Buildings’ importance in the fight against global climate change has been well established. However, the problem is diverse because new and existing buildings play different roles. A model code from the New Buildings Institute (NBI) is designed to help cities tackle emissions specifically from the large stock of existing buildings.

The model code Existing Building Decarbonization Code was published on Sept. 19, 2022. It is considered an overlay to the 2021 International Energy Conservation Code (IECC) and an addition to the Building Decarbonization Code published by NBI in 2020.

NBI describes the code as a “a new way for jurisdictions to reduce carbon emissions.” It will also help them “meet climate action plan goals and interconnected goals around public health and equity.”

The code is designed to address a challenge unique to building emissions. With new construction accounting for a very small percentage of building activity in a given year¾2%, according to NBI¾the effort to reduce building emissions must focus on existing stock to have a significant impact.

The issue is compounded by the fact that contemporary codes make new buildings and their construction more efficient. Existing buildings, which were constructed under older codes, have greater emissions. Reductions can and must be achieved through retrofits to reach specific goals.

NBI recognizes the enormity of the problem, noting that the United States currently has 5.9 million existing commercial buildings, which account for 97 billion square feet of space. However, it also sees the potential for significant reductions, projecting that cities could cut about 30% of all urban emissions by 2050 if they were to require existing buildings to be more energy efficient.

NBI acknowledges the challenges posed by retrofitting existing buildings and offers strategies to achieve reductions in a realistic way. It does so by identifying “replacement events” and “trigger events” as the most opportune time to implement changes that will help decarbonize buildings. For example, changes in occupancy, additions and alterations are envisioned as key opportunities to make cost-effective retrofits.

Some of the key technologies identified by the code to help existing buildings reduce their emissions include efficiency, on-site renewable energy generation, electric vehicle charging and battery storage.

Finally, while the code embraces an all-electric path for buildings, it is also flexible and includes options for an approach based on “mixed fuels,” including natural gas.

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