From solar panels to LED Christmas lights, Rockefeller Center is at the forefront of making old buildings new through sustainable technology. It was only fitting, then, that today, on Earth Day, Mayor Michael Bloomberg and Council Speaker Christine Quinn would choose one of the center’s roof gardens to announce what he described as the “nation’s most comprehensive plan” to green the city’s existing building stock.

“It will do more than anything to reduce our carbon footprint, the equivalent of making the city of Oakland carbon neutral,” the mayor said. “Making existing buildings more energy efficient is the key to our environmental and economic health.”

Through a half-dozen measures—four laws introduced today in the City Council and two provisions in the mayor’s PlaNYC program—the city could reduce its carbon footprint by 5 percent citywide, moving it closer to the PlaNYC goal of a 30 percent reduction by 2030. Furthermore, it would create 19,000 “green collar” jobs for the workers retrofitting older buildings, save $15 billion per year in energy costs, and, the mayor hopes, serve as a model for cities worldwide. “Just look at the cigarette tax,” Bloomberg said to drive home the point.

With 80 percent of the city’s greenhouse gases coming from buildings, according to PlaNYC data, they present the best opportunity to reduce energy usage. While it seems new LEED-rated buildings are announced almost every day, far more sit idly by, faucets dripping, windows leaking, lights left on.

The new plan is mostly targeted at larger buildings in the range of 50,000 square feet and up. (For comparison, 2 Columbus Circle measures 54,000 square feet.) Under the new legislation, these buildings would have to undergo an energy audit every 10 years to ensure they meet the current efficiency standards. Any that do not would have to make the necessary upgrades. Second, such buildings would be required to make an annual benchmark analysis so owners know exactly how their buildings are performing and where they might improve. And third, for commercial buildings over 50,000 square feet, one area that owners would be required to upgrade when a space is renovated is lighting—which generally accounts for 20 percent of energy consumption and carbon emissions—and would have to meet the city’s most current efficiency standards.

These three measures would be undergirded by the closure of a loophole in the city energy code that requires buildings to be retrofitted only when major renovations are undertaken. Under the new plan, any renovation would be required to meet the modern standards of the code.

While the larger buildings targeted by the city cover only 2 to 3 percent of the city’s area, they account for 45 percent of its energy consumption, Quinn said. It was also suggested that once the bigger buildings are tackled, the smaller ones will follow.

To ensure that the city has the workers to complete all this retrofitting work, the Economic Development Corporation will be setting up a worker training program in conjunction with NYSERDA, a state body that provides grant money for conservation programs. “Everyone’s been talking about green jobs, but this is the program that will actually do it,” Bloomberg said.

Joining him for the press conference were leaders of top labor unions, whose workers would obviously benefit from the program. “Our workforce is up to the hard job of de-carbonizing the city’s skyline,” said Jack Ahern, president of the New York City Central Labor Council.

One group that is apprehensive about the program is the city’s developers and building owners. “My members all want to make sure we have a green city and green buildings,” Stephen Spinola, president of the Real Estate Board of New York, said in a telephone interview after the event. “But the thing is, we don’t want to be stuck with something that doesn’t work.” Spinola said that he had been working with the mayor on the program for the last year, and hoped that any major differences could be ironed out.

Acknowledging the difficulties of the current economic climate, the administration has set aside $16 million of stimulus funding to be used in a revolving loan program to help finance the required energy improvements. This, along with the other five pieces of the program, would go into effect between 2010 and 2013, though the mayor emphasized that the program “pays for itself” and hoped building owners would begin immediately.

Carl Pope, president of the Sierra Club, said he wished his home state of California had come up with the plan, though he admitted the program would probably make its way out there through the city’s example. “New York City will create the marketplace for energy-efficient technology for the next 50 years in this one single act,” Pope said. “I don’t think we appreciate how drastically this will change the way Americans use energy.”

Today also marked the second anniversary of PlaNYC, and with it the release of its annual progress report (PDF). The mayor cheerfully announced that 85 of its 127 initiatives were on or ahead of schedule.