3: Define Sustainability, Carbon Reduction, Energy Performance
According to the U.S. Energy Administration, nearly 50 percent of greenhouse gas (GHG) emissions in the U.S come from the operation, renovation and construction of buildings. We have an obligation to reduce GHG emissions with an integrated, purposeful approach that protects our present and future. The need to reduce carbon emissions to confront the challenge of climate change is urgent. (Editor’s Note: Read about the push to decarbonize buildings in “Trend Alert”.)
A strategic renovation and reuse of an aging building can reduce overall GHG emissions compared with building new. This strategy relies on saving energy already “embodied” in the existing building through reusing, rather than newly constructing, its most carbon-intensive components. Steel, concrete and brick are particularly energy and carbon intensive because of the resources used to manufacture them. When we reuse the structure and building envelope rather than replace it, the topline reduction in carbon emissions is a hard-to-ignore achievement.
“Our analysis on embodied carbon in buildings reveals that 80 percent of the embodied carbon factor is in the building structure and enclosure,” says Chris Schaffner, P.E., LEED Fellow, WELL AP, the founder and CEO of The Green Engineer, a sustainable design consulting firm based in Concord, Mass.
Schaffner suggests taking the extra step of examining the “net present value” of carbon reduction on renovation projects. “It’s important to know not only the comparison of embodied carbon impacts for new construction versus renovation, but to also consider when they occur,” he says. “Reductions created now and elimination of carbon emissions released today provide a much greater impact than waiting for a 10- to 20-year timeline of system improvements within the building.”
To create maximum energy efficiency and low operating carbon emissions, HMFH Architects recommends a deep retrofit strategy on school renovations. This includes replacing mechanical, electrical, and lighting systems and maximizing the efficiency of these systems. This strategy also includes improving the building envelope’s performance to reduce energy demand.
HMFH Architects’ renovation of Gilbert Hall on the campus of Bristol County Agricultural High School in Dighton, Mass., employed such a strategy and illustrates the ideal scenario for renovation. The firm’s projections showed that restoring the building was less expensive than new construction.
By reusing, rather than rebuilding the concrete, wood and masonry structure, the design team was able to take advantage of the existing building’s attributes, such as abundant natural light, views to the outdoors and the building’s embodied carbon. At the same time, HMFH Architects significantly reduced operational carbon with new systems and a tighter building envelope. Each of these aspects contributed to stronger overall sustainability performance.
Renovating for Long-term Sustainability
Recent events are a formidable reminder that we are seeing the increasing impacts of a climate crisis stemming from our reliance on fossil fuels—a reality that demands long-term sustainable thinking. Although a new building may provide a greater level of operational energy efficiency than an existing building, this metric can be offset by taking advantage of the embodied carbon present in an existing structure. The urgent need to reduce carbon emissions in the short-term puts greater value on the immediate carbon savings of renovations.
Existing buildings can be as flexible and resilient as new buildings, and they often meet the needs of successive generations just as well as new buildings. Long-term sustainability is the goal. Planning for it when working with existing buildings requires that each of the aforementioned factors is carefully considered.
Before tearing down a building you already have, it is always worth a holistic exploration of the renovation options. Even though it may involve more complexity, the potential benefits of renovation—today and for many years into the future—will impact each of us and help protect generations to come.