Can someone help me with VPD?

I need some help with VPD, I’ve been trying to get my humidity lower but it makes the heat go up higher in the tent, since I put the humidifier outside of the room. What do you guys think I should do? How accurate is VPD and should I rather have higher temps or higher humidity?

Right now I’m running at 78F at around 72% humidity trying to lower it now. Starting early veg stage now too.

I don’t do the VPD thing but once you turn on a dehumidifier expect the room temperature to go up a few degrees … 72% is not the best to be at as you know…somehow you will need to get some cooler air into the room if you use a dehumidifier…some will hang those bags up to absorb moisture but I have no experience in that technique


I’m only using a humidifier for now, not a dehumidifier

then what do you plan to do about the 72% RH because this is going to be an issue for flower


I moved the humidifier to the outside of the tent

I am not sure why you want it running?


If you dont run a dehumidifier, you would need to have your intake air at a lower rh than the tent, or you will be spinning your wheels trying to find a solution. Ventilation could help, but again, if your intake air isnt better…

I personally ran a bigger dehumidifier outsie of my tent with the dry air blowing towards the intake. That helped with the excessive heat, while still lowering humidity.

The humidity in the room is pretty low, around 30-40% in the tent with no humidifier. It needs to be around like 50-60?

yes you are correct, I did not understand that point…so you do need some humidity added so putting it outside the tent is the thing to do but still try to get your air temp down a few degrees as well if possible

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I need the humidity to be around 60-70% in the grow tent during early veg stage, no? So I’m moving it from inside the tent into the outside so that it’ll lower the humidity in the tent and just be in the room.

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Yeah! I agree, I’m installing an AC this week, do you think it’ll be okay if I leave the humidity at 70% as is right now until the end of the week?

yes during veg should not be a problem…do you have a fan running to keep water from forming on the leaves

Yeah I have a fan blowing up and side to side, (oscillating) and another blowing air down


ok then you are set…


Appreciate the help, sorry for the confusion at the start

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I hope I helped you… I did misread what you wanted from the start

@Retiredoldguy I was confused too. Running a humidifier with 72% rh had me baffled.


Haha was my fault with the wording, do you keep a humidifier in your tent?

Yes when necessary. I also have a evaporative humidifier I run my closet. I find it helps to not use exhaust fans during veg while running them. Also I turn off intake fans. Basically limit intentional air exchange. Now I’m on the other end of things. Everything is in flower and running dehumidifiers and AC to keep temps and humidity as low as possible.

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