It’s winter in Brooklyn, but inside my sixth-floor apartment it might as well be July.

Like many New Yorkers, I can’t control the heat in my unit: Clanging pipes bring it up from the gas-powered boiler on the ground floor whether I’m cold or not. I spend much of the season in shorts with the windows open.

Multiply this scenario throughout the five boroughs and you start to understand why buildings are one of New York City’s biggest climate mitigation challenges – in fact, they’re responsible for about 70% of its greenhouse gas emissions. When we talk about climate-friendly architecture, we’re usually referring to state-of-the-art new buildings. But in much of the world, existing buildings offer more carbon-cutting potential.

“Most of the buildings that will be occupied and operating in 2040, 2050 – the time when we have really aggressive climate goals for reducing energy and carbon emissions – are already here. People are living and working in them as we speak,” said Jennifer Amann, buildings program director at the nonprofit American Council for an Energy-Efficient Economy. “That’s where there is the biggest opportunity for savings.”

A new focus on old buildings

In the U.S., local governments are increasingly taking on the issue. Existing buildings are at the heart of New York City’s Climate Mobilization Act, a package of legislation passed in April 2019 that aims to reduce the city’s emissions 30% by 2030. Its cornerstone, Local Law 97, sets emissions caps for buildings larger than 25,000 square feet – about 50,000 buildings in all. Officials expect the law to reduce large buildings’ emissions 40% by 2030 and 80% by 2050.

Local Law 97 projects that owners will meet their targets by making energy efficiency upgrades and/or decarbonizing their energy supply; the city is also exploring options for carbon trading. Owners who fail to bring emissions within established limits by the target dates (2024 for the worst-performing buildings, 2030 for the rest) are subject to fines of hundreds of dollars for each excess ton of carbon released.

Similar laws have recently been passed in other parts of the country, although the language and focus vary somewhat from place to place. In late 2018, Washington, D.C., approved a policy requiring that buildings over 50,000 square feet address their energy performance. Washington State adopted legislation targeting large commercial buildings.

And more is to come. Within the past year, Boston and Los Angeles have promised to craft performance requirements for existing buildings; Seattle is reportedly working on its own plan. San Francisco has pledged to transition large commercial buildings to 100% renewable energy and to create a decarbonization initiative for both new and existing buildings.

Policy precedents

“This wave of activity is very exciting,” says Amann of the American Council for an Energy-Efficient Economy, “because we don’t have the same kind of tools to address existing buildings’ efficiency and their contribution to climate change that we have for new construction.” Climate policies targeting building emissions have tended to focus on new construction simply because it’s easier, she said: Once a building is purchased, owners often consider it their right to do whatever they want with it. In the past, some have balked at making retrofits to comply with federal laws as some have done, for instance, with the Americans with Disabilities Act.

Amann stressed, however, that the new laws didn’t come out of nowhere – instead, they build on various government programs targeting different aspects of existing buildings. Building codes, for example: Adopted by state or local governments, many codes mandate energy efficiency upgrades during major renovations, particularly for commercial structures.

The federal government’s appliance and equipment standards program, launched in the wake of the 1970s energy crisis, has also helped improve building performance. This program, which focuses on increasing the efficiency of dishwashers, air conditioners, and the like, has helped existing buildings conserve energy by making it easier for owners to replace aging equipment with better-performing models. (The Trump administration has taken steps to weaken efficiency standards, however.)

Another important precedent involves energy benchmarking and disclosure legislation, which a number of U.S. cities have enacted within the past decade. These programs track and report the energy use of buildings across a city, helping owners and government officials understand how much energy individual structures consume compared to their peers.

Diverging trends – commercial and residential

According to Carolyn Sarno, director of buildings and community solutions at the nonprofit Northeast Energy Efficiency Partnerships, building performance regulations like those now seen in New York and D.C. are the logical next step after benchmarking and disclosure. “We’ve had a couple of cities that have these benchmarking policies that are now looking at, ‘OK, we have this data. What do we do with it next?’” she said.

But while many cities are interested in reducing existing building emissions, not all are following the benchmarking-to-performance-regulation trajectory, she said. In fact, efforts to pass commercial building benchmarking requirements have failed in a number of cities and states. A number of smaller cities are choosing to focus instead on residential property labeling, which provides a standardized system for communicating about the energy use of private homes.

Residential labeling programs have the political benefit of more directly touching the lives (and wallets) of average citizens. For current homeowners, some labeling programs offer incentives and rebates for energy audits, which could ultimately lead to lower bills. For would-be buyers, labeling provides transparency around a home’s energy costs.

But the primary reason that smaller cities are considering residential labeling instead of benchmarking and performance laws, Sarno said, is that the latter are seen as too heavy a lift. “There’s a lot of time, energy, resources, and stakeholder engagement that go into developing one of these policies. And quite frankly, a lot of states, a lot of communities, do not have the necessary resources to develop such a policy and implement that policy.” Instead, they see residential labeling as a manageable way to start tackling existing building emissions while they wait to see how building performance legislation plays out elsewhere.

Peer-to-peer assistance, and value of precedence

Mark Chambers, director of the New York Mayor’s Office of Sustainability, points out that Local Law 97 has implications beyond the five boroughs. Chambers and his staff maintain strong ties with their peers in other cities, particularly through networks like C40 and the Carbon Neutral Cities Alliance. These officials are watching Local Law 97 closely; if it’s successful, they could be more inclined to make the case for similar policies in their own communities. “There needs to be precedent, and there needs to be the ability for us to de-risk other cities pushing on this,” Chambers said.

Potential benefits: jobs, more satisfied tenants, lower operation and maintenance costs

He said early adopters like New York City could also help others overcome the common challenge of insufficient data about their buildings’ emissions. “Places that may not have existing benchmarking laws are going to have a slightly harder time making a defensible strategy for how they’re setting (emissions) caps,” Chambers said. But he said municipalities that have already followed the benchmarking-to-performance trajectory can assist. “We can use predictive analytics and modeling to get very, very close to understanding what these buildings’ performance is looking like. That, combined with energy use bills, I think can really help them ask the right questions and get the right data, quickly put it into models, and then be able to figure out how to set limits.”

Proponents also say they expect Local Law 97 to deliver co-benefits that could make similar legislation an easier sell elsewhere. Take jobs: The legislation is expected to create thousands of new positions for people in the building and tech professions – one estimate puts the figure at 141,000 new jobs by 2030.

Another benefit: better buildings. Chambers said that Local Law 97 was passed in New York partially because many in the city’s powerful real estate sector understand that higher-performance buildings mean happier tenants and lower operational costs. “A lot of the large real estate owners and entities have been benefiting from the type of work that this bill is pushing,” he said. “There are several large building owners that have high-performing buildings that they maintain really well, and they are not going to have to do that much in terms of meeting this agenda.”

“They know that ultimately this helps everybody.”

Also see: New York City law aims to slash global warming pollution caused by buildings

Sarah Wesseler is a Brooklyn-based writer focusing on cities, culture, and climate change.