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Can someone talk RH to me please?

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    Can someone talk RH to me please?

    Ok, so I've read a bunch of stuff - and it seems like most people are trying to keep their humidity DOWN in their tents and boxes. I, on the other hand, have quite the opposite problem. Humidity here hovers around 15% on a "muggy" day, and less than that normally.

    Do I need to do something to increase the humidity in my grow box? After a good watering, it can get as high as 30%, but only for a short amount of time. What specifically, are going to be the benefits of me trying to get the humidity level up? Should I even bother? Am I inviting problems I just don't have to deal with, or will it really affect the plants growth and bud quality?


    I would get a humidifier that puts out a mist, but use purified water in it.
    Team AutoMechanics


      I am surprised your tent numbers are so low. It is all of 8% RH outside here today, but still 51% in my tent (My exhaust is always on). I have three big plants in constantly wet coco.

      Perhaps play with your exhaust. Unless your plants are quite young, they should be producing humidity. I am curious how your exhaust system is set up and where you vent to and draw from. How many plants are they, and I assume you are growing in soil... how frequently do you water them?

      I think it is awesome to have really low humidity. It allows me to create tons of humidity with my grow style that others have to pay to de-humidify. Perhaps consider a grow style that produces more humidity.

      In the end the humidity in the tent should be higher than 30s.

      Finally, If it is that low you should run lower EC/PPM (more diluted nutrients).



      • SamHeinous
        SamHeinous commented
        Editing a comment
        Yes, it draws and vents from the same room - which unfortunately I can't close off, as it's my front room. It is air conditioned. That's probably not helping huh? Hmm. We'll see what happens when I switch to coco I guess!

      • Campesino
        Campesino commented
        Editing a comment
        Yeah, it would help if the tent was in a bedroom or similar space that you could close off to trap the humidity and essentially recycle it. That is how I manage it. My tent draws from near the floor and vents along the ceiling of my office (spare bedroom). I close the door when I need humidity to go up, and open the window when I need it to go down. (Note to others: This is only appropriate if you live in a VERY dry climate)
        SamHeinous , If your problem is always being too dry then you are probably good to go without changing the set-up if you run Coco!

      • Campesino
        Campesino commented
        Editing a comment
        My two main recs for dealing with your low RH on the current grow
        1. Run lower EC/PPM: Plants will need to take in more water through their roots because RH is low. High EC could burn them.
        2. Don't defoliate. The leaves will help increase RH. I think the main benefit to defoliation (if there is one) is lowering RH. This is clearly not in your interests.

      Have a look at my article (Environment Conditions) on the importance of humidity to plant health and performance.
      Written Articles:
      Light Metric Systems
      Using Light Efficiently
      The Light Cycle Debate
      Environment Conditions
      Grow Light Technologies
      How To Compare Grow Lights
      To Defoliate Or Not To Defoliate
      Having A Light Source Too Close

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        I routinely grow plants during the winter when the RH is in the 20's and the only thing I find is the plants start out slower- but seem to catch up once a good root system develops.
        There is no loss of both quality and quantity, over growing in the summer when it's 40-60% with higher amounts in the tent.

        Last summer, I set up a tent which ran at the optimum RH and was chasing/mindful of VPD- I had exceptional looking plants in veg- but again- quality and quantity at harvest was the same when I didn't do all the work involved to maintain RH.
        It's all bullshit - until you smoke it!

        KISS @ Dry/Cure:

        Staged Harvest:

        "Schedules? We don't need no stinkin' schedules!":

        Grow Journals:

        #3, Window Sill Grow - auto:

        #4, KISS grow- Girl Scout Cookies- auto:


          I struggle to keep RH at acceptable levels too, except during mid veg. I tried an ultrasonic humidifier but it puts out a white dust from minerals in water, unless you use RO water, that gets all over your plants. I have switched to an evaporation humidifier, with humidity control, and it is working great.
          DIY grow space 2.5' X 3.5' X 6.5'
          315 LEC
          6" Vortex exhaust fan w/speed control
          6" Carbon filter
          3- 6" fans
          temp and humidity gauge
          5 gal smart pots w/ FFOF soil
          FF trio nutrients


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