Andrew L. Shakely, PE, LEED AP BD+C | 4 Min Read
In 1996, California became the first state to remove state-level penalties for the possession and use of medical marijuana for approved medical conditions. Since then, through a mixture of voter ballot measures and legislative actions, a total of 28 states and the District of Columbia have passed laws allowing for use of medical marijuana. In 2016 alone, five states approved medical marijuana. Each state has its own requirements for the growth and processing of medical marijuana, but in those states that require indoor cultivation facilities, the design of these facilities must address unique conditions.
The construction and operation of a medical cannabis cultivation facility represents a significant investment, and the operators’ goal is to be able to produce a consistent, high-quality product that not only can be replicated between harvest cycles, but also maximizes product yield. To do this, the facility must provide a highly controllable, energy-efficient environment that minimizes risk of product loss. So, what are the key factors that make the design of these facilities unique?
High Energy Consumption
While companies are developing and experimenting with LED lighting options for grow lights, the standard of the industry remains high pressure sodium lights. Most cultivators believe high pressure sodium lights have proven to be the best lighting to maximize product yield. The impact of having these high-density lighting systems in an indoor facility is that they both consume a lot of energy and also produce a lot of heat. Not only does this require the electrical service and distribution systems to be much larger than with conventional buildings, it also causes the HAVC systems to be upsized to handle the high heat load of the lights.
Additionally, the HVAC systems must also be able to provide dehumidification in the grow rooms when the lights are off. During growing periods, when the lights are on, the plants are absorbing water and using it for photosynthesis. When the lights are off, a significant portion of the absorbed water is aspirated from the plants and released back into the grow room environment. The HVAC system must be able to control this humidity release, even though it doesn’t need to be providing cooling because the lights are off. Conventional HVAC systems aren’t designed to provide this type of humidity control when cooling is not required.
To reduce ongoing energy costs from operating this type of facility, it is imperative that the HVAC system be chosen with energy efficiency in mind. The energy savings from features such as free cooling and heat recovery loops will quickly offset the upfront costs of installing these systems.
Risk control in medical marijuana facilities typically falls into two categories: (1) Community Concerns; (2) Security and Crop Protection.
Security is almost always a primary concern of both states and communities in which these facilities are located. Security systems are typically a significant portion of the cost of the project. Typical systems include perimeter access control and video cameras for monitoring both exterior and interior areas of the facility. They also feature access control and logging of employee movement into and out of critical zones of the building. These systems must have back-up power from emergency generators and UPS batteries, in the event of a power outage.
Another concern to most communities is odor control. It is vital that a thoughtful method of odor control be developed to limit odor from escaping the facility. Carbon filtration, ionization, hydroxyl, and controlled exhaust systems are techniques used to avoid conflict within the communities surrounding a grow facility.
Crop protection is the primary risk control concern of the cultivator and operator of the facility. A pest infestation or outbreak of mold or fungi can spread rapidly through a grow room and cause a substantial financial loss to a grower. Indoor grow facilities must be designed with compartmentalized grow rooms to contain an outbreak, if it occurs. The materials used for walls, floors, and ceiling construction also must not promote mold growth and must be easily cleanable.
As mentioned previously, the HVAC systems must be designed to control humidity. Controlling humidity spikes is critical to avoiding an environment that can lead to mold or fungi growth. Systems must also not be shared between grow rooms so cross contamination cannot occur.
Because mold and fungi can cause a significant loss, the HVAC systems are also often provided with back-up power from a generator. The extent of backup power provided can vary depending on the reliability of the power system for the region in which the grow facility is located.
Controllability and Data Gathering
Because maintaining a consistent environment is critical to the success of an indoor grow facility, these facilities often feature advance control systems that monitor and control lighting levels, space temperature, humidity conditions, and control the fertilization and irrigation systems for the grow rooms. These systems also allow cultivators to continually optimize their grow practices by analyzing continuous data of growing conditions. Close coordination of the controls for lighting, HVAC, and irrigation systems is critical to avoid delays and added costs during systems start-up.
Indoor medical marijuana grow facilities have unique needs that must be addressed by proper design to ensure that the facility infrastructure supports the mission of producing consistent, high-quality, high-yield product. While this post has highlighted some of the key concerns that must be addressed during the design of the facility, it isn’t a complete summary. Other issues that need to be considered include water conservation, employee hygiene, and waste management. For an indoor grow facility to operate efficiently, the design must be a close collaboration between the owner, cultivator, and the design architects and engineers.
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