LEED (Leadership in Energy and Environmental Design) represents excellence in green building design, construction, renovation, and operations and maintenance. This continuously-evolving standard provides a concise framework to measure sustainability in all commercial building types – office, retail, schools or healthcare – as well as tenant improvements and significant retrofits. Two new additions, LEED for Homes and LEED for Neighborhood Development, extend the rating system into communities. On April 27, 2009, USGBC launched LEED Version 3 to incorporate the latest technical advancements in building science while prioritizing energy efficiency and CO2 emission reductions.