The U.S. Green Building Council is launching its LEED for Existing Buildings rating system. Independently, San Francisco’s green building ordinance went into effect recently. To date, 10 cities require LEED certification for their public buildings, says Washington, D.C.-based USGBC.

The San Francisco ordinance, in effect since September, applies to all city-owned building projects, including renovations and additions. It requires that projects achieve at least a Leadership in Energy and Environmental Design silver certification–the minimum. Gold and platinum ratings top silver.

The long-term goal, once everyone gets the knack of complying with LEED on city projects, is to have the ordinance extended to cover private projects, says Gloria Chan, public information officer for the city’s Dept. of the Environment.

We are pleased that the political leadership...has committed to attaining a silver LEED certification rating for its own buildings," says Gordon H. Chong, founder of the local Chong Partners Architecture. "Placing this demand on its own buildings is clearly leading by example."

LEED for Existing Buildings was developed from a pilot project, started in 2001, that included 99 buildings containing 31.5 million sq ft of space. Of these, 28 were in the U.S., two in provinces in Canada and others in Brazil. Of these, five LEED-EB certifications have been issued. More will be announced at USBDC’s Greenbuild International Conference and Expo, Nov. 10-12 in Portland, Ore., according to USGBC.

LEED ratings for schools, homes, core and shell, neighborhoods and hospitals are in the pipeline. LEED is a "feature-oriented," not a prescriptive, rating system for buildings, say its founders.