Arup study estimates carbon savings from office to residential conversion

The study measures estimated embodied and operational carbon savings from converting Manhattan office buildings into apartments against the equivalent footprint of ground up residential construction and the office buildings’ current energy use. Manhattan office buildings below 59th Street built between the 1960s and 1990s, which would be newly eligible for conversion under New York City’s proposed “City of Yes” zoning changes, could create significant new housing within the next decade. Arup’s study demonstrates that expanding conversion eligibility could result in a 54% reduction in whole life carbon emissions by 2050 by retrofitting and reusing these buildings rather than building the equivalent area of housing from the ground up. 

“Facing concurrent crises of housing availability, office vacancy, and climate change, this report emphasizes the need to intertwine our urban development with long-term sustainability goals,” said Tess McNamara, Senior Sustainability Consultant at Arup. “The significant carbon savings that are attainable from office to residential conversions should urge policymakers and property owners to see that expanding eligibility for conversions has value for both the people of our city and the planet.” 

To calculate carbon savings, the team developed a typological framework, dividing buildings by decade, floor plate depth, and window type — all factors that impact the operational and embodied carbon savings associated with the conversion. The team performed an in-depth carbon assessment, considering structural and massing changes needed to optimize deep floor plates for residential use, window or curtain wall replacement, and a range of energy and electrification improvements that would be triggered by the conversion. 

“Housing policy is climate policy, and our City of Yes for Housing Opportunity changes will help create a city that is not just more affordable, but more sustainable,” said Dan Garodnick, Director of the NYC Department of City Planning. “I’m grateful to Arup for this rigorous and thoughtful study of how converting underused commercial buildings to residential use can reduce carbon emissions while creating much-needed housing for New Yorkers.”

The report comes as urban centers across the United States experience high office vacancy rates and housing shortages. Proposed zoning changes in New York City, and a recently announced White House initiative to convert empty office buildings into apartments through funding and technical assistance, have created a renewed focus on this tactic’s potential to create new housing. 

“This study fills an important gap to more comprehensively evaluate office to residential conversion from the carbon lens,” said John Mandyck, CEO of Urban Green Council. “Now we have a new way to quantify the benefits of repositioning vacant space to much-needed new homes for New Yorkers.”

“Expanding eligibility for office-to-residential conversions is a crucial step towards a greener, more inclusive city. This study underlines the immense potential of repurposing commercial spaces into sustainable housing solutions, aligning with our commitment to combat climate change while fostering a vibrant, accessible urban landscape,” said Councilman Justin Brannan.

The report also discovered that enabling additional office to residential conversions will help the city and building owners make progress towards the decarbonization goals outlined by Local Law 97, New York City’s nation-leading legislation that will limit emissions from large buildings. Office to Residential Conversions: The Carbon Story adds further impetus, from a sustainability perspective, for both expanding conversion eligibility and providing incentives to encourage conversion.