Grow tent cooling


Hi all, new grower here. I’ve been doing all my research prior to starting this endeavor and I’m down to the last little bits. I know before you start it’s best to have your atmosphere down and the rest of the grow will go swimmingly. I have a question regarding fans/ventilation and cooling. I am running a small 36x36x72 grow tent with a 900w led light. With just the light running and with no ventilation the temps rise to around 100 degrees which I know is way too high. I have 2 duct fans (240cfm each) running currently some of the provisions in the tent for them, however the power draw and noise is insane. But it brings the temperatures down to right around 80 degrees or so give or take. My question to all the experienced growers, and I know this has probably been asked a thousand times by now so I do apologize in advance if this is redundant, but are there any fans that I can put in my grow tent that will cool the tent without the insane noise levels or power draw? Essentially I would like to remove both duct fans and run just fans inside the tent and probably leave a vent hole open in the top for hot air to rise and escape. Additionally I do plan on running CO2 supplementation and with these two duct fans my 50lb cylinder would not last long since the gas would be constantly being evacuated. Any help would be greatly appreciated.


Brand new myself but to my knowledge, you want intake bringing in fresh air and the exhaust removing hot/stale air. I wouldn’t remove any of those fans, they come with the indoor grow tents for a reason. As far as CO2 goes, the levels needed for plants to thrive is dangerous for humans so im not really sure about venting that into thw room you will be working with


You have plenty of c02 in the house you won’t need it if your talking a big grow then you would want to run c02 but there should be plenty in your house to suffice for what you’re doing


I agree with the others. What light are you using? If you’re not getting par readings well over 1000 ųmols, adding co2 won’t help you.

There are plenty of fans that will run with less noise and be more efficient. But they’re cost more too. I would strongly suggest getting some speed controllers that are compatible with your fans normally. But in this case, you may want to take a step back and reconsider your plan for atmospheric conditions.

First and foremost, you absolutely need good air exchange. Without it your crop will be covered with mold. And I’m very skeptical that any natural air exchange will be enough.

Next you’re going to have to worry about your temps. In reality, it takes quite a bit to get to “ideal” temps. Keeping them close is usually good enough. If you were moving 240cfm in and out, and could only get to around 80 without plants in place, you’re probably going to need some work there too. What is the temp of the air you’re bringing in? You have to expect the temp inside your grow area to be at least a little above whatever the temp of air is that you’re bringing in.

I didn’t see any mention of scent control. Is scent not an issue? If there’s any chance, you’ll need a filter. And even a good filter sized properly will restrict the airflow some. So running identical fans without speed control on inlet and outlet with a filter is definitely a no no. For the filter to work, you need to maintain a slight negative pressure condition inside of your grow area. Otherwise the smell will leak with any air the leaves without going through filter.

After you get all of those things in order, you can go ahead and look at things like supplementing co2. But you probably won’t need it, so it’s best to get control of the more important items first.

As I stated earlier, it’s probably a good idea to take a step back and look at the big picture. Once you get a better idea if what you’ll need, we can absolutely recommend a more efficient fan that runs quiet. But I have a pretty good feeling that won’t be the answer to all of your problems.


I had a Viparspectra 900w reflector series given to me so I decided to give it a try, I know it’s not the best out there but I can’t argue against free. I haven’t gotten to scent control yet, but yes it will be an issue. Trying to get all the biggest factors taken care of first. As far as the intake and exhaust fans, they are Vivosun 240cfm fans. The ambient air temperature outside the tent fluctuates from between 65 and 75 degrees. What fans do you recommend, is there any brand or model I should be looking for?


There nothing wrong with that light regardless of cost, but free is always good! However, as long as you maintain decent supply of fresh air it’s definitely not big enough to require additional co2.

I think your fans have a fairly decent reputation, and speed controllers should help with the noise. But let me tag @Countryboyjvd1971 and see if he can help. He’s an hvac guy, and been around much longer than I. I’m guessing he’s probably helped others with similar or identical setup. I know that slowing the fans down will help with noise. But I’m not entirely sure how much adverse reaction that will have on your temps.

Off the top of my head, I’m thinking if you get a little better control of your atmosphere outside of the grow it will help. Is that a reasonable task?


80 degrees shouldn’t hurt them. I’ve been growing mine in similar temperatures . For cooling and humidity (it’s dry where I live) I googled and built a cheap swamp cooler. Looks like this:


I’m with @Hogmaster as far as not needing the co2 !
but if you decide to run with it I would put fans on timer when you inject tent with the co2 fir a few hours allowing the plants to absorb the co2 then run exhaust and intakes back on
This will be the best for you so your not wasting the co2
Leave circ fans running all the time tho
Also best way to cool tent if needed is obviously Ac lower room temp about 5-10 degrees lower than you want tent to be
I run my Ac and maintain 75 degrees in my tents with 4 light running in each tent :+1: If I didn’t my tents would be well over 100 degrees when lights are on
And swamp Cooler set up like @Loneviking made my help a bit ?


How big is the room the tent will be in and how much ‘fresh’ air gets circulated in it? I have a 4x4’ tent in a 9x13’ central air conditioned room and I thought I’d be all set with temp. But, there are week long periods in the Spring and Fall when the house heating/cooling is never called for, therefore, no fresh air. My lights produce constant heat (when on). I ended up controlling the air temp in my grow room with a window A/C unit.