Let The Sun Shine In (Again)
Here's the latest news on glazing and poly products to help get the right kind and amount of light to your plants.
September 22, 2008
I've been noticing lately that my tendency towards unreasonable perfectionism has increased in inverse proportion to the amount of time I have to perfect something. In other words, I'm not mellowing with age, a revelation which comes as no surprise to those around me most. So when I received some suggestions that my glazings overview article ("Let The Sun Shine In," GG Mid-May '06) wasn't comprehensive enough, I figured I'd dedicate a column to patching the holes in my poly coverage. After that article, this column and all my laps of the tradeshow floor at OFA's Short Course this year, I'm really hoping the supply of new glazings is as exhausted as I am!
Kalwall Corporation has introduced its newest product, Sun-Lite HP, a glass fiber-reinforced polymer glazing that provides diffused light throughout the greenhouse. It transmits only the part of the UV spectrum (0.33 to 0.38 microns) that helps control viral and bacterial populations, while keeping out other, less beneficial wavelengths. Sun-Lite also transmits over 90 percent of visible light energy and allows short-wave radiation into the greenhouse, trapping it in once it is converted to long-wave form and therefore provides growers extra help during the heating season.
Klerks and Merck
Klerks USA, located in Richburg, S.C., has a variety of films available for greenhouse growers. The most interesting new product available is its KoolLite 380 film, which provides selective alteration of IR light, IR additives, light diffusion properties and UV blocking, as well as a patented anti-condensate process developed in partnership with worldwide pharmaceutical giant Merck laboratories.
The Impact Resister
Deglas has recently introduced its new Highlux High-Impact acrylic glazing. Growers won't lose crop consistency due to yellowing, and Highlux High Impact's superior light transmission, condensate control, manufacturer's warranty of 10 years and life expectancy of 25 years even in extreme weather all combine to mean that Highlux High-Impact is built to last.
Chicago-based Warp Brothers has been developing and manufacturing greenhouse coverings for the American marketplace since 1924, and continues this long tradition with the Flex-O-Glass line. Available as a 4-year UV Film, a 4-year Condensate Control Film and a 4-year Thermal Film with Condensate Control, all Warp Brothers products are guaranteed to last and made in the USA.
The Heavy Hitter
Perennial American innovators GE Plastics are partnering with AmeriLux International LLC to bring its Thermoclear Plus Polycarbonate twin-wall greenhouse glazing to the United Sates market. This product, already available in Europe, is a polycarbonate sheet that resists yellowing and comes with a guarantee that growers will not lose more than 2 percent light transmission over a 10 year period. (Editor's note: For those who were there, that was Amerilux's Poly Police on patrol at Short Course, issuing citations for yellowed glazings. Hopefully you all stayed out of trouble!)
The last gap in coverage concerns the Aluminet and Chromatinet shade nets from Signature Supply. Aluminet features twisted, knitted aluminum mirrors that disperse reflected sunlight throughout the greenhouse. This reflection diminishes the UV value, but not the photosynthetic value, of the sunlight. According to Signature Supply's Frank Giglia, Aluminet's fabric of twisted mirrors can actually overpower the shade factor of greenhouse glazing by increasing the amount of 90-degree angled photons that pass through to the plants over all daylight hours.
This reflective quality of products like Aluminet also helps to control temperatures over the course of the day. During daylight hours, the material reflects away 50 percent of the heat, and at night it blocks the heat from the greenhouse from radiating out through the roof.
Chromatinet, also by Signature Supply, refracts sunlight instead of reflecting it, which adds a whole different set of positive variables to the greenhouse mix. As sunlight passes through embedded pigments in the plastic ribbons, the colored fabric acts as a filter and alters the spectrum and direction of the photons that reach the plants.
Different colors bring different results. For instance, gray mimics tree canopy shade with its crystalloid structure diffusing light to the plants. It also creates a thermo-reflective barrier that Giglia asserts is 10 percent cooler in daytime and 5 percent warmer at night under the structure than more traditional black shade net.
Other colors perform other tasks - blue and red increase filtered light in their spectrums above the stated shade protection percentage, and pearl disperses light through high-density foliage.