How to get New York City’s biggest buildings to zero carbon

High-rise buildings can’t eliminate natural gas all at once. But they can and should start electrifying their heating right now.
By Jeff St. John

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The sun sets on the Empire State Building. (Gary Hershorn/Getty Images)

New York City got a lot of attention last month for its decision to ban natural gas in new buildings. But what can the city do about gas use in the buildings it already has?

Over the past six months, some of New York City’s biggest commercial property owners and managers have been working on a project called the Empire Building Challenge, which aims to demonstrate how high-rise buildings can start phasing out gas and ultimately decarbonizing.

That’s going to be hard — and it’s going to be expensive. New York City’s Local Law 97 calls for buildings over 25,000 square feet to cut carbon emissions by 40 percent by 2030 and by 85 percent by 2050. The New York–based nonprofit group Urban Green Council estimates that complying with the law will require $18.2 billion in efficiency retrofits over the next decade, a thirteenfold increase from current spending trends. And under the state’s mandate to decarbonize the entire economy by 2045, buildings will eventually need to ditch fossil fuels entirely. This could be achieved in part by tapping carbon-neutral fuels to replace natural gas, but the most straightforward approach is switching buildings en masse to electric heating.

How can building owners accomplish this rapid transformation without running out of money, overwhelming the city’s power grid or running the risk of leaving their tenants freezing when winter temperatures plummet? Few buildings can afford the kind of massive efficiency project taken on by landmark properties like the Empire State Building, which has poured $31 million into investments that have driven a 40 percent reduction in its carbon emissions over more than a decade.

Decarbonization efforts have to move beyond marquee projects like the $31M poured into improvements to the Empire State Building, according to Janet Joseph, senior vice president at NYSERDA. (Neil Cooper/Unsplash)

We have to get beyond the one or two marquee projects,” said Janet Joseph, senior vice president at the New York State Energy Research and Development Authority, in an interview this summer. That’s exactly why NYSERDA launched the Empire Building Challenge.

The Empire State Building is a model, but we need 20,000 of those a year” from now until 2050 to meet carbon-cutting goals for the state’s bigger buildings, she said. All of these retrofits and improvements must be done without displacing tenants and occupants” and in buildings that are moving energy, in some cases, 50 or 60 stories.”

A big-picture decarbonization approach for big buildings

How can big buildings accomplish this? The Empire Building Challenge’s first four projects, which last week were awarded $5 million each to help carry out their plans, hope to show the way, said Jared Rodriguez, a principal with Emergent Urban Concepts and adviser to NYSERDA on the challenge.

The companies behind the winning projects — Empire State Realty Trust, Hines, L+M Development Partners and Omni New York — collectively own more than 37 million square feet of New York real estate. Their projects range from Class A commercial high-rise properties, including the Empire State Building, to affordable-rate apartment housing, with different mixes of technology from different eras, as well as different structures for how they earn money and plan to pay for the upfront cost of efficiency upgrades.

But underlying each project is a common framework that encompasses two key ideas, Rodriguez said.

The first is to stop thinking of efficiency in terms of one-by-one projects that are measured on the basis of how quickly they can earn a payback on investment. That’s not what this is,” he emphasized. Instead, the Empire Building Challenge asks building owners to develop a strategic decarbonization strategy — or in other words, to explain how they will shift the building over 20 years,” he said.

Building owners make all kinds of investment decisions that lack simple return-on-investment payback calculations, such as amenities…that attract tech companies” or installing staircases that connect multiple floors of an office to attract that high-end consulting company,” he said. People put a new façade on their building. They put sprinklers in their buildings to meet fire codes. Do those projects have a financial return? We’re forcing energy and sustainability into a very small, stupid box, where everybody else gets to be more sophisticated.”

If short-term thinking can be a pitfall when it comes to devising effective decarbonization strategies, however, so can a certain kind of long-term thinking. To put it simply, building owners need to stop thinking of decarbonizing their buildings as an all-or-nothing proposition, Rodriguez said. In many cases, they won’t be able to go 100 percent electric in the next few years, but they must start upgrading their systems now no matter what.

Why can’t buildings go all-electric right away? The answer is that today’s heat-pump technologies may not be able to keep buildings warm when the city reaches its coldest temperatures, at least not without a massive overbuilding of heating infrastructure and an excessive electricity draw that, if multiplied across many buildings, could blow up the grid,” Rodriguez said.

Once you get down to 10 degrees, even with the cold-climate heat pumps, don’t try to do it — it’s not resource-efficient,” he said.

But that’s not a good reason to delay moving buildings to more and more electric heating, he said. Not only can partial electrification be a cost-effective way to cut a large portion of a building’s carbon footprint today, but it can also lay the foundation for deeper electrification as technologies improve and come down in cost.

The approach is to always phase in and go further sooner; don’t wait for the best, ultimate, all-electric option before you move. It’s move now, and move sooner, to get on that rapid trajectory to zero.”

This approach will be critical for the mass of New York City real estate that can’t command the high rents of marquee properties and thus can’t afford to go big into buildingwide retrofits, said Tristan Schwartzman, energy services director and principal at New York City–based building engineering consultancy firm Goldman Copeland Associates.

High-prestige, Class A buildings are going to be looking for ways to electrify. But that’s not attainable for your Class B building stock,” which tends to bring in $40 to $60 per square foot in rent, as opposed to $100 to $200 per square foot garnered by the city’s hottest properties. Schwartzman cited the example of a 500,000-square-foot building in midtown Manhattan that his firm recently studied for its potential to go carbon-neutral. The short answer is, they can’t” — at least, not with today’s technologies at today’s prices.

That’s why NYSERDA is looking for replicable solutions that can work in multiple buildings,” Joseph said. Finding workable solutions and replicating them throughout a portfolio of buildings is what the Empire Building Challenge is all about.”

The five R’s of resource-efficient electrification 

The agencies, real estate companies and building engineers working on the Empire Building Challenge call their approach resource-efficient electrification.” It’s built on a fairly typical hierarchy of actions for building retrofits, which Rodriguez and co-authors of a recent article on the subject have dubbed the five R’s.” The primary focus is heating because air-conditioning is already electric-powered. Most large buildings in New York still rely on fossil-fired boilers or furnaces to heat water and air, respectively.


The first step is to review” a building’s energy performance from top to bottom, he said. The next step is to reduce,” or take on the fundamental task of eliminating as much wasted heat as possible. That starts with an analysis of what are you injecting into your building, what are the outdoor conditions when you’re doing it, and how much are you losing through the walls, the sewer, ventilating out through the bathrooms and the roof and all of it,” Rodriguez said.

Reducing those heat losses can include insulating interior walls and windows, as L+M is doing as part of its challenge project, a nearly $14 million retrofit of The Heritage mixed-use apartment buildings in uptown Manhattan. Older structures built with less-insulative materials may require over-cladding,” or adding new materials to the outside of buildings, which Omni New York is taking on as part of its project, a $12 million decarbonization investment at the Whitney Young Manor affordable housing complex in Yonkers.

The Whitney Young Manor affordable housing complex in Yonkers (Omni New York)

Analysis of heat loss leads to the next step — recover” heat that’s not being used to warm parts of the building that need it. If you truly try to understand where all your heat flows are, you deploy ways of capturing them and…moving them,” Rodriguez said. Moving heat around is as important as making heat.”

So is capturing heat that’s otherwise being wasted, he said. Take the example of cooling systems that thread water pipes throughout buildings to absorb excess heat, then carry that heat to rooftop cooling towers that vent it into the air. Even in the wintertime when building heaters are running, there’s heat billowing from large office buildings,” sending clouds of evaporated hot water into the air — a characteristic of the city skyline that he described as the image of waste in New York.”


Capturing that heat instead of sending it into the sky is a trickier task than identifying the waste, however. Large buildings have traditionally heated and cooled themselves via separate systems, with no easy way to transfer thermal energy from one to the other.

That’s where the replace” step of the process comes in — and where the value of electric-powered systems, particularly electric-powered heat pumps, comes into play.

Making smart use of heat pumps

Heat pumps move heat from one place to another and increase temperatures in the process. Some move heat into a building, whether from the air, underground or other sources like wastewater or district heating systems. Others can be used as part of a building’s distribution system, bumping up supply temperatures or moving and recovering heat from where it is not wanted to where it is.

Heat pumps can also cool the air in rooms or the water flowing through pipes. That means a single system can replace separate cooling and air- and water-heating systems. Omni New York is going this route with a centralized heat-pump system it’s installing at Whitney Young Manor.

That’s a big change from traditional systems for generating and distributing heat, which rely on high temperatures being generated at a central location and distributed throughout a building. Most large buildings in New York City use steam or high-temperature water from their own natural-gas-fired boilers or from utility Con Edison’s massive Manhattan district steam system.

But steam systems waste a lot of energy compared to lower-temperature hot-water systems that heat pumps can use. Heat-pump-enabling hydronic” water-heating systems are a key part of making the resource-efficient switch to electrification, said Brett Bridgeland, a manager with the nonprofit research group RMI, which is supporting NYSERDA in implementing the Empire Building Challenge. (Canary Media is an independent affiliate of RMI.)

If you’re running a hot-water loop as opposed to a steam loop, it can run at a lower temperature,” he said. That generally improves system efficiency and matches well with the output temperatures from heat pumps.

It also opens up the option of using a number of different heat-recovery products out there” to make use of hot water in different parts of the building, Bridgeland said. Building heat systems can tap into these hydronic systems to deliver distributed heating solutions. Specifically, heat pumps can be installed to heat and cool individual floors or spaces within a building, which gives building owners and engineers the option to retrofit buildings one floor at a time.

That’s how Hines and its partners are going about renovating 345 Hudson Street, Hines’ challenge project, a Class A commercial building in downtown Manhattan with marquee tenants including Google, Viacom and CBS. The $30-million-plus project includes buildingwide renovations such as heat storage tanks on the roof, a heat-recovery ventilation system and a hydronic thermal network” that could eventually be expanded to other nearby properties.

345 Hudson St. in Manhattan (Timothy A. Clary/AFP via Getty Images)

The project plans to take advantage of tenant turnover to retrofit floors as they’re vacated, avoiding the hassle and disruption of doing retrofit work in occupied office spaces. That floor-by-floor strategy is adaptable to nearly any office building,” Rodriguez said, because it’s able to be implemented in an incremental approach.”

Getting to 80 percent electrification today 

The reduce, recover, replace” steps being taken by the four Empire Building Challenge projects offer an efficient and economic pathway to achieving 80 percent electrification today,” Rodriguez said. To be sure, that’s not the same as reaching 100 percent fossil-free heating — but it’s a major chunk of the target, and it’s achievable at relatively low cost, compared to what it would take to get all the way to 100 percent.

That’s how Ben Milbank, senior project development engineer at engineering firm Ecosystem, described the decision-making process for a major retrofit of a co-op residential building near Manhattan’s Union Square. The building’s owners considered expensive 100 percent low-carbon options such as geothermal, as well as a complete replacement of its aging central heating and cooling systems with electric heat pumps.

But the heat pumps needed to get to 100 percent electric would have been too large and costly to work in the building, he said. What’s more, the building owners were worried about grid blackouts leaving them without heat.

The compromise they eventually reached included air-source heat pumps on the roof to cover most of the building’s heating needs, paired with more efficient natural-gas-fired boilers for a hydronic system that can convey more heat to individual units when temperatures drop low enough to need it.

That reduced the building’s carbon emissions by about 80 percent — and at about one-third the cost of going with a 100% electric solution, he said. It also left the building with a hydronic system that will allow the owners to adopt a plug-and-play” approach with new technologies as they become more widely available at a lower cost.

A system’s ability to incorporate new tech in the future, sometimes referred to as optionality,” is a vital part of a decarbonization retrofit strategy, RMI’s Bridgeland said. The Hines project, for example, has this hydronic loop that serves each of the tenant floors. The tenants can choose how they can plug into that. And on the supply side, there’s also optionality on how you put heat into the system. It could be a district thermal loop; it could be waste-heat recovery.” 

Mostly decarbonized today, completely decarbonized tomorrow?

Optionality is an important factor to consider for building owners who might be reluctant to invest in today’s technology in hopes that future versions will be more efficient and cost-effective, Bridgeland said. That’s not to say that technology improvements won’t play a major role in meeting the city’s and state’s midcentury decarbonization goals, he added. Last month, NYSERDA and two other state agencies launched another competition to develop better all-electric heating systems, backed by a promise to spend up to $250 million to install the winning technologies in city public housing.

But waiting for better and cheaper technology isn’t an option given the deadlines at hand, Bridgeland said. In the world of building-equipment replacement cycles, from now until 2050 is one equipment lifetime. We’ve got one turnover [cycle] to work with.” Any new systems installed from here on out must be dramatically more efficient than the systems they replace.

Building owners largely view their efficiency options from an energy audit perspective — let’s look for projects with a high rate of return and relatively quick payback, do those interventions and move on to the next thing,” he said. We’re trying to take those things and put them on a roadmap to full decarbonization.”

The final stage in that process gets into the final R’s” of the resource-efficient electrification process: replace” and renew.” As already-completed retrofits are fine-tuned for better performance and new technologies come onto the market, building owners can get a better sense of what their final, toughest-to-meet heating needs will be. Then they can either renew” their remaining fossil-fueled heating to drive more unneeded emissions from the building, or, if it is no longer needed, simply remove it altogether.

I can understand [being reluctant] to rip out fossil fuel infrastructure, and then the polar vortex comes along and your technology doesn’t meet the load,” Bridgeland said. But let’s consider that separately and meet that with solutions as they come down the pike. Or maybe you get comfortable and realize you don’t really need it.”

The Empire Building Challenge hasn’t yet moved on to these final steps, but the participants are being asked to consider them into their long-range plans, NYSERDA’s Joseph said. 

The second piece, which is really important, is developing a multiyear capital plan that will move a building over time to carbon-neutrality, so that sustainability improvements can be integrated into the more routine implementations that occur over a lifetime of a building,” she said. When a heating and cooling plant gets to its end of life, that’s an opportunity to look at electrification. When a building façade needs to be replaced, that’s an opportunity to look at the building envelope.”

Jeff St. John is director of news and special projects at Canary Media. He covers innovative grid technologies, rooftop solar and batteries, clean hydrogen, EV charging and more.