Building successful indoor cannabis cultivation facilities

October 23, 2018

By James Lowe and Benjamin Franz

Photo courtesy MJardin[1]
Photo courtesy MJardin

Indoor controlled cannabis production is a rapidly growing business segment, with many industry specific aspects to facility design. Although many design elements can draw upon parameters from similar industries, some operational aspects remain unique to cannabis production facilities.

Cannabis cultivation has several elements and activities that must be taken into consideration including:

Landscaping around the exterior of the building is an often-overlooked aspect of facility design, but it can have economic consequences. When selecting plants for the exterior of the building, it is important to avoid species capable of harbouring pests and diseases common to cannabis facilities. Certain plants can act as a reservoir for the continued introduction of these organisms into the facility, resulting in losses to yield and increased costs for pest and disease control. The best practice is to place plants away from any entrances or paths where employees or maintenance staff members access the building to avoid human-mediated transfer of pests and diseases into the facility as much as possible.

Harmful pests to watch for include the two-spotted spider mite, cyclamen mites, rice root aphids, and thrips. Common disease organisms include botrytis, sclerotinia, powdery mildew, verticillium wilt, fusarium, and pythium.

Equipment considerations

Mechanical and electrical equipment for indoor cannabis facilities uses up to 100 watts per square foot (depending on technology selection and space capture), which rivals the amount of energy a data server room requires—between 100 and 200 watts per square foot (For information, read “Data Center Density Hits the Wall[2]” by Robert L. Mitchell in the January 2010 issue of Computerworld.). Further, it takes more than 23 t (25 tons) of cooling and dehumidification equipment to service a 93-m2 (1000-sf) cultivation room.

Floor plan for GrowForce’s 11,148-m2 (120,000-sf) facility. The company purchased a 5-ha (13-acre) campus previously used as a meat packing plant, and is in the process of retrofitting the building to be an Access to Cannabis for Medical Purposes Regulations- (ACMPR) licensed cannabis cultivation and distribution facility, capable of growing up to 907 kg (2000 lb) a month (at full capacity). Image courtesy GrowForce Holdings Inc.[3]
Floor plan for GrowForce’s 11,148-m2 (120,000-sf) facility. The company purchased a 5-ha (13-acre) campus previously used as a meat packing plant, and is in the process of retrofitting the building to be an Access to Cannabis for Medical Purposes Regulations- (ACMPR) licensed cannabis cultivation and distribution facility, capable of growing up to 907 kg (2000 lb) a month (at full capacity).
Image courtesy GrowForce Holdings Inc.

Although it is preferable to locate this equipment on the roof, many buildings may not be able to accommodate the weight, which is why it often ends up screened on the ground near the rooms it is serving to minimize
outside ducting.

When building from the ground up, a structural engineer will ensure the building is able to bear the weight of the large and heavy mechanical and electrical equipment that heats and cools the space. Some pre-engineered buildings being retrofitted for indoor cannabis cultivation are not designed to handle the weight of the equipment, so this can be an important consideration when selecting a structure.

To increase yield in cultivation rooms, CO2 is used to enrich the atmosphere. The CO2 must be stored in tanks located on the outside of the building, ideally as close as possible to the cultivation rooms to minimize piping, but also in a location accessible by a large truck. Keep in mind bollards are typically required near the tanks.

CO2 use varies based on operating procedures, mechanical systems, and room construction. While the plants in the room consume some of the CO2, usage is mainly driven by CO2 escaping the room. A good rule of thumb for CO2 usage is 45 to 91 g (0.1 to 0.2 lb) of CO2 per square foot of cultivation room, per month. The tank(s) should be sized so the local CO2 supplier can refill them without any supply interruptions. Often, the CO2 suppliers provide the tank and help with sizing.

Building considerations

Cannabis facilities are often mapped out based on operational activities to reduce the potential for cross-contamination between spaces, and improve supply flow within the facility from the shipping area. Separate areas are created for activities such as cultivation, processing, and fertigation (the application of water, fertilizers, and other agrochemicals through an irrigation system utilizing injectors). Due to the value of cannabis, it is important to have a secure shipping area when moving product offsite.

Microbial growth can be prevented and mitigated within the walls of a cannabis cultivation facility by insulating the exterior walls and ventilating the interstitial spaces. In the authors’ experience, the envelope of the building should be insulated to a high R-value per inch and incorporate a vapour barrier to prevent moisture penetration and condensation from forming inside.

In terms of internal layout in a new building, columns should be hidden in walls as much as possible to avoid the loss of cultivation space. When a building is being repurposed for cannabis cultivation, this becomes a design challenge. For example, GrowForce is retrofitting what was previously a meat-packing warehouse in Winnipeg into an 11, 148-m2 (120,000-sf) cannabis production facility compliant with the Access to Cannabis for Medical Purposes Regulations (ACMPR). The existing columns were used to help dictate where the walls would go. Whenever possible, the walls were placed along column lines to minimize the loss of space due to columns.

Horizontal or vertical airflow fans are used in cannabis cultivation facilities to break up the microclimates around the leaves and promote transpiration and growth. Photo courtesy MJardin[4]
Horizontal or vertical airflow fans are used in cannabis cultivation facilities to break up the microclimates around the leaves and promote transpiration and growth.
Photo courtesy MJardin

Floor plan considerations

Although operational activities are influenced by the individual cultivator’s processes and procedures, many unifying design elements apply to all indoor cannabis cultivation facilities.

Cannabis cultivation facilities typically contain the following areas:

The location of these rooms with respect to one another helps mitigate the issue of microbial contamination and minimize labour costs in the facility.

Security office

Health Canada has implemented several security measures to ensure all cannabis facilities—cultivation, processing, or retail—are secure from an external as well as internal perspective.

Two key items outlined in the security measures within ACMPR are visual monitoring and intrusion detection services. These measures are in place to enable a company to monitor all activity around a facility and be able to provide a report to Health Canada—upon request, at any time—detailing all persons who have entered and activities that have occurred at the facility. This protects the staff and product as well as the consumer.

The security office should be located near the entrance to the building so staff can monitor visitor sign-in and escort guests accordingly. It is outlined as a compliance practice by ACMPR that the security office has onsite security footage storage and every room in the building is visually monitored. Having cameras all over the facility creates a lot of wiring, so more than one information technology (IT) or security room might be necessary depending on the size of the facility.

Gown-in/decontamination areas

These areas are typically located toward the entrance to the facility to allow all visitors and employees to put on personal protective equipment (PPE) and clean outer garments, and decontaminate or replace footwear before entering the sensitive cultivation and processing areas. This minimizes the introduction of pests, diseases, and microbial contaminants into the facility. They typically include a washroom area, space to change and store street clothes, and an air-lock separating the decontamination area from the sensitive areas of the facility, such as cultivation rooms, processing rooms, and finished product storage areas.

Lockers should be sealed to the wall, and tops should be sloped to avoid the accumulation of dust and debris. These areas need to be frequently cleaned to avoid becoming reservoirs of contamination for the facility.

Floors, ceiling panels, and walls should be:

Fibre-reinforced plastic, polyvinylchloride (PVC), stainless steel, polyurethane, and epoxy are a few examples of materials and coatings that would work to achieve the above objectives.

Decontamination areas in cannabis cultivation facilities are similar to laboratories and food processing plants in terms of HVAC design, material selection, and process flow. However, there are many conditions within the facility promoting the growth of micro-organisms. For example, cannabis plants are rooted into a potting media containing ample water and organic matter, giving micro-organisms all the things they need to thrive and grow. This creates a risk of possible cross-contamination, as flowers can have incidental contact with the pots during harvest (Consult the May 2005 paper “Sanitary Design and Construction of Food Processing Facilities[5]” by R. H. Schmidt and D. J. Erickson.).

Air sanitation systems (e.g. filtration and ultraviolet germicidal [UV-C] sterilization) can be installed and used to control the quantity of unwanted spores in the air, which tend to be at higher levels than normally found in laboratories and food processing plants. Spore sizes of common fungal contaminants (e.g. Aspergillus and Penecillium) typically range from two to three microns.

Another design element that can aid in controlling micro-organisms in the facility is a water sanitation system. Even in systems that do not reuse irrigation water, biofilms and unwanted organisms can develop in the irrigation lines, which can result in microbial contamination in the crop as well as cause maintenance issues for irrigation systems. Ozone, calcium hypochlorite [Ca(ClO)2], and peroxide injections are common water sanitation methods for indoor cannabis cultivation facilities. These chemicals also reduce the growth of micro-organisms and algae on the surface of the media, as well as the runoff sitting on the benches.

Cultivation rooms

Cultivation rooms are a series of controlled environments containing plants, horticultural lighting, benching, and irrigation/drainage systems. The idea is to minimize the distance a plant travels through the facility to make things more efficient, and keep the cultivation areas grouped together to segregate them from the processing area and minimize cross-contamination. In all cases, maximizing use of available space is essential to designing a profitable facility.

Figure 1: Plant movement in a typical cannabis facility. Image courtesy GrowForce Holdings Inc.[6]
Figure 1: Plant movement in a typical cannabis facility.
Image courtesy GrowForce Holdings Inc.

The plant flows through the cultivation rooms in the following order:

Mother (stock) rooms provide the cuttings that grow in the propagation room. Rooted cuttings are then placed in the vegetative rooms to allow the plants to grow bigger, before being moved into the flowering rooms. Therefore, mother (stock) rooms should be near propagation rooms, propagation rooms near vegetative rooms, and vegetative rooms near flowering rooms. The receiving and storage area should be located close to the cultivation area for supplies since they are often bulky and can be quite tedious to move long distances.

Selection of horticultural lighting for cannabis facilities is driven by three main factors: fixture efficacy (micromoles of light per joule or watt), cost, and spectrum. In geographical locations where energy costs are high, selecting fixtures with higher efficacy values is desirable. Current light-emitting diode (LED) technology can reduce costs associated with plant illumination by 20 to 40 per cent, depending on fixture selection, increasing the return on investment (ROI). In areas where cost of power is low, double-ended high pressure sodium (HPS) lighting is typically utilized in flowering areas. LEDs have higher fixture costs but they increase ROI beyond the fixture life.

In vegetative areas, LED lighting makes sense at lower cost per kWh, compared to flowering areas, given the longer lamp operation time (18-24 hours of light for vegetative rooms versus 12 hours of light in flowering rooms). Ceramic metal halide is another option for vegetative plant illumination.
It has a spectrum suitable for vegetative growth, and has a lower capital investment cost. However, operating ceramic metal halide lamps is more expensive.

Plants are grown on benches that come in set widths. One less bench in a space can mean hundreds of thousands of dollars of lost revenue a year. The horticultural lighting is also designed to fit the bench area. The more regular the shape of the rooms (squares or rectangles), the better, because this allows for the best possible space capture for cultivation and a more uniform light set-up. Since the cultivator is looking to maximize benching in these rooms, it is desirable to work with an architect who has a nuanced understanding of building codes regarding door requirements, exiting distances, and aisle widths.

The combination of benches, plants, and mounting height of horticultural lights above the plant canopy means the ceilings in these rooms need to be between 4 and 4.5 m (12 and 15 ft) from the ground, and meet the same requirements as the gown-in area. While acoustic considerations are not an issue in cannabis cultivation facilities, air circulation is of the utmost importance. With ceilings of this height, benches and plant canopies can create vertical barriers causing temperature stratification and microclimates. Usually horizontal or vertical airflow fans are used in these rooms to break up the microclimates around the leaves and promote transpiration and growth, but often they do not solve the problem entirely.

The mechanical equipment for the facility must be sized to meet dehumidification needs, since the plants transpire the majority of the irrigation water entering these rooms into the air. Additionally, cultivation rooms require exhaust capabilities to counteract the CO2 enrichment and pesticide sprays.

Cultivation rooms are exposed to a lot of water from irrigation, transpiration from plants, and cleaning, and they cannot harbour microbial growth. The floors, walls, and ceiling finishes should follow the same requirements as the gown-in/decontamination area. These rooms will likely flood multiple times, so the joint between the wall and the floor should be waterproofed. To do this, the authors suggest wrapping the floor coating (epoxy or polyurethane) up the wall 102 to 152 mm (4 to 6 in.) to create a continuous seal across the joint. Floor drains, or trench drains with floors sloped towards them, are a must.

Thermal breaks for insulation on exterior walls are also important, especially in seasonal climates, as the large difference between indoor and outdoor temperatures can cause condensation to form on the wall, which can result in a variety of microbial contamination issues.

There are no windows in cultivation rooms for two reasons: the movement of the sun and moon would interrupt the plants’ light cycle (which is carefully controlled using artificial lighting for optimum growth) and windows also pose an unnecessary security risk.

Integrated automation systems are becoming standard in cultivation rooms. Features like automated irrigation, variable speed controls on fans, and automated horticulture lighting are often controlled by one system for ease of use. Space to place the control panels should be considered when sizing the cultivation rooms and corridors feeding these rooms. While these features make life easier for the cultivator, they certainly add more complexity to an already complex cultivation room design.

Control panel for automated system. Photo © Ellen Jaskol[7]
Control panel for automated system.
Photo © Ellen Jaskol

Drying rooms

Drying rooms are controlled environments facilitating moisture removal from the product over approximately eight days before processing it. Drying rooms are adjacent to harvest areas where plants are broken down before entering the drying rooms. Locate the drying rooms near the flower and processing rooms to minimize the travelling distance for the plants.
If possible, keep the drying rooms away from high traffic areas since the plants are most susceptible to contamination during the drying process.

These rooms share a lot of the same design and antimicrobial guidelines as cultivation rooms. Some of the things to keep in mind include:

Preventing the humidity from spiking in these rooms is essential, so mechanical equipment must be sized to be able to remove a large portion of the moisture in the first few days.

Processing rooms

The processing rooms are where dried cannabis flowers are removed from any remaining stem, manicured of excess leaf material, and packaged for final sale. The ideal location of these areas is near the dry room, directly adjacent to the vault/secured storage areas, to reduce the distance of product movement between processing steps. If possible, it should be nearest to the gown-in area to prevent human-mediated cross-contamination from other areas of the facility.

The equipment and design considerations of this room are very similar to food processing areas, and the walls, floors, and ceilings should meet the same requirements outlined in the gown-in/decontamination areas. This area needs a three-compartment sink to wash and disinfect cannabis storage containers, and allow personnel to follow hand-washing guidelines.

HVAC systems in this room should provide adequate cooled, filtered air for worker comfort. Like breweries and food processing areas, cross-contamination of yeast and mould between batches commonly occurs in processing areas, so the use of additional room sanitation equipment, such as the generation of ozone, is desirable in this location. The room should be under positive pressure, relative to adjacent areas, to prevent the introduction of contaminants.

Interior lighting in this area should be higher and more intense than other areas of the facility to allow the inspection of the final product. Fixtures should be shatter resistant, and cleanable. Water is typically used in this area to wash down the room and equipment, so lighting fixtures should be resistant to moisture ingress (ingress protection [IP] 65 or higher).

Vault/Secured Storage

Typically, the vault and secured storage rooms are near the shipping area to reduce the distance the packaged product has to travel, and mitigate security risks.


Cannabis facilities draw design inspiration and processes from similar industries, but they have many unique elements making them unlike other indoor horticultural or processing facilities. Years of trial and error and research are needed before industry specific guidelines are established and refined for the design and operation of indoor cannabis facilities in Canada.

[8]James Lowe is executive vice-president of operations for GrowForce. A co-founder of MJardin Group in the United States, Lowe is an entrepreneur in the legal cannabis space since 2009. He owns both recreational and medical licenses in every category of the industry including cultivation, extraction, and retail. Lowe has produced cannabis indoors, outdoors, and in greenhouses. He can be reached at[9].

[10]Benjamin Franz is senior vice-president of cultivation for MJardin Group and acts as a consultant for GrowForce Holdings Inc. in Canada. His work in plant nutrition has resulted in the creation of MJardin’s proprietary fertilizer blend. Prior to working with MJardin, Franz designed, built, and managed a large-scale, commercial cultivation facility in the Denver area. He can be reached at[11].

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