By David J. Barboza
SurveyLA is a historic resources survey, so it isn’t necessarily obvious how participating by suggesting places that you think are historically significant can help the environment. However, historic preservation can have a big impact on the environmental performance of Los Angeles. The Preservation Green Lab of the National Trust for Historic Preservation recently came out with a study entitled The Greenest Building: Quantifying the Environmental Value of Building Reuse. The study was covered by Elizabeth Heider in the September 2012 issue Environmental Design and Construction, a magazine published by the US Green Building Council, creator of the LEED green building rating systems.
The study used life cycle analysis (LCA) of buildings to determine their environmental impacts. At times it can be tempting to analyze a building’s environmental impacts by focusing only on things like how much electricity and water it consumes on a day-to-day basis. LCA recognizes that a fair measure of a building’s environmental performance must include this, but also analysis of the environmental impacts of making the building in the first place and demolishing it at the end of its life. As it turns out, the environmental impacts of construction and demolition can be pretty significant. Using LCA, the study compared several cases of reuse and renovation of buildings versus new construction over a 75-year term on four categories of environmental impact: climate change, human health, ecosystem quality and resource depletion.
The study found that when comparing buildings of similar size and functionality (e.g. a single-family home with a certain floor area with a single-family home with a similar floor area) building reuse almost always had a lower level of environmental impact than new construction assuming similar energy performance. This stands to reason, since in these cases reuse avoids the environmental impacts of demolition and new construction. The study also computed the “payback time” of new construction that is more energy efficient than what it replaces (still assuming similar building size and functionality). The finding was that for buildings that are 30% more energy efficient, it can take between 10 and 80 years for the more efficient operations to overcome the environmental damage caused by demolishing the old building and constructing the new one. The study argues that it is critical to understand payback time when making environmental judgements about demolition and new construction because “most scientists agree that action in the immediate timeframe is crucial to stave off the worst impacts of climate change” (p. XI).
Stepping back a bit, it becomes clearer how identifying historic resources (say at MyHistoricLA.org) can help protect the environment. If historic resources are identified, they can be preserved, and if they are preserved, the environmental impacts of demolition and new construction can be avoided. Preservation and environmentalism can thus get along well. If you are tying to improve the environmental performance of a historic building, this can be done in a way that is sensitive to the historic integrity of the building. For example, improved insulation or more efficient appliances would be better ways to save energy than changing out historic windows (which would change the building’s appearance). The LADWPs Green Power for a Green L.A. program would be a better way to generate renewable energy from a historic integrity perspective than solar panels on a building’s front facade.
New construction has its place, but this study reminds us that the greenest building might be the one that has already been built. Because of the large environmental impacts of demolition and new construction, it makes sense from both an environmental and a historic preservation perspective to think first about how we might reuse a building. It’s right out of the three Rs after all: reduce, reuse, recycle.