This project must provide quantitative information that enables a well-founded decision to be made regarding the investment in a double screen cloth, a cavity screen, or a double screen installation.
Investigation of the insulating performance of a cavity screen
The objective of the study
Projectdescription
Smaller growers with an unlit crop and without combined heat and power (CHP) are facing rapidly increasing greenhouse heating costs. Replacing a single screen installation with a cavity screen could offer a solution, as this is a more cost-effective option than a double screen installation.
To convincingly calculate what replacing a single screen with a cavity screen will mean in a given situation, accurate measurements must be carried out under laboratory conditions. This ensures that the physical processes are well substantiated and can be incorporated into models. In this way, the grower can make a well-informed decision.
The execution of this project is based on two pillars: laboratory measurements and model calculations. The project consists of the following work packages:
Measuring different screen materials
Processing the measured heat transfer parameters of the different screen systems
Adjusting the user interface of the KasEnergieWijzer
This project is funded by the Ministry of Agriculture, Nature and Food Quality (LNV).
Features
- Energy saving
- Sun Shading
- Lower Investment
Results
Cavity screen increases greenhouse insulation value
The research shows that cavity screens clearly improve the insulating performance of a greenhouse. When a second screen cloth is placed at some distance from the first cloth (for example, approximately 4 cm), an insulating air layer is created. The insulation value of such a cavity screen appears to be comparable to that of a full additional screen installation.
Two cloths placed directly on top of each other also provide better insulation than a single cloth, but creating a cavity results in a clear additional improvement. Measurements show that a cavity of approximately 4 cm is most effective; a larger distance provides little additional insulation.
Lower heat demand in different crops
The improved insulation translates into a lower heat demand in the greenhouse. In a lit tomato greenhouse, a cavity screen can reduce heat demand by approximately 9% (about 2.5 m³ of gas per m² per year).
In an unlit pepper crop, the savings are around 5% (approximately 1.2 m³ per m² per year), and in gerbera cultivation also about 5% (approximately 1.1 m³ per m² per year). These calculations take into account that the screen may need to be opened more frequently during the day to limit light loss.
Greatest savings with a separate screen system
When an additional cloth is placed directly on top of the existing screen without a cavity, the energy savings are clearly smaller and can even become negative due to additional light loss.
The greatest energy savings are achieved when the second cloth is installed in a separate screen system. In that case, heat demand can be reduced by approximately 15% in tomato and gerbera crops and about 9% in pepper crops, as the screens can be controlled independently and better aligned with the crop conditions.
Funding and CoordinationThis project was carried out by Wageningen University & Research. It was funded and coordinated by Kas als Energiebron, an innovation program of the Ministry of LVVN and Glastuinbouw Nederland. It was made possible by Kennis in je Kas (KijK). The trial was supervised by growers.
Quality starts with the right partners
For every screening project, we collaborate with reputable manufacturers.
This ensures quality, reliable delivery, and solutions tailored to your greenhouse.
We offer screen cloths from manufacturers such as Bonar, LS (Ludvig Svensson), Phormium, and Ridder Group.
Looking for a suiteble screening system?
We provide customized solutions for every project.
Whether it’s new construction, renovation, or maintenance – we’re happy to offer our expertise.
