Struggling with humidity in tent

Folks, I’m really struggling with reducing humidity in a 2x4 tent. I’ve never used a tent before, and I flipped to 12/12 and humidity is 83%. I bought a small dehumidifier, and it didn’t change a thing. What do I need to do? I’m not very handy, so keep that in mind.


Sounds like you need a vent fan, something to pull dryer air from room tent is in, and to evacuate the moist air. Depending on where you live this can be a big issue this time of year. Make sure you have good air movement inside the tent and get that moist air out as best you can


Definitely need the circular airflow coming in and pushing out air.

I recommend getting two inline fans. Most tents have holes on the sides of varying size.

Fans are cheap on Amazon and stuff. You’ll probably need 4 or 6" ones (youll have to measure).

I have the fans mounted in the right hand side of my tent. Lower fan is mounted so air blows from the outside in, and the upper fan is exhaust blowing out (heat rises lol)

Good luck!


Oscillating fans… water only when lights first come on… cover soil to prevent some of the evaporation that occurs from lights…and as the other person said…full on pulling in of fresh air down low, and exhaust up top…perhaps your plants will transpire a tad differently if you adjust your lighting height, and intensity (get your DLI, but from and different zone).
You can run 65%ish IF the air is constantly stirring the plants. Yes, ive hit 80% on occasion (before the big dehumidifier came in), and still never molded.
Hopefully outside your tent is an atmosphere worth pulling in. Good luck


Could you send me a pic?

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As @CLICKYBONES stated, there is only one way to condition the air in a small tent. You must control the temperature and humidity in your lung room, (the room that your tent is in). Then pull this air through the tent. For example one of my tents is located in the furnace room in the basement. This works petty good as the heat pump indoor unit is located there also, and it is cooling and dehumidifying in the summer and heating in the winter. As a result I only need to run a small humidifier located outside the tent during the winter months.

Of what, my tent or the fans on Amazon?

Looking back through my camera roll i dont really have much that shows the side of the tent.

You can the the lower fan in this one though. It blows air into the tent. A seperate fan mounted in the upper hole far above the lower one blows air out of the tent

Simple fans like these can be easily mounted in the tent holes, just make sure one is intake and one exhaust. Also need to figure out if you need 4 or 6 inch fans to fit the holes

@ThermoNukePanda, if your tent is 6 foot tall, Your total cubic ft is 48. A 4 inch fan should work OK, provided it doesn’t have move than 10 foot of duct hooked to it. This should give you a complete change of air through the tent at least every two minutes. Of course better yet would be both an intake and exhaust fan.

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I don’t use use ducts. I mount the fans directly in the side holes.

Lower intake fan is 6" and moves quite a bit of air into the tent. Upper exhaust fan is 4" pushing air out.

Tent is 8 foot

Dont you want the larger one blowing out?
You have more air coming in with a 6" then you can push out with a 4"

@ThermoNukePanda, when I said a 4 inch fan, I meant this type, it is rated at about 110 CFM. You need a fan with some ass behind it to over come the resistance of the tent’s screen and such.

What can i say? Im a lazy panda but it works :joy:

The 6" intake fan i have mounted is 240cfm lol

Also provides a lot of airflow around the bases of the plants and helps them move a bit

Your fans are working well enough to do the job but it doesnt change the laws of physics.

I know there is some cost here but, you want to consider buying two good fan and put them each on a speed control. This way you can match the intake CFM to the exhaust CFM, or it is very easy to dial in a slight negative pressure for odor control. You can always use the cheaper fans in a clone or veg tent in the future.
I going too go now and take care of my sh*t. Good Luck!

Thanks everyone, I’m tried rigging up something with stuff I had. I’ll see what happens tonight when light goes off, then I’ll go from there.

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If you need to run multiple fans, then you would most likely be best off leaving the intakes passive & using multiple exhaust fans in parallel (side -by-side). Putting fans in series creates an obstruction. Provided the install is already as efficient as possible, & if you don’t specifically need two fans but still need more CFM, then you would probably just be better off getting one properly-sized fan only. In any case, once you have the right fan, then size the passive intakes up until you lose negative pressure, then close them down a little to provide the least amount of negative pressure needed. Take care of circulating the air once it’s in the box. If the passive intake & the exhaust fan are sized & located/ installed well, there will be plenty of moving air entering from the passive intake(s). Then just use the desk fans throughout the box for circulation inside of the box.
Most CFM ratings are at zero negative pressure, check pressure maps to see how they do as negative pressure increases. Manufacturers either publish them, or they don’t. Most axial fans (“computer fans”), in-line “helper” fans, ‘desktop’ fans, etc lose most of their CFM when seeing the least bit of negative pressure. Eliminate any unnecessary lengths or bends of duct-work. You probably want to get a true inline centrifugal blower, or at least an hybrid axial-centrifugal fan for your exhaust. The hybrids don’t do as well as the true in-lines as negative pressure builds. My 4" true inline outperforms the 6" hybrid offered by the same company in CFMs, once they get below 1" of negative pressure. Vortex publishes their pressure charts right on their website, so I could compare them. In general, the hybrids seem to be what most of the manufacturers are promoting mostly these days, & at least one of them has a VPD controller for it, which seems handy.

Thanks, but all that’s way over my head.

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