Green buildings are generally assumed to be energy efficient and sustainable. However, such indefinite concepts need to be reduced to measurable criteria to be incorporated into construction documents, contracts and building codes. Although others are being developed, the most widely used green building benchmark is currently the LEED rating system developed by the U.S. Green Building Council.   To receive LEED certification, a project must meet a variety of prerequisites such as minimum energy performance and indoor air quality requirements, and then earn points for achieving specific goals or standards in seven categories. Based on total points earned, the building