A road map to New York’s low-carbon future

As officials from around the world converge upon the United Nations Climate Change Conference, known as COP22, in Marrakech, innovative urban solutions to reduce carbon use are front and center on the agenda. As Arup notes in a new report for the World Energy Council, cities consume the majority of the world’s energy and are responsible for much of its greenhouse gas emissions. The good news is that a range of technical solutions — some already on the market, others fast-emerging or potential innovations — take aim at urban buildings, one of the biggest climate-change contributors.

Few cities are more acutely aware of this than New York City, where the energy used in buildings accounts for a whopping 73% of the city’s greenhouse gas emissions, far above the nation’s average of 40%. So when two years ago Mayor Bill de Blasio vowed to reach the “80 × 50” goal  — reducing greenhouse gas emissions 80% by 2050 from a 2005 baseline — buildings became a key focus in New York’s bid to become the most sustainable big city in the world.

Following more than a year of work by real estate, architecture, engineering, construction, finance, and environmental justice experts, the city has formulated a multipronged approach that promises to yield significant carbon savings. “One of the clear messages here is that there is not a single solution,” said John Lee, deputy director for green buildings and energy efficiency at the New York City Mayor’s Office of Sustainability.

The energy used in buildings accounts for a whopping 73% of New York City’s greenhouse gas emissions.

Indeed, as detailed in the One City: Built to Last technical working group report, the city is mounting multiple lines of attack on outmoded systems. For example, a recently enacted update to the New York City Energy Conservation Code imposes aggressive air infiltration and insulation requirements for newly constructed buildings or those undergoing major renovations. In addition, owners of midsize buildings will be required to meet current lighting codes in nonresidential areas by 2025. And the City has proposed that owners of large buildings will need to assess deep energy-retrofit strategies as part of mandated energy audits.

High hopes for high-efficiency heating

As in other carbon-fighting cities such as Seattle, a key strategy for “deep-green” (or more intensive) building retrofits seeks to move heating systems away from fossil-fuel consumption. Across New York’s multifamily buildings, nearly 75% of greenhouse gas emissions are attributable to on-site heat and hot water. So the use of high-efficiency heating systems such as heat pumps — which rely on electricity instead of natural gas or oil to heat buildings — play a potentially key role. If New York is able to increase clean, renewable energy in the grid, then heat pumps become a viable greenhouse-gas-reduction technology.

Given the prevalence of steam heating in New York, however, a supply chain for heat pumps hasn’t yet developed in the city. Cities in northern climates have generally been slower to adopt heat pumps, since the technology has historically needed a backup heat source during the coldest times of the year. But that is changing. “Efficiencies have improved dramatically,” Lee said. “We’ve seen examples in Vermont and Canada where heat pumps are able to operate at very low temperatures approaching 0°F. We’re now working with a coalition of cities and manufacturers to increase adoption of the technology in our region.”

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Vapor rises on New York streets when water hits the subterranean hot steam mains used to supply heat, hot water, and power to buildings.

New York analyzed four different pathways of deep-green retrofit strategies for eight building typologies. All included upgrades to heating equipment, ranging from air-source and water-source heat pumps to solar-thermal hot water systems. In addition, they included improvements to the building envelope, ranging from sealing through-wall penetrations to recladding facades.

The bottom line? Through existing technologies, energy use and greenhouse gas emissions could be cut by 40 to 60% in typical New York City buildings.

Building a greener energy grid

Even the most dramatic energy conservation measures will only take New York so far toward its 80 × 50 goal. That’s because less than 2% of the city’s grid is powered by renewable sources. “When we project out 30 years, a high level of uptake of renewables in the grid has to be part of the solution,” Lee said. “We can’t make it to the 80 × 50 goal without that.”

And so the city is exploring other ways to kick the carbon habit. In concert with New York State’s Reforming the Energy Vision initiative, which seeks to provide 50% of the state’s electricity from renewables by 2030, the city is looking at ways to distribute cleaner energy production across property lines. Community shared solar, for example, could aggregate demand for solar power among small buildings, drawing from photovoltaic installations on larger sites such as educational campuses. Another approach would use geothermal loops to power an entire block instead of just a single building, maximizing gains from a geothermal build-out.

Drastic cuts in emissions depend upon a holistic approach that not only makes buildings more energy-efficient, but also puts renewables into the grid, balances energy loads, retrains the construction workforce, and knocks down barriers to clean-energy innovation. As New York now moves to advance measures identified by its working group, incorporating them into the energy code or as stand-alone mandates, what’s perhaps most powerful is the way buildings have become part of an integrated strategy to attain deep carbon savings.


Questions or comments for Jeff Byles? Contact jeff@beingheredesign.com.

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