Need a little help with ventilation setup..

High everyone! I’m in the dead of winter in the northeast right now and my humidity is STRUGGLING to stay above 30% in my tents with a humidifier running in the lung room constantly..

A little background of my little setup.. It’s a 9x11 lung room that contains a 3x5 tent for flower and a 2x4 tent for vegging. The ventilation setup is each tent has a dedicated fan and scrubber, the larger tent vents directly outside and the smaller venting into the lung room. With this setup, I keep both tents consistently at about 80-81F with lights on and run an oil filled heater in the lung room during lights out to keep the tents around 73-74F. My problem is keeping the humidity high enough and stabilizing it. I’ll be lucky to hit 40% in either tent. Obviously I can get a larger humidifier for the lung room, which I will get soon enough, but I’m thinking if I change around my ventilation setup that I might be able to solve the low humidity issues I’m having.
What would be the ideal setup in my situation? Would it make sense to connect the tents with 1 fan venting into the lung room and then make the other fan become a dedicated “exhaust” for the lung room controlled via thermostat and only pulling out the hot stale air as needed?
Let me know what you guys think, any advice is appreciated!!

What's the reasoning behind exhausting outside?

I have ac infinity humidifiers for each of my tents.
My lung room is 40%ish RH and the tents have no issue staying in the 70-80% RH range.

With humidity I've found it's easier to feed the tents directly instead of the lung room fwiw.

weedstoner420 said:

What's the reasoning behind exhausting outside?

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Maybe I’m wrong, but I feel like if I dump the exhaust from both tents into my lung room and don’t pull any of the hot air out, that temps would creep up in my lung room and eventually in my tents too.

.Smoke said:

I have ac infinity humidifiers for each of my tents.
My lung room is 40%ish RH and the tents have no issue staying in the 70-80% RH range.

With humidity I've found it's easier to feed the tents directly instead of the lung room fwiw.

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Do you exhaust any stale air outside? Does your lung room exhaust into another room?
I’ve found when I try to humidify the tents directly, I’m basically just sucking the humidity right out of the tent and exhausting it out of the house before it even has time to build up or rise. So my thought process is that if I exhaust the tents into the lung room, the lung room will eventually get hot and need to have air exchanged. A small exhaust venting outside on very low speed would hopefully keep the lung room at an ideal temperature while allowing fresh air into my lung room passively. Venting into another room isn’t an option, so it’s outside or nothing.

BigGreenThumb said:

Maybe I’m wrong, but I feel like if I dump the exhaust from both tents into my lung room and don’t pull any of the hot air out, that temps would creep up in my lung room and eventually in my tents too.

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I guess that would depend on how much air is able to move between the lung room and other areas of the house...even keeping the door to that room open would be enough.

Having gas-powered appliances in my house (boiler and hot water heater), the idea of exhausting my grow outside sketches me out, and my tent is okay being set up in an open area of my basement, but everyone's situation is different.

BigGreenThumb said:

Do you exhaust any stale air outside? Does your lung room exhaust into another room?
I’ve found when I try to humidify the tents directly, I’m basically just sucking the humidity right out of the tent and exhausting it out of the house before it even has time to build up or rise. So my thought process is that if I exhaust the tents into the lung room, the lung room will eventually get hot and need to have air exchanged. A small exhaust venting outside on very low speed would hopefully keep the lung room at an ideal temperature while allowing fresh air into my lung room passively. Venting into another room isn’t an option, so it’s outside or nothing.

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I exhaust to another room on the other side of the house.
I used to run with the same temps you did and had the same humidity issues. Once I started keeping my tents at 85F except for the last few weeks of flower everything improved including my ability to keep RH where it needs to be. (Fans run much less often and slower)

If you're using leds I highly recommend getting your leaf temps to 82F and you'll fix multiple issues at once.

BigGreenThumb said:

Maybe I’m wrong, but I feel like if I dump the exhaust from both tents into my lung room and don’t pull any of the hot air out, that temps would creep up in my lung room and eventually in my tents too.

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You won't know untill you try, it's often a challange and an education.

We can give you more ideas depending on your setup.
Variable speed fan with controller?
What type of heating system?
What prevents venting to or air exhange with another room?

Those are my humidity numbers in the winter too. I don't fight it. I don't run a humidifier. Small mist humidifiers don't do anything. You're better off with a towel half hanging out of a bucket of water than those. Large humidifiers might help some but seems costly to run. In my experience, my garden doesn't have any issue with low humidity. Ymmv.

1212ham said:

You won't know untill you try, it's often a challange and an education.

We can give you more ideas depending on your setup.
Variable speed fan with controller?
What type of heating system?
What prevents venting to or air exhange with another room?

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Very true about not knowing until you try .. you’ve motivated me
I pulled the exhaust from blowing outside and moved it to into the lung room. Temps crept up but seemed to stabilize around 82 after I cracked the window a tiny bit.. I’ll monitor it with my controller for the next couple of days and see what my numbers look like. Humidity is also already up and around 50-55% now which makes me feel much better..

To answer your questions.. the fans are both variable speed, not run with a controller for now. I manually dial them and like to keep them running as low speed as possible. For heating, wouldn’t call it so much of a system but it’s what I could figure out that seemed to work. It’s an AC Infinity Controller 75 (plug controller) and I set the temp according to schedule using an oil filled heater. I’m working on figuring out a way to just vent to another room but my issue is there isn’t much available wall space or access into the ceiling in the area.
Another issue is the boiler room is right next to the lung room that has a gas boiler and water heater. I’m just unsure if it would be safe to exhaust my tents into there or not.

MtRainDog said:

Those are my humidity numbers in the winter too. I don't fight it. I don't run a humidifier. Small mist humidifiers don't do anything. You're better off with a towel half hanging out of a bucket of water than those. Large humidifiers might help some but seems costly to run. In my experience, my garden doesn't have any issue with low humidity. Ymmv.

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I was trying that method but my tents were at 15% humidity and the plants were noticeably struggling. Since I’ve started adding humidity they look much healthier and happier. I’m currently using a small little room humidifier in the lung room and it runs 24/7 and can’t keep up with the task of maintaining the lung room at a decent percentage. I’m eventually going to get something bigger.
Does anyone here have that big Vivosun humidifier that has like a 5gal tank? Would love some feedback before I drop $150 on it