LEED Application in Sustainable Landscape Practices (second in a series)

Credit 7:  Landscape and Exterior Design to Reduce Heat Islands

Sustainability begins with design; clear, precise design objectives with long term management objectives.  Long term planning and management to reduce heat islands, is a LEED accredited application that can be obtained by several design methods.  Heat island effects are caused by solar energy retention on constructed surfaces in urban areas, elevating the temperature differential between urban and rural environments between 2 and 9 degrees.  Streets, sidewalks, parking lots and roofs are the primary contributors.  The increased urban development and rising temperatures caused by heat island effects also has proven to have a negative effect on wildlife and their habitats.  Mitigation techniques include maximizing shade-producing vegetation that can increase shade during all seasons to combat varying sun angles and by reducing heat island effect by increasing shade by 30 percent will meet LEED certification requirements.  Vegetation will reduce solar absorption on non pervious surfaces and also cool the air through evapotranspiration (commonly referred to ET).  Using an alternative material for paving or concrete that has a high-albedo solar reflecting value of 0.3 or higher will also reduce the heat absorption that leads to heat islands.  Materials such as subsurface grasscrete (a structural grid / paver installed below grade that is typically planted with vegetation) and turfstone pavers planted with vegetation are perfect alternatives to your traditional paving materials, allowing you the flexibility to reduce heat absorption and the cost per square foot is typically lower to install.  Green roofs and living walls will mitigate heat island effects and create passive solar and currently only green roofs are recognized certified LEED when a vegetated roof envelops at least 50 percent of the roof area.  Living walls are currently being reviewed by the LEED program and will be recognized and accredited in their new standards scheduled for release in 2012.

Innovation in design is a LEED certified application and by choosing sustainable design topics such as heat island reduction within a sustainable site, the accredited value for LEED recognition continues to increase.

Resources:

Heat Island Group Lawrence Berkeley National Laboratory:  http://eetd.lbl.gov/HeatIsland/