by Lori Ferriss
From governmental climate action plans to increasingly ambitious energy codes and rating systems, projects are driven to meet energy reduction targets from many directions, and the “green building” sector continues to grow. High performance new construction has become the epitome of sustainable design, while existing buildings are frequently seen as energy hogs: a liability rather than an asset.
This paradigm of sustainability in design has focused on reducing operational energy; the problem with this approach is that it neglects to account for either the carbon emitted to produce new materials and construct a building, also called embodied carbon, or the impacts associated with demolition and disposal at a building’s end of life. These embodied and end-of-life impacts were for many years dismissed as negligent over a building’s full lifespan; however, it has become increasingly apparent that these impacts are not insignificant, contributing at least 11% of global carbon emissions.
The importance of embodied carbon is also rapidly increasing. As buildings become more efficient and the grid becomes greener, the use phase constitutes an ever-smaller percentage of life cycle carbon emissions, and the embodied impacts become relatively more significant. At the same time, we are projected to build an astounding 2.5 trillion square feet of new construction globally by the year 2060. The city of Boston alone approved 17 million square feet of new construction in the year 2017, the materials and construction of which result in the potential emission of about 850 million kilograms of carbon dioxide equivalent, which is on par with operating 100,000 average single-family homes for a year. All of this construction is happening within the context of the global imperative to achieve carbon neutrality by the year 2050 at the very latest to avert catastrophic and irreversible impacts of climate change.
While there is an array of strategies available to reduce carbon emission in the built environment, a powerful answer is hiding in plain sight: Reuse more of what we already have. This can range in scale from reusing salvaged materials to the reuse of whole buildings. Comprehensive renovation results in the emission of 70-85% less carbon dioxide compared to equivalent new construction. Consider this alongside the already widely acknowledged need to improve energy efficiency of existing buildings to drive down operational emissions, and building reuse becomes an obvious path towards dramatically and quickly reducing carbon emissions.
When embodied and end-of-life carbon are accounted for, it is clear that we are not going to build our way to net zero with new construction, and the environmental benefits of existing building retrofits become obvious. The paradigm of sustainable design needs to be reimagined to account for the true carbon footprint of construction, and we must look more closely at our existing building stock to leverage the sunk carbon in buildings that already exist. Restoration is climate action.
Lori Ferriss
Lori Ferriss, AIA, PE, LEED is an associate at Goody Clancy and an active member of the Boston Preservation Alliance.
