While implementing proper airflow at an indoor cultivation facility isn’t necessarily complicated or overly expensive, Geoff Brown, VP of Technical Solutions for Quest, says it’s a necessary part of the grow environment that is often overlooked.
“Ductwork is not fun by any stretch of the imagination, but it’s an inexpensive and important way to make sure that your grow runs optimally,” he says.
Insufficient airflow in a grow room can lead to reduced yield, overheating or plant disease, among other issues, and is often the result of poor planning when installing equipment, Brown says.
For example, if the air supply and air return are both located above the canopy, the conditioned environment is far away from the crop, which leads to poor airflow around the plants.
“In my perfect world, we would see a mismatch between supply and return,” Brown says. “If you’re going to have a high supply, you’d want a return low so that you get good mixing, or vice versa—you could supply low and return high. But doing both at the same level means that it’s going to be very difficult to mix the air and not end up with a stratified air mass that’s not interacting with the plants the way you’d expect it to.”
Proper air supply and return setups would have the supply ductwork either in or hung from the ceiling, he says, and return grills would be placed low on the walls to draw air through the canopy. Alternatively, air could be supplied at or below the tray level and drawn up through the canopy, over the lights and into high ceiling returns.
Another common problem, Brown says, is when air movers, such as fans, are installed to compensate for poor airflow in facilities where the air supply and return are located at the same level.
“I’ve been in a facility with high supply, high return—this was a 118-light room—and it had vertical air blowers blowing up, contributing to the stratification that exists in that room,” Brown says. “They thought they were solving the problem, but they were actually making it worse. I think people need to think more intuitively on how to get airflow where they want it to be and not end up with situations where you’ve got a stratified environment.”
The goal, he says, is to achieve a canopy velocity of 3 to 5 feet per second without using horizontal or air rotation fans in the space.
Engineered air devices, such as airflow nozzles, can be installed to push air through the space and achieve this level of movement in the plants, Brown says.
“You should have enough air coming out of your HVAC equipment to not need air rotation fans,” he says.
Cultivators should walk through their grow rooms, identify problem spots and place air rotation fans only in those areas.
“It’s very difficult to get airflow perfect in a space,” Brown says. “You may end up with an 8-foot square in a back section that’s not getting what it should, but nobody knows about it because nobody’s actually walked the room. If you walk the room, you can actually feel a 5- to 10-degree difference in that corner. Get to know the difference and apply air movers to fix the problem, not as the default.”
Proper airflow benefits the crop, as well as the business, he says. It helps maintain a steady temperature, which can boost yield and avoid plant disease, and can also help operations save on energy costs.
“You end up with equipment that’s operating optimally, that’s not overcooling part of the room and struggling to cool down another piece,” Brown says.
By decreasing the number of rotation fans to boost airflow, operations can save on not only the energy it takes to run the fans, but also on the cooling needed to remove the heat that the fans create in the grow, he adds.
Designing a 5,000-square-foot grow room with proper airflow can cost between $10,000 and $15,000, Brown says, but using the right equipment can help cultivators save 5% to 10% on energy costs over the life of the facility.
“What I don’t want to see and unfortunately see a lot of is people using the cheapest stuff available,” he says. “We see a lot of disposable ductwork in the space. It’s dirt cheap and the goal is to throw it out between every flower cycle, but you also don’t have any real air devices. You’re not getting good control over where the airflow goes. … I would say it’s the cheapest way that a facility can both save money and ensure a consistent crop, is just developing a good airflow plan."