For buildings of comparable size and use, old buildings are almost always the greenest buildings.
Buildings eat up a huge amount of energy—about two-fifths of the country’s total use—so to suppress their appetite for power, efficiency entrepreneurs are churning out a suite of nifty technologies, like automatically shading windows, smarter thermostats, and high-tech heating and cooling systems. But a new report from the National Trust for Historic Preservation’s Preservation Green Lab concludes that constructing new, energy-efficient buildings almost never saves as much energy as renovating old ones.
Renovated buildings outperformed new buildings on energy savings in every category: single-family homes, multifamily complexes, commercial offices, “urban village” mixed-use structures, and elementary schools. Though the conclusion may seem counterintuitive in an age of ambitious LEED standards in many new buildings, consider that it uses more energy and creates more impact to construct an entirely new building than to fix up one of the same size for the same purpose. The only exception to the lab’s finding was converting a warehouse to a multi-family dwelling, which required enough extra materials that creating a new building was the greener choice.
The report doesn’t take into account the costs associated with renovations and new construction, but green builders say fixer-uppers are often the more economical choice, too. “It costs less to take an existing building and renovate that to build a new one, at least on the projects I’ve worked on,” says Helen Kessler, a board member of the Illinois chapter of the U.S. Green Building Council. She cautions, though, that these comparisons vary from building to building: “There’s always an “it depends” about this."
One goal of the report was to make the case for building reuse as smart development practice, an option that is often overlooked. For green-minded preservationists, the data in the report gives heft to long-held beliefs: As TreeHugger’s Lloyd Alter puts it, “As a writer about sustainable design [the report] backs up the arguments I have been making for years, and as a preservation activist, it gives me and everyone in the movement the ammunition we need to demonstrate that old buildings are green.”
But the report’s data doesn’t offer any insight into a perennial problem with old buildings: They’re short. While it might make not make environmental sense to replace an old two-story building with a new two-story building, what if the replacement is an energy-efficient seven-story structure that's accessible via public transit? To address these questions, the report’s authors call for more research into “the relationship between density and environmental impacts as it relates to building reuse versus new construction.” That rather dry formulation glosses over a real point of contention between preservationists and advocates for density, who often support creating a LEED-certified 12-story building where a four-story charmer once stood.
But as Kessler puts it, there’s always an "it depends." In some cases, the space in old building can be put to better use: Ashley Katz, a spokeswoman for the U.S. Green Building Council, points to the Treasury Department’s newly LEED-certified historic headquarters, where renovations added 164 “workstations." And the Natural Resources Defense Council’s Kaid Benfield argues that more density doesn’t necessarily require building the tallest skyscrapers possible. “To increase density enough to make a difference, we don’t always need to maximize it,” he writes. “Much of the time a moderate amount of human-scaled urbanism will be far more appropriate than a high-rise.”
In cases in which there’s no question of trade-offs, though—if, for example, a family plans to knock down an old house to build a new one of the same size with all the latest efficiency accoutrements—renovating is always the better choice.