Low humidity even w/humidifier

Kindon67 · Jan 14, 2025

Please help. I have 4x4 tent with AC Infinity heater, Vivisun Mist humidifier and 6” in-line fan and oscillating fan. The in-line filter and fan are bit inside the tent, as I see in pictures. My exhaust is vented out my window but faces directly west which is the direction wind normally blows from. I live in western New York and in the winter the tent get to cold if I don’t run fan. I put a backflow damper to help prevent wind from coming in. So the problem is that I can’t get the humidity above 30% even with humidifier running full strength when the in-line fan is on.

What I’m trying now is to turn off in-line fan (hoping backflow damper works good enough) closing all vents in tent except the top one. I am hoping that the heater will blow in enough fresh air, the oscillating fan will move enough air around and the top vent will allow enough stale are to escape. This is getting humidity up around 50% but not to the 60% the humidifier is set at. I have also lost negative pressure doing this. I should mention that my plant are at the beginning of vegetative stage and are short. I know as they get bigger I will have less issues with humidity but the plants really need more humidity. I can tell because they are “telling” me. Please post any comments that you think will help. I’ve only had a few crops and this is first in winter when air in apartment is 30% humid. Thanks for any input.

Kindon67 · Jan 14, 2025

R4V3N · Jan 14, 2025

Just slow everything down by restricting your exhaust output until you get positive pressure (swelling tent). Don't have your oscillating fan blow downwards towards the plants, that's where you need the humidity to build up, point it straight across the middle on low. You just need it to move the air a little. Pointing it at the plants will just dissipate the humidity around them, causing the humidifier to have a hard time trying to keep up. The less air that escapes, the higher the humidity will rise. Then you can control the exhaust with a "chimney", instead of an exhaust fan removing it too quickly. Also tightening the drawstrings around the exhaust fans, can act like a rudimentary valve.

Blastfact · Jan 15, 2025

The tent or plants don't care if it's positive or negative pressure. I keep a vent panel open that's near a wall. And sometimes have lower power cord port open a bit. And the exhaust fan does not need to run 24/7 and if your blowing all your humidity out the window in winter your screwing up from the get go. I exhaust into my office/lung room and let the central heat and air deal with it. We keep vaporizers in the house as is because it gets so dry in the winter. I don't know what control you have for the exhaust fan. But I always set my exhaust fans to come on by a heat set point. If I want 78F then I set them for 78f with a 1 degree differential. Fan comes on at 78f. When the temp hits 77f it shuts off. I can push and set the set points where ever I want them. Set the humidifier where I want and let it cycle. And almost never run the exhaust fan over 50% on the speed setting. And as you maintain humidity and get control of your environment temp will get easier to maintain. Good Luck!

LoveGrowingIt · Jan 15, 2025

I also vent into the grow room. I don't run the exhaust fan at all when the plants are little. Small plants don't need much fresh air. As plants age, I either cycle it or trigger it by high temperature.

Humidity decreases as the temperature increases. What is the temperature in your tent?

Do you have an environment controller for your tent?

amneziaHaze · Jan 15, 2025

Fire makes heat co2 and humidity...
But as soon as your plants get bigger they will make their own humidity

Kindon67 · Jan 15, 2025

Blastfact said:
The tent or plants don't care if it's positive or negative pressure. I keep a vent panel open that's near a wall. And sometimes have lower power cord port open a bit. And the exhaust fan does not need to run 24/7 and if your blowing all your humidity out the window in winter your screwing up from the get go. I exhaust into my office/lung room and let the central heat and air deal with it. We keep vaporizers in the house as is because it gets so dry in the winter. I don't know what control you have for the exhaust fan. But I always set my exhaust fans to come on by a heat set point. If I want 78F then I set them for 78f with a 1 degree differential. Fan comes on at 78f. When the temp hits 77f it shuts off. I can push and set the set points where ever I want them. Set the humidifier where I want and let it cycle. And almost never run the exhaust fan over 50% on the speed setting. And as you maintain humidity and get control of your environment temp will get easier to maintain. Good Luck!

LoveGrowingIt said:
I also vent into the grow room. I don't run the exhaust fan at all when the plants are little. Small plants don't need much fresh air. As plants age, I either cycle it or trigger it by high temperature.

Humidity decreases as the temperature increases. What is the temperature in your tent?

Do you have an environment controller for your tent?

Kindon67 · Jan 15, 2025

These are good suggestions. I will redirect oscillating fan, exhaust into room and not needing neg pressure is good to know. I will worry more about pressure when the plants are larger and humidity is harder to control. Thanks everyone.

Kindon67 · Jan 15, 2025

Because exhaust fan is off and blocked to prevent back flow, for now, I decided to do this. I’m hoping that some of the humidity that escapes the tent will be drawn into heater.

Kindon67 · Jan 16, 2025

So I vented fan into room, installed an AC Infinity controller, leveled the oscillating fan and was still struggling to get results I wanted. After hours of moving things around and trying different vents, I finally got the environment exactly the way I need and it changes during lights on and off perfectly. Thank you guys for your suggestions. I’m glad I become a member of this forum. I’m sure I’ll need further assistance and I’m glad I have a place to go for that.

Low humidity even w/humidifier

Low humidity even w/humidifier

Kindon67

Kindon67

R4V3N

Blastfact

LoveGrowingIt

amneziaHaze

Kindon67

Kindon67

Kindon67

Kindon67

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