Mar 16, 20225 min read

Perfectly Prepared: How To Nail Grow Room Climate Control

So, how prepared are you?

Cannabis growers like to talk quite a lot about the biology of the plant—and that’s smart. Cultivation details, the plant’s nutritional needs and strain selection are essential and can’t be overlooked.

But something invisible is always touching the plant. And it has a major bearing on success or failure—air.

A plant can’t survive without air, and the relative quality of that air can have an essential impact on whether the plant succeeds or fails. And when you’re talking about a commercial grow, that means air quality can spell the difference between making money and losing your shirt.

How do you do that? It starts with how you think about air.

Consider The Microorganisms

If we could see all the microorganisms in the air, it would be kind of scary. In what we’d call “clean” air, there are 5,000 various particles in a cubic foot—and dirty air can have as many as 50,000. Many of those particles are molds, mildews and other pests looking for the right opportunity to propagate.

But if those molds and mildews reproduce on your plants, they can kill your crop.

So, what are you going to do to solve this problem? It all comes down to climate control. And one of the most essential, and often overlooked, components of climate control for indoor grow operations is dehumidification.

And there’s only one way to nail dehumidification: It’s all about proper preparation. Especially in the following areas:

Pest Preparedness

Growroom pests come in a number of forms. Some growers deal with ants and aphids (which themselves often arrive on the backs of ants), but plant diseases like powdery mildew and bud rot, two major causes of crop loss, also fall in the pest category.

One smart way to help avoid pests is to keep your growroom pressurized. If you’ve ever opened the door to a high-rise building and been hit by a gust of air, you’ve experienced a positively pressurized building. The effect happens because clean—generally, filtered—air is being piped into the space.

Positive pressure is helpful because when a room is positively pressurized, every crack and crevice in your room has tension on it; the air is essentially blowing out toward those openings. That makes it a lot harder for pests to make their way inside.

This move toward positive pressure in growing environments is a change from the way growrooms operated when growing cannabis was an underground, illicit activity. It used to be that growers would suck the air out of their room in order to capture any odor in a carbon filter. But now that odor is less of a security concern, it’s time to flip the thinking to positive pressure.

To limit pests, you also have to limit some of the food they need. You can’t eliminate the plants as a food source, but you can eliminate the moisture that molds and mildews need to thrive. That is done through dehumidification. In a properly dehumidified growroom, any mold spores that make their way into your space remain dormant.

Dehumidification is an area where cutting corners isn’t a good idea. The risk from shoddy dehumidification systems is too high—with pests and molds, you could end up losing your entire crop. That’s why, if you’re running a commercial grow, you need a commercial dehumidifier. Plan carefully to make sure you’re maintaining the right climate for your operation, because we’re talking about a serious investment.

Temperature Preparedness

The lights needed for an indoor grow operation can drive up temperatures in your growroom—to the detriment of your plants. The problem is the natural inclination in response to the heat produced by grow lights is often to over-size air conditioning capacity.

But an over-sized air conditioning unit can cause fluctuations in temperatures and humidity throughout the day that can damage plants.

Here’s how it works: An AC unit has a 3- to 5-degree target temperature range. When the temperature crawls up to the top of that range, the AC kicks on. When it gets to the low end, the AC shuts off to keep the temperature from dropping off and making it too cold.

The problem with oversizing an AC unit is that the system will run on a short cycle and then turn off quickly—that’s both an energy drain on the unit and a recipe for an unstable growing environment. When temps spike and fall rapidly, humidity levels also change dramatically. Instead, you want consistent cycles that run for longer times, with the result being more stable temperatures.

An additional benefit is that a properly-sized AC unit helps pull more water from the air, which means your dehumidifiers don’t have to work as hard.

Air Movement Preparedness

Air movement is important for a few reasons. One, moving air keeps your growroom a consistent temperature and helps replicate ideal outdoor growing conditions—breeze helps strengthen plant stems. Air movement also helps distribute C02 throughout the air, which can help grow higher quality plants.

But what’s arguably more important, is that circulating air in your growroom helps you avoid damp microclimates around plant leaves. A humid microclimate around your canopy can create the perfect environment for molds to grow.

Ideally, use a floor fan that pulls fresh air through the plant canopy to create a consistent environment with even temperature and humidity levels.

Dehumidification Equipment Preparedness

Sizing your dehumidifier is all about doing the math and figuring out how much water you’re introducing to your growroom on a daily basis.

Plants transpire about 97 percent of the water they receive, so the amount of water you give daily is a good approximation for how much water will need to be removed from your room on a daily basis. However, the climate where you’re growing can also have an impact. Drier climates may need less dehumidification than more humid areas. One simple way to remember this: Water in equals water out.

As an example, if you were growing 60 plants and each was given 1/2 a gallon per day, you’d average about 30 gallons of water per day. Since every gallon of water is eight pints, you would need to plan to remove at least 240 pints per day—and commercial dehumidifiers are rated by pints per day.

Best practice here is to install multiple commercial dehumidifiers to meet that need, primarily so that if you do have an equipment failure, you’ve got backup. Growing is a 24/7 operation, and you can’t put your grow on hold while you work on repairing or replacing a dehumidifier that’s gone offline. Also, a multi-unit system lets you space units to create a consistent humidity level throughout the room.

Are You Prepared?

Bottom line: Your plants’ health depends on dialing in many elements of the environment. The success of your grow is reliant upon you being prepared for both the forecastable, such as your plants day-to-day needs, and those issues that you might not be as excited to think about, including pests and equipment maintenance and outages.