Green roofs, otherwise known as living roofs or eco-roofs, are the wave of the future in sustainable design. The long-term aesthetic and ecological benefits of green roofs far outnumber those of traditional roofs.

Environmentally-sensitive roofing systems allow plants to grow on the surface of what would otherwise be just a protective covering for houses and commercial buildings.

Two examples, one urban and one suburban, of green roofs in the Lehigh Valley include the The Plaza at PPL Center, Ninth and Hamilton streets, Allentown, which has a vegetated roof and filtered storm water said to remove 80 percent of suspended solids, and the Environmental Education Center, Pool Wildlife Sanctuary, 3701 Orchid Place, Lower Macungie Township, completed in 2003, said to be one of the area's first.

Green roofs can be good for the homeowner and the environment. Green roofs are known to retain 50 to 60 percent of a roof's storm water runoff.

The soil retains 90 to 100 percent of the critical first hour of heavy rainfall that can overwhelm storm water management systems. In urban and suburban centers, this could aid in alleviating the cost of storm water management and help in flood control.

Green roofs improve the quality of the water going into streams and waterways. Green roofs cut back on the amount of dust and other pollutants in the air. Green roofs trap and filter dust particles and other pollutants from entering our storm water, thereby, for example, allowing cleaner water to enter the Little Lehigh, a major source of drinking water for Allentown and surrounding townships.

A green roof can reduce the effects of "urban heat island effect." Because of hard paved surfaces and traditional roofs, cities are retaining heat and maintaining temperatures 10 degrees higher than the surrounding area. In the summer heat, the temperature on green roofs can be 20 to 60 degrees cooler than conventional roofing.

A green roof can control building temperatures. For hundreds of years, living roofs were used in countries around the world to prevent heat from escaping or penetrating during the seasons. Controlling a building's interior is possible by replacing the asphalt surface of the roof with plants and soil, which act as insulators to keep buildings cooler in summer and warmer in winter.

A green roof can reduce noise and glare. Noises produced by traffic, including automobiles, trucks and airplanes, are greatly reduced in the vicinity of a green roof, as are other human and mechanical sounds.

A green roof can be more aesthetically pleasing, giving the viewer a soothing vista to gaze upon. With improvements being made in every aspect of green roof technology, green roofs can offer a greater diversity of plants.

"Growing Green" is contributed by Lehigh County Extension Office Staff and Master Gardeners. Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-746-1970.