“Overall, we were heartened when those commitments were made,” said Anastasia Nicolaou, government affairs associate at NAIOP Massachusetts.

However, NAIOP Massachusetts, as well as the Greater Boston Real Estate Board, two groups that represent major developers and the many of the firms that work with them, say they have major reservations about a specific provision in the bill they contend would drive up construction costs and make development much costly and difficult.

In particular, a provision in the newly passed NextGen Roadmap bill would enable individual cities, towns and suburbs to mandate tough, net-zero-energy building codes could hurt construction and development at a time when the economy remains shaky, they say.

The rules are needed because “projects and buildings municipalities approve for construction this year will still be up and going strong in 2050, when the entire economy of Massachusetts, in all its aspects, must put out "net zero" emissions,” said State Sen. Mike Barrett and Rep. Thomas Golden, both Democrats and the chairs of the Legislature’s climate change committee, in a statement. “So we give the force of law to the creation of a 'net zero stretch energy code'."

Yet for developers, achieving net-zero emissions in new office or other commercial buildings is “rarely achievable,” especially when it comes to structures more than 10 stories, Nicolaou of NAIOP Massachusetts contends.

While some legislators have argued that a wave of new solar-power construction could help make net-zero a reality, Nicolaou is skeptical there is currently enough clean energy to fulfill demand.

“Carbon reduction is increasingly important – we just need to ensure we get there in a practical and feasible way,” she said.

The goal could drive up construction and maintenance costs, seriously undermining the feasibility of large-scale commercial or residential projects.

“Net zero increases the cost of construction … current rents would not be able to cover the increases,” Nicolaou said. “It could have the effect of driving our innovation economy right out of the state.”

Meanwhile, the relatively broad and ambiguous wording of the net-zero energy provision also has the potential to cast a large degree of uncertainty over development projects currently under review by local officials, or getting ready to start the review process, Nicolaou said.

The bill leaves it up to the state Dept. of Energy Resources to develop the new, net-zero energy stretch code, which could then be adopted by individual communities.

But as it stands now, there is no definition yet of what net-zero energy will mean in practical terms, or to what types of buildings it would apply to.

And while the tough new energy code would not go into effect unless it is adopted by various cities and towns, officials in Boston, Somerville and Cambridge, where the lion’s share of construction in Eastern Massachusetts takes place, wrote letters of support for the new legislation, Nicolaou said.

“Any project currently being planned or designed anywhere in Massachusetts will have to seriously consider moving forward without knowing what requirements will be in place,” she said.

Greg Vasil, president and CEO of the Greater Boston Real Estate Board, expressed similar concerns.

There will be an impact with process and there certainly will be an impact with costs,” Vasil said. “Everyone recognizes the need to do something with climate change,” Vasil said, calling it a “balancing act.”

Local communities that go beyond the state building code and implement net-zero requirements could force some developers who had planned on building more affordable workforce housing to instead focus on luxury units.

A project, for example that previously would have cost $400 to $500 a square foot to build, might cost $525 a square foot.

“These codes can be onerous and can really drive up costs,” Vasil said.

Gov. Charlie Baker (R) released his own plan this week that would cut emissions by a sizable but slightly smaller 45% over the same time period.

Officials in Baker’s office have said the governor is reviewing the climate change bill passed by the state’s Democratic-controlled legislature, and have not indicated either way whether he will sign it.

Meanwhile, both development and real estate groups said they will also be keeping a close eye on new rules proposed by Boston officials to deal with another facet of climate change— more frequent flooding as sea level rise.

The Boston Planning and Development Agency is pushing a plan for an overlay zoning district that could cover parts of the city that are increasingly prone to flooding.

New projects bigger than 20,000 sq ft, in turn, would have to go through an additional step in the city review process, one that would require developers to make design changes or take other measures to deal with potential flooding.

“It’s understandable why the review has to take place,” Vasil said. “The real catch is how it works practically and how it affects construction costs and what they market will bear and no bear in terms of those costs.”

Lawmakers also sent a $16.5 billion transportation bond bill to Baker's desk. The bill authorizes billions of dollars in bonds for highway and bridge maintenance, train modernization, and major capital projects such as an MBTA Red Line-Blue Line Connector and the extension of commuter rail service to the South Coast. It also funds the approaches to the two Cape Cod bridges.