Heat and Humidity Issues

Really starting to get frustrated. My grow tent is 2’X3’X5’, I’m running (2) 150 Watt HPS lights (running about 20" from plants), I have a Humidifier, I have a small fan (not blowing on plants), and I have an exhaust system. My PH is 6.3, I’m using Fox Farm Ocean Forest, If I run the exhaust system, my humidity goes down to 35%, if I shut it off, the temperature goes to 90 degrees. My leaves are now curling up around the edges. When I was in Viet Nam, this stuff was growing everywhere with temps in the high 90’s and humidity that was so high it would rot the stitching on our boots in a few weeks. The plants are (3) weeks old and are looking good other than the curling. I’m spending all day shutting one thing done and turning on another to try and stabilize the situation. I just watered them, so the soil looks a little dark.

Try putting the filter at the top of the tent where the heat is maybe?


No, tried that and it’s worst.

I have mine like this. Between intake and exhaust speed (and a humidifier) I was able to dial in the tent temps/humidity I wanted.

Ah, ok. I’m sure you’ll get plenty of ideas.
@Countryboyjvd1971 lives for venting…

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Try running without the filter to see if it gets better? Don’t really need it yet

One of the problems is, it sucks out the humidity.

Also check the temps in the top of the tent compared to plant level. If it’s hotter at plant level I’d say your lights are too close. Where’s that HVAC guru when you need em?

I assumed mine would do the same thing but somehow the humidifier was able to keep up. Even with my tent air turning over 2x a minute.

I have a different climate where I am and in my basement so somehow it worked for me. I can imagine it’s frustrating.

@joe1 where u located. What part of the world?

I’m running a IPower 4" exhaust system with a speed adjuster set to the lowest setting. I may just put it on a timer and turn it off and on as needed. Go Pats!!!


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My basement is a pretty good temp and humidity so even though I’m pulling my air thru, it’s bringing in similar air to replace it. And I imagine over time I humidified my basement since that’s where the tent exhausts. We’ll see what summer brings…

Go Pats!!! :football:

Yeah why not. That will let the humidity rise. And probably the temps to…

And you’re right. These mj strains are a long ways from what you saw in the 60s

You can also buy plugs that are thermostats. You can hook your fan to this to turn on at a certain temp and run until it lowers again, then shuts off.

Something like this but read it and shop around. Just an example.



I suspect you nailed it on the head hot air rises and extractor is pulling heat back down as well as drawing humidity out being so close to plant level and humidifier

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He said it was worse up top though.

it shouldn’t be unless your filter is clogged or your intake vent is up top cool air should pull in through bottom and warm air should be drawn out the top if humidity remains an issue use a dome over each plant short term heat rises
Rather an odd problem since I run 400w hps in 22"x44"x40" space atm rapidly about to change mind you I also am far less fussy about humidity and if temps hit 80’s and humidity hits 35-45% I am happy enough plants do acclimate as they get larger and drink more water I no longer need humidifiers even with exhaust cranked

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I’m right here

@Countryboyjvd1971 is taking a night off I think. Probably stuck in NY in a crowd of marchers.