LEED standard hits the roof.

A majority of new construction, high performance, "green" buildings have a greenroof, the most well known being the Solaire, the first LEED residential gold building in the world, located in Battery Park City.

The Solaire has two greenroofs, a lower 19th floor greenroof garden--an area with dedicated paths and deeper planting beds that is heavily used by the building's tenants, and the upper roof which has a very thin, "extensive" greenroof treatment that was installed for energy savings and environmental benefits alone, with no tenant access.

Both roof membranes are protected by insulation and protective matting that includes a root barrier, and are almost completely covered with plant material. In addition to having a roof garden that is enjoyed by the tenants, the Solaire also reaps the benefits of extended roof membrane life, energy savings in summer and winter and environmental benefits like scrubbing pollutants out of the air, greater bio-diversity and converting carbon dioxide to oxygen. The lower roof weighs in at a maximum load of 35 pounds per s/f, while the upper roof is not accessible to the public and weighs no more than 15 pounds per s/f.

In the United States, roofing manufacturers are just stepping up to warranty their membranes with a greenroof component. The single source warranty specifies that if there is any problem with the roof membrane in the first five years, the roofer will remove the greenroof, repair the membrane and replant the greenroof in the affected area at no additional cost to the customer. While American Hydrotech pioneered the "single source" warranty for greenroofs, this warranty is now provided by Henry and Soprema roofing manufacturers as well. With a greater number of manufacturers offering the single source warranty, any building ready for a new roof can consider purchasing a greenroof without voiding the roof warranty or concern about additional expense should they need to exercise it. With the single source warranty, greenroofs are a no-risk means of increasing roof life and utilizing roof space for recreational purposes.

When considering a greenroof, the first step is to have an engineer evaluate the maximum pre-snow weight load capacity of an existing roof. Once the maximum weight loads have been determined, the greenroof can be tailored to the structural and usage needs of the building. Though many people prefer to have a new roof with a warranty, the largest in New York, City, (30,000 s/f) recently built by Greener By Design on the roof of Silvercup Studios, was installed on an existing roof with no expectation of warranty beyond the maintenance of the plant materials. While most new construction buildings with greenroofs tend to have a lower tenant accessible roof and an upper extensive green roof, existing buildings can have the best of both worlds by limiting tenant access to one area with an intensive higher maintenance greenroofs, and surrounding it with extensive, lower maintenance plantings, reaping the rewards of energy savings and extended roof membrane life while limiting maintenance costs.

RICHARD HELLER

CLT