Professional Practice
Increasing Energy Efficiency: Residential Green Roofs
The roof and surrounding site contain 40 native species of plants and wildflowers. Edgeland House, Austin, Texas / Bercy Chen Studio LP Green roofs are energy-efficient vegetated roof systems. Once installed, they last longer than conventional roofs. While the energy saving benefits of commercial green roofs are already well known, residential green roofs can also dramatically improve home energy efficiency. Green roofs regulate buildings' internal temperature and reduce building heating and cooling costs.
Green roofs also function as sustainable, decentralized stormwater management systems by reducing run-off and decreasing the energy costs associated with extending and upgrading centralized systems.
Green roofs benefits include:
- Cost-efficiency: A University of Michigan study showed that more than 50 percent of the cost associated with installing a green roof will be returned in the form of lower maintenance and reduced energy usage over the lifetime of the green roof system. ¡°Nearly two-thirds of these savings would come from reduced energy needs for the building with the green roof.¡±
- Energy savings: A typical 2-3 story building could experience 15-25 percent savings in summertime energy costs.
- Lower air temperatures: A modeling study found that adding green roofs to 50 percent of the available surfaces in downtown Toronto would cool the entire city by 0.2 to 1.4¡ãF (0.1 to 0.8¡ãC).
- More efficient stormwater management: Green roofs can reduce stormwater peak flow rates by up to 65 percent and increase the time it take the water to reach the sewer by 3 hours.
- Long lifespan than conventional roofs: Green roofs can extend a roof¡¯s lifespan by two or three times. According to the General Services Administration, ¡°Green roofs provide a payback¡ of approximately 6.2 years nationally¡conservative analysis puts the average life expectancy of a green roof at 40 years, versus 17 for a conventional roof.¡±
- Lower long-term maintenance costs: According to Sustainable South Bronx, a non-profit organization, on a 90 degree day a green roof is about 80¡ãF, while a black roof is 175¡ãF. The higher temperatures cause substantial wear and tear.
- Reduces heat flux and provides insulation: Green roofs can limit the transfer of heat from a building exterior to its interior by up to 72 percent.
Sources: ¡°,¡± U.S. Environmental Protection Agency, , and ¡°,¡± U.S. General Services Administration
Organizations
, British Columbia Institute of Technology
, Pennsylvania State University
Resources
, Green Roofs for Healthy Cities
, Department of Horticulture, Michigan State University
, The Dirt, American Society of Landscape Architects (Ë¿¹ÏÊÓƵ)
Green Roof Tax Credits, Ë¿¹ÏÊÓƵ Advocacy
, U.S. Department of Energy
, Environmental Protection Agency
, The Dirt, American Society of Landscape Architects (Ë¿¹ÏÊÓƵ)
, University of Delaware Botanic Gardens
, City of Portland
Research
"," Edmund C. & Lucie L. Snodgrass, Timber Press, 2006
"," Susan Weiler & Katrin Scholz-Barth, Wiley, 2005
¡°,¡± Timothy Beatley, Island Press, 2016
¡°,¡± Nigel Dunnett, Dusty Gedge, John Little, Edmund C. Snodgrass, Timber Press, 2011
Government Resources
, Toronto, Canada
, State of Illinois
, City of London
, Environmental Leader, June 29, 2008.
, Washington, D.C.
, Austin, Texas
, Milwaukee, Wisconsin
, Nashville, Tennessee
, Portland, Oregon
, Milwaukee Metropolitan Sewerage District
Projects
, Austin, Texas
Bercy Chen Studio
, Santa Lucia Preserve, Carmel, California
Blasen Landscape Architecture
Macallen Building Condominiums, Boston, Massachusetts
Landworks Studio, Inc
, Chicago, Illinois
Omni Ecosystems
, San Francisco, California
Designworks Inc.
, Kennett Square, Pennsylvania
Land Ethics
Padaro Lane, Carpinteria, California
Keith LaBlanc Landscape Architecture
, Oakland, California
PGA Design
, New York, New York
Balmori Associates