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green roofs
This indicator is measured by:
  • Number of Green Roofs
  • Square Feet Green Roofs
Most square feet of green roofs installed, by North American Metro Area 
  1. Chicago, IL: 539,171 sq ft
  2. Toronto, ON: 439,892 sq ft
  3. District of Columbia: 410,245 sq ft
  4. New York, NY: 233,33 sq ft
  5. Vancouver, BC: 224,550 sq ft
  6. Ottawa, ON: 189,926 sq ft
  7. Philadelphia, PA: 147,592 sq ft
  8. Norfolk, VA: 132,869 sq ft
  9. Milwaukee, WI: 130,132 sq ft
  10. Baltimore, MD: 90,079 sq ft
Source: Green Roofs for Healthy Cities, 2011

Exploring the World Wildlife Fund's green roof in Washington, DC
Exploring the World Wildlife Fund's green roof in Washington, DC. Photo Credit: DDOE.
What do the Nationals Park baseball stadium, the Smithsonian Zoo, and the Internal Revenue Service building all have in common? Green roofs! Green roofs transform ordinary rooftops that contribute to the urban heat island effect and stormwater runoff into cooling, water-retaining gardens. Because of the large number of dark-colored buildings and infrastructure in urban areas, urban temperatures are often two to ten degrees hotter than nearby rural areas, which cause residents to use more energy to cool their homes and businesses. Fortunately, green roofs can lower the higher utility costs that accompany these temperatures and extend the lifespan of roofs by protecting them from damaging UV rays and extreme precipitation or wind. Additionally, green roofs reduce stormwater runoff by absorbing water that would otherwise fall on an impervious roof, and provide habitats for District wildlife. Roof vegetation also improves air quality, absorbing airborne dust particles and carbon dioxide. These roofs provide financial, aesthetic, and environmental benefits. 

A green roof often contains the following: a waterproofing layer, an insulation layer, a drainage barrier, a filter layer, planting medium, and various types of vegetation. Green roofs can support flowers, trees, shrubs, depending on their level of intensity and the level of maintenance an owner wishes to devote to the roof. 

American Society of Landscape Architects' Green Roof. Photo Credit: Sara Hammerschmidt.
How is the indicator defined? How often updated?
This indicator measures the square footage of green roofs and the number of green roof installations in the District. This indicator will be updated annually based on the calendar year. This data is provided by the District Department of the Environment. 

What factors influence this indicator? 

The number of rooftops in the District that are appropriate for green roof installation affects this indicator, as does the number of individuals who adopt green roofs for their home or business. The size of the roofs involved also affects this indicator. The initial cost of installing a green roof might detract from the appeal of green roofs to some building owners and businesses, but the promise of lower utility costs might encourage others to adopt the green roof system.

 What you can do to help:

  • Research your options for “greening” the roof of your home or business. See the links below for more ideas.
  • Fill out this Green Roof Rebate Form to apply for rebates for your green roof. DDOE’s 2012 green roof rebate program is administered by the Anacostia Watershed Society, and will provide base funding of $5 per square feet. Review the links for more details on funding. 
Related indicators: RiverSmart Homes, River Health, Air Quality 

Related Links

DDOE Green Roofs in the District  

Other links 

D.C. Greenworks  

Green Roofs for Healthy Cities  

“Environmental Benefits of Green Roofs” Report 

Local Grower of Green Roof Plants  

Sky Gardens Blog 
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