Green building or bioclimatic building is the practice of increasing the efficiency with which buildings and their sites use and harvest energy, water, and materials, and reducing building impacts on human health and the environment, through better siting, design, construction, operation, maintenance, and removal — the complete building life cycle.
Green building is also sometimes known as "sustainable building" or "environmental building", although there are slight differences in the definitions. The practice of green building can lead to benefits including reduced operating costs by increasing productivity and using less energy and water, improved public and occupant health due to improved indoor air quality, and reduced environmental impacts by, for example, lessening storm water runoff and the heat island effect.
Green building is an essential component of the related concepts of sustainable design, sustainable development and general sustainability.
Practitioners of green building often seek to achieve not only ecological but aesthetic harmony between a structure and its surrounding natural and built environment. The appearance and style of sustainable homes and buildings can be nearly indistinguishable from their less sustainable counter-parts.
Green design often emphasizes taking advantage of renewable energy and resources, e.g., using sunlight through passive solar, active solar, and photovoltaic techniques and using plants and trees through green roofs, rain gardens, and for reduction of rainwater run-off. Many other techniques, such as using packed gravel for parking lots instead of concrete or asphalt to enhance replenishment of ground water, are used as well.
The U.S. Green Building Council has developed definitions of what constitutes sustainable design of green buildings through the Leadership in Energy and Environmental Design or LEED ((R) USGBC) green building rating system. USGBC has attracted over 7,000 organizations as members to date. The U.S. Green Building Council maintains a list of state and local green building programs and initiatives in the U.S.
The Green Building Initiative  is a non-profit network of building industry leaders committed to bringing green to mainstream residential and commercial construction. The GBI believes in building approaches that are environmentally progressive, but also practical and affordable for builders to implement. The GBI has developed an easy to use, inexpensive and ANSI standard web-based rating tool called Green Globes.
The United States Environmental Protection Agency's EnergyStar program rates commercial buildings for energy efficiency and provides EnergyStar qualifications for new homes that meet their standards for energy efficient building design.
In 2005, Washington became the first state in the U.S. to enact green building legislation. According to the law, all major public agency facilities with a floor area exceeding 5,000 square feet (465 m²), including state funded school buildings, are required to meet or exceed LEED standards in construction or renovation. The projected benefits from such a law are
- 20% annual savings in energy costs
- 20% reduction in water costs
- 38% reduction in waste water production
- 22% reduction in construction waste