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Tips for raising humidity?

This is my second grow in a 2x4 tent.

First time I used a T5 for veg and a 150W HPS. I got a decent yield from it, but it was the middle of a cold winter and temps in the tent were low, 60-65F with the lights on. I feel like that really stunted my growth.

For this one, I got hooked up with a 500W HID for veg and 500W HPS for flower. Makes a huge difference! Temps are way up. I can keep it at 80-85F with my fan on medium with two passive intakes, but my humidity is at 10% RH. I’ve tried a humidifier and a wet towel, but the RH doesn’t budge. I’m assuming the problem is the fan is sucking out any moisture I’m adding.

Any tips are much appreciated!


Morning Ben!

80-85F is a bit warm brother, does that 500W HID have a dimmer at all? 500W in a 2x4 area is pretty extreme, that’s a lot of light for that space, especially for veg growth.

I’d dial back the light first, that will allow you to turn your fan down even more (on top of less heat generated by the light,) then crank that humidifier. If the humidifier is working and doing it’s job, then my guess would be you’re simply exhausting it out too fast for it to raise the RH.

Ever consider LED lighting with your setup?

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I know, I know. It’s probably overkill. But the light was gifted to me from a friend who has a much bigger operation. I’m trying to make it work.

It’s actually plugged into a 1000W ballast, and I have it dialed back 50%, which is the lowest it goes. Maybe I should get a different ballast that can be dialed back even more?


10% relative is extremely low, out of interest what is the external ambient humidity level? It does seem that the humidifier is not able to cope with the demand, what type of humidifier are you using?


Thanks for the follow up. Not sure what the ambient humidity was at the time, but I’m guessing it was quite low. The levels went up to normal after a few weeks. Likely a combination of an increase in transpiration from the bigger plants and the ambient levels naturally coming up.


Yup it is amazing what a difference size of plant can have on things like humidity.

You can pretty much track a plants growth cycle by looking at the data around how long humidifiers/dehumidifiers are coming on for.

Good to hear things are more normal again.