Why Screens?

This seems like a simple question that you can answer with "why not" and yet this is a question that is current for many growers. For growers who already have a screen, we can expand the question with 'Why a single screen?'

Nowadays a screen installation in the greenhouse is not only for energy saving or sun protection. A screen installation is used to control the greenhouse climate even better. By making the greenhouse climate as optimal as possible, the crop grows better and ultimately the yields are also better

To better answer the question 'Why screens?', we first start with the question, why do we grow in a greenhouse?

Year-round cultivation

Many crops can also be grown outdoors, certainly in warmer and more constant climates such as the Netherlands. There are also outdoor crops, but (almost) all crops do not produce year-round and are therefore not available to consumers all year round. Today's consumer is spoiled and does not take seasonal products into account, but expects the same products of excellent quality in the supermarket all year round. An example of this is the tomato. This was one of the first crops to be grown in the greenhouse or better say covered envoirement, even then year-round production was not possible and tomatoes were imported from warmer countries in the winter months.

With the introduction of artificial lighting in the greenhouses, it has become possible to grow tomatoes all year round and thus supply supermarkets with fresh tomatoes all year round. If the tomatoes were still grown outdoors in the Netherlands, then we would only be able to enjoy fresh tomatoes in the period from June to October, according to the plant's natural growth/flowering schedule.

By growing the tomato crop, but also many other crops in a greenhouse in the conditioned environment, we actually do nothing but make the crop in question think that it is in its natural climate all year round and thus produce fruits and/or flowers. Creating the natural climate for the crop does not happen by itself. Despite the fact that a greenhouse is a closed space, the climate in the greenhouse is also partly influenced by external weather influences such as sunlight.

Biggest impact

One of the components for controlling and regulating the climate in the greenhouse is also the most flexible component in the greenhouse with the greatest (direct) impact on the climate, that is the screen.

Depending on the type of screen cloth, a closed screen has different effects on the climate. A closed clear screen saves energy especially when it is colder outside than inside and shades the sunlight to a minimum during the day. A clear screen cloth with a knitted structure also has the advantage that moisture transport takes place through the cloth. In this way, the climate can be optimized even further with the help of the ventilation windows above the screen.

A closed screen fabric with an open structure contributes very little to energy savings, but has a cooling effect during the day when it is sunny outside. Because this screen type allows less light to enter the greenhouse, less heat also enters the greenhouse. In addition, the open structure ensures that the ventilation through the vents continues to work. Because the ventilation is moderated by the open screen cloth, this means that the climate in the greenhouse becomes much more stable. A separate blog will follow later on how to work with an open screen.

Essential

A screen installation has become an essential part of the greenhouse to influence and control the climate. Depending on the primary purpose of the screen, concessions must be made when using it in either summer or winter. A double screen installation requires a higher investment, but offers much more technical cultivation possibilities to create the optimal growth climate for the crop.

Therefore

Because a screen installation does much more than just save energy and/or sun protection, but contributes to a stable growth climate, a screen installation is necessary in a greenhouse. In addition to a properly functioning and reliable installation, it is very important that the choice of screentype is carefully considered.

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Johan van Erven

#climatescreens #energysaving #screenadvice