A 270,000-square-foot Cambridge school and community complex will become Massachusetts’ largest-scale net zero emissions project upon completion next year.

Cambridge is doubling down on its environmental commitment by converting its second public school into a “net zero emissions” facility, as the city pursues an ambitious goal of one day transforming all its municipal buildings into largely fossil fuel-free, clean-energy reliant centers. 

Officials will next month celebrate the topping off of the so-called “King Open/Cambridge Street Upper Schools & Community Complex” project, also known as the “King Open” project. 

When the $130 million project is occupied by students, teachers, librarians and administrators in the fall of 2019, the 270,000-square foot facility – comprised of two giant wings connected by glass corridors – will have more than 3,500 photovoltaic solar panels, 190 geothermal wells and array of other energy-efficient technologies and design components intended to reduce the complex’s overall carbon footprint by just over 60 percent.

The rest of its energy needs will be purchased off the electric grid via specific clean-energy contracts signed by the district. Even the complex’s emergency power generator will run on bio-diesel fuels, officials say. 

There will be no fossil-fuel energy connections whatsoever, making King Open the largest net zero emissions (NZE) facility in the state once it opens.

“We’re just excited about finishing and getting the building open,” said Kate Bubriski, director of sustainability and building performance at Arrowstreet Inc., the Boston architecture firm handling the design component of the King Open project.

King Open is the second NZE school project in Cambridge. The Martin Luther King Jr./Putnam Avenue Upper Schools and Community Center project, known simply as the MLK project, was completed in 2015. That $80 million project – which also entailed building a new elementary and middle school complex, combined with administrative offices – has fewer solar panels and geothermal wells than King Open. 

As a result, it produces less on-site renewable energy and it has to purchase more of its electricity from the grid. It does so by buying clean-energy credits via specific contracts, technically qualifying it as a NZE project, said Davida Flynn, a senior project manager at W.T. Rich Co., the lead contractor for both the King Open and MLK projects.

There are multiple definitions of net zero, based on how much onsite renewable energy is produced and if fossil fuel combustion occurs onsite or not.

The differences often come down to the site constraints – how small or large the lots and buildings are in the end. Those and other factors dictate how many solar panels can fit on a roof or how many geothermal wells can be drilled on a site. 

“Ultimately, net-zero emission is impossible to do,” if NZE is strictly defined by a project producing all its clean-energy power on a site, Flynn said. 

In addition, net zero emission buildings can be expensive, with final construction costs running 20 percent to 30 percent higher than for traditional buildings, Flynn said. But those extra costs are offset by huge operating savings achieved through use of renewable energy and energy-efficient equipment, insulation and building designs, she noted. 

 Making Changes on the Fly 

NZE projects have distinct construction challenges. One of them is the pace of change within the solar industry. 

“Every three months or so, there’s a new technological improvement, and (manufacturers) stop making the old (photovoltaic) panels,” Flynn said. “That forces you to make changes in the middle of the process, adjusting your budget and getting the new panels instead.” 

In addition, geothermal wells – whose water is used to help heat and cool buildings – must be drilled every 20 feet or so, leading to drilling in constantly changing ground conditions, whether it’s bedrock or sandy soil, Flynn said. 

“There are so many challenges involved,” Flynn said of NZE projects. 

Rob Blanchard, project executive at Commodore Builders in Waltham, said his firm has never built a NZE building. Commodore is more focused on “passive house” construction, or the building of high energy-efficient and super-insulated structures. But Blanchard can see a day when builders will use both techniques on the same projects, combining the best of both to produce facilities with virtually no carbon footprint. 

“It’s a win for the environment. It’s a win for the owners,” he said.