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How to use screens in the spring & summer months

As the sun shines more and more temperatures in the greenhouse will start quickly rising… In some cases, the outside air can still remain cold and dry which makes it necessary to ventilate the greenhouse carefully.

If the solar radiation is too high, a climate curtain can be used to better protect the plants from stress due to high amounts of solar radiation.

What is the most effective way to use screens in the spring and summer months?
1. If you are using an open type of screen in your greenhouse, for example, HARMONY 3315 O FR (also sometimes referred to as a summer screen), it is recommended to completely close the screen when solar radiation levels start to climb to high levels. In such conditions, it is not beneficial to leave a gap in the screen system. If the screen is closed, it is not necessary to reopen the screen. The most important focus should be to ensure the greenhouse climate is consistently regulated and there are no sudden temperature changes.

2. Plants need to be familiarized with natural sunlight levels. In the spring months, the screens can be closed since there is already a relatively low amount of solar radiation. The leaves of the plants are still fragile following the winter months and therefore won't tolerate high levels of direct sunlight well. As the sun begins shinning for longer periods and the rays begin to strengthen, it is necessary to increase the level of solar radiation at which the screen is closed. In the early spring months, screens can be closed at 600W and in summer most plants can withstand up to 800W. It is important to remember that these figures depend on the growing conditions specific to the climate, crop and greenhouse type.

3. Avoid adjusting the screen's position, it's especially important to prevent opening and closing the screen frequently at the beginning of the day, this leads to relative humidity and/or temperature fluctuations. Don't change the position of the screens without first taking the proper precautions, for example never change the position of the screen when clouds first move in above the greenhouse. If you continuously change the position of the screen, the air flow will in turn change and the plant will experience strain, finding it difficult to adapt to the new climate every time the screening position is adjusted.

4. As the amount of sunlight begins to decrease during the evening hours, it's recommended to open the screen again. As solar radiation does not create stress for plants, the process of stimulating evaporation should again be started. When the plants evaporate the optimum amount of moisture, this signifies that the greenhouse has been cooled to an ideal temperature. If there is not enough evaporation of moisture in the greenhouse, you need to gradually reduce the window gaps from the windward side. This process should be done in small, slow steps. After the relative humidity in the greenhouse reaches 85%, it is not recommended to further close the windows.

For more information: 
Ludvig Svensson

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