that is what I know regarding high RH... and I also know that if you don't control it things like mold and bud rot can set in if you're not careful.
 
Relative humidity is the total percentage of moisture the air can hold, relative to temperature. The higher the temperature, the more moisture it can hold.

Increasing temps with a heater will lower relative humidity.

Using aircon will lower relative humidity also, this is because humid air is condensed through the conditioning cycle and is replaced with dry air.

Replacing inside humid air with outside drier air with air exchange system. This is used in greenhouses. However, you can only ever reduce the humidity as low as the replacement air.

The effectiveness of these methods comes down to how big the room is, how much air can be replaced, how much leakage their is etc. Implementation is importent.
 
It would be just as or easier to use a dehumidifer.
Using air conditioning is less efficient and requires sufficient air replacement for a sized room. A air conditioner removes moisture by condensation over a evaporation coil. In order for moisture to condense, the coil needs to be cold. This happens through a process of compression and decompression of refridgerents. The inefficient part of a air conditioner for dehumid application comes in two parts. One is from it reducing air temperature which if you remember, temperature is relative to humidity holding percentage. The other is through the process of condensing the moisture with coils. When the air is blowing over the coils, it removes the heat from the room and extracts the cold from the coils. The warmer the coils, the less moisture is removed.
Also the design, shape and size of the coils also dictates its dehumid efficiency.
So to all you people using air cons, if you want to improve the moisture removing effeciency, reduce your fan speed setting to its lowest setting and add heaters. If possible.
This keeps the coil as cold as possible, meaning more condensation.

A dehmidifier is like a aircon system, except the evaporator is designed to a higher efficiency. Prioritizing on condensation.

You could use a airflow system but as greenthumb pointed out, night time temps are a bitch and RH reaches nearly max depending on where you live. Huge swing.
And then you are still dictated during the day by what the outside weather gives you, which could be a whole heap of crap if its been raining. Not the ideal solution.
 
41 RH is pretty good for flower. I kept my RH at 40% throughout flower on this last grow and had a lot more trichomes.
 
Why don't you want to get a dehumidifier? Mine works great and I direct the hot air it blows out out of the grow room. It's a 50 pint.
 
What's your RH outside the closet and the other rooms???? If the other rooms RH is 40% it is going to be hard lowering the Humidity with just air movement -- If you blow or suck air out of a room unless it get's air from a different source it's going to suck in or replace that air with something and if that air is also 40%rh I don't see any gain of reducing the closet RH. A dehumidifier might be your only choice -- perhaps not in the closet because now you will have to deal with a lot of heat. Maybe just run the dehumidifier in the bedroom, dry that air out and then suck that into your closet. My $.02
 
Tyler, I'm at the same place in my first grow. My setup is a 4x4x7 tent, soil grow. When I switched them, the outside humidity was about 90%....brutal! I couldn't get my RH below 60%, and I tried all kids of things, to no avail. I finally broke down and bought a dehumidifier, yea, a good one will set ya back about $200, but worth every penny in my opinion. My electric rates are pretty low compared to other places (0.11/kWh). My temp and ph are stable at 76-79 degrees and 40-45% humidity. I can set the dehumidifier as low as 35% which is what I'll shoot for in a week or two as local humidity is dropping fast as the sun is out and the area starts drying out. I'm in NorCal so I'm sure you heard how wet we were this year. Best of luck on your grow!!
Just know, I'm no expert, this is just what works for me. Peace
P.S. My dehumidifier is just in the room, not in the tent.
 
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Yes 40% it's perfect. Mold comes when RH is over 70% or with suden cold when the dew covers the leafs for long periods of time. You won't have any issue with that. I use an air conditioner to cool my room where my closet grow is and my humidity is 50%. Outside its 70-95% all the time. That's the worrying numbers
 
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