Purchasing fans to ventilate your grow space properly is a must, and this article will prepare you to make an educated purchasing decision. Airflow is a catalyst for several benefits in the grow room, from strengthening the plants to reducing occurrences of powdery mildew and even as a transporter of fresh CO2 for improved plant growth.
We’ll cover each of the three distinct points for creating effective airflow: intake, circulation, and exhaust. You can read more about the exciting journey that air takes through a grow space in part one of our series ‘How to Create Good Airflow’.
TL/DR | Key Takeaways:
Speed controls are an important feature
Oscillating fans are preferred for air circulation
EC motors are better than AC motors
Purchase fan models with more CFM than needed
Avoid outdated product design
Factors to Consider When Buying Fans for Your Cannabis Grow Room?
Buying fans for your grow tent or room will be directly impacted by the size of your grow area. You can determine the volume of your grow space by multiplying the L x W x H. The answer to that formula will guide you toward the proper cubic feet per minute (CFM) rating on the fan you intend to purchase. At ILGM, we like to make growing simple, which is why we’ve included a chart below with recommendations for intake, circulation, and exhaust fans based on the size of your garden area.
Speed controls are an option I won’t do without when it comes to the fans in my grow tents. Whether it be intake, circulation, or exhaust fans, the ability to adjust the fan speed/wind/velocity allows the grower to create optimal conditions for the plants. One speed does not fit all circumstances. At times, each of the three fan types will benefit the plants most at different velocities. Examples include
Increasing the intake levels of cooler outside air to reduce the temperatures in the garden area
Decreasing the speed of your circulation fan to avoid damaging young, stretchy seedlings
Increasing the exhaust levels to counteract higher humidity after watering or heavy transpiration
Noise is the other factor to consider. Cannabis growers enjoy their privacy and will often take measures to prevent the discovery of their gardens. Cheap and poorly designed fans can make an incredible amount of noise. For growers sharing walls with neighbors, suspending your intake and exhaust fan is suggested to prevent vibrations from creating an audible hum through the walls.
Essential Ventilation Setup for Cannabis Cultivation.
Intake fan
Not all grow spaces will require an intake fan. Large grow rooms may need active intake, whereas smaller tents often rely on passive intake to replenish CO2 levels. Growers also need to determine whether to use negative or positive pressure in the grow space, which an intake fan will directly impact. You can learn more about positive and negative pressure as well as passive and active intake in part two of our How to Create Good Air Flow.
Intake fans bring large volumes of fresh air into the garden space. Often, this air comes from outdoors, which can potentially carry pests and pathogens. Growers should filter outside air before it enters the grow space. Inline filter boxes like the ones shown on this page are an excellent solution.
Some intake fans conveniently fit into an open window. This option may not be discreet enough for many growers. More often than not, growers will use the same fan style for air intake as they do for the exhaust. These fans are capable of sucking in fresh air and rapidly sending it out of the other side into the grow room. These types of fans are often referred to as ‘inline” fans.
Circulation fan
Your circulation fans prevent pockets of stale, moist, stagnant air within the canopy. Dense foliage overlaps in the grow tent, creating prime conditions for powdery mildew (PM). Because we want an even distribution of air over the entire canopy, oscillating fans are preferred.
Heavy and constant wind in a fixed position can lead to several health-related issues for your plants. Fixed-position fans also create areas of less airflow, which often turns out to be in the corners. The corners of the tent are one place where stale, moist air likes to hang out, and for these reasons, it really is best to find a unit that offers oscillation.
**Pro Tip: Most grow tents are under negative pressure, which causes the walls to suck inward when the tent is sealed for the lights-out period. Negative pressure can affect the oscillation range of grow tent fans and cause the motor to wear out or malfunction prematurely from meeting the resistance of the walls. To combat this, growers can place a plastic coat hanger behind the poles in the corners where the fans are located.
Exhaust fan
A modern, more efficient inline fan design, which numerous manufacturers duplicate, has replaced the older style fans, which are louder, less efficient, and limited in uses. Most growers prefer fans with EC motors over AC motors due to their lower noise and smaller size. EC motors also perform better / quieter at lower speeds compared to AC motors.
Most growers exhaust stale air from their growing space using ducting. The length of the ducting and the number of bends reduce the maximum CFM of the fan. Performance numbers provided by manufacturers are often calculated at full strength and with no ducting attached.
I’ve always recommended growers buy a stronger exhaust fan than they need.
You can continue to use the same fan if you expand your grow space (plenty of available CFM)
Fans can be run at a lower speed (but still the necessary CFM), which produces less noise signature.
Gives you flexibility in the configuration and length of ducting.
A strong exhaust fan can create passive air intake, potentially eliminating the need for an intake fan.
Ventilation Exhaust System with Ducting for Cannabis Grow Tent.
What Size Fans Do You Need for Your Grow Space?
The Best Fans for Your Grow Tent: Chad Westport’s Top Picks
When I make these recommendations, I assume that most growers are in a 2’x4’ (61cm x 122cm) or a 4’x4’ (122cm x 122cm) grow tent. All of the fan companies mentioned here manufacture the listed products in larger and smaller sizes. You can refer to the chart above to see what would be appropriate for your situation.
The Best Intake Fan
The best intake fan is usually an exhaust fan. Instead of repeating my choice for Best Exhaust Fan, I offer the Vivosun AeroZesh G4 4inch inline fan. This fan has multiple speed settings, allowing growers to control negative or positive air pressure. It also features an EC motor that helps reduce the volume levels while operating. Vivosun offers a variety of monitoring options via the Grow Hub and App system, giving growers remote control over the device functions.
I admit, I don’t currently use an intake fan on my 4×4 (122cm x 122cm) grow tent. Passive air intake keeps my ambient CO2 levels in the desired range, and I’m able to control the environment. If I were using an active air intake in the grow tent, it wouldn’t negatively affect my plants, which is why I consider it a matter of preference for smaller grow spaces. However, cooler outside air can be a big aid in reducing grow tent temperatures if you cannot control them otherwise via a lung room.
Growers searching for intake fans may see “inline booster fans.” Stay away from this style of inline fan. They make an ungodly amount of noise and are not energy efficient. In fact, their efficiency is significantly lower than that of the fan style I recommend. These were commonly used in the past when there wasn’t the wealth of options we have today.
The Best Oscillating Fan
After being disappointed with a few other brands, I tried the Spider Farmer 6” Oscillating Fan, and I wasn’t disappointed. Where the others failed, these succeeded. My problem had been that the motors would strip the teeth of the gears when the fans met resistance from the walls. I quickly had clicking fans (annoying) with sporadic oscillation.
The Spider Farmer 6” oscillating fan met all the important criteria mentioned above: enough CFM, multiple speed settings, and quiet operation. This fan can also be stationary or oscillate with the touch of a button, creating an even distribution of airflow over the canopy. The oscillation range covers my tent from corner to corner, and the motor is specifically designed to disengage the gears when it meets resistance from the walls. That ingenious feature solved the problems I had with other brands.
The Best Exhaust Fan
AC Infinity Cloudline T6 w/ Smart Controller was a quick and easy choice for this category. My selection was influenced by the amount of connectivity that this unit offers and the fact that this model is tried and true. The Cloudline T6 fan has been on the market for nearly a decade and in my tents for almost as long. Build quality, customer service, and amazing connectivity make this exhaust fan stand out.
AC Infinity set the standard for grow tent exhaust fans in the current era of home gardening. The majority of exhaust fans from other brands look identical to this one. However, not all of them have an EC motor, and very few have the same potential for connectivity as the Smart Controller for this unit does. Build quality and choice of materials is another area where this unit stands above the rest.
The digital controller for this fan can automate turning the fan on and off or increasing/decreasing the fan speed when specific temperature and humidity levels are reached. Growers can also set a timer for their lights, control the speed of circulation fans, and much more using this simple unit. The digital display shows temperature, humidity, time, fan speed, and more. Who knew an exhaust fan could do so much?
Other Recommendations
There are many options created by companies with cannabis growing specifically in mind. Familiar brand names making these particular products include:
Mars Hydro
Vivosun
Spider Farmer
AC Infinity
Secret Jardin
Vevor
iPower
Many of these brands and products fall within the same price range. Accessibility can be an issue for people in certain regions of the world, so my hope is that you will be able to find at least one or two from this list that are available in your area. Using the criteria laid out at the beginning of this article and paying attention to the key factors from my top picks will help growers navigate the selection process if their options are limited.
Conclusion
Purchasing equipment to provide proper airflow when growing indoors is an important step. However it doesn’t need to be full of anxiety and confusion. Regardless of the brand name in front of you, know how much CFM the fan(s) need to be, and then look for the other features we’ve mentioned. Choose from companies with a good track record documented by years of product reviews.
Airflow is a “must-have” factor for any successful grow. You’ve already done your homework and selected top-shelf genetics from ILGM, so give them the right conditions to succeed. This article has prepared you for the excitement of buying the right fans for your indoor garden. Download a free copy of Roberts Grow Bible for all other grow-related topics and quickly become an ace.
Don’t make the mistake of saving a few dollars on a product that doesn’t fully get the job done. Only to have to buy a better one after the first run. Buying the right piece of gear the first time is always wiser. Luckily, most of these fans, whether intake, circulation, or exhaust fans, are all in a similar price range and offer comparable features. What fans do you like to use or commonly see? Let us know in the comments!
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