How to regulate the humidity in the grow tent

Can some give me some information on how to regulate the humidity in my grow tent . It made for 1 plant.

1 Like

The plant later in the grow cycle will drive the RH up. If you are in a dry climate then running an in line fan on a timer may be enough. If you need to reduce the RH then the only choice you have if environment is not dry enough is to buy a dehumidifier. The opposite is true for too low RH.

Ideally you condition the room your tent is in. I do have my dehumidifier in the tent but is way oversized for it and have to manage it fairly carefully.

The bottom line is you should look at the least expensive way to adjust using fans and timers before using active systems that cost a lot of money.


Thanks for information.

1 Like

A cheap way to bring up RH is to place a couple of plastic containers in the tent with water in them. It is best if one is taller then the other. Then drape an old towel from the taller into the smaller. Water will wick through the towel and up humidity especially if you have a fan blowing on it.
I have a 4x4 with a childs sand bucket which holds a qt & 1/2 with towels into a couple of glad containers that are shorter. I get humidity up almost 10% this way WITH input and exhaust 4" duct fans running 24\7.
Others talked about using a sponge in a single container.
It’s cheap. It’s free. Give it a try


Thanks for information. My grow tent temp is 62 and humidity is 31. It’s been 12 days and my baby seem to be thriving. I choose White Widow for my first grow because I know very little about growing other than what I’m reading. My understanding is White Widow dose well in cold environment and dose well against disease and insects. With that to be said I figure with little knowledge and some help from you all My baby will be fine. I’m starting to get nervous because I’m read so much information and not sure what to do next. When do I repot her ? Is it when she is 8-12 inches or after 3 weeks? According to my LED lights it said to leave the lights on 18 and off 6 for vegetive stage and for the flowering stage it is saying 16 hours off and 8 hours on. But I’m reading something different in books. I’m wondering if it depends on the type of lights being used. Can anyone elaborate on this for me ?

Courious…what would you’ll think the RH should be (target #) in a tent grow in each growth stage???

I keep my humidity around 65-70 for seedling. After two weeks I lower by 5% a week until I reach 40% at week 8 from seed. I have heard many ideas on when and how but honestly I have been told watch your plants as they decide not some schedule someone else wrote. They can be great guidelines as a lot of experience is shared here.

My tent seems to stay between 45/55% RH throughout grow. Do I need to address this???

Thanks for taking the time to read and respond to my questions.

1 Like

Yes… what @Reticence said. I have a freind whos home humidity is bone dry. He hangs damp towels i. The tent a d it works. Ive never done it but .akes sense. He puls them out daily, dunks them and hangs them up on the tent(not dripping).

supposedly 50-60% rh is good during veg and the later into flower you want to be closer to 40-50% range

1 Like

I grow hydroponically in one of the lowest RH areas in the U.S. and don’t see any reason to use a humidifier. Doesn’t really matter when its growing and humidity is the last thing you want in a flower room.
“That’s just me”

I don’t think so. You can up THC production with a low RH in flower but pay the price in terpene production. Did my last grow and the entire flower interval I was at 50% RH and came out great (yesterday).

1 Like

By the numbers it seems I dont HCA have to mess with RH at this point???

What dehumidifier do you use? I have this one coming Friday and only spent $125 on it. Still deciding to put it in the tent, or by the intake filters.

Jonny Utah

Mine is smaller: not sure what it is but large enough to have an external drain.

1 Like

55 is a bit high for my personal liking when it comes to flowering as bud rot sucks big time. 35-45% for flowering is what I have found to be the general consensus on what I have read. But as I said I am new to tents and am along for the ride.

Trying this now on a new set up. Will let you know the results. I have 85-90F and 31% humidity on a lit (600W) 4x4 vented and filtered tent with 3 growing Lemon Haze. Trying to get my RH up 10+. Only second day on new set up - so watching and balancing. The girls look really healthy and ready for topping soon,

1 Like