SHADING AND ENERGY SYSTEMS
There are various types of screen systems and different kinds of screen cloth. The choice of what type of screen is determined by answering the question: what do you wish to achieve with the system? Many production greenhouses employ wire systems with aluminum leading edges and slip blocks. The slip blocks are used to prevent slits in the installation and to create a regular narrow opening of the screen cloth, which allows humidity to escape. Because greenhouses are becoming larger and mostly equipped with aluminum gutters, the application of slip blocks compensates for any expansion or shrinkage in the installation. There are also push/pull systems with aluminum leading edges and optional spring blocks. These systems reduce the forces that are exercised on the gable walls.
Roll screen systems are mostly used in walls, but are also possible as roof roll screens in wide-span greenhouses, for example. Drive mechanisms consist of tube motors or motors especially developed for this purpose. Types of cloth vary from clear material intended to save energy, to screens with sun-blocking strips in order to partly protect against the sun, to completely opaque cloth that guard against assimilation light.
It is also possible to install screen systems above the greenhouse. There are several possible options. For a Venlo greenhouse, a horizontal structure is installed in the gutter or on the ridge to which the screen system is attached. For a wide-span greenhouse, a roof roll screen can be mounted on the roof, which is rolled down from the ridge to the gutter. The advantage of an external screen is that the warmth of the sun is deflected outside instead of inside the greenhouse.