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Light leak data from Ont. greenhouses

Light leak data from Ont. greenhouses

One engineer is on a mission to figure out how much light escapes greenhouses, to help both production and policy discussions

By Jackie Clark
Staff Writer 

A researcher at the University of Guelph is finding concrete data on the amount of light that escapes greenhouses. 

This information will help growers optimize their operations, and give a factual base for policy negotiations between greenhouse owners and their communities, Dr. David Lubitz told He’s an associate professor in the school of engineering at the University of Guelph.

Lubitz was working on greenhouse energy research when his collaborators at OMAFRA identified managing light as a potential future issue in the sector. 

“The greenhouse industry in Ontario is growing, and it’s moving to more year-round production, whether that’s vegetables or flowers, or, more recently, cannabis,” he explained. 

More farmers are needing to use supplemental lighting.

“If growers have an issue with stray light coming out of the greenhouses, what they do is use these light abatement curtains,” Lubitz said. “The challenge is, when you close those curtains, it blocks most of the normal ventilation, so it makes it much more difficult to control the humidity and temperature inside the greenhouse.”  

So, he set out to help growers optimize growing practices with abatement curtains.

“The project started mainly looking at ‘how do we make this manageable for growers, to grow with the curtains closed more?’ But as we were getting started over the last year, the issues with light pollution, in the Leamington and Kingsville area in particular, really kind of came to a head and they brought in bylaws,” Lubitz explained. 

So, “we expanded the scope of the project to include measuring the amount of light coming out of the greenhouses,” he said. “Everybody knows if you run the supplemental light at night and don’t have curtains, a lot of light comes out of your data, but there’s almost no measurements, there’s very little data.” 

To “have conversations between the growers, the neighbours, the municipalities and so forth, I think it would help everybody if there was some data, some actual numbers,” he added. “That’s how we got into the business of flying drones over the greenhouses at night.” 

Measuring light escaping greenhouses isn’t as simple as one might think. Many factors influence how well you can measure light, particularly if you want to objectively compare different lighting situations. Different colours on the light spectrum, weather, and measuring position all change the reading you’ll get, Lubitz explained

“You end up with a lot of variations and a lot of uncontrolled variables,” he said. 

His team discovered that the most effective and repeatable method was to use drones to measure from above. 

“It’s that upwards outgoing light that’s going to lead to that sky glow effect that people notice from a distance,” he explained. 

So far, he’s conducted one year of measurements, and has plans for more over the winter. 

Over the next year, “in addition to vegetable greenhouses, we’re working to get some sites in floraculture, and we might be getting some cannabis sites as well,” Lubitz said. He’s going to measure other sites, like parking lots and sports fields, to compare light.

“We’re also going to do some long-term sky brightness measurements in certain locations,” he added. The goal is to “try and tease out the effect of the greenhouses versus the effect of other lighting.”

Overall, “we’re really hoping this data can provide everyone with some concrete information, some objective measurements, to help with negotiations between growers, neighbours and communities,” Lubitz said. The data should also help growers optimize their operations while still utilizing light abatement curtains. 

Vladimir Zapletin\iStock\Getty Images Plus photo

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