Drivhusklubben/Greenhouse Forum/Gewächshausclub

08 Sep 2020 14:34

Air out with the right window opener

Updated july 2023

The temperature inside the greenhouse can easily reach 45-50 degrees in high summer, and therefore it is important to ventilate so that you create good ventilation and thus create optimal living conditions for your plants and reduce the risk of diseases.

Plants need water, light and heat to grow and bear fruit, but everything in moderation, as an old saying goes. It is like that with heat too, and since a greenhouse can get very hot during a sunny day, it is necessary to air out.

For example, the plants evaporate several litres of water in a day - water that ends up as humidity in the greenhouse. Especially in the evening, when the temperature drops, the moisture is released as the dew that can lie on the leaves and form a breeding ground for fungus.

Evaporation also means that you have to irrigate more than necessary in the greenhouse and thus you create an unnecessarily large water consumption, and finally, you get less yield from your plants if they are in too high temperatures. For example, tomatoes thrive best if they are at a temperature between 15 and 25 degrees.


Let the window opener do the work for you

Unless you love to open and close your windows several times a day, a window opener is an almost indispensable accessory for your greenhouse. Juliana has three different window openers, all of which work in such a way that at high temperatures they open automatically and at low temperatures they automatically close again. Then the question is just which type to choose. To make it clear, we have made a small guide.



Ventomax is the cheapest one in the series of window openers and by far the one most people can handle. The piston ensures that the window opens, and a strong spring closes the window when the temperature drops again. Opening and closing can be adjusted by turning the cylinder left for a later opening and right for an earlier opening.

Ventomax fits all common greenhouses.



Spiro is basically identical to Ventomax, however, this has a thermometer attached to the cylinder so you can keep an eye on the temperature inside the greenhouse.

Spiro fits all common greenhouses.

Installation and maintenance of the Ventomax and Spiro opener: 



Univent de Luxe has the same cylinder and the same functions as the other two, though this one differs by having double springs for closing the window. This model should be used in greenhouses with polycarbonate windows as they are not heavy enough to close and stay closed by themselves. Univent de Luxe also has a click system, so they are easy to dismantle in the winter.

Univent fits all common greenhouses.

Installation and maintenance of the Univent opener: 


Tips for winter protection

All three models have the same cylinder that can be purchased as a spare part. To ensure the longest possible life, we recommend that the cylinder is dismantled in winter and stored frost-free.

When the temperature drops and the window no longer need to open, you can protect and winter-proof your automatic window openers during the winter months. This can be easily done by removing the split end that holds the cylinder firmly in the cylinder suspension. Then unscrew the cylinder from the cylinder suspension and store the two items in your garage or in a warmer place. The winter protection prevents the wind from opening the window, and your automatic window openers can be used for the next greenhouse season. Sometimes it can be difficult to loosen the cylinders if they have been there for a long time. You can us acid-free oil to your advantage.


Tips for perfect ventilation

Roof vents are placed as far away from the doors as possible to ensure maximum draught. In addition, one or more louvre windows can be mounted. These are placed on the side of the greenhouse that has the most shade and preferably in the same bay but the opposite side of the roof vents. (Available for Juliana Gartner, Juliana Premium, Juliana Orangeri and Juliana Compact).


Read more and buy your window opener here.