Much to the consternation of developers and redevelopment agencies intent on demolishing historic buildings and constructing new ones, these days, in the name of going green, preservationists are making the case that “the greenest building is the one already built.”
“This whole idea that reusing existing resources — especially historic buildings — is the ultimate in recycling is beginning to get some traction,” agrees Donovan Rypkema, one of America’s most prominent and outspoken preservationists, and author of the classic book in the field, The Economics of Historic Preservation: A Community Leader's Guide.
Helping historic preservationists present their case are new studies that calculate what is lost — in measurable environmental terms — when we tear buildings down and replace them with new ones. Plenty of studies have demonstrated the merits of constructing new green buildings, but until recently, there’s been relatively little data available on the economic and environmental benefits of building reuse.
Some of the latest reports calculate both the enormous amount of energy and materials already locked into buildings (embodied energy), and the significant carbon emissions they represent.
Embodied energy is the energy consumed by all of the processes associated with the construction of a building, from the acquisition of natural resources to product delivery. This includes the mining and manufacturing of materials and equipment, plus their transport.
A discussion of embodied energy first arose during America’s energy crisis in the late 1970s and early 1980s. Embodied-energy researchers developed a handy calculation: By entering a building’s size and type (residential, commercial, hospital, etc.), it was easy to do the math and come up with a quick estimate of the amount of energy saved by preserving a building.
Embodied-energy calculations had little influence on the old-versus-new building debate, though because it was believed that the embodied energy content of a building was rather small compared to the energy used in operating the building over its life. Most conservation efforts were, therefore, put into reducing operating energy by improving the energy efficiency of the structure.
Nowadays, it’s accepted that embodied energy can be the equivalent of many years of operational energy, and that new construction requires enormous expenditures of energy and materials. A recent study by the Environmental Protection Agency estimated that 30 to 40 percent of natural-resource extraction every year goes to the building industry.
Meanwhile, to the delight of preservationists, old buildings have been adjudged to be surprisingly energy efficient. U.S. Department of Energy research on the energy performance of existing buildings ascertained that commercial buildings constructed before 1920 use less energy per square foot than buildings from any other period of time except after 2000. Older buildings, it seems, were constructed with high thermal mass, passive heating and cooling. And, obviously, were built to last.
Some builders acknowledge that historic commercial buildings use less energy than buildings of more recent vintage but insist the exact opposite is true of homes — the older the home, the worse the energy consumption is likely to be.
Yes, but historic preservationists counter that recent studies show older homes can be remodeled and upgraded to meet energy standards at less cost — and at less cost to the environment — than tearing down and building new ones. That was the conclusion from a study in England by the Building and Social Housing Foundation and another in Scotland commissioned by Historic Scotland.
Both studies also looked at the carbon impacts of building new homes compared to retrofitting old ones. The BSHF study commissioned by the Empty Homes Agency found it could take as long as 35 to 50 years for a new green home to recover the carbon expended during the construction process, while the Historic Scotland estimate was 15 to 20 years.
“The idea that even the most energy-efficient new house could require a minimum of 15 years to recover carbon ought to be reason enough to give us pause,” says Frey, “and take a second look at retrofitting our existing housing stock.”
Preservationists admit there is still some fuzziness in how exactly embodied energy and carbon emissions are measured. Noting that well over 40 percent of the nation’s carbon emissions come from construction and operation of buildings, The National Trust for Historic Preservation launched its Preservation Green Lab in Seattle to conduct further research.
“The goal of research at Green Lab,” says Frey, “is to develop tools and resources to enable policymakers and decision-makers to get needed residential and commercial growth and at the same time protect what is already there.” (Run your dwelling through their embodied energy calculator here.)
Most everyone, though, remains resistant to reusing and retrofitting buildings. Architects like to start from scratch, developers don’t want the hassles of rehabbing existing buildings, and new construction is a mainstay of the U.S. economy.
“The most unenlightened in this regard are the traditional environmental advocates and the U.S. Green Building Council and their LEED certification,” Rypkema jabs. “If it isn’t about a waterless toilet, solar panels or saving the rain forest, those groups don’t think it’s about the environment.”
As Rypkema sees it, the environment and historic preservation have one thing in common: to understand their importance to society, you have to think long term. But in his experience, “The myopically short-term perspective of elected officials means they focus on the next election, not the next generation.
“Fortunately, much policy on the national, state and local levels is effectively set by boards, commissions and public employees. With the right set of arguments, they are persuadable."