Published 01/05/2012

Black Shade Cloth Versus Reflective Screens

Research shows that reflective screens block more heat than black shades in the greenhouse. Use these findings to improve productivity and keep your plants - and your employees- from burning up.

Few factors can affect plant development as much as temperature fluctuation, particularly in the heat of summer. Monitoring and controlling both air and leaf temperature can drastically affect a plant’s productivity and quality.

Leaf and air temperature can differ greatly, by as much as 10°F to 30°F. Proper greenhouse shading, however, can help keep leaf temperatures in the most productive range.

As greenhouses transmit sunlight, they also trap heat, raising the internal temperature of the structure. Both plants and workers become stressed, and reducing the heat load becomes imperative. But what is the best material to accomplish that goal?

Recent studies conducted by Dr. Daniel H. Willits at North Carolina State University (NCSU) help shed light on the impact greenhouse shading selection has on plants.

These studies found that common black, knitted shade cloth provided little to no thermal improvement in the greenhouse. Installing reflective materials for external shading, in this case the Svensson *FLS, resulted in lower greenhouse temperatures and net radiation.

The studies reported a 30 percent decrease in greenhouse heat gain for reflective materials compared to black shade cloth at the 60 percent shading level. This translated to significant reductions in both leaf temperature and greenhouse temperature, which increases a greenhouse’s productivity potential overall.

Early Research
As early as 1983, researchers speculated that shade cloths should reduce temperature in direct proportion to shade value.

                                  Green-Screening-Black-Shade-vs.-Reflective-Screening.jpg

Studies by Willits and Matthew M. Peet, an assistant professor of aerospace engineering at the Illinois Institute of Technology, in 2000 and Willits in 2001 found that shade cloths reduced energy gains less than the shade factor would suggest. Field tests indicate little or no temperature reduction can be expected from 30 percent black shade. The best estimates suggest black shade cloths are about 40 to 50 percent effective at reducing energy gain inside a greenhouse...

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*In July, 2014 Svensson product names were updated; former FLS shade screens are now called SOLARO WB  and OLS shade screens are known as SOLARO AW screens.

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