What CFM Fan Do You Need For a Grow Room or Grow Tent?

Topics we cover in this grow room fans & blowers overview

best inline grow room fans by size and cfm

 

The Common Culture inline duct fan is a rugged entry level fan. It is designed to compete against more expensive brands with its features of high reliability and low noise. 

  • 165 CFM and compatible with speed controllers
  • Wall and ceiling mounts included
  • Matte black stealth color
  • 5 year warranty
  • Recommended grow room size: 2' x 2' to 4' x 4'

 

Vortex Powerfans are an industry standard used for areas where fan failure is not an option. Vortex fans are highly engineered for maximum performance.

  • 220 CFM and compatible with speed controllers
  • Impact-resistant, sound-absorbing heavy gauge steel casing
  • Rustproof hammertone powder coat epoxy finish
  • 10 year warranty
  • Recommended grow room size: 2' x 2' to 4' x 4'

Best 6 Inch Inline Grow Room Fans

 

The Common Culture inline duct fan is a rugged entry level fan. It is designed to compete against more expensive brands with its features of high reliability and low noise. 

  • 400 CFM and compatible with speed controllers
  • Wall and ceiling mounts included
  • Matte black stealth color
  • 5 year warranty
  • Recommended grow room size: 3' x 3' to 4' x 8'

 

The Max-Fan is the first fan that has been developed with a Computational Fluid Dynamics (CFD) program. CFDs are used for engineering aircraft propulsion engines.

  • 334 CFM and compatible with speed controllers
  • 50% more efficient than comparable fans
  • The perfectly designed 3D blades of the impeller maximize efficiency
  • 10 year warranty
  • Recommended grow room size: 3' x 3' to 4' x 8'

Best 8 Inch Inline Grow Room Fans

 

The Common Culture inline duct fan is a rugged entry level fan. It is designed to compete against more expensive brands with its features of high reliability and low noise. 

  • 720 CFM and compatible with speed controllers
  • Wall and ceiling mounts included
  • Matte black stealth color
  • 5 year warranty
  • Recommended grow room size: 5' x 5' to 10' x 10'

 

The Max-Fan Pro Series has a much more robust housing due to the fiberglass reinforced plastic compounds that meet all of the UL and CSA requirements.

  • 863 CFM with built-in 3 speed controller
  • 50% more efficient than comparable fans
  • Ultra low wattage to CFM ratio saving you money on power
  • 5 year warranty
  • Recommended grow room size: 5' x 5' to 10' x 10'

Is having a duct fan important for grow rooms and grow tents?

If you plan on having a closed environment (e.g., grow room, grow tent, etc...) then you need to properly ventilate your growing environment to ensure your plants yield up to their potential.

Proper ventilation helps regulate humidity and temperature in your grow room by exhausting the warm air that your grow lights and electronic equipment are producing. Cycling out this air also provides relatively carbon-rich air for your plants to breathe better, which will help them yield more.

What size duct fan and CFM do I need for my grow room?

Many websites give a blanket rule-of-thumb for CFM calculation that fails to take into account the uniqueness of each growing room. Below we will show you a way to calculate CFM taking different aspects of your growing environment into account to give you the minimum CFM recommended for your grow room. 

Growing Environment Volume: Calculate the volume of your room by multiplying the length x width x height. For example, if you have a grow tent that is 8' x 8' x 7', then the volume would be (8x8x7) = 448 cu./ft.

Volume To CFM: Your exhaust fan should be able to exhaust the equivalent of your growing environment's volume in two minutes, or one minute if you are having issues with high temperatures. Assuming we are not having issues with heat, the growing environment volume from our example is 448 cu./ft., which means we need to exhaust 448 cu.ft. / 2 minutes = 224 CFM. From this I know that I need a 224 CFM fan at a minimum.

Other Variables To Account For: We're not done yet. Now to account for other variables that can require you to have more CFM required for your grow room:

  1. Lights: For each air-cooled light (600-1000w) add the equivalent of 10% of the calculation you finished in the 'Volume To CFM' step. For non air-cooled light add 20% per light.
  2. CO2: Add 10% for rooms with CO2 enrichment via a CO2 burner or generator (they create heat).
  3. Carbon Filters: Add 20% if you're using a carbon filter.
  4. Ambient Temperature: For hot climates (Southern California, Arizona, etc...) add 25%. For humid and hot climates (Florida, Georgia, etc...) add 40%.

Let's run through a full example of calculations accounting for each one of the four variables noted above. Let's still assume we're using the 8' x 8' x 7' grow room used for the example above. We're at 224 CFM before we jump into adding in the accessories, so that will be our starting point. 

Let's now assume the room has two non air-cooled 700w LEDs, a CO2 burner, a carbon filter and we're located in Southern California.

Lights: Add 20% per light x 224 CFM = 48 CFM. 24 CFM x '2 lights' = 96 CFM. Add the 96 CFM to your calculation of 224 CFM to give you 320 CFM.

CO2: Add 10% x 224 CFM = 24 CFM. Add this to your 320 CFM to give you 354 CFM.

Carbon Filters: We are using a carbon filter to remove odors, so we'll add the 20% x 224 = 48 CFM. Add this to our 354 CFM to give us 402 CFM. 

Ambient Temperature: We're assuming we're in Southern California so we're going to add 25%. 25% x 224 = 56 CFM. Add that to our 402 CFM to give us 458 CFM. 

Our final calculation gives us 458 CFM in this example. Remember that this is the minimum amount of CFM we'd recommend for a grow room with all of these parameters. That said, we would want to shop for a fan with higher CFM than 458 and we can always use something like a fan controller or fan speed controller to adjust the speed down if needed.

In this example, I'd personally recommend going with a 8" fan that produces between 550 - 800 CFM and would adjust the speed down until it hit the sweet spot of temperature and humidity.

How long to keep a duct fan turned on in the grow room?

You should only keep your grow room duct fan on as long as it's needed to keep your temperatures and humidity in the correct range for your plants. As long as your temperatures are between 65 and 85 F and relative humidity is between 40% and 60%, your plants should be happy in their environment. 

How do you install a duct fan in a grow room or grow tent?

There are as many ways to install a grow room inline fan as there are ways to cook an egg. Below we're going to put a few diagrams of the most common ways to set up the inline fan + carbon filter for grow rooms. 

Four Different Ventilation Setups Inside Grow Tent
Actual Images of Fan + Carbon Filter + Ducting Setup In A Grow Tent

How do you clean to clean grow room exhaust fans?

First make sure to unplug your fan. Then go outside or lay down a tarp or newspaper inside to collect the dirt and debris. You'll want to get a damp cloth and wipe the blades and the inside of the exhaust fan. Next you'll want to take a can of compressend air and spray the inside of the fan in those hard to reach areas that you couldn't wipe down. 

Make sure the fan completely dries out before you re-install it and turn it back on.

Why have oscillating fans in the grow room?

Oscillating fans help bring carbon dioxide to your plants, even out the temperature and humidity inside the grow environment, increase the robustness of the plants stalks and branches and make it harder for molds and fungi to grow on and around your plants. 

https://cannabisgrowkit.medium.com/best-oscillating-fans-for-grow-tent-2020-update-299b27b43c42

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