During the recently held LightEvent in Bleiswijk, visitors could participate in various workshops. In one of them, researcher Frank Kempkes from Wageningen University & Research presented the results of various trials with Low-E glass, which limits the heat emission of greenhouses. Without major restrictions, the heat demand can thus be reduced by as much as 20%, was his positive message, shared by Jan van Staalduinen on Kas als Energiebron.
Glass with a Low-E coating allows as much light through as standard horticultural glass without AR coatings. For this, the glass is provided with an AR coating on one side. The side with the Low-E coating also has an AR effect due to the composition of the coating. Glass of this type (Geysir) has been used in trials at Wageningen UR and at Delphy IC, with an unlit tomato crop (2022) and two unlit eggplant crops (2023 and 2024). These trials, funded by Kas als Energiebron, have provided a lot of valuable information about the saving potential of Low-E.
Cultivation trials
Frank Kempkes: "The task was to run state-of-the-art crops under Low-E glass and compare them with parallel crops in reference sections without Low-E glass. That means: according to the principles of The New Cultivation and using the available, energy-efficient systems for heating and active dehumidification with AVS-C and heat pumps, supplemented with two standard screen installations."
In the three trials, the harvest patterns under Low-E and standard glass matched perfectly and the cumulative yields hardly differed from each other. This was true for the heat consumption, which was accurately monitored and allocated to the different sections.
"For the sections with Low-E glass in the roof and the outer facade, no less than 20% less heat was needed," said Kempkes. "This difference is entirely attributable to the properties of the glass and corresponds to the previously calculated expectations. The consistent pattern we saw each time leaves little doubt about the potential of this saving option."
Source: Kas als Energiebron