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Functions of shading screens in horticulture

Schermdoeken
Written by Lars Ammerlaan | Last update: 28-05-2020

In almost every greenhouse, on or more can be found: a shading screen. Shading screens or other sun protection, have multiple functions. Besides the protection from sunlight, energy can be saved. However, a shading screen should not be seen as a substitute from shading agents. It is the combination of both that ensures an optimal climate within the greenhouse.



In this article the following subjects are discussed:

» What is a shading screen?

What is a shading screen?

Shading screens are cloths/screens, which are placed just under the greenhouse’s gutter. Generally, screens are folded when used. However the screens can be closed mechanically anytime. By means of a shading screen, the cultivation can be adjusted easily.


The functions of a shading screen

Many different types of shading screens can be found, each with their own function. Below, the most prominent functions are listed: 

  • Saving energy
    Warmth is needed by the majority of the plants. Sometimes enough sun is present for the greenhouse to warm up. However, in the night or on cold days, the greenhouse should be warmed by the cultivator through a kettle or an cogeneration installation. In order to prevent the disappearance of warmth from the greenhouse, shading screens are applied. In this case, the screen is used as a blanket to maintain the warmth. The only disadvantage that can be named, is that shading screens reflect the (growth) light. The criterion that the saving of energy should be higher than the costs of ‘growth-loss’, is set for shading screens.


  • Blocking sunlight
    The irradiance of the sun is determined by the shading screen, once the light level is too high. Especially on summer days, damage to the crop (burning) can be caused by a high level of irradiance. Shading screens are used for protection. Shading screens are supplied in different shading percentages, in order to make sure there are several options.


  • Obscuration of light
    The excess amount of light is blocked by a shading screen. Different colors are used for a shading screen: black for the bottom and white for the top. Plants and flowers, such as chrysanthemums and kalanchoe, are believed to profit from these different colors. This because specific ‘day- and night-lengths’ are needed in order for the plants to flower. The correct day and night rhythm can be achieved by means of assimilation lights and shading screens. The advantage is that the plants can be cultivated at any time of the year.

  • Limit the loss of light
    Screens that are used to limit the loss of light, are opposite to the shading screens that block irradiance from outside. The shading screens that are used to prevent the light from ‘leaving the greenhouse’ are used by companies that utilize assimilation lightening. Through this screen, the loss of light is limited, resulting in the minimization of disturbance of the direct environment of the greenhouse. When these screens are used, they are fully closed. An advantage, is that in the ‘dark hours’ the screens lead to an energy saving of up to 25%. 


  • Spread diffuse light
    Moreover, light can be diffused with the help of a shading screen. Often, this function is combined with the sun blocking function of the screen. Due to diffused light, light on every part of the crop is ensured (also the parts that are harder to reach). Moreover, burning of the crop is prevented by diffusing the light. 

Installation and maintenance

The installation of a shading screen is believed to be work for an expert. Especially when an entirely new system has to be installed. Generally, the assembly of a new screen to an existing system is done. Here, the old screen is removed before the new screen can be placed.
Basically, not much maintenance is asked by a shading screen. However, after some years, a worsened transparency can be the result of dirt piling up on the screen. The loss of transparency can be prevented as much as possible by cleaning the screen regularly. For this, Menno Hortisept clean PLUS is often used.

Attention: Cleaning must be done very carefully, since these screens are fragile.

 

What is the difference between a shading screen and a shading agent?

At first, a shading screen and a shading agent seem the same. This is partially true. Because there are some differences: 

  • Short vs. long term investment
    The largest difference that can be named is the lifespan of the products. A screen can be used for several years, whilst a shading agent is only temporary. 

  • Energy collection vs. energy loss
    Saving energy is the most important function of a shading screen. When the warmth is kept inside, energy loss is prevented. The function of a shading agent can be seen as the complete opposite, namely to prevent sun coming into the greenhouse. This is done by the reflection of the sun’s irradiance, resulting in maintaining a constant temperature within the greenhouse. This actually means, the two different options cannot be replaced by one another. An optimal climate can be realized through a combination of these two products. 

  • Spread diffusely with and without difference in temperature
    The choice for the diffusion of light is often made on warm summer days. Burning of the crop can be prevented, and a deeper reach of light into the crop is ensured. Shading agents like D-Fuse or D-Fuse Extra can be used for diffuse light, without experiencing any problems of the greenhouse’s temperature rising. A rise in temperature can be caused by making use of a shading screen, since it has an isolation function. 


Can shading screens and shading agents replace one another?

Even though it is often thought that these two options can replace one another, we know this is not the case. Shading screens and shading agents serve the same purpose, however do this differently. So, the products are not substitutes. They can better be combined to achieve a perfect climate within the greenhouse.



Questions about shading screens

Do you have questions about using a shading screen or would you like tailor-made advice? Then please contact our chalk and screen specialist Lars Ammerlaan using the form below. We will contact you as soon as possible - on weekdays even within 24 hours.






Specialist Lars AmmerlaanAbout Lars Ammerlaan

Lars Ammerlaan, product specialist in shading agents and diffuse coatings, has been working at Royal Brinkman since 2017. After the position of assistant cultivation manager, and later on account manager, he made the switch to his current position. Lars has gained a lot of knowledge through his practical experience, which enables him to offer customers targeted and personal advice. Lars enjoys visiting the growers’ greenhouses and thinking along with them about suitable solutions. 'The challenging part of this job is the international part. Abroad things can sometimes be very different compared to the Netherlands and that makes it an interesting job, in which I can continue to develop myself.






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