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NREL: Helping Cities Achieve Just and Equitable Climate Futures Through Residential Energy Retrofits

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Already a pioneer in applied building simulations, the National Renewable Energy Laboratory (NREL) expanded its partnerships to the city level, utilizing its ResStock™ tool and place-based data to help develop a roadmap for residential energy efficiency in Chicago through the Chicago Advanced Building Construction project.

As part of its partnership with nonprofit Elevate, the city of Chicago, and electric utility ComEd to perform a tailored, actionable, city-scale analysis, NREL simulated a wide range of building energy retrofits using housing stock characteristics. These simulations produced a portfolio of energy efficiency measures that could result in up to $49 billion in utility bill savings through retrofit improvements to Chicago’s residential building stock, made up of primarily single-family homes.

“This has been a highly significant partnership for NREL,” said Janet Reyna, senior research engineer and NREL lead for the project. “From a technical development standpoint, we’ve strengthened our capability to take our national-scale tools and affordably adapt them to a local context with high-fidelity results.”

Tackling the challenges of retrofitting an older building stock—over 40% of Chicago’s residential housing was built before 1942—required both extensive knowledge of Chicago’s buildings, energy use, and communities and an understanding of how to effectively apply building modeling tools in a community context.

To run its ResStock tool using an accurate baseline for Chicago’s housing, NREL calibrated ResStock for Chicago to accurately model gas and electricity use, and customized inputs such as fixed and variable utility rates and city-specific housing characteristics.

“Elevate and NREL’s partnership has been very beneficial for the city of Chicago,” said Angela Tovar, chief sustainability officer for the city of Chicago. “Elevate brought experience working in and with communities and deep knowledge of the housing types, and we are excited to apply NREL’s ResStock models to Chicago to develop the roadmap for equitable home energy upgrades that will bolster community health, wealth, and resiliency.”

The analysis found that sizeable energy savings are achievable through the application of heat pumps and other off-the-shelf technologies, a finding especially significant given Chicago’s cold climate and high heating needs, according to Elevate and NREL. In addition, heat pump upgrades would provide families with access to efficient air conditioning, helping bolster the city’s resilience against future climate events, such as heat waves.

“What’s important about this work is that we’ll be able to tell homeowners, with confidence, how their energy costs will change when they do energy efficiency and electrification upgrades,” said Lawrence Kotewa, principal investigator for the Chicago Advanced Building Construction project and chief engineer at Elevate. “That’s really important, because with technologies like heat pumps that a homeowner isn’t familiar with, telling them what they can expect for their energy costs can help them be on board with installing this system in their home.”

Elevate will implement and validate these energy efficiency measures in Chicago homes through advanced whole-home retrofit packages. The project aims to demonstrate that 50% energy reduction is feasible in the existing Chicago single-family housing stock, identify opportunities in historically under-resourced communities, and ultimately decrease carbon emissions and improve energy equity.

This work will also help inform municipal policy decisions by demonstrating which energy efficiency interventions are low cost, energy saving, and scalable.

“This analysis prepares the city of Chicago well to deploy equitable beneficial electrification, efficiency, and solar at scale,” said Lindy Wordlaw, project manager for the Chicago Advanced Building Construction project and associate director of community planning at Elevate. “With the release of ResStock’s national building characterization and data, NREL is well positioned to partner with community-based organizations and municipalities across the nation.”

For NREL, the project is unique in that it links detailed simulations using ResStock with real-world data. This will provide NREL researchers with more confidence in ResStock results while helping identify technical and nontechnical barriers to wide-scale retrofits, making theoretical results more concrete and actionable.

The project, funded by the U.S. Department of Energy’s Advanced Building Construction Initiative, places NREL among a select group in the published building energy space to conduct city-scale energy analyses using a bottom-up, detailed simulation model that draws on local partnerships and place-based data. It is expected that NREL’s expertise in performing large-scale and detailed building stock simulations will help other cities improve energy efficiency, affordability, and equity in the future.

“It’s been exciting working with Elevate and the city of Chicago because our results are leading to real decisions and real outcomes that can deeply reduce energy use and improve quality of life for Chicagoans,” Reyna said. “From this project, we feel well positioned to support other cities throughout the country as they tackle retrofits and electrification of their building stocks.”

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