What is LEED?
Leadership in Energy and Environmental Design (“LEED”) certification, which was developed and is administered by the United States Green Buildings Committee (“USGBC”), is an internationally recognized voluntary green building certification system that provides third-party verification that a building or community was designed and built using strategies aimed at improving performance. The "seal of approval" is aimed at “encourag[ing] and accelerat[ing] global adoption of sustainable green building and development practices through a suite of rating systems that recognize projects that implement strategies for better environmental and health performance.” The LEED rating system weighs and considers a building's contribution to energy savings, water efficiency, CO2 emission reduction, improvement in indoor environmental quality, and stewardship of resources.
LEED ratings are for green building projects as a whole. While individual products can contribute to points to a project, specific products do not gain LEED certification. Some LEED criteria do, however, require specific product data as a part of a successful submittal.
Participation in the LEED program was designed to be voluntary and can be applied to any building type at any construction phase, although in recent years this program has been used as part of the building code and permit process and thus being made more mandatory as discussed below. The program recognizes performance in five key topical areas including: Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, Indoor Environmental Quality, Awareness and Education, Innovation in Design, and Regional Priority. LEED certification guidelines are available for all building types, including: new construction and major renovation, existing buildings, commercial interiors, core and shell, schools and homes.
Points are awarded on a basic 100-point scale and credits are weighted to reflect their potential environmental impacts, with additional bonus points available. Four of the bonus points are designed to encourage design teams to focus on regionally specific, priority environmental issues. All LEED credits are worth a minimum of one point. Each credit “receives a single, static weight in each rating system [and] there are no individualized scorecards based on project location.”
The USGBC provides features for support of for builders who choose to work with the rating system, including reference guides, instructor-led workshops and online courses. The LEED program and resources give building owners, operators, and developers the tools they need to have an immediate measurable impact on their building's performance. In addition to building owners, professionals within the industry that use this system including architects, real estate professionals, facility managers, engineers, interior designers, landscape architects, construction managers, lenders and government officials.
For commercial building projects, LEED is the leading (no pun intended) green building rating program within the U.S. Generally, people seeking a "green certification" for a residential project will research the available certifications in their area that corresponds with their specific goals. There are more than 70 highly regarded local or regional green home building programs in the United States. Each of these programs is unique and offers different specifications and requirements. LEED is different from these regional programs because it is a national program that takes into account regional considerations.
How Rating Systems are Developed
These rating systems are developed through an "open, consensus-based process" led by LEED committees. Each committee is comprised of diverse practitioners and experts representing an array of individuals in the building and construction industry. Also, within this committee structure, there are technical advisory groups that ensure scientific consistency and rigor, opportunities for stakeholder comment and review, member ballot of new rating systems, and a fair and open appeals process. 
There are several LEED rating systems that have been developed based upon building type and project. For example, USGBC launched an significant revision to the LEED programs in 2009, which included an upgrade to certifications for New Construction Projects. This particular rating system is intended to distinguish high-performance commercial and institutional projects, including office buildings, high-rise residential buildings, government buildings, recreational facilities, manufacturing plants and laboratories. The system lists the intent, requirements, technologies, and strategies for each credit available.
Attached to each rating system is an Addendum which lists changes to the rating system. Each project attempting certification under their particular rating system is required to adhere to any changes located in the addendum based upon the registration date of project. These updated requirements allow for the programs to be kept current with technological developments and provide a structure for attaining any specific regional benefits.
New versions of LEED green building certification systems are being launched periodically to keep the rating systems current with technological advancements. In the latest version launched in 2009 (referred to now as LEED-2009), there were three technical advancements: (1) LEED prerequisite/Credit Alignment and Harmonization, (2)Transparent Environmental/Human Impact Credit Weighting, and (3) Regionalization. The additions provide the opportunity for developers to obtain additional credits for identifing and taking action to prevent regional environmental issues. While projects certified under a previous version of LEED are not required to upgrade to the 2009 version, they are encouraged to do so and have the option to do so at any time.
New rating systems are currently in the testing stages. These new programs look to things such as systems for neighborhood development, retail, and healthcare. Additionally, USGBC has partnered up with The American Society of Interior Designers' Foundation to launch REGREEN, the nation's first green residential remodeling guidelines. The USGBC continue to develop and provide guidelines for new innovations and design principles.
How are the LEED Rating Systems Being Used
As mentioned above, the primary usage, and original intent of the developers, for the LEED program is through the voluntary rating of a building project. However, some localities have added a requirement to obtain LEED certification part of their building permitting and code enforcement, thus making this a mandatory program in those situations. Recent developmentsin the U.S. have created standards that are written with the intent of adoptionas part of local building codes, such as the International Green Construction Code (IGCC), created by the International Code Council (ICC), and ANSI Standard 189.1-2009 created by a partnership between the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE), the USGBC and the Illumination Engineering Society (IES). Standard 189.1 is an alternate compliance path for the IGCC.
The LEED programs have been modified for use in several countries across the globe, including India. Other countries have developed their own programs that are similar to LEED as well.
1^ USGBC - What LEED Is - www.usgbc.org
3^ USGBC - What LEED Is - www.usgbc.org
4^ USGBC - What LEED Is - www.usgbc.org
5^ 2009 LEED For New Construction and Major Renovations xiii.
6^ LEED 2009 for New Construction and Major Renovations Rating System 85
7^ LEED 2009 for New Construction and Major Renovations Rating System xii
13^ USGBC.org - FAQs
14^ USGBC.org - FAQs
15^ USGBC.org – LEED v3 FAQs
16^ LEED 2009 New Construction and Major Renovations xiv.
17^ USGBC - Addenda