While the greenest building may be the one that’s never built, the next greenest may be the historic one that’s being rehabbed.
A couple of years ago, the National Trust for Historic Preservation released a study quantifying the environmental benefits of rehabilitating old buildings instead of construction new ones. The study concluded that it can take “between 10 and 80 years for a new, energy-efficient building to overcome, through more efficient operations, the negative climate change impacts that were created during the construction process.”
Renovation of historic buildings has environmental costs, too—the materials used in renovation take energy to make and put in the building. But the environmental costs are 4%-46% less than those incurred by new construction.
The study offers some caveats. Renovation needs to improve the energy performance of the building to pay off, and you need to be careful about the types of materials you use. Turning warehouses into apartments, for example, requires many new materials and may not offer any environmental benefits over building new.
Making an older building meet the demands of the twenty-first century isn’t a simple process. In the Brooks House, for example, we had to add framing to increase the available space for insulation. Many of the windows were replaced, and others (the ones that were especially important historically) were rehabilitated to make them more energy efficient.
Many of the features of historic buildings are inherently energy-efficient. Large, operable windows allow daylighting and ventilation, meaning you can turn lights and air-conditioning off more often. Massive brick walls take a long time to heat up and cool down, which means that interior spaces stay comfortable longer without air conditioning or heat.
Many historic buildings are located in neighborhoods and downtowns that were built before the automobile was invented. Historic buildings make up Main Street, the icon of mixed-use walkability in this country. Kaid Benfield noted recently that “Main Street is a terrific model worth preserving and emulating…It has a human scale, neither skyscrapers nor sprawl, but something in between.”