Hello all! It's been a long time since I've been in these neck of the woods. Please accept my apology before hand for this long post/question. I just want to provide as much info as possible so that I can receive the best advice possible. I am having a humidity issue in my grow tent that I cannot figure out what is going on. I am in the 2nd half of flowering and my humidity levels are not stable. When the lights are on, my humidity is okay-ish. Normally, I can keep the temp inside the tent at around 72-77 and the RH around 52-57 (depending on outside weather temp and what I have my AC set), but when the light goes off, my temp goes down 67-72 but humidity goes up to 60-70% RH. I have a dehumidifier running 24/7. I'm able to keep the tent open most of the time so that I don't have to run an intake or exhaust fan (but they are installed and ready to go if necessary), and I also have a 4 inch oscillating fan on inside of my tent when the lights are on blowing across my plants. I turn it off at night because if I let it run when the light is off the humidity RH will increase above 70%. Normally I would not grow this time of year, and usually wait until September/October to begin an indoor grow. But this was suppose to have been an auto-flower and I was trying to squeeze one last grow in before it got too hot outdoors. Unfortunately, the auto flower didn't "auto-flower" and I had to induce flowering after 45 days of veg. Right now I am at the end of week 6 of flowering and it looks like it's going to be another 4 weeks until it's finished. Any help/advice would be wonderful. I would rather allow it to go as long as possible, but I am willing to pull it early to avoid any mold. Setup: 2ft x 2.5ft Gorilla grow tent. Mars Pro 700 watt custom LED with IR and UV (295 actual watts) Eva Dry Petite Dehumidifier model EDV-1100. 4 inch oscillating fan 2- 6 inch inline duct fans (1 for intake and 1 for exhaust with carbon filter attached) Growing 1 - Blue Dream'Matic and 1 - GSC Auto.
Well you could add another fan in there. Or run a heater I know that’s probably not ideal but it would bring your RH down. I woulda said just leave your lights on 24/7 to finish but it sounds like you had to go to 12/12 to Flower? Sent from my iPhone using Grasscity Forum
@Smokexbreak, if running one fan while the light is off increases RH, wouldn't another fan just increase RH more? And I think I get what you're saying about the heater because when the light comes on, the temp does increase, and the RH goes down. But that sounds strange because normally when the temp goes up RH should as well, right? This is a strange and new issue to me. Never had this happen before until I moved to my current location. But this is also my first time growing during this time of year. Growing indoors during the fall and winter is a lot easier to manage and control.
That fascinates me (a know-nothing). I think it begs the questions; What is the RH in your house otherwise? What is the RH outside? ... do you live near the equator?
@tooslow, currently the outdoor temp is 83 and the humidity is 48%. Indoors the temp is 72 and humidity is 55%. Note, the indoor temps I'm giving are the temps for the room the grow tent is in. They are both the same because I am able to leave the tent open. I am in the Midwest and the latitude is 39 degrees. Also, your first line "That fascinates me (a know-nothing)" <--- what is that suppose to mean?
Just keep a fan blowing at your lower canopy and air circulation going with your exhaust fan and you’ll be fine. I’ve grown in a garage with 109 degree weather and 80% + humidity and didn’t get mold by keeping air moving.
How are you running the dehumidifier? Is it a bucket system that you have to empty or a drain where you don’t have to worry about it. Bottom line is the tent is in a area with a high relative humidity (basement maybe) and the humidifier I’m assuming is outside the tent and probably not powerful enough to keep up with the area of the grow room. I ran into this before growing in my basement with a dehumidifier that I had to empty the bucket every 6 hours or so. If I had lag time between when the dehumidifier was full and emptied the reservoir my rh would always shoot up. I was always playing catch-up with the reservoir bucket to keep and never had my Humidity where I wanted during especially humid days. My recommendation depending on your setup is to create a drain for your dehumidifier or really keep up on emptying the reservoir so it runs 24/7
@Devo86, my setup is listed at the bottom of my post. The humidifier is a Eva Dry humidifier, model EDV 1100 and its small enough to fit inside the tent, and I run it 24/7. I may have to empty it every three days or so. I am growing in Super Roots Air Pots (drain to waste). The tent is on the first level of a duplex (yes there is a basement and it's humid down there also). I try to keep the indoor temp no higher than 70 (but today is a bit of a challenge because it's 84 degrees outdoors).
I'm a rookie grower. I couldn't imagine how a fan, turned on, could raise the RH. I knew an expert would come along and explain it. Me? I know nothing.
The humidifier can’t be just in the tent to control the humidity. It has to control the humidity in the ROOM the tent is in. set It up outside the tent and keep emptying the bucket and keep the room the tent is in shut off from the rest of the house via a closed door or whatever. That dehumidifier will probably struggle with a decent sized room. You should have to empty a dehumidifier x2 a day at least (on humid days),not once every 3 days.
@Devo86, also the dehumidifier is really small and not that powerful, that's why it takes so long for it to fill up. It only removes .25 pints per day.
I think a new humidifier as you said would work wonders here. I spent 225$ on a dehumidifier for a 1000 sq basement and that thing struggles like a fat kid on a pull up bar, requiring emptying every 4-6 hours on a humid day. Best of luck my man
82f is my target for autos under qb. I live in midwest, temp and humidity are all over the place. Optimum is acheived about one week in spring and one week in fall. Pot still grows, I'm still stoned. I turn on the humidifier below 50% and that's about it. But temp 78 to 82 is ideal for me. I run my lights 24/0 germ to harvest.