Pittsburgh has one of the largest environmentally friendly buildings in the world, but until yesterday had no city incentives for green construction.

That put it behind many cities -- from Calabasas, Calif., to Morgantown, W.Va. -- that reward or require eco-friendly building design.

Yesterday, City Council played catchup with the approval of one green building incentive and the introduction of another.

"I want to put together an entire green agenda for Pittsburgh so that our city is known as one of the leading examples of sustainable development," said Councilman William Peduto, author of two bills that he says would do that.

The bill he introduced yesterday would require that any large project involving new construction or renovation undertaken by the city get a green-building rating of silver. Any private development backed by a city tax-increment financing subsidy would also have to get the rating.

Silver is the third-highest rating in the nonprofit U.S. Green Building Council's Leadership in Energy and Environmental Design, or LEED, system. The requirements for a silver rating are less stringent than for platinum and gold but ahead of a basic LEED certification.

Buildings get points toward their rankings based on demolition waste disposal, energy and water efficiency, access to public transportation, use of nontoxic materials, and more. Accredited professionals charge fees to determine building ratings.

The David L. Lawrence Convention Center, Downtown, at one point laid claim to being the largest building in the world to attain the rank of gold under the LEED system. Holding silver ratings are PNC Firstside Center, Downtown; the Greater Pittsburgh Community Food Bank in Duquesne; and Carnegie Mellon University's New House Residence Hall, in Oakland. Two other buildings have the basic certification.

Under Mr. Peduto's legislation, any new or renovated city fire station, recreation center or public works shed would have to reach at least the silver ranking, and so would anything built by private developers seeking tax-increment financing, or TIF. That's a tool the city uses once or twice a year in which government borrows money to aid a development, then pays off the debt using most of the new taxes it creates for as long as 20 years.

TIF is usually reserved for big projects, like the $113 million Bakery Square development in Larimer that is seeking a $10 million subsidy. Council yesterday postponed a vote on that TIF, citing union concerns about inclusion of a nonunion hotel.

Bakery Square is aiming for a gold rating, said Todd Reidbord, of developer Walnut Capital Partners. He views environmental features as keys to attracting discriminating tenants.

He called city incentives for environmental design "a decent idea," but said he's "not 100 percent convinced that public financing should be tied to a private rating organization."

There's debate in the legal community about whether private ratings should affect public processes, said George J. Mongell, a real estate attorney at Washington, D.C.-based Covington & Burling who advises on green projects. Using the private U.S. Green Building Council's ratings "is really the way it goes" in most cities adopting legislation. A few, including Chicago, have written their own standards.

He said it's important to have some city incentive, noting that studies show going green adds as much as 2 percent to the cost of a new building.

Some cities allow green buildings to be larger, as council did yesterday with a final vote on Mr. Peduto's legislation allowing certified structures to be 20 percent taller than others in their zoning districts.

Others tie subsidies or speedier permitting to green ratings. Others just say that if you want to build in their jurisdictions, you have to build green, whether you're getting a subsidy or not.

Washington, D.C., demands that any new construction of more than 50,000 square feet be certified under LEED rules.

Little Calabasas, Calif., a city of 23,123, requires that any new building larger than 500 square feet be certified, and anything bigger than 5,000 square feet must get the silver rating.

For more than a year, Morgantown has required that anything larger than 10,000 square feet built by the city for its own use reach the basic certification.

Mr. Peduto's legislation most closely resembles Atlanta's. Both require that all new city-owned buildings of more than 5,000 square feet, or costing more than $2 million, be rated silver. The need for public hearings could put off a vote until next year.