Winter is here and that has you thinking more about ways to save energy. Proper glazing not only helps keep the heat inside during the winter months, it can also improve the quality of your crops, but only if you choose the right material for your needs. When choosing a covering, important considerations include light transmission and distribution, longevity, versatility and cost. There are plenty of options available, and they vary from glass and plexiglass to polycarbonate and poly film.
Mike Kovalycsik, national sales and marketing director for Delta T Solutions, provides a good review of glazing materials and covers the latest in film technology.
Choosing The Right Material
Plastic 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 weatherable, 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 percent 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 percent light, and multi-wall panels, which transmit about 80 percent 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 Technology
Here’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 percent energy savings.
Multi-wall polycarbonate twin wall sheet products from Co-Ex Corp. provide high light transmission, good thermal insulation, high temperature resistance and hail resistance, and includes a special coating that eliminates condensation and water droplets.
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.