Greenhouses are made of glass, right? Yes, but certainly not always and not completely. Even in the Netherlands, where most greenhouses are made of glass, polycarbonate is more common than you might expect.
"Polycarbonate has proven to be an excellent choice because of its long warranty period and superior insulation value," says Mark van den Tempel. "This has led to growing acceptance and implementation of polycarbonate in modern greenhouses." It is also in high demand internationally. Where UV irradiation is not essential, the sturdy polycarbonate sheets are ideal for various applications: on the roof, against the façade, or in front of the greenhouse.
"In the greenhouse, for example, it can be used for a sliding door, a window, or storage space. Polycarbonate is an incredibly versatile product," lists the Managing Director of Stabilit Benelux. The company has been active in polycarbonate since 1984. The polycarbonate phenomenon is certainly not new in horticulture, but not everyone is aware of the latest developments. For instance, an extended warranty period of 15 or even 20 years is regularly chosen for polycarbonate sheets, and more and more is possible with the insulation values of sheets. Not insignificant in times of energy crisis.
The polycarbonate specialist once started in the Westland but is now located in Benthuizen. Here, in addition to the office, the 3,000 m2 distribution center is also located. Stabilit Benelux supplies sheets to greenhouse builders, but also in other sectors. "When it comes to really large projects, it is also possible to deliver custom-made products directly from the factory. If machining is required, such as guttering or sloping, we do that here in Benthuizen."
The power of lightweight
One of the advantages of polycarbonate is the weight of the material. "This exceptionally lightweight material offers the same structural integrity as glass but with significantly less mass. This means greenhouse builders can enjoy easier installation, less need for heavy support structures, and generally less stress on the greenhouse system." The result? "A cost-effective and efficient solution for modern greenhouse construction."
While some variants of this material may be heavier, they still offer advantages such as longer warranties, better insulation values, and impact resistance compared to traditional glass. "We supply solid polycarbonate in thicknesses from 2 to 15 millimeters. A 15-millimeter sheet weighs 18 kilos per m2, so you'll need some strong arms to lift it," laughs Mark.
The factory, or rather factories, are in several locations worldwide. Stabilit Benelux, formerly Macrolux Benelux, is now part of Verzatec, a Mexican family company. Stabilit Benelux is the exclusive distributor of the sheet material and systems of the Swiss manufacturing company Stabilit Suisse SA. "Many of our products go all over the world with greenhouse builders. We deliver the product to them on site, and they transport it in containers with the rest of the materials needed to build the greenhouse (such as steel, for example)."
Insulation: retain heat and save
In these uncertain times, with high energy costs, multi-walled polycarbonate, in particular, is in demand. "The more walls there are in a sheet, the better the insulation value." At the polycarbonate specialist, they then talk, for example, about 16 millimeters 3-walled, 16 millimeters 5-walled, or 16 millimeters 5X, where the number then stands for the number of walls. "And we also have 16/10X. A board with excellent insulation value, which retains heat and does not let it escape, thus maintaining a constant and favorable temperature."
So, the boards come in different types and strengths, from 4 to 60 millimeters thick. "For a lot of light transmissions, choose a 16-millimeter 3-walled board, for better insulation, a 5-walled one. The single or double X structure emphasizes the rigidity of the board. The last thing you want when the sheets are on the roof is for the sheets to be blown out of the roof by a storm or fold inwards, for example, due to snow loads."
Glasshouse project equipped with clear sheet type 16/3
Guarantee: invest in sustainability
One aspect that has further fuelled interest in polycarbonate is the longer warranty offered. Due to extreme weather or calamities, damage may still occur. This then leads to an insurance issue. To accommodate growers, Stabilit Benelux can increase the warranty period to 15 or 20 years.
Over 39 years, the polycarbonate product has undergone continuous development. At HortiContact, the company is a returning participant with a stand full of different types of plates. "We don't have a new product every year, but we offer a lot of choice."
Recently, due to the energy crisis, there has been an extra focus on insulation. "Growers are choosing extra screening, for example," Mark notes. "If you do this at a time when the polycarbonate greenhouse cover is already 20 years old, there are gains to be made there. What we see a lot of in practice is replacing a 16 mm 3-walled sheet with a 16 mm 5-walled sheet or even a 10X sheet. With the latter plate, growers gain significantly in U-value, the value that expresses insulation." Mark cites a 15-20% improvement in insulation value.
Carlo Bol and Leonard van Vliet at HortiContact 2023
If the light transmission is not the most important consideration, it may pay to use even thicker boards than 16 millimeters. Garden centers have been doing this a lot recently. "There you see that people choose to replace the 16-millimeter boards with 20, 25, or 32-millimeter boards, obviously, these boards have an even higher insulation value."
For companies like this, saving gas and sustainability is an important argument for replacement and investment. In this respect, the polycarbonate specialist himself is still hard at work. "We have actually never shouted it from the rooftops, but we recycle all our pre-consumer materials and have been driving around with the field service in electric cars since 2019."
The Benthuizen office has also recently had solar panels on the roof. "In that respect, it's a good day today," Mark laughs at the end of May. He concludes by pointing out one last piece of customization. "We can also offer an IR-Gold panel, this panel has the properties of letting light through but largely emitting the heat back outside. Wonderfully pleasant on these hot days."