The LEED rating system is a voluntary, consensus-based national system for designing, building, operating and certifying high-performance, sustainable buildings.
LEED defines green building by providing a standard for measurement, and serves as a design guideline to help green designers and builders achieve the positive results they intend. Additionally, the standard prevents false or exaggerated claims of the environmental effectiveness of a building. LEED is also intended to raise green building awareness and establish market value for green buildings with a recognizable national "brand."
The LEED rating system establishes performance goals in five environmental categories:
Energy & atmosphere
Materials and resources
Indoor environmental quality
A sixth category, "innovation & design process," addresses environmental issues such as acoustics, community enhancement and expertise in sustainable design that are not included in the other categories. Buildings earn points in these areas with the goal of gaining LEED certification.
The six LEED categories have 41 prerequisites and are divided into a number of credits that total 69 points. Prerequisites are required for LEED certification and do not receive points. Credits are made up of a variable number of points. Some credits are based on performance levels, while others are based on distinct measures within an overall sustainable concept.
Projects that qualify are awarded a specific LEED certification level based on the total number of points earned by the project. The levels of certification in ascending order are: