Retractable greenhouse roof systems are becoming more and more popular but need to have endurance. Not only must the construction of the framework be strong enough to handle strong winds, but the manufacturing of the exterior screening material is foremost the biggest challenge. On the one hand it has to be long-lasting and as tough as possible and on the other hand it has to be feather light and remain transparent. As a response to this request, Novavert developed HS². 
Unlike others screens, the HS² screen does not need hooks or support tape. "That is the secret from where we gain the strength," said Niclas Heescher from Novavert. "It is pretty similar to existing materials, but our material is less thick, less heavy and therefore it has a higher light transmission. Due to the absence of the hooks and other supporting parts, we now can provide a thin material that does a better job, which is economically very attractive."
In order ensure that the HS² screen is strong enough, Novavert did some heavy testing on the material. "For all of our materials, we want to be very sure that they last long, are strong, and still obtain the right light transmission or climatic aspects," Heescher said. "For the HS² screen, we made several test setups and exposed them to heavy loads, both static and dynamic. A lot of these trial loads will never occur in real-life situations, but they gave a good impression of what the material and the system can handle. For example, during the trial we put 1200 kg per square meter on the screen, and it held it. The only thing that broke, was the frame construction itself." Click here for a video of the load trial.
The HS² screen material “SHS WOVEN CLEAR 200” consists of a woven material with a transparent coating. The material is waterproof and UV-stabilized. "For a roof-screen, HS² is highly-transparent," said Heescher. "Because there is nothing mounted inside the screen, there is no friction, which makes it long lasting. No point transmission of force, that result from the use of hooks, means less screen wear. It can be applied to all kinds of greenhouses around the globe. But we have very good experience with the material in areas with high UV-intensity and we expect it to last 8 to 10 years minimum. Thicker versions of this material are available but with the consequence of a lower light transmission. On the other side high-tech materials like ETFE-films are currently being tested, with very good results so far: More than 90% light and UV-transmission, no colour change of the material due to UV, flame-retardant properties and expected lifetimes of more than 20 years. This would be the biggest breakthrough. No other system can be fully retracted and make use of this film at reasonable cost,” said Heescher.
For more information:Novavert GmbH & Co.KG
Niclas Heescher
Hansaring 146
48268 Greven
Germany
Telephone: +49 2571 588890
Telefax : +49 2571 5888929
www.novavert.com
[email protected]