1. New article in Cannabis Science & Technology: Understanding VPD and Transpiration Rates

    In the latest issue of Cannabis Science & Technology, our team explored the concepts of transpiration and vapor pressure differentials (VPD), and how these affect the health and growth of cannabis plants. The piece was written through a collaborative effort, with our founder Laura Breit co-authoring alongside Michael Leavitt and Adam Boyd, who are both licensed professional engineers on the Root team. The article dives into how several factors can come together to influence important equipment selection decisions for cannabis operations.

    This latest article discusses how plant transpiration drives plant growth, and VPD drives plant transpiration. Temperature and humidity both impact VPD, a factor that must be considered when making decisions surrounding facility systems – especially when it comes to heating, ventilation, and air conditioning (HVAC) equipment selection. We write: “Understanding the drivers behind this process is key to selecting the appropriate HVAC system for your operation. In our experience, a setpoint difference of just 10% can have a significant impact on HVAC system sizing, upfront cost, and ongoing energy costs. It’s worth exploring if a small difference in design setpoint will make a large impact on your HVAC system costs, without having much impact on the product yield of your operation.”

    The article defines and discusses terms and their effect on equipment selection such as:

    • Transpiration
    • Vapor Pressure Differentials (VPD)
    • Dry Bulb Temperature
    • Wet Bulb Temperature
    • Relative Humidity

    The Root Engineers team analyzes data surrounding watering rates and transpiration rates to show their effect on equipment selection, coupled with a real world case study using VPD to determine setpoints and ultimately select the appropriate HVAC equipment.

    The article concludes with the following: Proper HVAC equipment design –> consistent temperature and relative humidity in the space –> consistent vapor pressure deficit –> plant transpiration –> plant growth.

    You can read the full article here: