I’ve often written and spoken on my belief that cannabis greenhouse operations should invest in the most sophisticated environmental control system (ECS) they can afford—perhaps even more than they think they can afford. This is because all efficiencies made to the structure or equipment will pale in comparison to this investment. It’s useful to integrate as much equipment as you can—not just heating and cooling, but also irrigation, ventilation, lighting and shading, energy usage and water treatment. Eliminating standalone systems will ensure that all equipment is working in concert according to the environment and your target setpoints. An underappreciated advantage of a fully integrated ECS is a reduction in training required to run the greenhouse systems.

A common question I often receive at facility startups is: What data should be logged after integrating these systems? There really is no downside to collecting as many data parameters as you can; data are just ones and zeros stored on a server. What can be daunting for your storage space is collecting data at too high a frequency, such as every minute. Ten-minute intervals typically suffice, while longer intervals are preferred for slow-changing data input, such as soil moisture.

From my 25 years of experience with advanced ECS systems, below are tips on which data parameters to collect in a greenhouse and why.

1. Keep tabs on atmospheric data for greater control in the greenhouse.

Greenhouse temperature, relative humidity, vapor pressure deficit, photosynthetic active radiation (PAR) and accumulated light (daily light integral) are all important metrics to track. PAR sensors will occasionally be shaded by the greenhouse rafters, ridge, purlins, suspended equipment, and glass and plastic, but weighting functions can be programmed to buffer large swings. Canopy temperature is extremely helpful to track, as plant stress and leaf wetness can be better avoided. Also collect outdoor temperature, relative humidity, precipitation, wind speed and direction, and light using a pyranometer that will measure beyond PAR to better anticipate heat load. Collecting weather data not only allows anticipatory control, but also allows you to customize seasonal adjustments for your region; the trickiest seasons to control greenhouse climate in the northern half of the U.S. are fall and spring, when the sunlight may be bright while air temperatures are low.

Monitoring atmospheric data allows you to tweak programming to optimize climate. The second advantage to monitoring the parameters described above is for troubleshooting your programming or equipment. You will learn the graphical signatures of specific problems and be able to remedy them faster. For example, I could remotely recognize when a low-speed motor of one of the greenhouse exhaust fans had failed by observing the air temperature pattern, even though the high-speed motor worked, making the fan appear to be functioning perfectly.

2. Rhizospheric data helps optimize growth.

Monitor substrate volumetric water content (VWC), either by a soil moisture sensor or weight scale. If your facility collects irrigation leachate, monitor substrate pH and electrical conductivity (EC). VWC is currently the best practice for initiating automatic irrigation to optimize growth.

A leaf temperature sensor monitored by a climate control computer
Photos courtesy of Robert Eddy

3. Track equipment usage and cycles to time repairs.

One early mistake I made in my career was not paying attention to equipment cycling rates. Motorized shade curtains were moving over 100 times per day in partly cloudy weather, resulting in several motors burning out prematurely. Once I was aware of this, I reprogrammed them so they moved no more than eight times per day. Tracking usage minutes can aid in replacing bulbs in high-intensity discharge (HID) fixtures. Likewise, fan belts on exhaust fans can be replaced before breaking, and fans can be programmed to come on in different orders to spread wear by tracking accumulated minutes of operation.

4. Energy usage data helps improve efficiencies.

Many of us in the industry want to reduce energy use to preserve our planet’s climate, so it makes good business sense to track usage and demonstrate a commitment to improving production efficiency (this can be done by measuring grams of flower per kilowatt hour, or kWh). But energy tracking can be tricky, as it involves sub-metering your facility (having more than one electric meter) to get more granular data to validate conservation strategies. At the very least, try to sub-meter your facilities’ operations separately: cultivation, processing, packaging, etc. Ideally, one or more flower rooms would be sub-metered where the impact of different equipment or programming could be compared.

5. Monitor water and fertilizer usage to minimize contamination.

The value of our nation’s water supply is at the front of many of our minds given the images of drought in the West. Even where water is abundant, we need to protect local waterways and aquifers from irrigation runoff that might taint them. Therefore, it is valuable to monitor water usage, pH, EC and status of our water treatment systems. Two large sources of waste are brine from reverse osmosis purification systems and “bleed-off” valves of evaporative pad systems used to prevent scaling (calcium buildup) on cooling pads. Using data collection, I confirmed that water usage from evaporative cooling pad systems was far greater than summer irrigation demand and was able to curtail this waste.

Robert Eddy is the former Purdue University Plant Growth Facilities manager and the founder of CEA Consultancy LLC.