United States. Like most cannabis industry cultivation operations in North America, Real Leaf Solutions (RLS), located in Kalkaska, Michigan, is still perfecting its cultivation methods, but the company may have finally found an HVAC system design that will help it achieve optimal yields in the near future.
Tom Beller, co-owner and co-chief operating officer of RLS, believes his latest HVAC upgrade for two 1,500-square-meter flowering rooms is an important step toward optimal harvest goals. It consists of a fabric duct powered by six- and eight-ton variable refrigerant flow (VRF) systems; a combination it will use by doubling the operation this year from 12,000 to 24,000 square feet. Beller's confidence is backed by the 20 percent yield improvement from the last harvest, which he attributes in part to the new HVAC design.
Beller's HVAC modernization design team was led by mechanical contractor, Marc Burnette, president, Superior Heating and Cooling (SHC); Brad Bonnville, regional sales manager for fabric duct manufacturer FabricAir; the Fujitsu VRF team, and Jeromy LaRock, external sales of the manufacturer's representative, Major Lozuaway.
Previous RLS HVAC challenges revolved around getting airflow into plants and their soilless peat/coca mixture at the proper speed, uniformity, temperature, and relative humidity (RH). The fabric duct solution incorporates a matrix of linear holes at the 4 and 8 o'clock positions in each 20-inch diameter. Combi 70 fabric also disperses about 12 percent of the airflow through the duct's permeable surface to prevent condensation. Factory-designed permeability and linear dispersion result in a uniform air distribution of 2500 CFM per duct that helps plants thrive.
Meanwhile, the four Fujitsu V-II Airstage Fujitsu evaporation units hanging on the ceiling of each flowering room, supplied by two outdoor heat pump condensers, can keep the 77°F and 56 percent RH preferred by Beller within a tight tolerance of ± 1. SHC's Burnette configured each room to provide cooling/dehumidification and heating from any of the four evaporators simultaneously, if needed. The design is invaluable when latent and sensitive heat load changes during light/dark room cycles create environmental changes unsurpassed by conventional HVAC air handling equipment. Beller said the VRF stabilizes and signals temperature/HR settings without adding portable dehumidification or humidification equipment that other cultivation operations depend on.
Finding the Best HVAC Combination
When it opened in February 2019 as one of the first medical and recreational marijuana cultivation operations certified and licensed by the Michigan Marijuana Regulatory Agency (MRA), RLS struggled to maintain optimal growing conditions, resulting in harvests that "we knew could be improved," according to Beller. The flowering rooms of the all-metal building were supplied with conventional DX splitting systems. The metal spiral ducts of the air handlers hung on the ceiling with registers every 10 feet created drafts, hot spots and air stratification that affected yields.
However, the new HVAC environment not only increases yields, but increased air comfort also increases staff productivity. "(The flowering room with the fabric duct/VRF system) is a totally different environment; you have a very strange feeling when entering compared to the other rooms," said Tyler Pickard, the leading cultivator of RLS, who upon entering for the first time immediately gathered his cultivation team to experience the difference in air comfort.
RSL will also save energy costs, because the more even air distribution of fabric ducts has proven to be more efficient than metal duct systems, according to a study by iowa State University's Department of Mechanical Engineering. Improved air dispersion leads to narrow temperature gradients in the room, reduced HVAC runtimes and up to 24 percent less energy consumption compared to metal ducts, according to the study.
In addition, the company ensures that the metal duct is prone to condensation formation in humid environments. The metal duct galvanization process contains toxic silver oxides that drip into the soil with condensation, are absorbed by plants, and eventually infiltrate the cannabis user. State governments regularly monitor the presence of heavy metals and can order the destruction of a failed cannabis crop. "The use of antimicrobial fabric ducts is an advantage for us, because the Michigan MRA has the strictest heavy metal and mold testing standards in the U.S.," Beller said.
Maintenance of healthcare environments
RLS cleans all flowering rooms after harvest. Disassembling and commercially washing the fabric duct, which requires less than half a day for an employee, is also part of the disinfection process even if the fabric is antimicrobial. "Cleaning metal ducts is difficult in one place and disassembling them would require the additional costs of a contractor with the right equipment," Beller said. "Washing the fabric duct just creates a more sterile environment."
Other disinfection efforts include the 100 percent return bipolar air ionization modules of air handlers manufactured by AtmosAir Solutions, which flood rooms with positively and negatively charged ions. The ions disinfect and electrically adhere to airborne contaminants, making them large enough to become trapped in the MERV-8 media filters of air handlers.
The lighter weight and ease of installation of the fabric ducts allowed SHC's two-person team to install five 35- to 38-foot-long ducts in less than three days and without heavy-duty lifting equipment or without removing the dozens of 1,000-watt mixed-spectrum high-pressure sodium lighting fixtures, double-ended. Each span is suspended from a PVC-coated metal cable that hangs two feet below the 14-foot-high ceilings. The metal conduit would have required twice the time, larger installation equipment, and interfered with post-clean fast-track planting.
Future RLS plans include doubling its space by spring 2021, installing more efficient lighting with variable spectra, and modernizing the current third and fourth flowering rooms with fabric ducts and VRF.
