The proposed 11-21 Bromfield St. office building in downtown Boston will be a "net zero carbon" building, its developers promise, in part thanks to the purchase of carbon credits. Image courtesy of Arrowstreet

Almost a month after Gov. Charlie Baker returned sweeping climate legislation to lawmakers with a series of recommended amendments, House Speaker Ronald Mariano said he’s willing to work with the governor on some technical changes but will “not back down on our ambitious emissions reduction targets.”

The bill – which the House and Senate passed for the second time in January after Baker rejected a version sent to him in the final days of the last legislative session – proposes to lock the state into its goal of achieving net-zero carbon emissions by 2050, set interim emission reduction targets, establish appliance energy efficiency standards, authorize additional purchases of offshore wind power and codify protections for environmental justice communities, among other measures.

The real estate industry has raised significant concerns around the creation of an opt-in municipal stretch energy code and energy reduction targets for the commercial real estate sector, arguing that they could dramatically increase construction costs and thereby reduce housing construction. The only “net zero carbon” building proposed in Boston right now – Midwood Investment and Development’s 11-21 Bromfield St. – will rely on purchasing renewable energy and carbon credits to achieve this status, according to a filing with city development officials.

Baker’s amendments (S 13), which have been before the Senate Committee on Bills in the Third Reading since Feb. 8, address topics including the proposed new energy code, the 2030 greenhouse gas emissions reduction target, and the sector-specific emission reduction sublimits proposed by the legislature.

“Nothing substantive will change in this bill,” Mariano said Thursday on WBUR’s Radio Boston.