2014 Marks The 50th Anniversary Of The Double-Poly Greenhouse [sponsor content]

Photo credit: NGMA

Photo credit: National Greenhouse Manufacturers Association

In the early 1960s, Rutgers University Professor William J. Roberts fastened two polyethylene sheets together, mounted them on a simple wooden frame and proceeded to inflate the space between the sheets with a low-pressure fan. His
simple structure was the first air-inflated double-layer polyethylene greenhouse, known simply and universally today asdouble poly. It would start a revolution in greenhouse engineering.

Robert’s idea spread quickly, across the United States and then throughout the world. Commercially, the low-cost, easy to install, energy-efficient system was readily accepted. The first air-inflated double-poly concept would also spur
further research that would eventually lead to the invention of other milestone greenhouse products. This year, 2014, marks the 50th anniversary of Roberts’ monumental achievement.

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A Solution Created Out of Necessity
Early on, Roberts recognized the importance of a double-layer covering to reduce the condensation drip that plagued growers using single-layer greenhouses. He was also cognizant of growers’ early struggles to install double layers, an unwieldy procedure that involved attaching one layer to a rafter, adding a 2×2 spacer, and then attaching another layer. The process was costly, time-consuming and not always effective.

The double-poly system significantly reduced the labor and materials required for installation, thus bringing down costs. Additionally, the inflation of the two layers reduced the pressure on the film, which in turn minimized tearing and strengthened the entire structure. The insulated air space also reduced heating requirements.

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David Mears, also a professor at Rutgers University, worked closely with Roberts on some of the early research associated with film stress and structural loads. Other research efforts at Rutgers University led to the development of movable
insulation/shade curtains and various in-floor heating systems.

The first commercial greenhouse to use the double poly was located at Kube-Pak Inc. in Allentown, N.J. Co-owner, Aart Van Wingerden, was one of the early leaders in the development of frame structures for multi-span and single-span structures, along with Kenneth Bryfogle, owner of Power Plants Inc. Frank Stuppy, owner of Stuppy Floral Inc., was also a major player with his contribution of the first extruded aluminum film fastener.

Lasting Impact Still Today
Roberts’ original air-inflated double-layer poly greenhouse still stands today, relatively unchanged except for a few minor upgrades, on the Rutgers University Cook College campus in New Brunswick, N.J. In 2004, The Society for Engineering in Agricultural, Food and Biological Systems (ASAE) dedicated the site as a historical landmark in recognition of Roberts’ achievement and the impact these structures have had on the plant industry.

The original double poly system not only led to the development of groundbreaking greenhouse products, it also paved the way for new growth in the industry. Small businesses, farms and garden centers suddenly found it more affordable to expand their operations with the addition of new greenhouses. In developing countries, these structures have allowed growers to support their families and produce affordable food for their communities year-round. Today, Roberts’ accomplishment still has a lasting impact on the industry — more than half of the plastic greenhouses in use worldwide utilize the air-inflated double-poly system.

For more information, go to www.ngma.com.

Source: ASAE Historic Landmark Dedication

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