The importance of environmental control when growing cannabis


When the East Coast Cultivation team decided to build their new indoor grow operation in Rhode Island, they knew they had to master one thing: environmental controls.

“The key factor to successful growth is controlling your environment,” said Joe Welch, CEO and co-founder of East Coast Cultivation. “Once you lose control of your environment, serious crop crushing problems start to set in. “

The two main “crop crushers” are concerns that many growers face at one time or another: powdery mildew and botrytis, more commonly known as bud rot. Either of these problems can destroy growth and lead to thousands of lost income.

With this knowledge, Joe Welch and his team, including COO and co-owner Susan Welch, spent a lot of time setting up their grow room dehumidifier. This setup, along with an HVAC system, is the backbone of a well-controlled environment, Welch said.

To fine tune a setup, growers need to focus on three things when it comes to their dehumidifiers, said Coleman Retzlaff, a factory representative at Quest, which supplies business units to hundreds of cannabis growers across the country: proper sizing, placement and airflow.

Courtesy of the quest

Strength in numbers

“Incoming water equals outgoing water” is the mantra of growers trying to control their humidity. It may sound simple, but it is a bit more complicated in practice.

Plants release almost all of the water they absorb into the air, so in a sealed grow room, growers should take this water into account and remove from the air to ensure proper humidity levels. If a grower uses 25 gallons of water a day, for example, and 5 gallons go down the drain, they have 20 gallons left. There are eight pints per gallon (dehumidifiers are measured in pints per day), so you should be able to remove about 160 pints of the air per day.

“When we do that math, it’s really that simple,” Retzlaff said.

A common misconception that leads to undersizing a grow room dehumidifier setup is the idea that having an air conditioner means additional humidity control is not needed. Although air conditioners can remove some moisture, they are designed to cool, not remove water, and therefore do not keep pace with the needs of a growing environment.

Additionally, air conditioners rarely run at night when the lights are off and there is no additional heat added to the room. These are exactly the conditions that can allow mold to take hold. At East Coast Cultivation, Welch and his colleagues found that it was best to oversize their dehumidifier setup with equipment that allowed them to prepare for potential worst-case scenarios.

“The best advice for dialing in your humidity is to properly size your units and have dehumidifiers that work with automated controls,” Welch said.

He’s in good company on this advice. Seth Lee, a seasoned grower from Colorado, has calculated how much water his flower room will use when the plants are releasing the most water. It operates six dehumidifiers, each capable of drawing 225 quarts of water from the air per day. Lee admits that his flowered bedroom might look slightly oversized, but he’d rather be safe than sorry.

“If you don’t invest in proper environmental controls, it’s almost negligence,” Lee said. “You set yourself up for failure because humidity control is a key part of an integrated pest management strategy, and I include late blight and fungi as pests. “

The importance of environmental control when growing cannabis
Courtesy of the quest

Perfect placement

Whether a grower uses a single dehumidifier or a legion of ten, proper placement is key to their effectiveness. Knowing how to place dehumidifiers helps maintain a stable environment and reduces the risk of creating microclimates where humidity spikes and mold can take hold.

To ensure proper placement, Lee advises growers to leave even spacing between each dehumidifier. It is also essential that growers pay attention to details, like facing the filter side towards the middle of the room and checking regularly to confirm that each unit is draining properly.

“We install dehumidifiers above the lights to save space and rely on good airflow from fans to keep the air evenly mixed,” Lee said.

As grow rooms grow in size, Retzlaff said spacing has become increasingly important as it allows for zone-based humidity control. For example, rather than running 15 dehumidifiers at a time and then turning them all off, each is automated to independently sense when humidity increases in its area. This approach keeps the relative humidity in the room more stable and increases energy efficiency, he said.

At East Coast Cultivation, Chief Growers and Co-Founders Alex Welch and Tyler Greenless took a modular approach instead, spacing out the dehumidifiers so that if one needs maintenance, the others can maintain appropriate humidity levels in its absence. “You have to build in redundancy,” Greenless said. “We’d rather have three units pulling 225 pints each rather than one pulling 700 pints. If that 700-quart unit breaks down, you have no backup, and if it isn’t fixed quickly, you risk a spike in humidity and mold growth.

The importance of environmental control when growing cannabis
Courtesy of the quest

Watch out for air flow

Finally, understanding the shape of each room and how the air will flow and mix in that space is essential to ensuring that any dehumidifier setup maintains a constant level of humidity in a grow room.

In a long room, growers need dehumidifiers evenly spaced to create a circular airflow. If the room is narrow, with a dehumidifier, Retzlaff said the exhaust air can be pushed over the room to achieve a cohesive air mixture through the plant’s canopy. It’s a stark contrast to a large room, where growers may want to channel the air back down to the floor to create a constant flow of air.

“We can channel our dehumidifiers from the supply and return ports to directed air where growers want it and in a way that best suits their environment,” said Retzlaff. “This extra bonus can play a big role in establishing consistent humidity levels.”


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