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Improved greenhouse climate with fans under the gutter

At tomato farm van Rens in Meterik, Netherlands, Vostermans' Multifan Greenhouse fans were installed, where they provide a more uniform greenhouse climate. Remarkably, the circulation fans were not placed above the plants but under the gutter.

With a greenhouse surface area of 6 acres and a ridge height of 4.5 meters, Tomato Farm van Rens cultivates vine tomatoes. "We were suffering from dead spots in the greenhouse where the air was stagnant, and last year we had a relatively high incidence of Botrytis," Jordi van Rens, the third-generation owner, starts off. "Due to the limited height of the greenhouse, we use one screen, supplemented by an AC screen in the colder months. This resulted in a cold snap. In short, there were plenty of reasons to improve air circulation in the greenhouse using fans.

"Originally, our plan was to purchase fans to be placed above the plants. To explore our options, we approached several suppliers to advise us and make an offer. The results were varied. While one supplier's had a particularly long delivery time, another supplier's price of about 12 euros per square meter felt too high.

Through VTI Horst, which is part of the Lek/Habo Group, we came in contact with Vostermans Ventilation. Given the limited height of the greenhouse, they advised us to hang the fans under the gutter. Above the plants, the fans would be too close to the plants, and we would run the risk that the plant tops would dry out due to the airspeed. This would, in turn, slow down the growth of the plants. With a circulation rate of 2.5 times, we arrived at an estimated investment of about 0.5 euros per m2. And with a delivery time of about 3 to 4 weeks, we still had time to install the fans before the new crop came into the greenhouse."

When the sulfur pots got removed, power sockets opened up under the gutter. These were attached approximately every 35 meters. Since the Multifan Greenhouse fans consume only 110 watts per hour, they could be connected to this existing power network without modification. Fans with higher consumption would overload this network leading to a larger investment. But this energy-efficient version is powerful enough to span these 35 meters and create an efficient and effective series ventilation system.

"At the moment, we have been using the fans for a few months. We analyze the greenhouse climate in 8 places in the greenhouse and in 8 places along the fa├žade," Jordi continues. "Previously, we sometimes saw a temperature difference of about 4 degrees. Nowadays, it is only 0.5 to 1 degree. Finally, the first condensation occurs on the large fruits at the bottom of the plant. By creating air movement precisely there, you prevent this condensation and, thus, moisture-related diseases. Botrytis and cold fall have not yet occurred this year. It is probably too early to draw any firm conclusions, but our gut feeling is that we have made a good investment. The fans aren't in the way and hardly make any noise. If I had to make the same choice tomorrow, I would again pick this circulation solution."

For more information:
Vostermans Ventilation

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