RH During Flower..help!

I cannot seem to keep RH below 50% i am at day 30 flowering I have an exhaust/intake both cloudline T6 I have 2 6” fans hanging from ratchet ropes in the tent I have my exhaust venting outside of the house via roof as of right now temp:81 RH:52% lights are on, when lights out RH can get up to 60% I have a 30 pint dehumidifier in my bedroom (tent is in my closet) I cut a 6” hole in my wall so intake is in my bedroom, I bought a mini dehumidifier that I put in my tent in between my 2 plants. I feel like I have done everything correctly maybe I need another fan that circulating air in the bottom of tent ? I have no idea some one help me lol

2 dehumidifiers?
What’s your room rh?

Outside room rh?

I live in fl outside humidity is 90% in my room is 49%
I’ve had the dehumidifier in my room for about 2 weeks lowest rh% I’ve gotten is 47% which would be fine if it stayed that way but it doesn’t
Yes 2 dehumidifiers a 30 pint and then just a mini one for inside tent

The warmer the air, the more moisture it can hold at a set rh. When the lights shut off, temps drop quickly, but the air is still holding the same amount of moisture. This causes the rh to suddenly spike. The spike is what’s dangerous during flower because if the humidity spikes rapidly enough it’ll cause dew to form on the buds, which promotes bud rot. I run my flowering tent at 72%-75%rh for most of flower with no rot so far. Not that I’m recommending it, just stating that low rh is not mandatory, just “easier”.

If your room rh that the tent is pulling air from is @49%, it’s tough to get the tent rh much lower. Simply because of the volume of air exchange with 2 t6 fans.

Where is the intake vent located on your tent, where is the exhaust vent located?

What happens if you shut off the intake fan and just let the exhaust fan pull things in passively? Try it for an hour, see if perhaps the rh drops a little in the tent. Watch the canopy temp too. Be sure it doesn’t get too hot with just one fan.


That’s intake
And my exhaust is going outside through the roof my canaopy temp lights on is 80-82 degrees
Just shut off intake fan and has gone up in RH by 1%

Okay it’s dropped to 60% one thing I don’t understand is fan speeds and what to put them on lights on I have my t6’s intake:6 exhaust:8 I think that is also a little high for a 2x4x6’7” am I wrong? I’ve been reading about inkbirk controllers not sure if I need one might make things easier. Temps now just the exhaust fan are 75 with both fans going the temps get anywhere from 68-72

My RH has been 46-53 all day ! Thank you so much you have no idea how much that helped me out ! @Drinkslinger

1 Like

Day late and a dollar short on this thread but…I am in late flower and have never had a problem with the Rh levels until now. What happened? Glad you asked! My ppm was way too high so I did a simi flush to lower it. Ran 1gal 1/2 of water through FF HF twice with 20% run off. I have never watered my ladies this much but was getting Cal-Mag issues due to low uptake because of high ppm. When I put my plants back in the tent the Rh jumped from 54% to 64%. I increased my fan speed, increased my exhaust speed, but nothing will bring it down. And do you know why? Because of so much moisture in the soil that is being evaporated into the air. So my question is 64% Rh is ok for a few days while the soil dry’s out?

64% might be fine. One runs the risk of encountering bud rot with high rh in late flower, but it doesn’t seal your doom. Most of the issues occur from lights out temp drops and condensation on the buds.

If you draw air from a conditioned low rh lung room it will keep your grow area conditions optimal.