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Grow tent humidity problems

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    Grow tent humidity problems

    Week 2 of flowering cycle. Grow tent seems to have too high humidity for bloom. Been ranging from 60-70+%. Worried mold may pop up. Room has air conditioner with a dehumidifier function. Been running the dehumidifier but it does not seem to be helping so much inside the tent. But when the tent flap is open for a little bit the humidity drops quickly to 50%. What is the ideal humidity for flowering in a tent? Weather here lately has been slightly foggy side with high humidity. Put a few towels above the window curtains to block the light from outside until its time to open the curtains after the lights kick on. Notice that one of them nearer to the ac machine seems to be consistently damp. Seems weird because mostly running ac in dehumidifier mode 24.7 Tent has an intake and exhaust fan and also a small oscillating fan. Keep the observation window open and the intake fan is strong enough that it is bringing a little air in passively due to negative pressure. The intake and exhaust run 24.7 the oscillating fan is off when the lights are off. Using t5 tubes so they do not generate a lot of heat versus other types of lights. Thinking to put another fan inside tent. Is a dehumidifier inside the tent a good idea? don't really feel like opening the tent flap all the time or leaving it open. Appreciate the advice. Total noob here.

    I actually find the heat from my LEC actually helps lower the RH significantly. You might consider a hotter light? Especially if you’ve got a good ventilation plan, which it sounds like you do.
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      Trying to understand your setup

      you have a tent, in an air conditioned room
      tent runs humid, you open the tent and RH drops.
      you use towels to block window light (into room), and one of them is regularly wet

      now, questions

      What is tent temp
      what is room temp (tent closed)
      what is RH of room when tent is closed?
      where does tent exhaust to? (Room? outside?)
      moisture near the AC unit? Where does the AC/humidifier unit drain? Where does the AC unit exhaust?

      what's your setup?
      how big a tent?
      how many plants?
      what's your medium
      how big a canopy do you have (lots of leaves, or stripped

      2nd week of flower, 70% RH is high, you are hoping to be down to 50 or lower
      Last edited by LurkingInTheGrass; 10-21-2019, 05:16 PM. Reason: Humidty


        So first off are you emptying the dehumidifier/ac unit? it may be leaking the water it has taken from the air. Also ac dehumidifiers typically dont cut it if you have chronic high humidity. You may have to shell out a little money to get a better one. Second, how leafy are the plants. The more leaves the plant has the more humidity there is. Maybe some defol will help a little.

        Just a thought, not a ventilation expert, why have an intake fan? I find that the negative pressure is enough. I dont know if it's putting more humidity in or not but try leaving it off for a few hrs just to see if there is a difference. Also what kind of exhaust fan do you have? how many CFM? What size is the tent number of plants ect (like LurkingInTheGrass asked)...

        You could try a small dehumidifier, but im not sure that it will work unless you get the rh of the room it is in down. If you have high humidiy air getting pulled into the tent then the dehumidifier in the tent may be ineffective.

        More fans may help keep you from getting bud rot but i would inspect your buds often.

        I also have an LEC that helps keep rh down a bit.

        These are my thoughts and opinions!


          hey stick, if you can give some more info, like LurkingInTheGrass's questions, i have some ideas. Im growing in a tent in a garage where the garage temp is 65 the inside tent temp is 78%, grew all summer with A/C dehumidifier challenges. Whats the RH of the room the tent is in? Im questioning your A/C should be bringing the rh down to around 50% or maybe it draining somewhere..i was drawing out around 10 gallons every 12hrs when it was humid(above 50%)for my flower period. maybe shut down your air intake and just vent..add another fan or two...
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            Hi guys so the tent is 4 x4 x 6.5. The dehumidifier drains outside. The tent exhaust fan vents into the room. The room is mostly sealed but the roof is a bit drafty, minor leak when there is a heavy rain. Luckily not often rainy. Ran experiment last night. Left the dehumidifer function on for 24 hours. In the morning the temp inside the tent was 68 f/20 c and the humidity was still around 65%. Got a second room for the males which is tent and ac free, and the rh in there was ~70%. 4 plants in the tent. 2 are bush. Noticed the rh inside the tent generally seems higher since installing the intake fan. The negative pressure before without the intake probably was enough but was thinking more air coming in and at ground level versus window level might be good. Decided to buy a small dehumidifier to put in the tent. Between that and unplugging the intake fan hopefully will be enough. First time farming, been a life long dream and a learning process. Thanks again for the tips guys.


            • alltatup
              alltatup commented
              Editing a comment
              Is there any way that the exhaust fans can vent out of the room? More fresh air circulation.

            Unfortunately no. But have been trying to open the grow room door and occasionally the window to get in some fresher air. Seemed to help but now got a mold problem popping up. Making a post about this now.


            • Mr.furley
              Mr.furley commented
              Editing a comment
              Are your plant really bushy? Pictures?

            Well mr mr furley 3 is a company. Not sure what 4 is besides a bit crowded, hehe. 2 are bushy. 2 not so much. But the skinny ones are almost in the lights. Not able to bend them over due to lack of room. Not sure how it will work out. But at least the humidity is down.


              Got a decent humidifier. A bit big to put in the tent, but the humidity is now down to 47-50%. Thanks for the tips. Also cleaned the ac machine filter. May have been impacting the performance, as it was a bit dust loaded. On to the next challenge!


              Are you closing the tent when the lights are on? If you do, don't. It only needs to be closed during the 12 hour dark period.
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