What’s the Best Way to Cool My Greenhouse?

By Kent Gruetzmacher
Published: June 6, 2022
Presented by AC Infinity Inc.
Key Takeaways

Many consider greenhouse growing to be the most difficult type of cannabis cultivation. To be a great greenhouse grower, you must understand the nuances of both indoor and outdoor cultivation.

Not only must you know controlled environment agriculture (CEA) methods and technology, but you must also understand how to deal with outdoor weather fluctuations.


As seen with indoor growing, a critical part of regulating greenhouse temperature is the application of proper airflow principles. Yet, unlike indoor gardens that are limited to exhaust setups and HVAC systems, greenhouses have many more options for keeping cannabis gardens cool. These systems range from simple roll-up walls to complex cooling wall and fan setups.

When deciding the best way to cool your greenhouse this summer, there are several factors that you should consider. Beyond obvious influences like infrastructure, you also need to consider the climate where you are growing, as well as your overall operating budget.


Cooling Greenhouses for Cannabis Growing

If you are growing cannabis in a greenhouse during the summer, you are going to have to figure out a way to keep temperatures cool during the daytime. This notion is particularly important in places like California, where summer temperatures regularly climb above 90° F.

Luckily, engineers have come up with a variety of ways to keep temperatures under control in greenhouses. In fact, there are entire subcategories of greenhouse cooling methods known as “passive ventilation” and “active cooling.”

The most defining characteristic of passive ventilation systems is that they do not run under machine power. At the most basic level, passive ventilation systems are openings in walls and ceilings that allow cool fresh air to move through a greenhouse.


While passive cooling systems let air move through by creating openings in greenhouse walls and vents, active cooling systems use machine power to move air in and out of greenhouses. Active cooling systems range from simple inline fan exhaust setups all the way up to sophisticated HVAC systems

cannabis growing in a greenhouse


Passive Ventilation Systems

Passive ventilation systems are generally the simplest and most affordable options for cooling greenhouses. Passive ventilation systems are designed according to a couple different airflow principles.

The most basic passive ventilation systems rely on wind power from outside to move hot air out, while also drawing cool air in. With a large enough opening in greenhouse walls or ceilings, even a slight breeze from the outside is enough to adequately regulate greenhouse temperatures.

In more complex systems, engineers design greenhouses to take advantage of “thermal buoyancy.” With thermal buoyancy, openings are strategically placed in greenhouses so cool air gets pulled in through the lower regions while forcing hot air out of the top.

Passive ventilation systems are generally affordable, but they don’t provide the precision temperature regulation that many people want. Also, passive ventilation leaves your cannabis garden largely under the influence of outdoor weather.

Roll-Up Sides:
One of the easiest ways to regulate heat in your greenhouse is to simply roll-up the sides and let fresh air move through. Roll-up sides are one of the most popular ventilation systems for small greenhouses such as carports and hoop houses.

Roof & Wall Vents: Roof and wall vents are openings that are strategically placed to help fresh air move throughout a greenhouse. Importantly, well-designed greenhouses used vents to establish thermal buoyancy and air-movement without machine power.

Retractable Roof: Certain commercial greenhouse designers have devised structures with roofs that can be entirely removed. While retractable roofs are not cheap, they allow excellent airflow by having zero restrictions on the ceiling.

cannabis growing in a greenhouse with inline fans

Active Cooling Systems

Active ventilation systems take on many different shapes and sizes. While designs vary greatly, all active cooling systems use machine power to move air in greenhouses.

The most basic active cooling systems use a single component like a vent fan to regulate temperature. In certain small greenhouses, a little bit of machine-power is all that is needed to get the job done for airflow. In large commercial operations, growers might use a combination of cooling technologies to get the job done – including wall fans, wet walls, exhaust systems, and more.

Many cannabis greenhouse growers use a combination of passive and active cooling systems. Doing so gives them more versatility with different weather conditions and allows them to better regulate the use of electricity. However, active cooling systems can be quite expensive to install and operate.

Inline Fans: Inline fans are a great active cooling method for small, hobbyist greenhouse gardens. Especially if you have a carport or hoop house, a quality inline fan like the Cloudline Series from AC Infinity will get the job done.

Evaporative Cooling Wall: Evaporative cooling walls are popular active cooling options for commercial greenhouse growers. With these systems, industrial fans pull air through a “wet wall” and through the length of a greenhouse.

Vent Fans: Vent fans resemble exhaust fans you find in industrial settings. Simply put, fans are positioned directly on vent ports to move air in and out of a greenhouse under machine power.

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Summary: What’s the Best Option for Me?

If you are growing greenhouse cannabis in the heat of summer, there are luckily a lot of options for regulating temperatures. To make the best choice possible for a cooling system, you need to understand the parameters of your greenhouse as well as the outdoor climate in question.

While passive cooling systems are generally more affordable than active cooling setups, they don’t offer the precision control of machine power. On the flip side, many of the larger active cooling technologies are simply overkill for small greenhouses.

If you are only growing in a carport or hoop house, passive cooling like roll-up walls is likely all you will ever need. However, things like privacy concerns with neighbors might restrict your ability to raise walls, prompting the need for active ventilation. In like fashion, light deprivation gardens require and active exhaust at night when greenhouses are totally covered by tarps.

While many greenhouse growers can likely get away with just passive cooling, it seems that a combination of both schools of thought is the best option for cannabis gardens. Combining both gives you more versatility and the ability to deal with just about any type of weather.

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AC Infinity is the foremost name in air delivery systems, designing and developing the latest innovations in cooling and ventilation technology. They offer a suite of quiet inline fans that automate the growing progress and track key metrics. Visit or contact [email protected] to learn more.


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Presented By

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Written by Kent Gruetzmacher | Writer, Owner of KCG Content

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Kent Gruetzmacher MFA is a Colorado-based writer and owner of the writing and marketing firm KCG Content. Kent has been working in the cannabis and hydroponics space for over a decade. Beginning in California in 2009, he has held positions in cultivation, operations, marketing, and business development. Looking specifically to writing, Kent has worked with many of the leading publications and marketing agencies in the cannabis space. His writing has been recognized by such icons as Steve D’Angelo and Rick Simpson.

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