Choosing the right materialPlastic films are most commonly used for commercial greenhouse glazing, according to the National Greenhouse Manufacturers Association (NGMA), and that includes polycarbonate, ethylene vinyl acetate, polyethylene and acrylic films, among others.
Acrylic is the most weather-strong, and it also has the highest light transmission of the clear multi-wall panels, allowing for greater energy efficiency. In addition, it’s shatter resistant and not affected by UV rays.
For greater durability, impact modified acrylic is an option to consider. The clear, multi-wall panels allow for 85% light transmission and improved energy efficiency. Like regular acrylic, impact modified acrylic is not affected by UV rays, but it has 10 times the impact strength of acrylic, making it a good choice in areas affected by hail.
Polycarbonate offers the highest impact strength and good long-term performance, according to the NGMA and, of all the plastic glazing materials, it’s the most fire resistant. It is available in single pane corrugated panels, which transmit about 90% light, and multi-wall panels, which transmit about 80% light.
The most affordable glazing available is polyethylene film. These films are flexible and often include UV absorbers (chemical compounds that can selectively absorb UV radiation to reduce damage from UV light), allowing for multi-year use. High-density polyethylene film is stiffer and stronger, while low-density polyethylene film is more flexible.
The latest film technologyHere’s a look at just a handful of film options available to growers:
- The IR-AC (infrared anti-condensate) film from Klerk’s USA includes an additive that absorbs and re-radiates infrared heat back down to the crop during the evening hours, resulting in up to 30% energy savings. It also allows for 87% light transmission and high light diffusion, resulting in more uniform plant growth.
- Multi-wall polycarbonate twin wall sheet from Co-Ex Corp. is produced in 4mm, 6mm, 8 mm and 10 mm sizes. These products provide high light transmission, good thermal insulation, high temperature resistance, hail resistance and include a special coating that eliminates condensation and water droplets. The similar multi-wall polycarbonate triple wall provides even greater thermal insulation.
- AmeriLux International’s Lexan Thermoclear Plus High Performance Polycarbonate line is durable and long-lasting, with a 10-year warranty against yellowing and loss of light transmission. An anti-drip/anti-fog coating helps carry condensation away from the roofing so droplets will not damage crops. Another product, the Lexan Thermoclear Plus Softlite multiwall sheet is a 100% diffused panel that uses advanced polymer technology to scatter light while maintaining a 79% PAR light transmission. In addition to having excellent thermal properties, the diffusion feature allows plants to benefit from high levels of light for growth while protecting them from harsh, intense sunlight. The scattering of the light encompasses both top and bottom leaves for more uniform growth.
For more information
Delta T Solutions
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