What do we mean when we speak of green buildings or high-performance buildings? According to the USGBC, these buildings incorporate design and construction practices that significantly reduce or eliminate the nega-
The"house" of green building showing the five major categories of concern.
tive impact of buildings on the environment and occupants in five broad areas:
• Sustainable site planning.
• Safeguarding water and water efficiency.
• Energy efficiency and renewable energy.
• Conservation of materials and resources.
• Indoor environmental quality.5
Typically, green buildings are measured against code buildings — structures that qualify for a building permit but do not exceed the minimum requirements of the building code for health and safety. In addition, green buildings are often measured according to a system such as the LEED rating system (usgbc.org), the Collaborative for High-Performance Schools (CHPS) ratings (chps.net), the Advanced Building™ guidelines (power yourdesign.com), Green Guide for Healthcare (GGHC)6 or, in some cases, local utility or city guidelines (a number of utilities have rating systems for residential buildings). Such buildings must score a minimum number of points above "standard building" performance thresholds to qualify for a certification, or a rating as "green" or high-performance.
Since the introduction of LEED in 2000, it has become essentially the US national standard for commercial and institutional buildings. LEED is primarily a performance standard; in other words, it generally allows a developer, architect or building owner to choose how to meet certain benchmark numbers — saving 20% on energy use versus current building codes, for example — without prescribing specific measures. In this way, LEED is a flexible tool for new construction or major renovations in almost all commercial and institutional buildings throughout the US. Canada has an almost identical version of LEED,7 which has achieved significant popularity. Since its inception, LEED has proven to be a valuable design tool for architectural teams tasked with creating green buildings, as well as a way to evaluate the final result.
LEED provides for four levels of certification, in ascending order of achievement: Certified, Silver, Gold and Platinum. In 2003 and 2004 three projects in southern California achieved the Platinum rating: one project for a local utility, another for a county park (in cooperation with the local Audubon Society) and another for the Natural Resources Defense Council. By early 2007 the largest LEED Platinum project was the Center for Health and Healing at Oregon Health & Science University, in Portland, at 412,000 square feet. At the same time, more than 500 projects had completed the certification process under LEED for New Construction (LEED-NC). Platinum-seeking projects that are under construction in 2007 promise to extend the size of the top-rated buildings to more than one million square feet.
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