The Grass is Always Greener On The Other Side of The Roof

by Dave on July 4, 2009

As first seen in Coastal Sussex Weekly, June 18, 2009:

by Eric Wahl

One of the biggest trends in the environmental preservation and conservation movement is finally taking root in the United States…green roofs.  Countries across Europe have long seen the benefits, both environmentally and economically, in establishing green roofs on their buildings, all the while making extraordinary advancements in the technology of these living systems.  Following their lead and making advancements of our own, the United States is continuing the efforts in reducing stormwater runoff, minimizing heat transfer, and gaining priceless open space within our built environment by utilizing green roofs.

When green roofs first entered the design discussion, many myths and negative connotations surrounded them.  Two of the most common were that they were too heavy and that they would leak.  In reality, a green roof system that is about 4 inches deep is comparable to a gravel ballast system of the same depth.  Furthermore, a properly installed roof will not leak because of the addition of vegetation.  Another myth that continues to circulate is that green roofs are expensive, both to install and to maintain.  Actually, with today’s advancements in these living systems, green roofs are comparable to the installation of traditional roofs.  In addition, with a proper plant palette and correct installation, green roofs only require watering in the first season of establishment and during extreme drought conditions.

The benefits of green roofs are many.  In economic terms, green roofs can add property value to a site by increasing the usable space on the lot.  Commercial endeavors can take advantage of a green roof’s marketing and advertising appeal.  In addition, potential savings in energy costs are dramatic.  A green roof will substantially moderate the temperature on the roof and reduce the heat transfer through the ceiling, thereby lowering cooling costs.

Another benefit of green roofs can be found in storm water management.  A traditional roof will direct rainfall into the local drainage system or it empties onto the site through a gutter and downspout arrangement.  With a green roof, the first flush of a storm event is absorbed into the planting medium and taken up by the vegetation.  This water is utilized by the plants and returned to the atmosphere by evapotranspiration, an integral part of the water-cycle.  Excess storm water is directed away from the building using an underdrain system.

Aesthetically, green roofs offer a myriad of plant combinations that provide visual appeal to the building’s occupants as well as to surrounding structures and their onlookers.  A plant palette for a green roof can range from typical meadow vegetation such as solidago, alium, coreopsis, and native grasses, rushes and sedges to larger plantings found in a typical garden.  (The depth of the planting medium and the supporting roof structure will influence what type of green roof is installed.)  A green roof can be as shallow as 2 to 4 inches.  These shallow systems are usually planted with a variety of succulents, such as sedums, that are drought tolerant and provide year round interest.  Other types of vegetation for this type of living system can be mosses, lichens, and native grasses.

Other benefits of a green roof are improved air quality, reduced heat island effect, cooler local air temperatures, and aesthetically pleasing view sheds, just to name a few.

Furthermore, green roofs do not always have to be passive spaces; they can also be places of recreation, relaxation, and education. Urban areas have often played hosts to a plethora of rooftop gardens and terraces.  Not only do they positively impact the environment, but they also provide a place of respite for those that enjoy them.  A rooftop on a medical institution could be the ideal place for a healing garden, accessible to both staff and patients as a point of relaxation and meditation.  Campuses and schools could house educational gardens, providing a teaching tool to educators and helping to lay the groundwork for future
“green” enthusiasts.

We are proud to have an example of a green roof right here is Sussex County.  A green roof is being installed June 16 at the new Bethany Blues located along Route 1 in Lewes, Delaware.  Architecture, site-layout design, and planted by Element.

The design possibilities and benefits of green roofs are

endless. I encourage you to
further investigate this and other green design topics and help cultivate greener solutions for a greener tomorrow.

Eric Wahl is a landscape architect with Element Design Group in Lewes.

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