Green roofs, essentially rooftops covered with a layer of lightweight growing material and planted with drought tolerant plantings that sit on top of waterproof barriers of existing roofs, have been embraced throughout Europe for the past 30 years. The market for green roofs continues to grow throughout the world. In Germany, for example, more than 145 million square feet of green roofing has been installed in just the past 10 years. In comparison, New Jersey has millions of square feet of black roof surfaces available for "greening."

Green roofs have become so popular in Europe in part because of government legislation and financial support. Yet the many benefits of this emerging technology are reason enough to consider the investment.

At its most basic, a green roof system is simply an extension of a building's existing roof. The green roof system includes a high-quality waterproofing layer; root barrier; drainage system; a filter fabric; and a lightweight, engineered growing medium designed for green roofs. Depending on the size of the roof, the types of plants selected and whether or not the system is accessible to building tenants, the project can range in cost from $10 to $24 per square foot.

The benefits of a green roof are almost too numerous to count. For developers and building owners, the major benefit is cost savings. Just by virtue of being installed, a green roof protects the roof membrane from the sun and other environmental forces, resulting in a longer material lifespan--in many cases doubling the useful life of a conventional roof. A green roof also decreases the amount of maintenance that needs to be performed on a traditional roof, further reducing upkeep costs.

A green roof significantly reduces heating and cooling costs. Depending on the size of the building and the type of green roof installed, a building owner can reduce the size of standard HVAC equipment in new or retrofitted buildings, resulting in capital and operational savings. Green roofing ultimately reduces the ambient air intake temperature near top-mounted air conditioner units, resulting in reduced energy cooling usage and cost reductions of up to 30%.

Rooftop planting, particularly using a lightweight engineered growing medium that allows the plants to grow with as little as three inches of soil, can also work in conjunction with other standards for green building. The growing material for green roofs prevents water pollution, for example, by retaining storm water that would otherwise flood drains in urban areas. Storm water management is an essential part of any new development and a sound plan for dealing with or eliminating runoff is necessary for achieving Leadership in Energy and Environmental Design and other green building standards.

A green roof can directly benefit building tenants in a number of ways, which increases the marketability of buildings where rooftop plantings are located. For example, the construction of a green roof, with soil, plants and a layer of trapped air, can insulate the building for sound, which otherwise can be a considerable yet necessary expense for buildings located in noisy urban areas. Sound waves that are produced by machinery, traffic and airplanes are absorbed by the roofing materials and reflected back or deflected accordingly. Recent estimates show that green roofs with material layers of less than five inches can reduce sound by 40 decibels.

Though a green roof does not, by definition, have to be accessible to building tenants or the general public, investing in this feature for general use can produce a significant return on investment for building owners and developers. Recent studies show that good landscaping and tree cover surrounding a commercial property can increase the building's value by as much as 6% to 15%. A green roof offers the same aesthetically pleasing surroundings and additional environmental benefits. Of course, a green roof might have even more of an aesthetic impact, since it can serve as a space for meetings or simple recreation, greatly increasing the value of a property and increasing employee productivity by giving them a place to relax outdoors without having to travel.

Perhaps one of the most overlooked benefits of a green roof is one of the most obvious – they are an extremely visible symbol of a company's commitment to environmental awareness and responsibility. In an era where everyone is striving to "go green," a green roof showcases that commitment in a way that a plaque or certificate never could.

The numerous benefits of a green roof to an individual building, its marketability, and to building tenants are only the beginning. Beyond providing a proven return on investment, green roofs represent significant opportunities for social, economic and environmental benefits, particularly in urban areas. A green roof can improve general air quality, reduce resistance to new development and, depending on the uniqueness of the project, garner local, regional and national exposure for the developer.

Green roofs are not a fad or a gimmick--they are a proven way to reduce the environmental impact of a property, benefit the community and provide a highly visible way to demonstrate a commitment to sustainable development.

Robert Schucker is the president of Eco Earth Design, one of the region's leading environmentally responsible landscape design and development firms. The views expressed here are those of the author.

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