When Mayor Michael Bloomberg visited London earlier this month to talk with Mayor Ken Livingstone about that city’s congestion plan, he slept in his own bed in the 3,500 square-foot apartment he owns in London’s exclusive Cadogan Square neighborhood. He told reporters that in New York he lives simply and efficiently – in a 7,500 square foot Upper East Side townhouse. “I get my haircut two doors away,” Bloomberg told a reporter from the International Herald Tribune. “I never have to leave the neighborhood.”

He can afford not to. But even staying home can take a toll on the environment – as the mayor’s own environmental plan makes clear.

The streams of traffic crashing against the city’s various choke points may be New York’s most iconic image of waste and pollution. But, in fact, the city’s buildings – its defining physical elements – account for the bulk of New York’s energy use and carbon emissions. The city’s 750,000 buildings – residential, commercial and government -- are responsible for nearly 80 percent, or 47 million metric tons, of New York City’s total carbon dioxide output. That’s the equivalent of 150 Empire State Buildings worth of greenhouse gas being pumped annually into the atmosphere – hanging heavily over its economy, landscape and environment.

Buildings in the city’s commercial sector, alone, which includes offices and retail space, kick out 25 percent of all emissions (transportation, by contrast, accounts for 23 percent).

Despite this, Bloomberg’s ambitious PlaNYC2030 is largely silent on reducing pollution from buildings other than those built or owned by the city. It says virtually nothing about commercial buildings. Can New York City expect to meet its goal of reducing overall emissions by 30 percent by 2030 if it does not move aggressively – like London – to encourage and, in certain cases, impose efficiency standards on commercial property, one of its largest polluting sectors? Or will the combination of market forces and moral responsibility prove powerful enough to bring the city’s business leaders in line with the city’s push for sustainability?

Polluting Buildings

Though the world’s largest cities account for 2 percent of land area, they generate 75 percent of the world’s carbon emissions. Despite that, New York already fares well on some measures of efficiency and sustainability. PlaNYC acknowledges as much. “Our density, apartment buildings and reliance on mass transit means we are one of the most carbon-efficient cities in the United States,” the plan states. “New Yorkers produce 71 percent less carbon dioxide per capita than the average American.” (Carbon dioxide emissions are the key cause of global warming.)

To take a page from Bloomberg’s playbook we can look at London and its sprawling metropolitan area with a mĂ©lange of aging and new buildings and a population of 7.5 million. There, buildings account for an almost identical proportion of energy use, according to a statement by London deputy mayor Nicky Gavron.

The two cities not only have similar demographics and man-made environments, they have recently begun reckoning with their obligation to make those built environments more sustainable. Two months before Bloomberg and his Office of Long Term Planning and Sustainability rolled out PlaNYC 2030, London’s Mayor Ken Livingstone released his own 148-page report called the Climate Change Action Plan. The two documents are strikingly similar in approach and have been applauded by environmental and business leaders alike. Each plan outlines key sources of energy use and carbon emissions and presents an array of policy proposals for each of the cities as they reckon with a future marked by increasing populations, rising costs of living and warming temperatures.

Yet there is at least one conspicuous – and significant – difference between the London and New York reports. The London plan devotes a full section to commercial and institutional buildings – analyzing in minute detail their energy use, recommending ways to improve efficiency and outlining various regulatory measures intended to force the commercial sector’s hand. New York City’s report, however, has no such section.

Bloomberg’s report does offer an exciting yet jarring portrait of New York City two decades from now: an influx of a million people, the creation of 750,000 new jobs, the construction of 265,000 new housing units and 60 million square feet (more than four former World Trade Centers) of new commercial space. Despite the new construction, existing buildings will account for 85 percent of the buildings standing in New York City in 2030, according to deputy mayor for economic development Dan Doctoroff.

Buildings pollute in a number of ways. Most building pollution, however, does not emanate from the residences and offices themselves but the smokestack of a power plant when a light switch, computer monitor or coffee maker is switched on. Various emissions are also generated on-site from natural gas and oil-burning boilers, gas stoves and hot water heaters and the gasses released in the breakdown of certain building materials such as paint and insulation.

To address this, plaNYC calls for making the buildings we already have more efficient. “If we’re concerned about energy efficiency and carbon we need to start with buildings that have the largest carbon footprints,” said Rohit Aggarwala, director of the city's Office of Long Term Planning and Sustainability. “As a city I’d like to see us prioritize those retrofits and projects that have the biggest bang for the buck.”

Improving What We Have

Reducing energy use and carbon emissions is architect Chris Benedict’s goal as well. Benedict, who has headed her own firm since 1996 and teaches environmental technology at the Parsons School of Design, has a number of rehabilitation projects, including one at a residential building on West 126th Street in Harlem. Benedict says she is achieving energy savings in the range of 50 percent in her renovations and that her new buildings are achieving a rate of efficiency 80 percent greater than “average” buildings. And she says she’s doing it at no extra cost.

On a recent morning she is running a plastic cylinder into small boreholes made in the walls, extracting insulation and testing its density on a small digital scale. This lets her make sure that the amount of insulation blown into the walls is adequate for maximum efficiency – not the kind of work you typically find an architect engaged in, let alone early on a Saturday morning. But it’s the “magic” that makes efficiency happen, says Benedict.

Her prescriptions are elegantly simple – but require care in execution. Efficient buildings, she says, must be carefully designed to make sure air moves efficiently throughout. The key in this small apartment is making it airtight except in places where drafts are wanted – in this case, through trickle valves (small one-way vents activated by fans) installed in the high-performance windows. The fans push hot air out, allowing it to be replaced by cool air streaming in through the vents. In order for the system to work properly, a “bubble” must be established: All joints and cracks throughout the apartment must be meticulously sealed. The apartment’s efficient heating system relies on multiple thermostats that are able to regulate temperature room-by-room.

Other “simple” prescriptions include high efficiency appliances and green building materials such as recycled cellulose insulation and dimmers. Benedict says that for this reason it’s vital that work be carried out to the standards set forth in her plans. “We make the contractors working on our projects sign off that they will commit to following the plans exactly,” says Benedict. “If they don’t, none of this works.”

As reasonable as many of these improvements appear, the stark economics facing the city’s residents could limit the use of such improvements and make it difficult for the city to achieve further gains in residential efficiency. In 2004, more than 45 percent of renters – accounting for roughly a third of all households in the city – paid over 30 percent of their income toward housing. The price of real estate continues to gallop away from wages. While the average house price sits at $550,000 (in Manhattan, the average is $1.3 million) the average income hovers around $40,000. Such statistics paint a gloomy picture – one of strapped renters and homeowners with little free cash to invest in efficiency upgrades.

Projects such as the well-known luxury apartment building, the Solaire, which boasts photovoltaic cells and a green roof garden and where three-bedroom apartments are pushing $5,000 a month, inevitably raise the issue of whether efficiency can be affordable. Benedict says that there is no reason why it can't be.

And builders seem to be catching on. A number of efficient projects intended for low- and moderate-income families are popping up around the city. These include Via Verde in the South Bronx, the Ocean Hill-Brownsville Complex in Brooklyn and the Diversity Houses on East 2nd and 3rd Streets in Manhattan (another one of Benedict’s projects).

The administration hopes that projects such as these will encourage others. PlaNYC, though, does not set specific rules for increased efficiency in New York City’s homes and apartments.

Efficiency in Government

For its own buildings, though, the city has made some headway in promoting wide-scale building efficiency. With the recent passage of Green Buildings Act (in .pdf), the city’s code now sets more stringent efficiency guidelines for municipal buildings. For example, capital projects costing (with the exception of schools, which are held to less rigorous standards) $30 million or more must reduce energy consumption by at least 25 percent. According to Aggarwala, next summer the city will introduce even more energy efficient measures for city buildings. He also says the Department of Buildings has stepped up enforcement of the state energy code to ensure that developers do not cut corners during construction.

Aggarwala said, by 2015, he would like to see rules requiring all buildings over 100,000 square feet to have an energy audit. This would provide the city an overview on the performance of all its buildings, he says. But little has been done to force the commercial sector to adopt the stringent building codes embodied in the Green Buildings Act. “Our plan is less prescriptive than London’s. We don’t have the authority to regulate, say, what kinds of computers are used in the city,” he said.

The commercial sector has made some eye-popping gestures toward efficiency. New projects like the Hearst Tower, 1 Bryant Park and the new New York Times Building in Midtown jut skyward with massive dimensions – and promises. The 600-foot tall Hearst Tower boasts energy-saving measures such as high efficiency heating and cooling, motion sensors that regulate power usage and “Icefall,” a three-story waterfall driven by “harvested” rainwater, which helps humidify and cool the building’s open atrium. In all, its cutting edge features will reportedly make the building 22 percent more efficient than other office buildings.

Still, 22 percent is a far cry from Benedict’s 80 percent. Moreover, that figure does not factor in the energy costs of demolition, site clearing and rebuilding, which one Canadian study found required more than two and half times as much energy as rehabilitating an existing building.

Some developers have tried rehabilitating office space, though such projects are fairly unusual. In the 1990s, the National Audubon Society renovated the Schermerhorn Building in lower Broadway to create an energy efficient and generally environmentally friendly headquarters for the organization.

Audubon, of course, is a non-profit. For big corporations, new high-profile projects seem to be the preferred way to go – if they consider sustainability at all.

“There are some visionary, innovative and hopefully high performing commercial buildings going up here and there,” said Nancy Anderson, executive director of the Sallan Foundation, a non-profit that looks at urban sustainability. However, Anderson said a large number of buildings erected during New York City’s decade-long construction boom do not meet the highest efficiency standards. “We’re not going to where we have to go to in terms of our carbon dioxide reduction goals with a building here and there. We need to quickly achieve a scale – of many large numbers of buildings plus new buildings and renovations.”

Cheap Energy and Lots of It

Along with the many technical obstacles to increased efficiency in commercial buildings lies a more fundamental issue: economics. Even though energy is as costly as it has ever been, it is still cheap when compared with the other costs associated with building operations in New York City.

“ In our region, commercial building utility costs typically run at $3 to $5 a square foot. Overall operating costs in New York City run in the area of $30 to $50 a square foot. And rents in Midtown Manhattan are pushing $100 a square foot,” says Michael Bobker, a senior fellow at the CUNY Institute of Urban Systems. “So there you can see where energy fits into the overall economics of operating a building.”

Chris Benedict

Bobker, who is currently working with companies to develop environmentally friendly vision statements and integrated efficiency training programs, said, though, that there is reason to be optimistic. He sees movement for efficiency at the highest levels of the city’s commercial establishment. It is spurred, he said, more by ideology than money.

“ We’ve had price drivers for a long time and that hasn’t really driven the message the way we’re seeing it happening in the marketplace today,” says Bobker. “What’s different is that people are aware now that energy use is linked to climate change – and that’s what’s driving executives. It’s no longer just an economic issue. It’s an ethical issue.”

How far does that concern go? In business, the bottom line will always be ideology number one. Companies will balk at environmental regulations if they impose excessive construction costs, said Stephen Hammer, director of Columbia University’s Urban Energy Project. “Businesses say, New York City is already 25 percent more expensive than across the river and in Westchester. If you’re going to make us do all these extra things, construction costs are going to go up, and we’re going to leave.“

That kind of thinking is outmoded, said Hammer, because energy efficiency is vital to a firm’s long-term competitiveness in a global marketplace. What’s more, it can be profitable. London, Hammer said, shows us that environmental mandates can actually spur economic growth. In spite of Mayor Ken Livingstone’s uncompromising approach to efficiency mandates, London’s economy has grown steadily since his election in 2000. One prestigious magazine (albeit an English one), The Economist, has gone so far as to declare London the world’s new financial capital.

A tough love approach on efficiency, said Hammer, might be just what New York’s private sector needs to see the potential long-term savings of green building. “[London’s] businesses are finding that they can do this stuff without breaking the bank,” said Hammer. “In fact, they’re going beyond the mandates and finding that there’s economic reason to do it – that the return is good on efficiency.”

Jeremy Miller is a New Jersey-based freelance writer, who writes about people, science and the environment. His most recent work has appeared in The Boston Globe and The Boston Globe Sunday Magazine.