A new software tool developed by Cornell researchers can model a small city's building energy use within minutes on a standard laptop, then run simulations to help policymakers prioritize the most cost-effective approaches to decarbonization.
Using the City of Ithaca, New York, as a case study, the urban building energy model quickly mapped more than 5,000 residential and commercial buildings and their baseline energy use. Simulated investments in weatherization, electric heat pumps and rooftop solar panels, while also factoring in financial incentives, generated insights that are informing city efforts to achieve carbon neutrality by 2030.
The tool's automated workflow, accessibility and accuracy - without advanced computing power - could be particularly valuable for smaller cities that lack resources and expertise dedicated to decarbonization, the researchers said. But they said the new model - now also supporting the county that surrounds Ithaca - could be further scaled up to serve big cities or an entire state.
"We're really excited that this can scale and is efficient enough even for a state to map out energy consumption and the potential for retrofits - what they mean from a carbon emissions perspective, a financial perspective or just an efficiency perspective," said Timur Dogan, associate professor in the Departments of Architecture and Design Tech in the College of Architecture, Art and Planning. "From a small city to a county or state, this can really shape policies and how you prioritize policies."
Dogan is the first author of "A Bottom-up Urban Building Energy Model for Evaluating Thermal Load Electrification Measures," published July 24 in the Journal of Building Performance Simulation. Co-authors include Chengxuan Li, a doctoral student in systems engineering and research assistant in Dogan's Environmental Systems Lab; Hung Ming Tseng, M.S. AAD '24; Amber Jiayu Su, B.Arch. '25; and Patrick Kastner, M.S. '21, Ph.D. '22, an assistant professor of architecture at Georgia Tech.
The building and construction industry accounts for more than 37% of carbon dioxide emissions globally, according to the United Nations Environment Program. "Digital twins," including urban building energy models, are seen as key to enabling data-driven decisions about decarbonization, but their complexity and cost have limited their adoption and scalability. Oak Ridge National Lab's Model America initiative, for example, used supercomputers to process vast quantities of data to build models or test scenarios - an impractical approach for most municipalities.
Dogan said his lab's model achieves similar results - sufficient to guide planning - in a fraction of the time, while enabling iterative simulations to explore all viable scenarios. That's achieved through a series of small innovations, Dogan said, including a fast, physics-based simulation engine using lower-order energy models, and the ways buildings are described and their unknown properties inferred, aided by machine learning. The models incorporate publicly available data from geospatial maps, tax records, building permits and census data, and energy-use data from the local utility - for Ithaca, New York State Electric & Gas Corp., through an agreement with Avangrid.
The Ithaca case study revealed several "compelling and sometimes counterintuitive insights" relevant to similarly sized cities, the researchers said. For example, it showed that replacing gas furnaces with heat pumps would increase many buildings' operational energy costs, suggesting that step should be paired with weatherization and rooftop solar panels to make the transition financially attractive. And while large commercial buildings had seemed the logical first place to focus, accounting for financial incentives shifted the priority: Multifamily residential buildings would be the most affordable to retrofit, the model showed.
"The models allow you to flag properties that are interesting to look into more closely," Dogan said. "You go from 5,000 buildings and we don't know what to do, to 'These 100 are the clear ones to go after first.'"
Rebecca Evans, Ithaca's director of sustainability, said the city welcomes the ongoing partnership with Dogan's lab.
"What Timur's team is building is innovative, scalable and already being used as part of larger city and county projects," Evans said. "Urban building energy models have the potential to significantly reduce the capital necessary to identify buildings primed for electrification, bundle those buildings into portfolios and create attractive areas for investment."
The nation's biggest cities may have staffs and budgets focused on decarbonization challenges and analyses, Dogan said, but more accessible and scalable models, like the one his team developed, promise to help many smaller municipalities that otherwise would be flying blind.
"Taken together, those cities will have a massive impact," he said. "Our hope is that we can give them something they can use to make good decisions."
The research was supported by the Cornell Atkinson Center for Sustainability and the Park Foundation.
