The Benefits and Challenges of Green Roofs on Public and Commercial Buildings

From the United States General Services Administration, this report presents the costs, benefits, challenges, and opportunities of green roofs with a focus on the National Capital Region (Washington, D.C. and the surrounding area). The study finds that over a 50 year period the stormwater, energy, carbon dioxide equivalent, and community benefits of green roofs outweigh the costs associated with installation and maintenance.

The report summarizes the research and economic analyses behind various environmental, economic, and social benefits of green roofs, including:

  • Helping site-level stormwater management through reduced runoff rates
  • Attracting species and increasing biodiversity, habitats, and microclimates
  • Mitigating urban heat island effects
  • Reducing a building’s energy use
  • Providing space for urban agriculture
  • Improving acoustics by absorbing sound better than conventional roofs
  • Improving air quality by removing air pollutants
  • Improving aesthetics and quality of life by providing attractive and relaxing spaces
  • Generating jobs for installation and maintenance 
  • Contributing to higher real estate values and economic development 
  • Saving replacement costs over time as green roof longevity and durability is greater than that for conventional roofs

The report also examines the challenges associated with the design, installation and management of green roofs and presents best practices in regard to:

  • Ensuring the building can structurally support a green roof
  • Installing green roofs on historic buildings
  • Knowledge of applicable codes and standards
  • Quality installation and leak prevention
  • Maintenance requirements to avoid plant loss and other problems

The study’s cost-benefit analysis was based on a comparison between installing a conventional roof or replacing a conventional roof with a green roof.  Over a 50 year period benefits to the community (eg. increased biodiversity, improved air quality, heat island mitigation) were found to have the greatest positive impact on green roofs’ net present value (NPV) --a measure of potential profitability. Highlighting this potential in the Washington D.C. area, the report states:

In the National Capital Region, if green roofs were to replace conventional roofs on all 54 million square feet of real estate (an estimated 5.9 million square feet of roof area), the cost-benefit analysis projects a 50-year NPV of $22.7 million, or $0.42 per square foot of building area. The community, or public benefits in the National Capital Region could total almost $180 million, or $3.30 per square foot of building area. 

 

Publication Date: May 2011

Related Organizations:

  • U.S. General Services Administration (GSA)

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Resource Types:

  • Best practice

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