PROJECT PARNTER(S)
American Society of Landscape Architects, Michael van Valkenburgh Associates

LOCATION
NE Washington DC


GREEN INFRASTRUCTURE ELEMENTS
Green Roof

DESCRIPTION
The ASLA Green Roof was developed by the American Society of Landscape Architects to showcase the potential for landscape architects to be involved in the greening of the city. Michael van Valkenburgh was the prime consultant for the project, which showcases extensive, semi-extensive and intensive green roof membranes in downtown Washington DC.
A year and a half after its installation, Executive Vice-President Nancy Somerville noted some of the significant features of ASLA green roof:

• the roof is attenuating 100% of a 1" rainfall and 74% of the annual rainfall, which is a savings of 27,500 gallons
• similar to other applications, the roof has a lot of chemical leachate during its first year. Somerville notes high levels of nitrogen. The source has not been identified, but she speculates that either soil or detritus from the constructution process may be to blame and notes that those chemical runoff numbers will diminish in a few years.
• the roof has been measured to be 32 degrees cooler than the adjacent building roofs, meaning less cooling costs in the summer. (Somerville related the amusing anecdote that some employees had taken to running their space heaters during the summer because it was so cool on the upper floors--a problem that she vowed to correct).
• The total reduced energy costs have been 10%.

PHOTOS AND DRAWINGS


LESSONS LEARNED
The ASLA's performance data, below, is an exceptional source of data for the performance of this roof over time. The roof is very interesting due to the variety of green roof profiles and the experimental plants that MVVA installed to test their fit for green roof applications.

ADDITIONAL RESOURCES
ASLA's Green Roof Central
ASLA Green Roof Performance Data
ULI/ASLA Green Roof:A Case Study Monograph