Green building rating and certification systems are intended to foster more sustainable building design, construction and operations by promoting and making possible a better integration of environmental concerns with cost and other traditional decision criteria. Different building assessment systems approach this task from somewhat different perspectives, but they have certain elements in common. Most, if not all, deal in one way or another with site selection criteria, the efficient use of energy and water resources during building operations, waste management during construction and operations, indoor environmental quality, demands for transportation services, and the selection of environmentally preferable materials. And they do an admirable job of fostering and facilitating integrated design practices and a holistic approach. In short, the systems generally capture the complicated, web-like relationship between a building’s construction and operations and its impacts on human health and the environment, a relationship that is similar to the complexity of ecological systems in nature where nothing functions or changes without resonating in another part of the system.