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Cannabis Construction

Recently Massachusetts legalized the recreational use of Cannabis or marijuana, and it opened up a brand new specialty in the construction industry. Because it is so new, most project teams will have multiple members where specific cannabis experience is lacking.

The requirements or preferences of individual growers concerning the environmental conditions, means that the projects can vary greatly between grower, much the same way as in other specialty construction, such as laboratories.

At first glance it may seem conditions for growing indoors are pretty straight forward, however there are many requirements, some unique, that need to be considered. The main areas of consideration are light selection, HVAC requirements, CO2 supplementation, fertigation, and drainage.

Lighting

There is a large range of lighting options available, the main categories are LED, High Pressure Sodium (HPS) or metal halide.Each grower has their own preference for lighting and even a single grower will choose different lights for different stages in the plant’s development. Another consideration in light selection is the CCC’s (Cannabis Control Commission) regulations for energy consumption, which are based on the size of the facility. All of these factors must be taken into account during the light selection process.

HVAC

The selection of lighting has a significant impact on the design of the HVAC system, due to the heat loads. The heat loads produced by lighting vary dramatically depending on the lighting selected. LED lighting produces considerably less heat load than HPS or Metal Halide. A facility that is designed for LED lights would not be able to support the heat load from HPS.

As bad as it is for the plants the problem isn’t just with excess heat, but that it also leads to stratification of the air in the facility – which affects air distribution. This phenomenon requires a method to properly eliminate the stratification issue which can inhibit good air circulation and heat load distribution.

The major reason for crops failing the stringent Massachusetts testing is MOLD. Mold happens  when the humidity gets too high.

With these high heat loads you cannot just supply colder air. The cold air has a lower dew point and it is not acceptable for the plant to come in direct contact with too much cool air. You cannot expose the plants to chilled air. An exiting air temp from the Air handling units at or close to the dew point can lead to condensation. Condensation, combined with the high amounts of water each plant receives daily can make mold a real issue without a properly designed system.

Most facilities elect for a higher exiting air temp from the units to allow for more flexibility in the dew point. However this approach requires significantly more CFM air exchange to accomplish the same level of cooling. And still this is typically not enough to provide consistent temperatures throughout the room and disrupt the stratification phenomenon. Air flow may be supplemented by a series of fans within the room to increase the air mixing.

Due to the heavy watering during the adult phase (flowering) of the plant, the main concern with humidity is dehumidification in flowering rooms due to the high transpiration rate of the plants. However, during the plant’s initial growth phase, the amount of water the plant gives off can be significantly less and dehumidification may not be required.

During various post-growth processing stages good humidity control is vitally important. The timing of the drying process is critical, and is greatly affected by humidity. In the processing areas both humidification and dehumidification can be required in a single room.

CO2 Supplementation

Co2 can be supplied via a bulk liquid CO2 system to aid in plant development and may be dispersed into the room at higher than typical atmospheric conditions. However, the greater the CFM, the greater the fresh air and the greater the consumption of CO2. The high flow of air and the subsequent code compliant fresh air requirements have a cascading effect on the CO2 system.

Fertigation

Plants need not only water but they also need fertilizer, hence the fertigation system. Often on larger facilities a central fertigation system is used. This can provide precisely controlled quantities of select nutrients and water multiple times per day to ensure consistent plant growth. Fertigation systems can be fed from a RO water source and may also need to be tempered in order not to shock the plants, especially during the winter months. Systems with as much as 3000 gallons of water or greater are not uncommon.

Drainage

Moveable tables are typically used in order to maximize the flowering (canopy) area while allowing for code compliance and access to the crop through the process. With all that water flowing around on moveable tables you also need a drain system capable of catching any runoff. The movable nature of the tables makes single point drains impractical and typically a trench drain would be used. You need a robust system capable of capturing and cleaning water for reuse wherever possible.

Cleaning

Between crops each room is thoroughly cleaned to prevent any contamination. This requirement creates the need for clean room like surfaces that can stand up to rigorous cleaning over an extended period.

CCC Requirements

In addition to the standard AWJ on any construction project, the CCC (Cannabis Control Commission) has regulations of its own. There are particularly strict rules surrounding security, and a tremendous number of security cameras are needed. Monitoring of every portion of every room that contains product is required. There is also a requirement for keeping 90 days of recordings from the security cameras, triggering a requirement for large storage capacities in the security system.

 Other Considerations

The height of the plants as they grow as well as various pieces of equipment that may be in the room at various times to support the grow operation, such as canopies, etc., have to be taken into consideration when designing and building a functional grow facility.

In general, there is not any one especially unique construction requirement for a grow facility but the combinations of requirements to meet the needs are unique to the industry. One of the real keys to a successful grow facility project is having a good understanding of all the parameters early in the process so that they can be incorporated into the design up front.