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Ventilation windows can freeze shut at temperatures around the freezing point

Vents freeze partly due to radiation and the insulating effect of the screens, which is the case during night frost.

Vents freeze partly due to radiation and the insulating effect of the screens, which is the case during night frost. With multiple screens and greenhouses being increasingly closed off, it is often colder above the top screen. The rubber seal of the vents freezes to the aluminium greenhouse frame. “Every year, business owners open vents without realising they are frozen shut,” Theo Herngreen, a greenhouse technical specialist, explains. “The temperature difference between the greenhouse air and the windows is considerable, and temperature sensors or separate measuring boxes are not always installed above the screen. Opening the vents while frozen damages the rubber seals, or worse: the vent mechanism and window actuators can be deformed or broken.”

The result: severe damage and delayed production 
If the vents are frozen to the greenhouse frame, the vent mechanism may be deformed, and the window actuators may be broken. This renders the entire vent mechanism unusable, and vents can no longer be opened. If the vents are broken, vegetables (e.g., tomatoes) cannot be harvested for six weeks for food safety reasons, resulting in severe damage. It will take a few weeks to repair the actuators and vent mechanism. Ordering materials and disassembling and assembling everything takes time, during which it is difficult to control the greenhouse climate. 

The solution is simple: measure the temperature above the screen 
The problem is easily solved by hanging a temperature sensor above the screen. A temperature sensor on the aluminium deck system provides extensive insight into the deck temperature and will help you know when you can safely open the vents. 
Do not allow the temperature above the screen to fall below 4 °C 

This is particularly important in the early morning. Notice: 4 °C is a recommendation; your situation may vary depending on the winter weather conditions. Monitor the temperature closely. 
We are happy to help 
It is important to know that you are not alone. Your insurance broker s happy to give you advice to help you prepare for a harsh winter as well as possible. 

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