In December, world leaders came to Paris with an ambitious task: cut global carbon emissions to prevent the worst of climate change. They succeeded in reaching a historic agreement.

The United Nations has held international climate talks each year for more than two decades, but for the first time, this year, the official schedule included a “Buildings Day”­—a meaningful if symbolic nod to the construction community. At the center of the COP21 conference—the 21st Conference of the Parties to the United Nations Framework Convention on Climate Change—negotiators from nearly 200 nations hashed out a deal setting targets for each country to reduce greenhouse gases.

Past summits have largely ignored sustainable urban design and green construction. But diplomats have been increasingly acknowledging the role of businesses and cities in tackling climate change.

“People are getting it now,” said Elizabeth Beardsley, a senior policy counsel for the U.S. Green Building Council (USGBC) in Paris for the talks. “Finally, we are seeing focus on buildings as part of the answer.”

Host country France, the United Nations Environment Programme (UNEP), World Green Building Council, Architecture 2030, and other bodies organized the official Buildings Day, which centered mostly on panel discussions. The day also served as a launchpad for a series of novel initiatives, including a new Global Alliance for Green Building and Construction. Green building councils used the conference to create a “Build Better Green” campaign, setting fresh commitments to renovate existing buildings, certify just-finished green buildings, and train building professionals.

“It is really going to be the best and fastest way to get short-term improvements,” said Beardsley of the initiative.

The Intergovernmental Panel on Climate Change says that designing energy-efficient buildings is one of the most cost-effective ways to cut back on emissions. Buildings account for about a third of all energy used worldwide and for a fifth of energy-related greenhouse gases, according to the scientific panel (other estimates are as high as a third). Those emissions could double or triple by midcentury, as cities expand and the world’s population rises.

The growing awareness of buildings’ role in climate change was evident in nearly a quarter of the voluntary climate plans prepared by countries attending the summit. But only one in 10 detailed concrete steps for improvement, according to an analysis by the World Resources Institute.

The presence of construction-sector representatives—from architects with booths in the business pavilion to members of green building councils crossing paths with national delegates—sends a signal to the global community that the technologies exist, suggested Jennifer Layke, the director of the building efficiency initiative at the World Resources Institute in Paris.

“If a [delegate’s] business community is here from their country saying, ‘We have solutions,’ that matters to how ambitious they feel,” said Layke. “There’s a critical role for negotiations, and there’s a critical role for how we deliver on those goals, and that’s where buildings are really important.”

Rallying these actors—investors, mayors, and construction firms—helped advance that argument, more so than top-down diplomacy, she said. Other discussions focused on topics including how cities could engage multiple stakeholders or how they could incorporate building energy efficiency into lasting sustainability plans.

Technology displays and presentations outlining waste strategies were meant to inspire private design firms, but a major group of stakeholders did not come to Paris. Rives Taylor, a principal at Gensler, had gone to the city to connect with potential clients, and was disappointed in what he saw as a poor showing of private developers. “The ‘how to’ seems to be coming at the city scale instead of at the individual building scale,” he said. “It tended to be more academic, less practitioner-oriented.”

While Building Day was a promising step forward, buildings are not explicitly mentioned in the international deal. Countries agreed to a goal of limiting global warming to 1.5 degrees Celsius, giving markets a strong signal to pursue a low-carbon future. But the countries’ construction promises are nonbinding, and financing remains a key barrier to major building retrofits, especially in developed countries.

But on-the-ground changes will come from elsewhere, suggested Taylor: “It takes us, the design leaders, to be the coordinators of many different things beyond on-time design and construction,” he said. “Manufacturers, transportation, even city utilities are getting it. The building industry needs to get there.”