In a preliminary vote, the D.C. city council unanimously decided to phase in green building standards that would apply to private as well as public development in the district.

The district is poised to become the first major city in the country to require that private developers build environmentally friendly projects that incorporate energy-saving measures.

By 2012, most large construction in the city — commercial and city-funded residential — would have to meet the standards, if the D.C. council gives final approval to a new bill next month.

Under the bill, within two years, all new district-owned projects, including schools, would have to meet the green standards, and in 2009, any building receiving more than 20 percent public financing would have to do the same. By 2012, every new commercial building over 50,000 square feet — about the size of a medium-size retail store — would have to meet the guidelines. The rules would also apply to affordable housing.

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