Last month’s report from the United Nations Intergovernmental Panel on Climate Change (IPCC) warns that we are falling behind in the race against global warming. To avoid what one of the report’s coauthors describes as “a sub-optimal future,” we must use every tool available to reduce carbon emissions.

One of those tools is building reuse. Reuse avoids the upfront embodied carbon emissions that occur when materials are mined, harvested, manufactured, transported, and assembled to create a new structure. Preservationists have long touted the environmental benefits of building recycling and argued that “the greenest building is…one that is already built.” We have published research (download The Greenest Building: Quantifying the Environmental Value of Building Reuse) showing that it can take from 10 to 80 years to pay back the carbon debt that is incurred when an existing building is replaced with a new structure, even if the new building is highly energy efficient.

The carbon savings achieved through building reuse are even more important today. Building construction and operations are responsible for approximately 40 percent of human produced carbon emissions worldwide. These emissions are cumulative, remaining in the atmosphere for hundreds of years. According to the IPCC, at current emission rates we will exceed our remaining carbon budget in less than 10 years. The only way to buy more time is to reduce emissions sharply and quickly.

As building operations become more efficient and the energy grid shifts to renewable sources, reducing the embodied carbon emissions from construction will become even more urgent. Although low carbon construction techniques are becoming more viable, decarbonization of the construction industry is still years off. The best way to avoid embodied carbon emissions right now, when our carbon budget is shrinking fast, is to conserve and reuse as many existing buildings as possible.

There are signs that a cultural shift toward building reuse may be underway. Voices from beyond the preservation field are joining our call to conserve buildings and materials, from climate and housing advocates to architects, and journalists. In a recent New York magazine article titled “What If New York Stopped Knocking Down Buildings,” author Justin Davidson contends that “it’s time for American cities to confront their addiction to teardowns.” But in looking for policies that might slow the pace of demolition, Davidson finds that “the only law protecting architecture from demolition is the landmarks preservation statute, which confers an inherent right to exist on buildings with aesthetic or historical value. Everything else counts as future rubble.” In New York as well as most cities, “everything else” makes up about 95 percent of existing buildings. On average, local landmarks laws protect only about one out of every 20 buildings in U.S. cities (download Atlas of ReUrbanism: Buildings and Blocks in American Cities).

To meet the climate challenge, we must extend our preservation policies farther, beyond those properties that are already designated as historic. There are approximately 125 million buildings in the United States, and more than 50 million of these structures are at least 50 years old. How can preservation policy grow to help conserve, reuse, and retrofit a larger percentage of the older buildings in our communities? Below are five suggestions for how new and expanded preservation policies can help increase building reuse and reduce carbon emissions. These ideas represent my personal views and are offered to spur discussion, debate, and innovation.

Expand preservation and zoning tools. Move beyond a “one-size-fits-all” approach to local landmarking. Offer multiple designation and design review options to increase the number of buildings and neighborhoods protected through local preservation programs. Use adaptive reuse ordinances, conservation districts, and context-sensitive zoning to encourage reuse and discourage speculative demolitions in areas outside of historic districts.

Create more building reuse incentives. Reinstate a tiered system of rehabilitation tax incentives that includes older buildings generally, as well as those designated as historic. Support enhancements to the federal rehabilitation tax credit. Work with climate advocates and other allies to position building reuse as a carbon offset in future local, state, or federal carbon tax programs.

Prioritize materials conservation in rehabilitation. Add a new “reuse” treatment that prioritizes retention of structural elements and other high carbon building materials, while allowing greater flexibility to improve energy performance. Use this treatment for buildings in conservation districts as well as non-contributing buildings in historic districts. Allow rehabilitations to include use of modular, temporary elements that can be easily dis-assembled, removed, and reused elsewhere as needs change. Add guidance on how to responsibly deconstruct unneeded building elements. Recommend life-cycle assessment of the carbon impacts of all major rehabilitations.

Strengthen demolition review policies. Flip the demolition review policy paradigm. Instead of approving all demolition requests unless a last-minute preservation alternative can be found, adopt policies that presume demolition permits will not be approved without documentation that replacement will achieve life-cycle carbon savings. Work with climate advocates on new policies that require carbon impact assessments for large redevelopment projects.

Add deconstruction to the preservation policy toolbox. Support adoption of deconstruction ordinances to require salvaging of usable materials in cases when full building reuse is not feasible. Use deconstruction programs to create jobs and build awareness of the carbon content of building materials and their value for the future. Include deconstruction as part of a full spectrum of building and material reuse policies and incentives.

These ideas are described in more detail in “Avoiding Carbon: Mitigating Climate Change through Preservation and Reuse,” a chapter in a new publication from Columbia University that explores challenges and opportunities for the preservation field as we seek to address climate change.

Preservation, Sustainability, and Equity includes essays from preservation advocates and academics on topics ranging from community relocation and energy justice to the need to better align the Secretary of Interior’s Standards with climate action. Developed and edited by Erica Avrami, Preservation, Sustainability, and Equity is the third in the three-part “Issues in Preservation Policy” series from Columbia Books on Architecture and the City. Print copies of the three books in the series are available for purchase (Volume 1 | Volume 2 | Volume 3), and all chapters may be read for free online.

The urgent need to reduce carbon emissions through building reuse will be one of the topics explored as part of an upcoming Climate Action webinar series organized by the Sustainability and Climate Action Working Group of the Preservation Priorities Task Force, the National Trust’s collaboration with the National Preservation Partners Network.

The webinar series will begin on April 12 with a session on a new “carbon calculator” that will allow preservationists, developers, policy makers, and others to evaluate the CO2 impacts of building reuse and rehabilitation compared to demolition and new construction. The Boston Preservation Alliance received a Moe Family Fund grant to develop an accessible, online application of the carbon calculator tool. Other topics in the webinar series will focus on climate justice and the outcomes for preservation from the recent COP26 meetings. Look for more details about the upcoming Climate Action webinar series on Preservation Leadership Forum.