Editor's note: The following is an excerpt from "The Past and Future City" by Stephanie Meeks with Kevin C. Murphy. Copyright © 2016 National Trust for Historic Preservation. Reproduced by permission of Island Press, Washington, D.C.
By Stephanie Meeks and Kevin C. Murphy
Although climate change has added additional urgency to our efforts, the idea that older buildings have a key role to play in forging greener, more sustainable communities has been around for a while. In 1980, when President Jimmy Carter first made energy efficiency a national focus, the National Trust had a poster that showed a building in the shape of a gasoline can. It read: “It takes energy to construct a new building — it saves energy to preserve an old one.” That, in a sentence, is why preservation is so fundamentally important to our future health and well-being.
According to the U.S. Department of Energy, building operations account for 41 percent of the nation’s energy consumption, 72 percent of its electricity consumption, and 38 percent of its carbon dioxide emissions. In urban areas, these numbers are even higher. Commercial buildings are estimated to be responsible for 70 percent of Chicago’s total carbon emissions and 80 percent of New York’s. Given these statistics, there is no way to feasibly address the climate crisis without changing how we manage our urban landscape.
At the same time, roughly one billion square feet of buildings are demolished and replaced every year in the United States. According to an analysis by the Brookings Institution, the country is in the midst of demolishing and replacing 82 billion square feet of existing space — nearly a quarter of the existing building stock — by 2030.
That is an astonishing amount of waste. In fact, the energy used to demolish and rebuild that much space could power the entire state of California for a decade! According to a formula produced for the Advisory Council on Historic Preservation, about 80 billion British thermal units (Btus) of energy are embodied in a typical 50,000-square-foot commercial building.
As my predecessor Richard Moe pointed out in 2008, that’s “the equivalent of 640,000 gallons of gasoline. And if you tear the building down, all the energy that went into creating the building is wasted. Demolishing that same 50,000-square-foot building also creates nearly 4,000 tons of waste. That’s enough debris to fill 26 railroad boxcars — a train nearly a quarter of a mile long, headed for a landfill that is already almost full.”
It simply does not make sense to recycle cans and newspapers to save energy and not recycle buildings. As architect and green advocate Carl Elefante wrote in a 2009 essay, “Taking into account the massive investment of materials and energy in existing buildings, it is both obvious and profound that extending the useful service of life of the building stock is common sense, good business, and sound resource management.” Put simply, he said, “The Greenest Building is the one that’s already built.”
This holds particularly true when you consider that it takes decades for even most of the new efficient buildings to recover the carbon that is expended in their construction. In short, we cannot build our way to sustainability. In a perfect world, every new building going forward would be net zero — meaning it produces as much as energy as it consumes.
But even if that were the case, it would have the same effect over a full year as cutting energy use of all existing buildings by just 1 percent. “Seeking salvation through green building,” wrote Elefante, “fails to account for the overwhelming vastness of the existing building stock. [That] is the elephant in the room: Ignoring it, we risk being trampled by it. We cannot build our way to sustainability; we must conserve our way to it.”
That is why what we do with our existing fabric is so important. In our rush to embrace green construction, we cannot lose sight of the tremendous value of saving and reusing buildings that have already been built.
In January 2012, a few years before conducting the Older, Smaller, Better research cited throughout this book, the National Trust’s Preservation Green Lab published its first major report, entitled “The Greenest Building: Quantifying the Environmental Value of Building Reuse," on this nexus of preservation and sustainability. The Green Lab first looked at the full life-cycle — from the extraction and transportation of the raw materials used in construction through decades of use—of different types of buildings, such as single-family and multifamily homes, schools, warehouses, and offices.
To ensure that their data accounted for different climates and a variable mix of energy sources, Green Lab researchers surveyed buildings in four U.S. cities: Chicago, Atlanta, Phoenix and Portland, Oregon. Using this life-cycle analysis methodology, they then compared the relative environmental impacts of building reuse and renovation versus demolition and new construction over the course of a seventy-five-year life span.
In almost all cases, when they compared buildings of similar size and functionality, they found that building reuse yields fewer environmental impacts than new construction. In fact, depending on the type of structure, it takes between 10 and 80 years for a new “green” building that is 30 percent more energy efficient than the existing one to make up for the amount of carbon unleashed through its construction. These findings accord with other studies on the subject. For example, a report by Britain’s Empty Homes Agency found that it takes 35 to 50 years for a new, green home to recover the initially expended carbon as well.
The range of environmental savings varies based on building type, location, and presumed level of energy efficiency, but when comparing buildings with the same energy performance level, the environmental savings from reuse are between 4 and 46 percent over new construction. The one exception is when industrial warehouses are converted into multifamily residential units, which resulted in a 1 to 6 percent greater environmental impact. Foremost among the reasons for this difference are the amount and type of materials used for rehab, which can significantly mitigate or even cancel out the energy savings from recycling buildings.
So, it is important to use the right materials — and minimize the amount of new materials — in renovation projects. If done correctly, however, the impact reductions of reusing old buildings can be substantial, particularly when taken to scale.
To take just one example, if the city of Portland, Oregon, were to retrofit and reuse the single-family homes and commercial office buildings that it is otherwise likely to demolish over the next 10 years, based on its demolition rates from 2003 to 2011, the potential impact reduction would total approximately 231,000 metric tons of carbon dioxide. This figure is about 15 percent of Portland’s stated carbon reduction target over the next decade. The city could save 15 percent immediately just by conserving and reusing its already existing buildings.
What is true in Portland can be true all over the United States. In 2014, as part of the United Nations Climate Summit, 451 cities around the world — including 122 in the United States—pledged to reduce their carbon emissions and begin preparing for climate change. Similarly, in 2015, a number of U.S. and Chinese cities agreed to deep cuts in carbon emissions as part of a bipartisan climate summit in Los Angeles — a city that, like New York, has pledged to cut its emissions by 80 percent by 2050. As noted earlier, Seattle has gone a step even further and declared that it will be completely carbon neutral by 2050. All these cities can get a leg up on reaching these necessary emissions cuts by stopping demolition and working with their existing building fabric.
Ultimately, we can’t build our way out of the global warming crisis. We have to save our way out. That means we have to make better, wiser use of what we’ve already built.
Put another way, many older buildings are inherently green by design through features like thick walls, high ceilings, use of daylight, operable windows, awnings, generous eaves, and porches. They reflect the wisdom — wisdom that has sometimes been lost — of earlier generations.
Stephanie Meeks and Kevin C. Murphy are the authors of "The Past and Future City."
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