Cavity screen barriers are back for energy saving

JANUARY 2023

The cavity screen is back after a long absence. Earlier research in 2018 by Peter van Weel had already demonstrated its benefits. Now that there is more demand than ever for energy-saving measures, the cavity screen seems to be starting a second life. That’s also what Gerdo Wennekers of Doek en Draad is seeing. The installer recently fitted a cavity screen made up of two Luxous screens at Carni Flora in Aalsmeer, the potted plant nursery of grower Justin van Kessel.

Justin is the type of grower who bases his strategy on research, facts and figures. He carried out extensive research into the cavity-screen concept, where a layer of still air forms between two screen cloths installed close together, creating an insulating effect. 

“Logically, the concept is watertight”

“It’s not a new technology, of course. Cavity walls have been around for years and are a proven way to insulate. Logically, the concept is watertight. The research by Peter van Weel confirms the insulating effect,” Justin says. Sticking his neck out to be one of the first to go for a cavity-screen installation didn’t feel risky to him. “I trust the research that’s been done and Peter’s advice.”

The only real question mark for Justin is how moisture management in the greenhouse will behave. “But I have good sensors for that, so I can monitor it closely. If it turns out there’s too much moisture, then we’ll see what makes the most sense to do — ventilate or dehumidify.”   

Justin chose two Luxous screens (Luxous 1147 FR) for the cavity screen, in order to bring in as much light as possible. “Luxous is a relatively small package compared with other screens, and it lets a lot of light through. Those were my main requirements.” Underneath the cavity-screen installation there is also a separate sun-shade cloth.

Growing demand for cavity screens

Doek en Draad installed the screens. Gerdo is pleased to see demand for cavity screens increasing. “Last week alone I sold another two installations for next year.” For some growers it is a smart, or even the only, option. “Not everyone can fit two energy screens. With a cavity screen you only need one installation and you can still save energy. There are also growers, like Justin, who want a different type of screen on the second installation. That’s possible too.”

The cavity-screen installation at Carni Flora took a little longer than usual because of the complexity of the greenhouse. “It’s a wide-span house with fixed tables underneath, so we had limited room to work,” Gerdo explains. Justin hardly noticed any disruption. “Originally, the sun-shade screen was on top and the energy screen underneath. We reversed that. The energy screen could still be used by Justin at night, while we installed the cavity screen above it. Once that was finished, we then installed the sun-shade screen underneath.”