Retrofit (Usually) Greener Than New Construction, Study Says

Is the greenest building the one you don’t build? The answer is a resounding “usually.”

Conventional wisdom about building reuse is questioned and quantified in a much-anticipated report released today by Preservation Green Lab, part of the National Trust for Historic Preservation. Using a life-cycle assessment (LCA) approach that takes both operational and embodied impacts into account, the report compares the environmental impact of retrofitting an existing building for high performance vs. tearing down the building and replacing it with a high-performance one. It also looks at a more common real-world scenario—pitting high-performance new construction against continued use of a building that has only average energy performance.

While reuse generally has less impact, the advantages of retrofitting vary greatly depending on building type, climate, and materials used. In one notable exception to the overall results, adaptive reuse of warehouses for multifamily housing can actually have a greater environmental impact than demolition and new construction—highlighting the fact that decisions about retrofit vs. demolition will still need to be made on a case-by-case basis.

Carbon payback

The most catastrophic effects of climate change can only be prevented in the next 20 years or so, making global warming potential one of the most pressing environmental impacts to consider. Since it can take decades for a new building to “pay back” its embodied carbon through improvements in operational efficiency (see “A 2030 Challenge for Building Product Manufacturers,” EBN Feb. 2011), this study’s conclusions about carbon emissions should come as no surprise: based on climate-change considerations alone, almost every useable building in every region of the U.S. should remain standing—even if these buildings are not retrofitted to improve energy performance. Carbon payback time for the buildings studied ranged from 10 to 80 years.