He repeatedly talked about how urgent the issue was, but the announcement, reported by The Washington Post, contained few specifics. City officials struggled to answer questions or provide a fuller picture of what was being proposed.
Legislation would set maximum levels of energy that a building could use. For instance, market rate apartment buildings would be permitted to use 50,000 B.T.U.s of fossil fuel per square foot per year. Today, an average apartment building over 25,000 square feet uses from 65,000 to 70,000, according to Michael Shaikh, a spokesman for the mayor’s office. Such buildings would need to reduce their energy consumption by about 25 percent.
Landlords could achieve the energy savings through a variety of means, such as improving steam heat systems, adding insulation, and installing more efficient boilers, water heaters and energy efficient windows.
Mr. de Blasio said that the owners of smaller buildings would be offered low-interest loans. But of larger landlords, he said, “They can handle it.”
Buildings that do not meet the requirement would be subject to fines, based on the size of the building and the degree to which they exceeded the energy use thresholds. A 30,000-square-foot building that substantially exceeded the threshold could be fined $60,000, according to a news release from the mayor’s office.
Of the 23,000 buildings that are larger than 25,000 square feet, officials said that 14,500 are “the worst performing” in terms of energy efficiency, according to the news release.
An inventory of greenhouse gas emissions completed earlier this year showed that 67 percent of the city’s emissions are produced by buildings, through energy used for heating, cooling and electricity.
But there were many uncertainties about the proposal, and the mayor admitted that some elements still needed to be worked out. Among them was how to prevent landlords from passing along the costs of the retrofits to tenants by raising rents, and how the mandate would apply to affordable housing.
Mr. de Blasio said that there was “a high level of alignment” with the City Council on the proposal, adding “We felt this package was ready to go now.”
The message from the Council was different.
“The City Council will continue to explore more comprehensive legislation that will fully address the environmental needs of our city,” Robin Levine, the spokeswoman for Council Speaker Melissa Mark-Viverito, said in an emailed statement. “The mayor’s current proposal simply does not go far enough.”
Costa Constantinides, the chairman of the Council’s environmental protection committee, said that he has long been discussing green building policy with the mayor’s office, but that there were still many aspects of the legislation to resolve. He said that he was taken aback when he was told on Tuesday that the mayor would be making an announcement this week.
“One partner in the dance has decided to dance without us, and that’s his right,” Mr. Constantinides said.
“There’s going to be a robust legislative process here that we will have to go through and we will have to hear from stakeholders,” he added.
Real estate industry officials and local environmental groups said that they also were told about the mayor’s proposal a day or two in advance.
“For this specific issue, there was not prior consultation or an opportunity to weigh in in a meaningful way,” said John Banks, the president of the Real Estate Board of New York, although he said that the group had previously participated in many discussions with City Hall on issues related to sustainability.
He said that his organization, which represents large developers, supported the goal of reducing greenhouse gas emissions, but he said that he was troubled by the lack of detail in the administration’s proposal.