Humidity Control in Indoor Cannabis Grows: Importance, Challenges, and Solutions

by | May 24, 2022

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Humidity control is a major issue in indoor cannabis grows. It’s an inevitable part of growing in a closed environment, and it’s highly problematic, leading to molds and other issues. So, controlling humidity is a must.

However, the way you control humidity has a huge impact on your energy bill. With energy prices rising around the globe, being able to improve efficiency and reduce energy usage is becoming a necessity for growers of all sizes.

Why Is Humidity a Problem?

As mentioned above, moisture is inevitable in any form of closed environment agriculture. The plants, as part of their physiological activity, constantly transpire water vapor to the air. That’s not a bad thing. In fact, you want your plants to transpire as much as necessary. That means they’re taking in and breaking down nutrients. But when relative humidity is too high, they can’t transpire, leading to slower growth and development.

So, all you need to do to allow your plants to grow as best as possible, is keep humidity down. However, in indoor cannabis grows, which tend to be crowded, that’s a challenge.

Slow growth and low bud development isn’t the only problem with high humidity. In fact, it’s not even the biggest problem. One issue every cannabis grower faces, is mildew, most commonly bud rot (botrytis) and powdery mildew.

Besides killing your plants and harming your buds, mold poses a very serious regulatory issue. Moldy cannabis flower, whether meant for distribution or further processing, doesn’t uphold regulations, such as GMP.

Bottom line, moldy cannabis has no value for growers. So avoiding mold development is critical in any cannabis grow room.

As cannabis is highly regulated, using common fungicides isn’t an option either, as it is in other horticultural sectors – which leaves growers with one option – preventing it through climate control. Or more specifically – dehumidification.

It’s important to note that humidity control and mold prevention isn’t limited to any single stage in cannabis cultivation. Mold can develop at any growth phase, or even post-harvest and during packaging. So, keeping tight control over humidity is important for every process along the way.

Is It Possible to Control Humidity Using HVAC?

Many indoor growers rely on their HVAC system for humidity control. That makes a lot of sense, as HVACs, and other temperature controllers, are already necessary and prevalent in cannabis grow rooms. Like any air conditioner, HVACs do remove some moisture from the air, as a side effect of their operation.

Controlling Humidity in Indoor Cannabis Grows: Importance, Challenges, and Solutions

However, HVAC systems aren’t designed for optimal water extraction. In order to continuously reduce humidity, the HVAC must run non-stop, often alternating between cooling and heating, just to maintain moisture extraction. This is highly inefficient, as HVACs require a lot of energy.

Crowded cannabis grow rooms generate massive amounts of moisture. So, due to HVAC’s inefficiency, it takes a very large system to be able to handle it. If the HVAC were to deal solely with temperature, on the other hand, you could get by with a much smaller system.

Needless to say, installing oversized HVACs, simply to be able to control humidity, is very expensive, and drives up both initial and operational costs.

The Benefits of Using Dehumidifiers for Humidity Control

When you consider the bottom line of building and running an indoor cannabis grow op, dehumidifiers simply have the upper hand in humidity control. Especially if you use a dehumidifier designed specifically for indoor cannabis cultivation, such as DryGair’s DG-X. These dehumidifiers are engineered for this highly specific task, and so provide the most effective and efficient solution.

A good rule of thumb, when considering different options, is to compare energy efficiency. For example, a DG-X extracts 4.2 gallons per hour, under common grow room conditions. Running on 4.8kW, that comes out to 0.87 gallons of water extraction per kWh.

Furthermore, one of the biggest benefits of using a dedicated dehumidifier, is that it lets you separate humidity and temperature control. So, you can turn off the HVAC when your temperatures are within optimal range and let your dehumidifier control humidity on its own. This option can save a lot of energy, as dehumidifiers are much more efficient at their task, and require a lot less energy to operate.

Beyond more efficient energy usage, separating temperature and humidity control also gives you more control over your growing conditions. It allows you to optimize your indoor climate to a much higher degree, ensuring uniform flower growth and high-quality bud production.

Overall, using HVAC may give you some relief from major humidity problems. But it’s not the most effective, or efficient solution. If you’re looking to cut costs and improve your grow simultaneously (who isn’t?), then using dehumidification for humidity control is your best bet.