How Many Fans Should You Have In Your Grow Tent?

How Many Fans Should You Have In Your Grow Tent?

Don’t you love it when a cool breeze soothes your skin as it slitters away? The gentle wind tickles your senses and clears the atmosphere of impurities. Cannabis plants enjoy the breeze just as much, but they need it more for survival than for enjoyment.


Outside, cannabis plants’ leaves dance effortlessly in the wind because the wind swishes past them in continuous motion. Thus, outdoor cannabis growers never care a thing about fans.


If you’re growing indoors, fans are must-have growing equipment, and you won’t need just one. For the plants to flourish optimally and yield better, the airflow in the grow tent must be within a favorable range.


How Many Fans Should You Have In Your Grow Tent?

Two fans will be enough for most tents. Every grow tent should have an oscillating fan and exhaust fan to keep the flow of air balanced in the tent. However, the number of fans you will need in your grow tent depends on the size of the tent, the type of lights you use, and the size of the fan. 


Finding the correct number of fans for your grow room is essential because fans are essential to the growth and well-being of your cannabis plants. 


As the fans enhance airflow within the tent, they strengthen the stems of the plant. The swooshing breeze shakes the branches back and forth, forcing them to build the muscle necessary to host the forthcoming big buds.


The wind flowering inside the grow room is also super necessary in keeping it sanitary. The plant takes in CO2 to help during photosynthesis, and the airflow is vital in distributing CO2 for optimum food production. 


Before we even think of circulating the air within the tent, you need an inlet fan to suck the fresh air from the outside into the grow tent for the plant to imbibe. Most exhaust fans can do both, so that saves you a few bucks. 

Unless you plan on adding CO2, the intake fan should be efficient. You don’t want the level of CO2 to fall below 250 ppm as that might stunt the growth of your plants and reduce your yield considerably.

Worse, if the level drops below 150 ppm, the plants will wilt of starvation and might die. This rarely happens, but it might just befall your dear plants if ventilation is severely inhibited. 


Afterward, the plant will give out oxygen as the byproduct of photosynthesis; an exhaust fan helps release ‘stale’ air out of the grow tent. This controls humidity and temperatures; thus, the plant becomes less susceptible to bugs, mold, and mildew.


To enhance the plant’s metabolic and photosynthetic processes, you need enough fans for your growing needs. Let’s look at the factors that affect the number of fans you should have in detail.

Oscillating fans improve airflow within the tent, have one!


Factors That Influence The Number Of Fans You Should Have In A Grow Tent

The number of fans to use isn’t something you whip from the back of your head. If you have too many fans in the grow tent, the breeze might enhance transpiration.


If you have few fans for the tent, the heat from the light and precipitation might pose a risk to your plants. Here are the factors to consider when deciding the number of fans for your grow tent; 


Accessories Attached To The Fan 

Sometimes you need to do more to keep the tent environment favorable for the plants to enjoy or for your grow operation to go smoothly without prying eyes. This involves adding accessories like carbon filters to contain the smell and ducting. These affect the fan’s performance. 


These accessories reduce the efficiency of the fans, inhibiting airflow. The more the bends and narrow tubes the fan has to pump the air through, the slower it travels. 


According to AC INFINITY, the sharper the bends, the more it reduces efficiency. A 90 °curve will hurt the efficiency by 60%, and 30 ° hurts the efficiency by 20%, which is still significant. So when you use these accessories, you might have to use a bigger fan or just a few more small fans.


Size Of The Fan

Bigger fans work better than small fans. They are built for superb performance. An 8” inline duct fan that gives you 420 CFM will have a higher airflow than a 6” duct fan with 280 CFM. 


Tent Size

The tent size matters a lot when you’re deciding the number of fans to use. More giant tents push the plants away from the fan, and that reduces evenness in air circulation. 


The reduced airflow can leave patches within the tent where the air stays stale, with higher humidity and temperatures. If the tent is too big, you will need more fans.  One 6” inline exhaust fan and an oscillating fan can serve you well in a 5×5 tent.


The Type of Light

Lights that emit more heat will need the fan to be running for longer to encounter the higher temperatures. Having more fans increases efficiency, and thus a better airflow. 


Thus when you’re dealing with too much heat from HPS grow lights, investing in more powerful fan ducts can be a lifesaver. More fans keep the space cooler and reduce water loss through evaporation. 


When the plants lose so much water, the grow tent will have high humidity levels, making the plants more prone to deficiencies and mold infections. LED grow lights are more relaxed and thus won’t emit enough heat to warrant the use of a second fan.

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Frequently Asked Questions About Grow Fans 

How Long Should A Fan Be On In A Grow Room?

The fans are necessary during the light hours when the plants are busy with photosynthesis and lights are pouring down on them, increasing the temperatures in the tent. Leave the fans on for 1 hour after you’ve switched the lights off. 
Leaving the fans on for too long increases water loss, reducing humidity to dangerous levels. 

How Many Fans For A 5×5 Grow Tent?

You will need two fans when growing in a 5×5 tent: one exhaust fan and one oscillating fan. The exhaust fan is responsible for removing stale air and bringing in fresh, CO2-rich air for photosynthesis, while the oscillating fan enhances air circulation within the tent. 

Can You Have Too Much Airflow In A Grow Room?

When you leave the fans running for too long after the lights, your plants will suffer the damages. Too much airflow reduces humidity, dries the leaves out, and can cause leaf tearing. 
However, the amount of airflow shouldn’t be troublesome because you’ll need good airflow to inhibit the proliferation of mold spores. The longer the air stays stagnant in the grow tent, the higher the risk of mold infestation. So allow as much airflow in the tent without drying out the leaves. 

In summary, your growing realities will determine the number of fans you need. If you have a bigger tent and use lights that generate too much heat, you might have to use more fans in the grow room.


However, when you’re growing in a 5×5 tent, you only need one exhaust fan and an oscillating fan to have perfectly ventilated your grow tent.