Dear EarthTalk: What does it mean for a building to be "LEED certified?" Does that mean it is a "green" building?
—Bo Thibault, Slidell, Louisiana
LEED stands for Leadership in Energy and Environmental Design and is the U.S. Green Building Council's (USGBC"s) national program for certifying environmentally sustainable design, construction and resource use practices for the American building industry.
The organization launched the rating system in 2000 to try to provide the building industry with consistent, credible standards for what constitutes a green building. Since then, nearly 10,000 different building projects have become LEED certified. The program sets best-practice benchmarks that builders trying to "go green" on their projects can follow. Once a building or project has been LEED certified, it can use the designation as a marketing advantage to attract buyers or tenants interested in healthy and environmentally safe working or living spaces.
Specific LEED programs focus on several different kinds of projects, including new commercial construction, major renovation projects, existing building upgrades and maintenance, residential homes, neighborhood development projects, and multiple buildings and campus building projects, among others. There is also a LEED program for schools, and USGBC is in the midst of developing specific programs for retail business construction, commercial interiors, and health care.
Builders trying to achieve LEED certification can follow checklists developed by the USGBC specific to their kind of structure or project. Each checklist takes into account five key sustainability aspects of the design and construction processes: sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality. To earn certification, a building project must meet certain prerequisites and performance benchmarks ("credits") within each category. Projects are awarded Certified, Silver, Gold or Platinum certification depending on the number of credits they achieve.
The LEED program also includes a full suite of training workshops and a Professional Accreditation program to develop and encourage green building expertise across the entire building industry. Thousands of architects, real estate professionals, facility managers, engineers, interior designers, landscape architects, construction managers, lenders and government officials have been accredited as LEED professionals. They bring the skills and knowledge they learn through the program to bear on their own projects and help make the certification process run as smoothly as possible.
The green building certification concept is also alive and well in Canada, where the Canada Green Building Council has adopted its own version, LEED Canada, tailored specifically for Canadian construction practices and regulations. LEED registered projects are also in progress in 22 other countries around the world, including Mexico, Brazil and India. And the World Green Building Council, founded in 1998, supports LEED and other green building rating systems in Australia, Japan and elsewhere.
Dear EarthTalk: What is an "urban heat island" and does it have anything to do with global warming?
—Max, via e-mail
An urban heat island is a metropolitan area that is significantly warmer than its surrounding rural areas. Unlike global warming, which entails a worldwide rise in temperatures, heat islands occur at the local level. According to the U.S. Environmental Protection Agency (EPA), many cities and suburbs have air temperatures up to 10 degrees Fahrenheit warmer than their neighboring areas.
Heat islands form as cities replace their natural land cover with pavement, buildings and other infrastructure. These changes contribute to higher urban temperatures in a number of ways. For one, displacing trees and removing soil and vegetation takes away the natural cooling effects that shading and water evaporation from soil and leaves ordinarily provide. Meanwhile, tall buildings and narrow streets can heat the air trapped between them and reduce airflow. And waste heat from vehicles, factories and air conditioners adds warmth to the surroundings, further exacerbating the heat island effect.
The intensity of a heat island will also depend upon its topography, its proximity to water bodies, and local weather and climate. Urban heat islands can also impact local weather, altering local wind patterns, spurring the development of clouds and fog, increasing the number of lightning strikes, and influencing the rates of precipitation.
And although urban heat islands are distinctly different from the phenomenon of climate change, during the summer months they can contribute to global warming. The increased use of air conditioning and refrigeration needed to cool indoor spaces in a heat-island city, for example, results in the release of more of the heat-trapping greenhouse gases that cause global warming. Furthermore, the poor air quality that results from this increased energy usage can affect our health, aggravating asthma and promoting other respiratory illnesses.
Costs are impacted, too. The Heat Island Group, a research and advocacy organization that works to educate the public and policymakers about the heat island effect, estimates that the city of Los Angeles spends about $100 million per year in extra energy costs to offset its heat island effect.
The heat island effect can be reduced through the use of white and light-colored construction materials (including white roofing materials) in buildings, which will work to reflect the sun's heat skyward rather than absorb it, as dark surfaces tend to do. Also, preserving or creating pockets of green space and vegetation help to cool areas naturally. A national program called Cool Communities, coordinated by American Forests and supported by the U.S. Department of Energy, encourages building owners and local policymakers to adopt just such practices. Another useful practice is the creation of "green roofs" or rooftop gardens, in which roofs are partially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing layer.