Two layers of foil with an inflatable air layer in between makes it possible to grow stronger and faster marketing plants, explains Steven van Hoof of Vermako Greenhouses. "With a thermal and a diffusion film, you can create an ideal growing climate in the greenhouse, making photosynthesis much faster."
Vermako Greenhouses has specialized in producing, constructing, and assembling foil greenhouses, unlimited in width and length, since 1989. Thanks to this experience, they saw the opportunities for combining a thermal and diffuse layer of foil with an inflatable air layer in between. "Because of the light transmission and diffuse reflection of light, light penetrates deeper into the plant, resulting in a high-performance, energy-efficient greenhouse. The season is brought forward, and the plants are stronger."
The foil conservatories are built on a classic substructure of a Venlo type and are available to any classic greenhouse builder for both glass and foil.
At Vermako's request, a master's student from the University of Ghent recently conducted research into the growth curves of plants in different types of greenhouses, including those of other brands. This research was done at the Belgian plant nursery Willy DeNolf, a very well-known plant company with worldwide sales. "A reference in the plant world," says Steven. Willy has several types of greenhouses of all brands and all types of ventilation. "Single, double-walled and glass greenhouses, so the ideal test area."
Tests have shown that the combination of both layers of foil with the air layer in between results in reduced heating costs by 25 percent on an annual basis. "The air layer between the foil combined with the chimney effect, created by opening the roof, ensures a slightly cooler temperature in summer than outside. A plant slows down in growth from 25 degrees upwards, so this ensures a better growth curve and the cycle of the product."
Steven explains that for fungus-sensitive plants, a double-walled film produces better results because it causes almost 0 percent condensation. "And in rainy weather, the climate computer allows the entire roof to be closed at three minutes, keeping the heat in longer and the rain out." The study can be requested from the company.
Aluminum snap-in system
This is compounded by the fact that the company assembles the film in a different way from its peers. "We install our foil in pieces with our specially developed snap-in system," he reveals. As a result, the roof does not open in parts, as in the classic Venlo types. "Due to the full opening of the roof, the outdoor climate for the plant is almost the same as inside. In case of temperature differences between inside and outside, cloud formation occurs at the bottom of the greenhouse, but it can be quickly ventilated, resulting in quicker drying of plants and a more stable growth curve."
"You also save in labor costs because the plants in the greenhouse are better protected from wind, so falling over is almost nil. And in stormy weather, the fear of glass or sheets blowing out is nil with our double-walled flexible film greenhouse," Steven continues. "If damage does occur, we can have it repaired thanks efficiently to the snap-in system: you don't have to have the entire conservatory covered with foil."
According to Steven, Vermako's aluminum snap-in system ensures a perfect balance between the inside and outside of the film. "Because of the flexible and high-performance foil that does not let in rain or hail, you also achieve a safer energy-efficient conservatory and reduced heating costs by 25 percent on an annual basis."
Movable push-up walls
If growers want to go even further, Vermako's team can equip the greenhouse with movable push-up walls in double-walled film. "When these are closed, depending on the continent and metrological conditions, we can demonstrate a temperature difference of at least 7 degrees without having to use heating. This results in earlier and longer harvests, and thus better profitability."
From a price point of view, Steven says a double-walled foil greenhouse is more advantageous than a glass greenhouse because it lasts longer than 30 years on average. "You can say that even with a classic substructure, but with a double-walled foil, you have replaced your foil three times in normal circumstances, and you are still not at the price of a glass conservatory." A factory warranty of a classic film comes to an average of 3-5 years, depending on the area and country, but Steven explains that they have film types that enjoy a 10-year factory warranty. "So it makes sense that it would last much longer."
These benefits have also been seen internationally. Steven explains that due to water scarcity in African countries, Vermako foil greenhouses have been chosen for many years now. In Brazil and Mexico, the company currently has partnerships with local technical sales and construction teams who, as in Europe, market the brand under their commercial name. "Anyone can visit our 20,000m² production hall and come and look at the test models, or we can make a guided tour of existing conservatory projects by appointment for each country where you operate."
For more information or the results of the study:
Steven Van Hoof
GSM/ 0033-6-78-38-64 54 France
Office/ 0032-51-40-10-440 Belgium