Diane Landis was in a meeting with Mayor Liz Lempert Monday when the good news came through in an email: Princeton has been awarded silver level certification by Sustainable Jersey, the statewide non-profit organization that helps communities become more energy efficient and less wasteful.

“It’s very exciting,’” said Diane Landis, the executive director of Sustainable Princeton, speaking before Ms. Lempert announced the news at Monday night’s Princeton Council meeting. “A lot of effort has gone into this. It’s been a real collaboration between us, the different municipal departments, and Sustainable Jersey.

“It means that we are moving in a coordinated fashion as a town to address sustainability in different departments of the municipality,” she continued. “We are in good company. There are a number of municipalities that have received this certification in New Jersey. It has really grown. It’s so important to keep moving on the initiatives so we can stand out and have the kind of town we want.”

At the Council meeting, Ms. Landis said 160 communities across the state earned certification. Princeton is one of 27 to attain the silver status.

The town’s forming of a “municipal green team” last October was key in helping Princeton move from bronze to silver certification. A total of 350 points are needed to secure the designation, and Princeton submitted 420 points. “We were approved for 34 actions in 19 different categories,” Ms. Landis said. “These actions can range from forming a municipal green team to having a tree inventory, or a fleet inventory [of vehicles].”

The team met the submission deadline in September. It was reviewed by Sustainable Jersey and sent back for revisions. “We had to redo about 100 points,” said Landis. “It’s very technical. We had to do things like go and take a photo of the drop box at the police department where you can put the old drugs; stuff like that.”

The process has also been helped by changes in attitude by the public. “Since we applied for the bronze level three years ago, there is much more interest in sustainability,” Ms. Landis said. “People are really seeing through the lens of being sustainable, and that’s helped us move our agenda forward. We’re not asked so much anymore, ‘Why should I do it?’ Instead, it’s ‘How do I do it?’ ”

Sustainable Princeton is housed in Monument Hall, formerly known as Borough Hall. The non-profit organization got $15,000 in funding from the town last year, Ms. Landis said.

Ms. Lempert was elated by the news of the silver level. “This is not a trivial process,” she said Monday afternoon. “For each level, you have to do a substantial amount of documentation, which Sustainable Jersey helps us with. We got credits for several things, like the Farmer’s Market in Hinds Plaza. It’s another way for us to learn from other communities and for them to learn from us about best practices.”