Green initiatives are saving the city’s school district $295,738 a year but getting blame for more than doubling the price of renovating its Putnam Avenue campus, to $76 million from $33 million.

The first thing is true. The second is an unfair rumor, said school officials at Tuesday’s meeting of the School Committee’s building and grounds subcommittee, which was turned over mainly to a report on environmental efforts overseen by district sustainability manager Kristen von Hoffmann.

“It looks like you have a job for life,” Mayor Henrietta Davis told von Hoffmann, who began her work with the district in November 2010 after moving to Cambridge four years earlier upon graduation from Yale. She has helped install energy-saving equipment, including high-efficiency boilers and lights that stay on only while people are in the room, added recycling and composting programs and even replaced cleaning products that aren’t environmentally friendly.

Her successes by individual projects — such as decreasing electricity use since last year at 11 district properties, ranging from 2 percent at the Peabody School to 52 percent in the Longfellow building — also had district chief operating officer James Maloney joking that maybe von Hoffmann could be paid “on a commission basis.”

In acknowledging their appreciation, von Hoffmann stressed that it had all been done with partners, including with the city’s Public Works, school facilities department and even students.

She and the subcommittee members ran through some ways in which students can be even more engaged, including putting a school’s green efforts into its own math and science curriculum (the King school is a leader in that, Davis said), and agreed to look at how the entire community could be made aware of the work done in the district — starting with the Green Heroes certificates von Hoffmann hands out every couple of months. “I think there’s an appetite for this in the community,” said subcommittee head Patty Nolan, suggesting von Hoffmann’s own report could be presented more widely. “I feel like we’ve got a great story here.”

Some student-driven initiatives pay off. It was roughly two years ago that King Open students complained to the City Council that its composting program was meant to be expanded into other schools, and now von Hoffmann is able to report that while King Open remains a leader, at 20 tons of food scraps kept out of the trash through April, it has been joined in the “Food to Flowers” effort by five other schools.

Some student-driven initiatives are problematic, though. The “bioware” compostable containers and plates wanted by the same group and now used in the Cambridge Rindge & Latin School cafeteria cost rather than save money, with some products costing twice as much as nonrecyclable wares. Trays, the cheapest of the products, are still 30 percent more expensive than conventional cafeteria trays, von Hoffmann said, although the cost of all the products have come down in the past few years and are likely to come down further.

While a cost-crunching is needed, including the time and pay of those who would do the washing, the high school could go back to using traditional flatware, Maloney said.

The cost of campus renovations

Some, though, were focused on that much bigger suspected cost of going green: campus renovations. Parent subcommittee member David De Celis raised the issue as a rumor going around especially among “Innovation Agenda naysayers” since it became known the estimate for design and construction at Putnam Avenue was jumping to $76 million. Maloney said he’d heard the rumors, and agreed “a lot of it is” related to sustainability; Davis acknowledged that installing solar panels on the roof might cost some $7 million.

But the officials noted that the budgets for the renovations and Innovation Agenda, which created the four upper schools to open Sept. 4, are unrelated — that schools built up to six decades ago will need to be refreshed, just as the high school was renovated over the past few years for $112 million. “Many of these buildings we would be doing something with anyway,” Nolan said. In addition, “We the School Committee have a commitment to sustainability practices dating back to 2007, and that followed on city goals that were passed long before that.”

The city has adopted policies that require all large construction to be green and energy efficient.

In light of that, Maloney said, “we could have a discussion as to whether the original estimate was on board if you compare the square footage of that building with, say the library, police station or something else [that’s been recently renovated], but there’s no cost overrun.”

“It surprised me that a number was put out at all,” considering the building is still in the early stages of design, parent member Bill Boehm said.

Apples to apples impossible

Asked after the meeting if she could make an apples-to-apples comparison to another local school, Nolan said the closest she could come — barring specific, unknown site conditions — might be the Thompson School in Arlington, which is getting a new building this year for $20 million for a student population of 380.

“Since our building on Putnam will have two schools, King Elementary with about 300 kids and a middle school with about 300, a cost of $76 million seems high, based on the Thompson school comparison,” she said. “A reasonable comparison would be $40 million.”

Boehm, an architect specializing in recycling buildings, said the city might be able to lower the costs of renovation and more easily meet its green goals by doing a “rehabilitative reuse” of the site instead of tearing it down for an all-new structure. “The greenest thing you can do with buildings is recycle them. We should go into projects with the assumption we’re going to recycle the building and only don’t do it if we find out there’s some reason it’s impossible,” he said. “When you calculate the embodied energy that goes into the existing building and then the energy to destroy that mass and to create a new building, the calculus says it’ll take you between 10 and 80 years depending on your building type to repay your energy budget and be green again.”

The school officials suggested putting Boehm in touch with the architects working on the Putnam Avenue campus, which is getting the first of three renovations in the district.

They also intend to seek discussion on laying out safe and environmentally sound routes to schools for students and teachers — minimizing the risk of students who ride bicycles and encouraging adults to leave their cars at home. Parking is in short supply at most campuses, making it hard to fulfill a traditional drivers’ attitude: “People who drive their cars feel like they’re supposed to be able to park in their classroom,” committee member Alice Turkel said.