Water: Green Infrastructure
Lower Building Energy Demands
How does it work? Through shading, windbreak, and evapotranspiration, trees and vegetative cover can lower ambient air temperatures in urban areas, lessening the need to turn up air conditioning in summer months. Since roofs are the site of extensive heat loss in the winter and hot temperatures in the summer, insulation provided by green roofs can greatly reduce the amount of energy needed to keep the temperature of a building comfortable year round. A study published by the National Research Council of Canada found that an extensive green roof reduced daily energy demand for air conditioning in summer months by over 75 percent.
bioswales to amplify the cooling and shading capability of spaces already dedicated to water quality. Build a healthy canopy stock in your community by including tree planting as part of regular capital improvement projects like street upgrades or road maintenance. Partner with tree-focused non-profits to encourage residential or street-tree volunteer planting or canopy mapping events.
Provide residents with access to tools and resources to understand where and how to plant trees for maximum energy efficiency. Studies by the Lawrence Berkeley National Laboratory and the Sacramento Municipal Utility District introduced trees around houses at various orientations to evaluate effects on residential air conditioning and heating use. While cooling energy savings ranged between 7 and 47 percent, the study found heat reduction gains were greatest for trees planted to the west and southwest of buildings.
Incentivize green roof construction: Private development incentives such as Portland, Ore.’s Ecoroof Program are one way to encourage community investment in green roofs. Portland’s program reimburses private property owners $5 per square foot of green roof created. The city also provides resources and technical assistance to small businesses interested in entering the green roof industry.
Communities may find it useful to estimate cooling and energy efficiency benefits using publicly available tools like U.S. Forest Service’s (USFS) iTree suite. The Mid-America Regional Council (MARC) recently partnered with USFS to quantify multiple benefits from existing tree canopy in the Kansas City area. By mapping existing canopy concentrations using the iTree tool, MARC and USFS were able to estimate the value of building energy efficiency gains from existing tree canopy in the region.
AVERT: AVoided Emissions and geneRation Tool: Developed by U.S. EPA’s Office of Air and Radiation, this tool helps estimate the emissions benefits of energy efficiency and renewable energy policies and programs.
iTree : A U.S. Forest Service analysis tool for urban forest managers. It uses tree inventory data to quantify the dollar value of annual environmental benefits such as energy conservation, air quality improvement, carbon dioxide reduction, stormwater control, and property value increase.
Urban Forestry Index (UFind) : A database of current and historic urban forestry and arboriculture publications and other media compiled by the U.S. Forest Service, the University of Minnesota, and TreeLink. It's goal is to increase access to urban forestry material and preventing duplication of products.
Green Roof Energy Calculator : Co-developed by Green Roofs for Healthy Cities, University of Toronto and Portland State University, this tool compares a building's annual energy performance with a green roof to its performance with either a conventional or highly reflective roof.
ADAPT : ICLEI's Adaptation Database and Planning Tool guides local government users through ICLEI’s Five Milestones for Climate Adaptation planning. It is available as part of ICLEI’s Climate Resilient Communities Program.
References1. Pandit, R. and D.N. Laband. (2010). A Hedonic Analysis of the Impact of Tree Shade on Summertime Residential Energy Consumption. Arboriculture & Urban Forestry 36(2):73-80.
2. Huang, J., H. Akbari, and H. Taha. (1990). The Wind-Shielding and Shading Effects of Trees on Residential Heating and Cooling Requirements. ASHRAE Winter Meeting, American Society of Heating, Refrigerating and Air-Conditioning Engineers. Atlanta, Georgia. Online Resource. Available: http://www.osti.gov/scitech/biblio/6839888 .
3. Karen Liu and Bas Baskaran. (2003). Thermal Performance of Green Roofs Through Field Evaluation. National Research Council, Institute for Research in Construction. Proceedings for the First North American Green Roof Infrastructure Conference, Awards and Trade Show, Chicago, IL., May 29-30, 2003, pp. 1-10. http://archive.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc46412/nrcc46412.pdf (11 pp, 400K, About PDF) .
4. Simpson, J.R. and E.G. McPherson. (1996). Potential of Tree Shade for Reducing Residential Energy Use in California. Journal of Arboriculture 22(1): 10-18.
5. Akbari, H. and S. Konopacki. 2003. Streamlined Energy-Savings Calculations for Heat-Island Reduction Strategies. Final Report. Supported by the U.S. Environmental Protection Agency through the U.S. Department of Energy under Contract No. DE-AC03-76-SF00098, March 2003.