10x20 Tent - First Timer Battling: Air Circulation, Temperature and RH - Please Help ;)

Hi everyone. I’m in the middle of my first harvest and things are getting complicated. So far the plants are fine and I’ll keep this thread to a single specific item for clarity sake but all suggestions and help are greatly appreciated. If you have advice, please post it so I can make some adjustments ASAP before a little trouble becomes a big problem.

First, My Setup.
Gorilla Grow Tent 10x20 with vents and meshed inlets/outlets galore. I’m running x6 Gavita 1700e LED lights that put the ambient temp up into the high 80’s until I kick on 1 or 2 of my 12" can fans. Lot’s of oscillating fans pushing air around inside the tent. Plants appear happy.

The Process.
For whatever reason my can fans need to both be on low to medium to control the temp on the tent. I have my lower meshed vents open or else there’s too much negative pressure and the tent looks like it will implode. Sooo, we’re basically just circulating that air in/out/in/out the tent. Temp and humidity rise pretty quickly in the grow room outside the tent. As we begin sucking the hot/humid air back into the tent my internal temps rise to the high levels.

So, I opened a wall fan that blew hot air and humidity to the exterior of the building. This was fine for a few weeks but now it’s snowing and that needed to be shut to keep interior temperatures from falling too far. So the hot/wet air is stuck inside. I have my humidifier going steady and pull 3.5 gallons a night.

The Problem
My front room is getting too wet. When I come in the mornings there is severe condensation in the windows are it’s a battle to keep it below 70% RH. I’ve tried fans to circulate the air back through the building so it returns to the dehumidifier but it seems like the air hits that cooler room and the moisture just falls out onto my floor, walls etc.

Should I?
-Add more vents between the grow room and the front room to get MORE hot/wet air circulating? Although counter intuitive, this would probably move the air better through the whole building.
-Attempt to seal off the grow room and keep the hot/wet air in there with the dehumidifier? Not so easy to do, the wall is very placeholder and a seal would be nearly impossible.
-Other options?


Add more vents to the living room. Think of environmental control like old Chinese cities. They had a square city with walls and in that a smaller city within walls. It’s easier to control the “inner city” (your tent) if you have better control of your outer area. If you add the vents to the room you can control best then the tent becomes easier to control.
Edit. You can also use damprid as a natural (no electrical required, just small pellets in a tub) dehumidifier too. I love it for small areas like tents and closets.

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I’m not sure I understand your system even with the pictures. Why is your tent exhaust blowing against a wall? And your vent to exterior, it doesn’t have a damper or anything to act as check to keep cool air from coming in? How big is the dehumidifier?

Exhaust is blowing simply out of the tent into the room. Duct leaves the tent, connects to fans and fans blow simply into the room air.

Vent to exterior (fan) seemingly creates negative pressure so airflow must be sucking back in around the edges of the fan. I’m not sure why but its both blowing out and there’s a cold draft there so it’s also sucking cold air in.

Humidifier is 155 pints/day (Quest D155)

for starters you need to have another fan pushing air into the tent as well as the ones u have to stop the negative pressure,… :grin:

man… that’s some coin… :grinning:, can you take a photo of the de humidifier… how many plants?

Nice looking plants very healthy. Personally I think I would exhaust the hot stale air outside the building. Keep exhaust fan running 24/7. As mentioned. @RandomlyRan to me the easiest way to control temperature and humidity inside tent. Is to control the lung room you are pulling fresh air from.


@kellydans I’m sorry if I was unclear. Thats what I’m saying too, in essence. It’s more managable, if your intent is to control a small area, to start with the house as a whole. From there find the room that you can control the best with consistency and route it to the grow room . From there dialing the tent in is easier because the room it’s in or drawing from is now less succeptable to extreme swings in temp/rh.
For example my house is 68-79F 70+%RH avg, the room I can control best is my master bathroom. It stays 71-77F 60+%RH. So my intake pulls from there thru the wall into the tent. My tent stays 73-75F 50%RH, I only need my diffuser to humidify in veg. If I could control my bedroom better than my bathroom I’d just pull from the room it’s in. Of course I built sterile rooms so I overkill environmental control. Lol.


I have heard Dbrn32 call it a “lung room”


I agree with you 100% @RandomlyRan maybe I was the one that wasn’t clear. It’s all good creative minds working together.


This solves the issue with moisture in the rest of the home. You don’t necessarily need to seal of the rest of the house, just provide intake air from somewhere else.

I think I would go for recycling the air in the tent within the garage where your dehumidifier is. Install an intake circuit from something like an attic or basement to the garage, and a backdraft damper on the fan exhausting garage to outside. Then get an inkbird controller to run that fan so it will dump the garage if your dehumidifier can’t keep up.

Your biggest issue then will be maintaining temp and co2 in garage. Not exactly cheap, but it’s not difficult either. That’s pretty much cost of running 200 square foot indoor grow. If the fan runs a lot, you can combat by adding another large dehumidifier.


Simply exhausting outside thru a damper would solve the problem.


Sorry forThe delay, I was at my daily limit on replies on this forum.
Currently I have 36 plants.

We instead vented the canfan more directly to the front room to take advantage of the heat during this winter season. It seems to be working with a5% drop in rh.

I agree with you guys that a better solution will be to exhaust straight outside and pull air from another room. Will move to that if this continues to be a problem or as soon as the weather improves.

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Update … and more issues :joy:

I’ve exhausted 1 of the 2 12" can fans to blow to the building exterior. It comes on for 20 minutes every 3 hours and the intent is to provide a majority air exchange to purge heat and humidity from the tent/building. The second 12" can fan is constantly on (medium) and circulates the air from the grow tent to the grow room.

Prior to exhausting the air to the building exterior, my normal operating numbers are 68-70 rh and 82 degrees in the tent. I switched the fan to exhaust two days ago.

So… my RH and Temp swings have been very large for the past 48 hours. The hardest his is my temperature which was sitting at 70 degrees in the tent when I came in this morning and the range since has been:

Grow Room (outside tent)
(past 24 hour ranges: rh 39-78, 61-70 degrees)
7:15am - rh 66, 64 deg

Grow Tent
(past 24 hour ranges: rh 48-78, 64-77 degrees)
Cam fan turned on at 6am
7:15am - rh 73, 70 deg
Cam fan turned on at 9am
9:02am - rh 64, 73 deg
9:11am - rh 60 , 72 deg
9:17am - rh 58, 72 deg
Cam fan turned off at 9:20am
9:30am - rh 55, 70 deg

Front Room
(past 24 hour ranges: rh 37-82, 55-66 degrees)

Front Room - 61 rh, 64 degrees
Grow Room - 54 rh, 66 degrees
Grow Tent - 66 rh, 72 degrees

Any thoughts on this strategy?

Our temp across all rooms is pretty low for the past 24 hours. Ambient heater is set to 69 degrees but as it’s winter that’s not even getting our front room up to 67 ever. The grow room and tent are 61-77 degrees. We can stand to raise those numbers a few degrees. Thinking I’ll increase the intensity of the lights by 10% and turning the ambient heater temp up to 72 degrees.

RH is swinging wildly. We don’t seem to have a problem dropping it significantly but the problem is that it must raise right back up to sky high numbers quickly. 82 in that front room is troublesome AND over 70 in the tent is bad for plant growth (right?) but we also don’t need it down into the 40s and 50s while we’re in veg. SO… instead of turning on for 20 minutes every 3 hours, let’s try having this turn on for 15 minutes every hour?

An ERV would solve your problems and be more efficient than a dehumidifier.

I’m happy to elaborate if necessary.

Edit I think I mean HRV. Regardless,the point is to get an air exchange with outside air while recovering the heat from your vented air. I’m pointing you in the right direction.

I’m not even sure what you’re talking about. Can you link me to something online that I could look at as a reference?

Let me ask a few questions first.

Is your operation legal?

Do you own the building?

How long are you planning to operate in your location?

Yes it’s legal, yes we own the building and plan to be in operation here indefinitely.

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An HRV (Heat Recovery Ventilator) brings fresh air in, and vents stale air out. But it also pulls the heat from the exhaust and heats the incoming air. This is a passive exchange, and the most efficient models can transfer 90% of the otherwise lost heat to the supply side.

An HRV will dehumidify, but not to the degree a dedicated dehumidifier will. I think between the fresh air exchange and the limited amount of condensed water pulled from the incoming air, you should be able to bring this under control.

It’s worth hiring an experienced technician to spec and install this. Bare minimum, I’d want it designed by a professional.

You probably want to pull air directly from the grow space(s) and duct it to the HRV. The partition between the garage and the front office should be solid. The condensation on the window is probably due cold glass and warm humid air; but that has me concerned about the dew point of your wall system and mold development inside your exterior walls/roof.

It may be cheaper to install a whole house dehumidifier running off of 220v. I’d look to save on operating costs rather than equipment, so a more efficient high end dehumidifier would be my leaning.

An HRV will not solve your humidity issues during AC season. You may need an ERV for that. Someone with more knowledge about this will be able to help you design a system that meets your needs.

If you have more questions, I’ll help where I can.

HRVs explained