It may be time to reconsider energy efficiency exemptions for historic buildings
Despite the longstanding rhetoric, older buildings are not always greener. For example, a recent analysis found that the Federal Reserve Bank of New York in 1919 was exceeding its 2024 emissions target, and the American Stock Exchange Building in 1920 is now exceeding it. (Photo: beyond my ken and Shinjoji)
By now, it is well known that the construction industry and the built environment contribute significantly to greenhouse gas emissions and energy consumption.For example, over 70% New York’s greenhouse gas emissions come from buildings. Still, although many cities have adopted stricter energy code requirements in recent years, historic buildings in the United States continue to receive exemptions for energy performance and environmental impact.
This status quo has been largely unchallenged since energy code exemptions for historic buildings were introduced in the 1970s. Environmentalists have since argued that older buildings are, on average, more energy efficient, but there isn’t much data to support that claim.
Our team, led by Columbia University professors Erika Avrami, thought it might be time to reconsider these default energy code exemptions for historic buildings.in a Recent studies, we try to clarify the facts: despite longstanding protectionist rhetoric, old buildings no Always greener.In fact, the energy code exemption will only historical buildings In a more challenging post today, as cities like New York begin mandating greenhouse gas emissions to combat the climate crisis —no Exemption of Historic Status.
Quantitative Problems: The Case of New York City
In recent years, more data sources on building energy use have become available, making it possible to analyze how “green” older buildings are. Many cities and states have established energy auditing and benchmarking programs, and owners of non-historic and historic buildings are obligated to disclose energy performance metrics for properties that exceed designated square footage.New York City is one of the cities that has implemented such a policy, starting in 2009 local method 84 and due to the Local method 133 2016.
Using the report’s 2018 baseline data, our research found that the conclusions of a 1977 study of New York City office buildings of different ages — which underpinned the claim that older buildings were greener — actually had controversial. Not only did this earlier study examine a fairly limited sample to reach these conclusions, but their findings were based on comparing the average energy consumption of buildings over different decades. The average is a poor measure of energy performance because it fails to indicate the variability and range of energy consumption data, resulting in a misleading single value characterizing a building’s performance over a specific period. The 2018 baseline data provides more data points than earlier studies, providing a more reliable picture of the existing building stock. This updated dataset shows that the energy consumption of older office buildings has become more widespread over time. Taken together, these conclusions question the generalization that older buildings inherently have better energy performance.
The 1930 building now known as 30 Rockefeller Plaza is exceeding its 2024 emissions target. The Empire State Building in 1929 is achieving its goals. (Photo: Library of Congress)
Too late to adapt?
This more accurate understanding that not all older buildings are greener — in fact, some have staggering rates of energy consumption — raises a pressing question: Are historic buildings ready for the climate crisis?
Long-standing energy code exemptions for historic buildings suggest the answer is somewhat daunting. Code revisions are made every few years, and requirements typically become more stringent with each iteration, taking into account previously unavailable techniques and approaches to improve energy performance. Most existing buildings have been affected by these changes, and their owners have responded accordingly by retrofitting, opting for cleaner energy and other measures. This sequence of regular updates makes each change relatively manageable with small increments.
In contrast, historic buildings do not have to keep up with changing energy regulatory requirements through this cumulative update. This stagnation makes it harder to imagine what would happen if historic buildings were suddenly required to meet the same energy demands as other buildings: they would save decades of energy to catch up, resulting in huge costs and complex renovation projects. The sheer number of exemptions illustrates the magnitude of the challenge: Our analysis shows that, in New York’s case, roughly one-third of Manhattan’s floor space is exempt from energy regulations based on historic status.
Recent New York City legislation to limit greenhouse gas emissions from buildings broke the pattern of historic building exemptions. local method 97, City 2019 Climate Mobilization Act, which sets emission limits that buildings larger than a threshold square foot must meet by 2024. Among the buildings affected are designated historic estates — 3,821 tax lots and more than 578 million square feet across New York City — which to date are energy code-exempt. If these historic buildings are to meet the restrictions of Local Law 97, the rule would require many owners to face a steep energy efficiency “learning curve.” Baseline data once again provides a glimpse into the problems ahead: About a quarter of designated historic properties subject to Local Method 97 exceed emission limits, according to values reported in 2018.
Distribution and concentration of historic buildings affected by greenhouse gas laws in census tracts. source: Avrami et al. 2021
wide range of challenges
While our research used New York City as a case study, greening historic buildings that have long been exempt from energy regulations is a national problem.
To assess the prevalence of such exemptions, we also examined building codes used across the United States. A review of state energy regulations found that in all 50 states and the District of Columbia, buildings listed on the National Register of Historic Places or eligible for the National Register of Historic Places qualify as “historic,” making them exempt. Some state-level regulations also grant exemptions to buildings designated on state and local historic registers, further expanding the number of buildings that can bypass energy code regulations.
Given the ubiquity of exemptions, there is an undeniable challenge to retrospectively greening historic buildings. Now more than ever, it is important to reassess the relationship between the historic built environment and the climate crisis—challenges that should not be tackled by conservationists alone, but by climate scientists and others committed to fighting the climate crisis. People who struggle face together, through close partnership and ongoing, meaningful dialogue.
Anna Gasha is a PhD student in Historic Preservation. Jennifer Most and Shreya Ghoshal are also co-authors of the study.
