DESIGNING MEDIUM & LARGE SPACES

by Bill Faulconer

Medium-Sized Rooms: Setting Up a 20 x 20 x 8 feet (6 x 6 x 2.4 m) Bloom Room

Equipment

Lights: (12) LEDs that each provide 1,550 µmol/s or (9) double-ended HPS lights that provide 2,100 µmol/s
Ratchet pairs: one per light
Light controller
High-limit controller
CO₂ supplementation
CO₂ tank and tank controller
Or CO₂ generator and controller
Strip timer
Reverse osmosis system if indicated by tests
55 gallon (208 l) barrel with float valve
(2) neoprene light socks (algae black)

If the space will not be ventilated:

Air conditioning

If the space will be ventilated:

1700 cfm charcoal odor filter
12 inch (30 cm) 1,700 cfm inline, exhaust fan

Construction

Seams are covered with aluminum tape. The base of the walls is protected using black rubber cover base. This makes regular mopping easier, seals out bugs, eliminates drafts, and traps water, preventing grow room leaks should a flood occur.

Ventilation

Skip this step if the space will not be ventilated.

Toward the right side of this room is an exhaust system designed to ventilate the space. The fan pulls fresh outside air from the opposite side of the room. The system consists of a charcoal filter with a dust sock (sitting on floor), a 12 inch (30 cm) 1700 cfm (48 m³/m) inline fan (sitting on the filter) and a 12 inch duct connection to the ceiling. A replaceable dust filter is installed at the ceiling, and a duct elbow is installed above the ceiling to direct the exhaust toward the exterior vent. The fan is connected to a timer set to run during the dark hours (when CO₂ is off) and pulls air out through the charcoal odor filter for about 15 minutes every few hours. The charcoal filter is necessary to avoid exhausting strong odors outside. The fan has a built-in silencer. The main purpose of this system is to provide fresh air periodically, but it can also be used to purge the room after activating bug bombs (when no plants are in the room) or, if necessary, to cool and ventilate the room during air conditioning failure.

Plant Support

Trellis netting supports plants without installing and removing stakes and tie wire each cycle. In addition to providing support, trellis nets are used to spread the branches to increase light penetration.

A “floating net” trellis designed by the author has the advantage that the front of the net frame can be lifted up while the back is left in place, making it much easier to harvest and replant.

Rather than building legs for a PVC frame at a set height above the floor, the net hangs from ceiling hooks with rope ratchets that are easily raised and lowered. The adjustable height makes it easy to customize for different cultivars. The second layer of netting usually hangs about 10 inches (25 cm) above the first net. Half inch (1.25 cm) electrical aluminum tubing is used because it’s lightweight and inexpensive. The tubing is attached to the ropes, holding up the one and a quarter inch (3 cm) PVC frame with zip ties. Don’t cut the ends off the zip ties and don’t over tighten them. With just enough zip-tie tension, the tubing can be slid up and down and still hold firmly where it is positioned.

Circulation

Circulation refers to how the air moves through the space rather than in and out of it. The mounted wall fans were installed just above the base of plant containers to ensure good air circulation. Note that all cords are securely installed and not lying on the floor or the plants. Good circulation minimizes potential for mold and helps ensure that the temperature, humidity, and CO₂ levels are consistent throughout the growing environment. Fans are disabled until the plants are tall enough to have been bottom-pruned to avoid blowing directly on lower leaves. Breathable fabric pots and plastic saucers have been chosen for this garden. Plant roots like to breathe. Movable saucers are easier to move around and clean than large plastic trays. Saucers are also less expensive than larger trays.

However, using trays or plumbing and tubing, water can be drained automatically while avoiding spills, which are much more likely when using saucers.

Cleaning & Maintenance

A garden can be cleaned and maintained more easily using the right surface materials. Drywall is acceptable, but foam board is mold resistant, has high reflectivity, is easy to install, is lightweight, has a moderate cost, and is easy to clean thoroughly. Polyethylene plastic can be easily installed over other surfaces and can be washed. Epoxy-coated floors are easy to install, incredibly durable, and easy to clean, and they make the whole room seem more like a laboratory.

Air Conditioning

This space is cooled using a four ton (900 kg), 48,000 Btu air conditioner. A frame was built to support the air conditioning unit and to provide a filter frame for the return air being pulled from the room near the floor.

This unit has a quick connect feature, allowing someone who is not an AC technician to install the flexible copper refrigerant lines from the indoor unit to the outdoor unit without having to charge them.

The unit also has a grower-friendly feature called low ambient control. The low ambient feature diminishes or disables the cooling fan on the outdoor unit. Mainstream (as opposed to cannabis horticulture specific) AC units are not designed or warranted for operating in cold temperature. This unit is designed to automatically restart if the power fails and then restores. Mainstream units require a button to be pushed to power them back on after an outage.

Control Equipment

For most projects, a painted plywood backboard, usually two by four feet (0.6 x 1.2 meters) is mounted to the wall so that all controls and wire supports can be securely and easily mounted. Half inch (1.25 cm) plywood was installed under the foam board so that anything could be mounted anywhere.

Power wiring from the main electric panel has been installed in flexible conduit. All wires are labeled, and each light is numbered. At the top of the image is an electrical subpanel to distribute power to individual circuit breakers for light controller (45 amps), AC (30 amps), and wall outlets (20 amps). Breakers are labeled.

Lighting

The lighting regimen is managed using a controller. It can accommodate sixteen lights.

The 240 volt power supply enters the bottom of the controller via flexible conduit connected at the other end to a 50 amp, 2-pole, 240 volt circuit breaker in the main panel, using three #8 gauge wires.

No power is provided to the light receptacles until the “trigger cables” receive 120 volts of power from a timer. A high-limit controller is connected between the timer and the light controller to disable lights if the room overheats. A trigger cable controls power to the controller. In an emergency, it can be turned off, eliminating all power to the lights.

High Limit Controls

The wall-mounted device is connected to a timer to activate the lights. This device can avert a costly destruction of the entire crop. The light controller trigger cords are plugged into the controller. The maximum temperature is set so that if the room temperature exceeds 90°F (32°C), due to AC failure or any other cause, the lights are disabled to avoid excessive temperature.

In each room at least one recording thermometer and hygrometer (RH meter) and a surface temperature thermometer aimed at the canopy are used to check plant temperature, rather than just where the display is placed.

Humidity

The humidistat is mounted on the wall, but the humidity sensor is positioned in the canopy to measure humidity in the plant zone. The controller is connected to the ceiling-mounted dehumidifier. Another humidistat controls a humidifier that turns on should the humidity level dip below 55% RH.

CO₂

The CO₂ controller is connected to a timer or photocell so that the system operates only during the light cycle.

The CO₂ tank is plugged into the controller and activated when CO₂ levels fall below 1250 ppm during the lit period.

Fuzzy logic is only recommended for CO₂ bottle systems as opposed to CO₂ generator systems because gas generators cost so little to operate that fuzzy logic is unnecessary and the function simply causes the generator to be ignited too frequently. Aluminum tape was installed over the LCD display to minimize the potential for the display to emit light and disrupt the light cycle during dark hours.

In addition to having a CO₂ controller to monitor levels, a second monitor can be useful to check the controller’s accuracy and to check CO₂ levels in various areas in the space.

Timers & Timer Strips

There are two wall-mounted strip timers. The top row of four outlets is controlled by the timer, and the bottom row of four outlets is always on. For this project, the light controller and the CO₂ controller are connected to timer outlets; the humidity controller, the music box, and wall fans are connected to the hot outlets. Timer strips are handy for eliminating multiple timers, cords, and adapters. The timer is a simple thermostat for control of room temperature.

Drainage

This is an effective drainage system for excess water. The blue tubing on the left is discharge water from the reverse osmosis water purifier runoff. The white tubing in the center is condensate water from the air conditioner. The clear tubing toward the right is condensate water from the dehumidifier mounted above. The black tubing drains to the sewer system and has a P-Trap to prevent sewer gas from entering the room.

Ducting

An innovative fabric duct was selected to supply cooled air into this room. The 16 inch by 20 foot (40 x 60 cm) duct is connected at one end to the air conditioner and is capped at the opposite end. The duct is supported by a steel cable fastened to the ceiling. Moderate bends can be made. The duct clips attach to the steel cable to suspend the entire length. Because the entire length of ducting is perforated along the sides, the cool air is evenly distributed throughout the entire growing space and all the leaves flutter gently. The AC thermostat is set for the blower to be on 24/7 to maximize circulation.

Convenience Lighting

Several ceiling lights (white bulbs) enable the gardener to work in the room (light schedule permitting) without having to turn on the cultivation lights. Working in the garden with thousands of watts of firepower can be unpleasant or unnecessary when pruning, inspecting, spraying, building or taking down a space, or just checking.

Toward the rear of this room is a three-bulb green LED fixture. Green lights provide a working light that can be sparingly used during the “lights off” hours. Without a green light, the bloom cycle is disrupted when lights are turned on during dark hours.

Convenience Light Controls

These old-fashioned yet clever devices prevent serious problems in the garden. Similar to the devices seen in gas station restrooms, these “ticker timers” can be used to turn on white or green convenience lights. In most gardens a wall switch can be accidentally left on, but this does not happen with these ticker timers.

Door Seals

Doors are a notorious source of unwanted light leak, bugs, dust, and contaminants. This door is sealed at the edges with a one inch (2.5 cm) wide and one quarter inch (6 mm) deep felt strip stapled to the door. The door bottom is sealed with a rubber sweep that works like a squeegee and is fastened to the door with screws. To moderate temperatures in the entry room, a vent was installed. The vent is protected with a washable bug screen, and it is protected from light leak with a rooftop rain vent behind the door.

Secure Entry

An entry room or “vestibule” allows the operator to keep unwanted light from entering the bloom room and possibly disrupting the light cycle. It also allows the operator to keep light from escaping and minimizes the potential for contaminants to enter the bloom room.

Nutrient Test Meters

This meter remains in the solution, constantly monitoring the nutrient pH level, temperature, and nutrient strength. The grower can see the levels change as products are added.

Water Purification

A reverse osmosis filter is needed if the source water exceeds 150 ppm dissolved solids (0.6-0.8 EC). Reports are available from the local water company or agency.

Rainwater is a good source because it contains low ppm of minerals. Adjust it to 100-125 ppm prior to adding any supplemental nutrition using CalMag. (See Nutrients & Fertilizers.)

This reverse osmosis purifier can provide up to 150 gallons (568 liters) per day of pure water. The water supply is connected at the pressure gauge. A minimum of 60 psi is needed. Higher pressure results in higher flow. The discharge tubing is connected to a drain.

The purified water is connected to a barrel that has a float valve to stop water flow when the barrel is full. When the inexpensive pre-filters look dirty, they should be replaced. When the purified output exceeds 100 ppm, the costly filter membrane should be replaced.

Water/Nutrient Reservoir

This reservoir barrel is a 55 gallon (208 l) food-grade, high-density polyethylene reservoir. Non-food-grade, low-density polyethylene reservoirs (trash cans) are made from low-density plastics, which degrade and leach petrochemical polymers into the water.

Here the test meter is wall mounted above the reservoir. An air pump is installed outside the reservoir with an air stone inside it to oxygenate and circulate the nutrients.

A submersible water pump in the barrel is connected to a garden hose with a long wand attached to minimize the need to bend over when watering plants. A hose support wheel is mounted above the barrel to store the hose and prevent it from kinking.

Considerations for Designing Large Cultivation Spaces

By Justin Arriola

Designs must be up to code and must comply with all regulations, legal limitations, and requirements of all aspects of the project. Style and design must also be considered.
Owners of large-scale commercial gardens often have already chosen a “head grower” or “cultivation supervisor,” sometimes referred to as a “master grower.” This individual has usually already chosen cultivation methods and the cultivars that will be used in the facility. Serious consideration must also be made on whether the grower’s knowledge base and experience is up to the challenge. It is better to decline a project than work on one whose success is not probable.
The space may be designed to adapt what the grower is already doing and to make it more efficient at a larger scale. On the other hand, scaling up a method that has inherent flaws can lead to disaster. New approaches may be considered.
Efficiency is achieved using data capture and automation, which allows for continual improvements on quality and consistency while reducing inputs including labor.
For the most part, growers are moving toward automated light-deprivation greenhouses because they are the best of both worlds: the climate variables are as controllable as a large-scale indoor facility, but with no-cost sunlight.

Getting Started: The Limiting Factors

Start the design by addressing the two most significant limiting factors on the operation: local regulations and harvest style.

Laws regulating cannabis vary widely by jurisdiction, and compliance needs to be factored first. Designing around compliance means planning for security, zoning, local ordinances, interactions with regulators and/or law enforcement, and all other applicable building requirements and regulations.

Compliance to cultivation space size requirements varies by jurisdiction. In some places the cultivation space is measured by square footage of canopy, and in others, by plant count. When limited by plant count, the goal is to grow very large plants. In that case, the design focuses on maximizing the yield per plant. When the cultivation space is measured in canopy area, it really comes down to filling that space with as much plant canopy as possible, usually using a SOG technique. (See Vegetative Growth.)

Although planning for harvest is a crucial step in large cultivation space design, it is very often overlooked. Harvesting involves a lot of logistics and often more labor than the day-to-day operation. Dedicated climate-controlled spaces for processing, drying, curing, and manufacturing should factor heavily when designing the space.

There are several details that must be worked out about the harvest before designing. How often will the operation be harvesting? Traditional outdoor farms will have one to three harvests a year. Many indoor cultivation spaces are designed to harvest smaller batches perpetually. What is the end product? If flowers will be sold as top-shelf dried buds to a final customer, hand trimmers are likely to process the crop. In a large-scale outdoor farm, or in the case of flowers that are being harvested for processed or manufactured products, trim machines and industrial drying equipment may be necessary.

Defining the Operation’s Goals

Some cultivation licensees are vertically integrated, so goals may be driven by the need for product diversity. Decisions must be made on whether the in-house brand will be a value-provider or a top-shelf producer, and what sort of end products the operation needs to produce to satisfy its market. Work backward to design the space with these end goals in mind.

Postharvest manufacturing presents logistical challenges: the need to provide space and electrical capacity for large industrial equipment. Planning and management of workflows is imperative to minimize overhead costs in a complex operation that is vertically integrated. If one or two thousand steps are taken out of a worker’s daily routine, or a faster or easier way to accomplish a task is introduced, then efficiency goes up, with more time spent on tasks. A 10-minute savings daily adds up to 41 hours, a full work week.

Automation & Data Acquisition

If it can be measured, it can be managed. Using data acquisition and automation, every piece of data can be used to reduce time spent on menial tasks and making all inputs consistent. Data are used to quantify inputs resulting in consistent outputs.

For instance, positive pressure emitters can be set for consistency in watering so that plant 1 and plant 200 down the row are getting the exact same amount of water for the exact same amount of time.

Another piece of equipment tracks when the pumps are turned on and off and how long they run, and translates that to the amount of water delivered to each plant. From there, day 1 to day 25 can be compared to determine whether all the pumps were working correctly. The pumping sequence from the last three harvest cycles can be compared. If there is a difference in yield between cycles, data can help determine the cause.

Refining and analyzing the microdata around the facility is crucial to operators who want to make sure GG #4 vape pens purchased in a California store are uniform with the ones sold in Massachusetts.

Although many day-to-day gardening tasks can be automated, there is still a need for people on the ground to manage the operation. If not using monitoring equipment, staff members must be assigned to actively scan for signs of disease or pest infestation to assess plant quality.

Once methods and settings have been selected, quantifying what went into that production makes it a lot easier to repeat.

Growing Zones

Some greenhouse and indoor cultivation spaces are large but are broken up into smaller rooms, or climate zones each with different plants in varying stages of growth for a perpetual harvest. Each space’s environment is customized to each cultivar’s preferences and growth stage.

Climate zones are great for large-scale growers who have been using the same cultivars for a while and have perfected a “recipe,” or protocol, because they know its idiosyncrasies such as growth patterns, height, and ripening time. This sort of “zoning” is also important for pest and disease management: infestations are more easily contained in the smaller spaces. These climate zones can be designed in a variety of ways, such as creating walls and other physical separations or sophisticated light-deprivation systems programmed to the different zones.

In larger spaces with separate climate zones, each zone is programmed and monitored, controlled, and adjusted through a tablet or mobile application that uses data to remove the variability of decision making from workers. Instead, the decisions are based on data that the cultivation supervisor interprets.

Although these smaller spaces have several advantages, such as smaller, more frequent harvests, isolation from infections, and customized conditions for specific varieties, they preclude the introduction of automation and robotic controls. Having a large, automated space, unimpeded by walls and barriers, can become far more efficient in every phase of cultivation and harvesting.

The advantage of this is that it’s easier to attend to plants that have the same requirements rather than dealing with each space’s particular requirements. Single-harvest operations are less likely to have infections because the entire space can be cleaned after each crop, leaving no residual pests on living plants.

Future Goals

A lot of new licensees want to start small and generate revenue without taking on too much investment. If growers are planning to start small and scale up, they should think about where they want to be in three to five years. If the key components are built with expansion in mind, a lot of headache (and money) is saved down the road.

Labor, Staffing & Workflow

When designing the space, it is important to look at all the processes in the growth of the plants, from seed to harvest, and the labor and equipment involved.

Before design begins, there are some important decisions to make.

Where will propagation take place?

Will the operation make its own clones, or will it purchase them?
If clones will be made in-house, will they be from “mothers” or clippings from plants about to enter flowering?
Will there be a separate research space where controlled cultivation experiments are performed?
Will there be space for a dedicated breeding program, including isolation of males and pheno-hunting?

After propagation comes the vegetative growth stage. What will that space look like? In cultivation spaces with high ceilings, climate-controlled stackable shelf trays are used so that the area of the space is maximized vertically as well.

Growing sea-of-green (SoG) also changes the needs of the vegetative space. Vegging for SoG takes a maximum of two weeks, so there’s quicker turnaround for many more plants. A conventional style of production requires fewer plants, but the vegetative growth time takes much longer.

In climate zones, vegetative spaces can become flowering spaces by simply altering the photoperiod in that zone.

Large outdoor farms that harvest once a year will most likely need to work with a cannabis-friendly staffing company to provide the extra workforce needed to process the crop. Extra people on-site means a need for extra accommodations such as restroom facilities and break spaces. Spaces for bucking and shucking the plant and trimming the buds must be designed. It should be an organized workspace, with designated spaces for each task and an open design so that managers can easily see the product as it moves through processing.

By focusing on efficient organization and workflow, strategy, and labor-saving devices, fewer people are needed, less total labor is required, and a smaller investment in equipment and space is needed. (See Automation.)

Additional climate-controlled spaces for drying and curing must be planned too. (See Drying, Curing & Storing.)

Security

Monitoring tools are an important piece of security and cultivation plans. Usually cameras are required to cover the entire inside and perimeter of the space, and footage is to be stored on-site for up to 60 days. Through seed-to-sale tracking software and security systems, regulators have access to yield and harvest data as well as detailed logs of who is provided access to the facility.

“Geofencing” is an efficient way to secure the site. Using sensors in key cards, the grower can see and restrict how people move through the zones in the space. High-value inventory can also be tagged and traced in the space. If a container is moved out of its designated space—or even around it—programmed alerts will go to the appropriate people. This is an effective way to prevent diversion and theft.

Pest Management

Sanitation is the best way to manage pests and disease. It is especially important in large operations that are constantly cycling crops through the space. Rolling benches, racks, and other equipment must be sanitized in between cycles. A lot of construction is designed around easy cleaning, as sanitation is really just diligence.

It is critical to have a good protocol regarding access to the cultivation space for security and pest management. Guests to the site such as investors, members of the media, legislators, and friends may want to tour the space. Sometimes groups will tour multiple cultivation sites on the same day, potentially spreading pests from one site to the other.

A staging area outside the cultivation space entrance is effective at maintaining hygiene. Guests remove coats and put on protective gear such as booties, hair and beard nets, and Tyvek suits or lab coats. Also included are hand-washing stations, and in some spaces sophisticated blowers that “dust” people as they enter the space.

Planning for Electricity & Equipment

One of the biggest concerns is making sure that there is adequate power. Increasing power may require working with the electric service provider to upgrade equipment. This requires time and perhaps a costly investment.

Prepare for the possibility of losing power by having a generator set to start should the power from the grid fail. Solar batteries can be used as a main source or a backup. This can save a crop.

A CoGeneration (CoGen) system based on the co-generation of power is a good option for a large-scale cultivation facility. CoGen systems use a proven natural-gas-fueled engine to generate electricity. Electricity is fed into the building, thereby reducing the facility’s electrical consumption and utility bill significantly.

At the same time, free “waste” heat is recovered from the CoGen system’s engine oil, jacket, and exhaust heat. Captured heat is then used to offset fuel that would otherwise have to be burned in the site’s water heaters and boilers. This allows the site’s boilers to not have to work as hard, so the gas bill is also reduced. The space heating, domestic hot water, process hot water, pool heating, and more run on gas. “Waste” heat captured from the CoGen system can also be fed into a device called an absorption chiller, which is able to convert the “waste” heat into cooling, relieving the site’s electrically powered chillers from having to do as much.

Carbon Dioxide & Climate Controls

Climate controls in large-scale cultivation spaces, whether one large space or several climate zones, are best managed with sensors and automated controllers.

Automation and data capture can now literally tie into everything. Fans and air systems, temperature, humidity, heating, cooling, and carbon dioxide can be dialed in with precision. Although these systems can be expensive, they are incredibly valuable. They provide consistency, reliability, and usable data to refine processes. If there is a problem in the cultivation space or facility, those who need to know about it will get an automatic alert.

Sensors and automation tools in the cultivation spaces allow growers to maintain exact concentrations of carbon dioxide in the space and automatically shut off and air out the room prior to workers entering the space. It is not recommended that workers are exposed to high concentrations of carbon dioxide, as studies suggest that it may be unsafe.

Lighting the Space

One of the nice things about LED lights is that with certain fixtures the light spectrum can be controlled by the grower. Varying light spectrums directly affect the plant. LED lights produce far less heat than an indoor or greenhouse system full of HPS lamps.

Light manufacturers may aid directly with design as it pertains to lighting efficiency. Usually the companies will provide access to software that will calculate the lamps needed to achieve a specific light level over the canopy. Often manufacturers will provide assistance in the lighting plan, especially if it helps them make a large sale.