Part II: Getting the design parameters right
Designing commercial-scale cannabis grow rooms is still a new frontier, and technologies are changing constantly. There’s also a considerable level of secrecy and competitive confidentiality relating to what works, what the secret sauce is and how not to let hard-won industry expertise become common knowledge with competitors.
Careful cost-benefit modeling
Clearly, there’s a lot of pioneering work being done that is not setting industry standards. This is very different than the traditional construction industry where the American Society of Heating and Refrigeration Engineers (ASHRAE) sets standards. General construction is not a competitive business with trade secrets guarded in the same way as growing cannabis. So far, ASHRAE has no engineering standards or best practices published about how to design HVAC systems for grow rooms.
That means that even the technically qualified firms have to guess at a considerable amount of the science and mechanics behind creating optimal grow environments. Their jobs are extremely complex and involve dozens more variables than designing traditional HVAC systems for commercial buildings.
Getting grow room specification right requires careful modeling of grow cycles, transpiration rates, temperature and humidity specifications, lighting loads and irrigation loads, just to name a few components. It also requires careful modeling of external factors including annual temperature and humidity ranges, type of building structure, solar impacts of mixed-light sources, etc.
All of those factors must be carefully modeled to ensure the HVAC engineering specifications can be met, but there’s another critical piece of modeling that should be included in the business decision: the cost-benefit analysis of extreme-condition management capability. What latitude of temperature and humidity ranges could be acceptable on the most extreme hot and humid days or cold and dry days? And what’s the cost of designing a facility for that range of temperatures versus designing for optimal temperatures 90% or 95% of the time and allowing the remainder of the year — the most extreme days — to be slightly warmer or cooler? That can make a significant difference in the capital cost of equipment as well as the operating costs of handling those extreme days.
Work closely with your HVAC design engineers to discuss and incorporate all factors that will affect temperature and humidity loads into your ideal specifications. Be certain that they have the expertise to properly model the dozens of load factors and variations that your plants and your grow cycles will require.
Then model those conditions and the equipment capacities required to meet them on the most extreme days, considering how much latitude of temperature and humidity you can accept during those outlier days relative to the costs of maintaining perfect conditions. The cost-benefit analysis will inform your decision about how much you really need to spend on HVAC equipment. You may find that allowing a few degrees of latitude in temperature and humidity on those extreme days can save a lot of money and not have much impact on your yield or quality.
Geoff Brown is the brand and product manager for the Agronomic IQ Series of dehumidifiers, specifically designed for growing cannabis in every size of grow room. He started his HVAC career more than 15 years ago and has honed his expertise, dealing in every aspect of dehumidification throughout his career. Prior to managing the Agronomic IQ brand, he was a senior sales manager and sales engineer, who consulted on and managed various successful dehumidification projects.
For additional information about Agronomic IQ’s purpose-built, unitary grow room humidity and temperature control solutions, visit AgronomicIQ.com, or contact the company at ContactUs@AgronomicIQ.com.
This article is the second of a three-part series on the biggest HVAC challenges of modern grow rooms. In the April 2019 issue of Marijuana Venture, Part III will cover HVAC solution design. Part I of the series can be found at www.MarijuanaVenture.com.