We Must Decarbonize Existing Buildings by 2050—but How?

A carbon-neutral city by 2030: that’s the goal of Ithaca, New York’s Green New Deal, adopted in June 2019. We’re not just talking about municipal operations or new building construction, though these are part of the resolution. No, this is about city-wide carbon neutrality, including the electrical grid and privately owned transportation and existing buildings. Implementation of the resolution must correct historic economic and racial inequities.

“They gave me the resolution and were like, ‘Good luck! Go at it!’” jokes Luis Aguirre-Torres, who came on as Ithaca’s sustainability director in April 2021. At the time, the city hadn’t yet conducted a greenhouse gas inventory to find out where its emissions were coming from, so that’s one of the first things he set out to do. Based on a study commissioned by the City, 57% of emissions are coming from buildings, he said, making them the single highest priority for action.

Although the Green New Deal called for creation of a green building policy for existing structures by 2021, that hasn’t happened yet, so Aguirre-Torres just has incentives to work with for now. “We’re at the very beginning of this crazy adventure,” he told BuildingGreen.

But Ithaca is much further along than most of the rest of the world. And that needs to change.

“Even if every new building designed from today forward meets the zero-carbon operations standard, buildings and cities will continue emitting more carbon pollution than industry, agriculture, or transportation,” writes Carl Elefante, FAIA, senior fellow at Architecture 2030 and a former president of the American Institute of Architects (AIA). “There is no pathway to a zero-emissions building sector without zeroing out emissions from America’s 325 billion square feet of existing buildings.”

“Existing buildings are where it’s at,” agrees Z Smith, FAIA, principal and director of sustainability and building performance at EskewDumezRipple. Smith is also the coauthor of a forthcoming American Institute of Architects (AIA) publication titled Building Reuse for Climate Action. Based on his research, Smith argues, “The only way we can decarbonize at scale and speed is to sweep through the existing building stock.”

The problem? Existing buildings are all over the place in terms of age, condition, historic value, envelope efficiency, mechanical system replacement cycles, regional grid fuels, and many other factors. So there can be nearly as many decarbonization strategies as there are existing buildings.

Yet there are some guiding principles that transcend this problem. Here we take a look at how teams are approaching existing building decarbonization—making the case, ensuring it pays for itself in a reasonable time frame, and developing strategies that can be applied at scale.