Like most North American cannabis industry grow-ops, Real Leaf Solutions (RLS), based in Kalkaska, Michigan, USA, is still refining its growing methods, but the two-year-old company may have finally found a state-of-the-art HVAC design that will help it reach optimum yields shortly.
HVAC retrofit
Tom Beller, RLS’ Co-Owner and Chief Operations Officer (COO), believes his latest HVAC retrofit for two 1,500-square flowering rooms is a major step toward optimum harvest goals.
It consists of a fabric duct supplied by six and eight-ton variable refrigerant flow (VRF) systems; a combination he’ll use when doubling the operation this year from 12,000 to 24,000 square feet. Beller’s confidence is backed by last harvest’s 20-percent yield improvement, which he attributes partially to the new HVAC design.
design team and challenges
Prior RLS HVAC challenges revolved around getting airflow to the plants and their soilless peat/coca mix
Beller’s HVAC retrofit design team was headed by mechanical contractor, Marc Burnette, president, Superior Heating and Cooling (SHC), Traverse City, Michigan; Brad Bonnville, Regional Sales Manager at fabric duct manufacturer - FabricAir, Lawrenceville, Georgia; the Fujitsu VRF team at Johnstone Supply, Traverse City; and Jeromy LaRock, outside sales West Michigan at manufacturer’s representative, Major Lozuaway, Grand Blanc, Michigan.
Prior RLS HVAC challenges revolved around getting airflow to the plants and their soilless peat/coca mix at the right velocity, uniformity, temperature, and relative humidity (RH).
uniform air distribution
The fabric duct solution incorporates a linear orifice array at the 4 and 8 o’clock positions on each 20-inch-diameter.
The Combi 70 fabric also disperses approximately 12 percent of the airflow through the duct’s permeable surface to prevent condensation. The factory-engineered permeability and linear dispersion result in a uniform 2,500-CFM air distribution per duct run that helps plants thrive.
heat pump condensers
Burnette set up each room to provide dehumidification and heating from any of the four evaporators
Meanwhile, each flowering room’s four ceiling-hung V-II Airstage Fujitsu evaporator units supplied by two outdoor heat pump condensers can maintain Beller’s preferred 77°F and 56-percent RH within a tight ±1 tolerance.
SHC’s Burnette set up each room to provide cooling/dehumidification and heating from any of the four evaporators simultaneously if needed.
VRF benefits
The design is invaluable when latent and sensible heat load shifts during light/dark room cycles create environmental changes unsurmountable by conventional HVAC air handling equipment.
Beller said the VRF stabilizes and pinpoints temperature/RH settings without adding portable dehumidification or humidification equipment that other grow-ops depend on.
Finding the Best HVAC Combination
When opened in February 2019 as one of the first recreational and medical marijuana grow-ops certified and licensed by Michigan’s Marijuana Regulatory Agency (MRA), RLS struggled to maintain optimum growing conditions resulting in yields “we knew could be improved upon,” according to Beller.
The all-metal building’s flowering rooms were supplied with conventional DX split systems. The ceiling-hung air handlers’ metal spiral ductwork with registers every 10 feet created drafts, hot spots, and air stratification that affected yields.
enhanced air comfort
The new HVAC environment not only raises yields, but the enhanced air comfort is also increasing staff productivity
The new HVAC environment, however, not only raises yields, but the enhanced air comfort is also increasing staff productivity.
“It (the flowering room with the fabric duct/VRF system) is a different environment; you get a very strange sensation when entering compared to the other rooms,” said Tyler Pickard, RLS’s Lead Cultivator, who upon entering the first time immediately gathered his cultivation team to experience the air comfort difference.
energy costs savings
RSL will save energy costs as well, because fabric ducts’ more uniform air distribution was proven more efficient than metal duct/register systems, according to a study conducted by the Iowa State University Mechanical Engineering Department.
Improved air dispersion leads to narrow temperature room gradients, decreased HVAC run-times, and up to 24 percent less energy consumption versus metal ducts, according to the study.
antimicrobial fabric duct
Using antimicrobial fabric duct is an advantage for us because Michigan’s MRA has the strictest standards"
Furthermore, the metal duct is prone to condensation formation in humid environments. Metal duct’s galvanization process contains toxic silver oxides that drip into the soil with condensation, get absorbed by the plants, and ultimately infiltrate the cannabis user.
State governments regularly check for heavy metals and can mandate a failed cannabis harvest’s destruction. “Using antimicrobial fabric duct is an advantage for us because Michigan’s MRA has the strictest heavy metal and mold test standards in the U.S.,” said Beller.
Maintaining Sanitary Environments
RLS cleans every flowering room after harvesting. Disassembling and commercially laundering the fabric duct, which requires less than a half-day for one employee, is also part of the disinfection process even though the fabric is antimicrobial.
“Cleaning metal duct is difficult in place, and taking them down would require the added costs of a contractor with the correct equipment,” said Beller, adding “Laundering the fabric duct just makes a more sterile environment.”
disinfection efforts
The ions disinfect and electrically attach to airborne contaminants thereby making them large enough for entrapment
Other disinfection efforts include the air handlers’ 100-percent return air bipolar ionization modules manufactured by AtmosAir Solutions, Fairfield, Conn., which floods the rooms with positive and negative charged ions.
The ions disinfect and electrically attach to airborne contaminants thereby making them large enough for entrapment in the air handlers’ MERV-8 media filters.
Ease of installation
Fabric duct’s lighter weight and installation ease enabled SHC’s two-person crew to install five 35 to 38-foot-long duct run in less than three days and without heavy-duty lifting equipment or removing the facility’s dozens of 1,000-watt, double-ended, mixed spectrum, high-pressure sodium light fixtures.
Each run is suspended on a PVC-coated metal cable hung two feet below the 14-foot-high ceilings. Metal duct would have required twice the time, a larger installation crew, and interfered with post-cleaning fast-track planting. RLS’s plans include doubling its space by spring 2021, installing more efficient lighting with variable spectrums, and retrofitting the current third and fourth flowering rooms with fabric duct and VRF.
