LEED (Leadership in Energy and Environmental Design) is a green building certification system, the main goal and function of which is to provide contractors, architects, project owners, developers and other representatives of construction sector with tools to implement and identify true ''green'' building standards. It was created by U.S. Green Building Council (USGBC) and began to develop in 1994. Since its inception, LEED has formed a number of rating systems, in cooperation with experts of the field and specially created LEED committees. The pilot version was called LEED NCv1.0. At date, there are nine Rating Systems for the design, construction and operation of buildings, homes and neighborhoods. The 9 Rating Systems are:

1. New Construction & Major Renovations (The LEED for New Construction Rating System is designed to guide and distinguish high-performance commercial and institutional projects, including office buildings, high-rise residential buildings, government buildings, recreational facilities, manufacturing plants and laboratories. Source: USGBC).

2. Existing Buildings: Operations & Maintenance (The LEED for Existing Buildings Rating System helps building owners and operators measure operations, improvements and maintenance on a consistent scale, with the goal of maximizing operational efficiency while minimizing environmental impacts. LEED for Existing Buildings addresses whole-building cleaning and maintenance issues (including chemical use), recycling programs, exterior maintenance programs, and systems upgrades. It can be applied both to existing buildings seeking LEED certification for the first time and to projects previously certified under LEED for New Construction, Schools, or Core & Shell. Source: USGBC).

3. Commercial Interiors (LEED for Commercial Interiors is the green benchmark for the tenant improvement market. It is the recognized system for certifying high-performance green interiors that are healthy, productive places to work; are less costly to operate and maintain; and have a reduced environmental footprint. LEED for Commercial Interiors gives the power to make sustainable choices to tenants and designers, who do not always have control over whole building operations. Source: USGBC).

4. Core & Shell (LEED for Core & Shell is a green building rating system for designers, builders, developers and new building owners who want to address sustainable design for new core and shell construction. Core and shell covers base building elements such as structure, envelope and the HVAC system. LEED for Core & Shell is designed to be complementary to the LEED for Commercial Interiors rating system, as both rating systems establish green building criteria for developers, owners and tenants. Source: USGBC).

5. Schools (The LEED for Schools Rating System recognizes the unique nature of the design and construction of K-12 schools. Based on the LEED for New Construction rating system, it addresses issues such as classroom acoustics, master planning, mold prevention and environmental site assessment. By addressing the uniqueness of school spaces and children's health issues, LEED for Schools provides a unique, comprehensive tool for schools that wish to build green, with measurable results. Source: USGBC).

6. Retail (LEED for Retail is comprised of two unique rating systems, LEED 2009 for Retail: New Construction & Major Renovations and the LEED 2009 for Retail: Commercial Interiors Rating Systems. LEED for Retail is designed to guide and distinguish high-performance retail projects, including banks, restaurants, apparel, electronics, big box and everything in between. Source: USGBC).

7. Healthcare (The full suite of resources for the LEED for Healthcare rating system, including certification functionality in LEED Online, is now available! Project teams have been able to register for USGBC's latest green building rating system since November 2010. LEED for Healthcare guides the design and construction of both new buildings and major renovations of existing buildings, and can be applied to inpatient, outpatient and licensed long-term care facilities, medical offices, assisted living facilities and medical education and research centers. Starting on January 1, 2012 projects that meet the requirements outlined in the Rating System Selection Guide must use LEED for Healthcare. Source: USGBC).

8. Homes (A LEED-certified home is designed and constructed in accordance with the rigorous guidelines of the LEED for Homes green building certification program. LEED for Homes is a consensus-developed, third party-verified, voluntary rating system which promotes the design and construction of high-performance green homes. Source: USGBC).

9. Neighborhood Development (The LEED for Neighborhood Development Rating System integrates the principles of smart growth, urbanism and green building into the first national system for neighborhood design. LEED for Neighborhood Development is a collaboration among USGBC, Congress for the New Urbanism, and the Natural Resources Defense Council. LEED-ND certification provides independent, third-party verification that a development's location and design meet accepted high levels of environmentally responsible, sustainable development. Source: USGBC).

For each of these Rating Systems USGBC developed a “Green” level appraisal method based on 7 Categories (5 base and 2 additional) and granted points:

1. Sustainable Sites (26 possible points)
2. Water Efficiency (10 possible points)
3. Energy and Atmosphere (35 possible points)
4. Materials and Resources (14 possible points)
5. Indoor Environmental Quality (15 possible points)
6. Innovation and Design (6 possible points)
7. Regional Priority (4 possible points)

For each of these Categories there are a different credits (points) for every Rating System. The rated sum of the points for each category is the base for Green building certification Level determination.

There are four levels of Green Certification:

1. PLATINUM (80 points and above)
2. GOLD (60-79 points)
3. SILVER (50-59 points)
4. CERTIFIED (40-49 points)

The highest level in LEED Certification System is the Platinum Award. Platinum Certification requires 80-110 points.

For Certification of Green Building one should submit an application documenting compliance with the requirements of the specified Rating System and pay registration and certification fees. LEED certification is granted solely by the Green Building Certification Institute, which is established by USGBC.