Grow tent running hot

Hey Guys,

Fresh new grower here, while I’m waiting for my seeds to arrive I’ve been setting up my tent. I’ve noticed that I have a consitent heat problem. Currently my grow tent is in the garage which isn’t insulated the greatest.

I have:
3x3x6 Grow tent
1- 4" intake fan with a carbon filter attached w/ speed controller
1- 4" ventilation fan with carbon scrubber w/ speed controller
2- 6" clip on fans
2- 300 watt LEDs
1- humidifier set at a max of 70%

My grow room with the lights on likes to stay in the low 80’s and I’ve yet to get it below 80 with the lights on. Help!!!
(I’m also running my lights at night.)

I know you already bought the 4" fans but really I think 6 inch fans work better on that situation you need to be able to extract out the air so that you don’t get heat issues or mold issues suck the air out and also remember the more air you bring out you need clean air going in so another filter on the inlet side coming in would keep things clean… PS … I use 6" shop vac filters for 10 bucks a pop verse’s 80 to a100 bucks for a filter…


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Thanks for the advice Peach! I was advised to get the 4" because the size of my tent and its vent ports. It seems to be moving air just fine, but apparently not since it’s running hot. I’m in SoCal so I’m hoping for a cooler fall to come around. Very nice, I would have to consider this.

How are you getting air into the tent?

I had that same problem and a very similar set up only I am using 400 w MH/HPS light.
I had to use an air cooled reflector to get some heat down but it’s still wasn’t enough. After it was all said and done for me it ended up the overall temp in the room my tent was in. Check the temp in the garage as it might be a contributing factor.
Hope this helps


I would not run my fan inside the tent because the inline fan will add heat , I would run ducking tubing to my scrubber out the vent hole to the fan and I also will not connect my scrubber directly to the side of my fan , give it space so the air can flow properly instead of being force out but that’s just me in my opinion .


I have a 4" intake fan. It’s the second to the bottom in the pictures.

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I’m sorry but I still don’t understand exactly what I’m seeing?

in the second to bottom filter isn’t that a carbon filter and a centrifical fan, is that what you’re feeding in with ?

so how was there also a fan & filter at the top of the tent ?

forgive me if I’m not seeing it correctly, just trying to help, I have a background in HVAC and some growers here helped me when I was setting up, so if I can help I will but I’m just not following right now

When my lights come on I can show you what I’ve got, my filters up top, my fans outside and I’ve got a 220 in line can-type fan feeding in, it goes through a second light in a veg tent (I use hid)

Correct, I’m feeding it with a carbon filter to keep mold spores and insects out. But I also have another on the inside of my tent filtering out the smell and mold spores.

Okay so this is a first on me but I’m wondering if your fans are struggling against all that resistance from the carbon filters?

That would cause them to:

… not to operate at peak efficiency
… to operate hot
… and to not adequately vent the tent

That’s all I got ? I’ll follow this thread, hope I can help ?


Would any of you recommend a small swamp cooler?

As long as you can get that air out and make sure its fresh going in ( not recycled air coming out of tent) that should be fine. If you play around with the set up of your airflow you should have those temps sorted out. I think what you gots fine mate. Just work on creating good airflow.

I’m not exactly sure what a swamp cooler is but if you’re checking your ambient room temp then I think you might have something going on with your air flow, I think you have a restriction inline

I light a fatty up and check my air flow that way, I would check with and without restrictions and I think you’re going to find a big difference if you run it with that Inlet open I think you’re temperatures would go right down I would check at least and see

If you could try some other type of filter that’s less restrictive you might stop that problem I haven’t seen anyone have issues with LED heat that I can recall, so I would check for restrictions

I might also check that my lights were functioning properly and not overheating but I can’t think of anything else let us know what you find out
-good luck

A swamp cooler would work good in veg but would bring u problems in mid to late flower…


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I totally agree that a 6" fan (at least) is the way to go. My grow space is 3.5’ x 2’ x 7’ (home made) and after trying 2 different 4" fans I am still not getting the results I want. I have heat build up and the sweet smell is escaping into the rest of my house. As soon as I harvest this crop I will install a 6" fan with speed controller so I can (hopefully) get a handle on the heat and the smell. It just occured to me that your humidifier may be generating a lot of heat. Is it inside the tent? I did not use a humidifier, my humidity has never been as high as I’d like it but my grow seems to be going fairly well.
Call me crazy but…I set it up to where my exhaust fan draws air from floor level. Seeing as how cool air settles I feel like I’m drawing in cool air and I think that by adjusting the speed of my exhaust fan I can regulate heat as well as smell. My exhaust is to the outside. Let me suggest that you leave your intake fan off and provide a means of allowing cooler “floor” air to enter your tent to be drawn through and out by your exhaust fan and see if that makes any difference. Hope this helps.


Here I go again!!! If you are drawing air from outside the tent and then exhausting it, it would seem that the air inside the tent is not getting circulated. That would definitely cause heat buildup given all the equipment you have operating inside your tent. AS I mentioned earlier…turn your intake fan off and unzip or otherwise allow floor level air to be drawn through the tent by your exhaust fan. I am thinking that will make a big difference.

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Let me clarify a little…If the air coming in and going out is 100% through your duct work the n the air in the tent, it would seem, is not getting circulated which would cause heat build up. Hope this helps.

There is absolutely no way I can use 6" venting in my tent. I can barely fit 4" without having to cut a slit into my tent.

Does anyone ever open up a flap on their tent and put a fan in front of it to blow air into the tent the reason I ask is because I have a 18 inch fan that blows air into two of my tent with the flap open and on my bigger tent I have a 10 inch fan blowing air into another flap that is open in my temperatures and humidity stay just about perfect if that doesn’t make any sense I can take some pictures

Turn of your dehumidifier, that will get save you at least 3-5F

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