large rooftop air conditioning equipment

Natural gas-powered HVAC systems are in Boston officials’ and designers’ crosshairs as they look to slash the commercial real estate sector’s carbon emissions.

Boston Mayor Michelle Wu is proposing that all new buildings larger than 20,000 square feet should emit net-zero carbon from the day they open.

The proposal is part of a package of climate-minded reforms to the Article 37 development approval process released Wednesday. It comes as Wu is also pursuing efforts to ban new natural gas hookups in the city as part of a state-run pilot project. However, the future of that bid is uncertain as it depends on suburban communities being denied entry.

Buildings generate around 70 percent of Boston’s carbon emissions, by the city’s reckoning.

“This initiative ensures that large, new buildings in Boston donʼt come at the cost of our future,” Wu wrote in a cover letter attached to the report recommending the changes.

The proposal comes after two years of public consultations, Wu said. Wednesday’s proposal will also be the subject of a public comment period that lasts until Oct. 28. Comments may be submitted via an online form or to John Dalzell, the BPDA official shepherding the process.

If a newly-designed building can’t meet the net-zero requirement, the proposed zoning reforms lay out three options: Generate renewable electricity on-site with solar panels, purchasing renewable energy from the power grid or pay fines under a framework set up by the city’s BERDO energy-efficiency law.

Unlike the BERDO law, which was recently reformed to push existing buildings to carbon-neutrality by 2050 and include buildings as small as 20,000 square feet in size, Wu’s proposed Article 37 reforms will require new buildings to be constructed to minimize carbon emissions from their building materials, from how the materials get to the construction site and from how the building is built, as well. These aspects of the development won’t need to be carbon-neutral, however. The city is currently working with a group of development teams to pilot mass timber construction in different types of projects city-wide, to offer developers examples of how a promising carbon-reduction technology could be used.

In addition, buildings will all have to meet LEED Gold standards, instead of simply being LEED-certified as current rules require.

Along with their submittals for the development review process, developers will also have to file reports detailing how their proposed building meets the new carbon-neutrality requirements.

Reducing the carbon impacts of new buildings has been a controversial topic in the real estate industry in recent years.

Speaking to members of the Greater Boston Chamber of Commerce at a downtown hotel Thursday morning, Wu cast her package of green-building requirements as a need to “ensure that even if we can make numbers pencil in this moment that it’s not a transient feeling that we’re surviving instead of thriving.”

Studies by the state as part of its own carbon-cutting initiatives show that current rebates for electrically-powered HVAC and water-heating systems make small multifamily buildings cheaper to construct and operate than those with traditional, natural gas-powered systems. But some developers have disputed the notion that those studies can scale up to large multifamily buildings with 50, 100 or 200 units. And energy-intensive lab buildings – which require internal temperatures to remain constant to protect experiments going on inside – have historically been exempted from efforts to shift the real estate industry off natural gas-powered building systems.

Three designs for lab buildings on the city-owned parcel U in Boston’s Flynn Marine Industrial Park offer potential routes for aggressive sustainability designs, potentially pointing the way forward for developers if Wu’s package of climate requirements is approved.

Boston to Developers: Make New Buildings Net-Zero

by James Sanna time to read: 2 min