Marijuana ( Cannabis), Hemp Plant Growing Inside Of The Green HoAn estimated 500,000 Canadians use marijuana for medical purposes. As of August 25th, 2014, Health Canada has received 1,009 Licensed Producer applications. Over half of these applications were returned as incomplete, or rejected entirely.

We want to stress the importance of suitable HVAC design for these facilities. The HVAC design required is more complex than that for a typical light industrial warehouse or greenhouse as there are critical environment requirements such as temperature, humidity, and control.

Here are 5 common pitfalls to avoid:

  1. Insufficient Cooling. It is important to properly size air conditioning equipment to match the total load. Lighting is a 100% sensible load, and most air conditioning equipment cannot cool more than 75% sensible load relative to its overall capacity. For example, if the calculated lighting load was 7.5 tons (26kW), you would generally need a 10 ton unit to handle the load. In addition, it is important that additional heat sources such as CO2 burners and humidity from the irrigation system is factored into the calculation.
  2. No Humidity Control. Most of the grow rooms we see require 40% to 60% relative humidity. A standard roof top unit system cannot provide this level of humidity control. Besides the mechanical requirements of humidification and dehumidification equipment, there also needs to be a vapour barrier in the envelope to prevent moisture transferring between spaces.
  3. Insufficient Controls. The building code only requires programmable thermostats for HVAC systems. A full DDC control system is very beneficial to the overall mechanical system providing near unlimited scheduling capabilities, controls, and alarms. While this does add a small amount to the upfront capital cost, the advantages and cost- savings during operation provide near immediate payback.
  4. No Redundancy. The most inexpensive designs tend to not have any level of redundancy for cooling. There are many different methods to achieve redundancy in the system without adding significant costs. Some users have required a backup system of exhaust fans, while others are use redundant motors, fans and/or compressors.
  5. Excessive Energy Usage. These facilities are very heavy consumers of energy and can use almost 10 times the power of a typical office. BC Comfort is a member of the BC Hydro Power Smart Alliance and can help obtain energy rebates for selecting high efficiency mechanical systems. In addition, using higher efficiency lighting such as LEDs, can reduce the cooling load by up to 60%.

BC Comfort has a long history of designing and building critical environments. BC Comfort can provide a complete mechanical design-build solution for your facility as the first step in becoming a licensed producer. Please call 604-412-0206 for more information.

Article Courtesy of Henry Leung, P.Eng., MBA, LEED AP Senior Design Engineer at BC Comfort Group.