NYC’s climate legislation journey began in 2007 with PlaNYC, a strategic plan addressing environmental sustainability and climate change. PlaNYC pledged a 30% reduction in annual citywide GHG emissions by 2030 (PlaNYC, 2007). To this end, the 2009 Greener, Greater Buildings Plan (GGBP) focused on measuring and optimizing the energy efficiency of large buildings. Table 1 outlines the GGBP four-law policy package. Between 2005 and 2012, NYC’s building emissions dropped by 19.3%, largely due to the replacement of carbon-intensive fuel oils with natural gas. The GGBP itself achieved only modest emissions reductions; nevertheless, it gathered energy efficiency data which would inform future policies (City of New York, 2013).

In 2019, under Mayor Bill de Blasio’s direction, NYC enacted the Climate Mobilization Act, colloquially termed NYC’s Green New Deal (Willdan, 2021). While its centerpiece was LL97, several other laws to curtail building emissions were included (Table 1). Between 2010 and 2022, GHG emissions from LL84-benchmarked buildings fell by 27% (Urban Green Council, 2024a).

Beginning in 2024, LL97 set limits on GHG emissions from large buildings in NYC. Table 1 outlines covered building parameters, with exceptions including power-generating facilities; certain condominiums less than or equal to three stories with individual tenant heating, ventilation, and air conditioning (HVAC) systems; certain public housing; buildings with rent-regulated units; and dedicated places of worship. The annual emissions limit for each eligible building is calculated by multiplying its square footage by an emissions factor tied to its occupancy type. These annual limits will become increasingly stringent in 2030, 2035, and every 5 years thereafter. A building’s annual emissions output is determined by multiplying its annual energy usage by a “greenhouse gas coefficient” specific to the fuel type(s) utilized. GHG coefficients are subject to change over time: for instance, the electricity coefficient is expected to decrease as NYS’s power grid transitions to cleaner energy sources. Noncompliant buildings face penalties of up to $268 per ton of CO₂e emissions exceeding the cap. However, leniency in the determination of penalties is available for buildings that exhibit “Good Faith” efforts to comply, suffer unforeseeable circumstances preventing compliance, or lack the financial means to comply, especially if civil penalties affect the operation of life-saving facilities. LL97 also permits deductions from annual reported emissions by (i) investing in climate change-mitigating projects (i.e., GHG offsets); (ii) purchasing renewable energy credits; (iii) using onsite clean energy resources (e.g., solar panels); and (iv) installing certain electric appliances that meet minimum efficiency standards prior to 2030 (i.e., building electrification credits) (New York City Council, 2019a).

NYC’s “Getting 97 Done” plan offers further assistance to ease compliance. The plan addresses four focus areas: (i) identifying government and utility-based financing and funding for upgrades; (ii) providing buildings with technical advice through the “NYC Accelerator” program; (iii) implementing flexible enforcement mechanisms (e.g., “Good Faith” provision); and (iv) decarbonizing electrical systems in partnership with NYS (New York City Office of the Mayor, 2023).

Ultimately, LL97 impacts 50,000 buildings spanning 3.15 billion square feet or roughly 60% of NYC’s building area. 59% of these buildings are residential, and 41% are commercial. The 2024–2029 limit is expected to affect the most carbon-intensive 20% of buildings in NYC. The 2030–2034 limit will cap the most burdensome 75%, yielding an anticipated 40% reduction in citywide emissions compared with a 2005 baseline (Urban Green Council, 2023a). As of 2022, benchmarking data demonstrate that 88% of all LL84-covered buildings comply with the 2024–2029 limit and 35% with the 2030–2034 limit (Urban Green Council, 2024b).

Table 2 highlights key NYS laws that work in tandem with LL97 to advance climate objectives. Most notably, the 2019 Climate Leadership and Community Protection Act (CLCPA) sets legally binding targets for carbon emissions over time. The CLCPA aims to achieve statewide net-zero GHG emissions by 2050 (New York’s Climate Leadership and Community Protection Act, 2024). To support this, the CLCPA commits NYS to 100% emissions-free electricity, with an interim target of sourcing 70% of electricity from renewable energy by 2030. The plan includes deploying six gigawatts of solar energy by 2025, three gigawatts of battery storage by 2030, and nine gigawatts of offshore wind power by 2035 (The State University of New York, 2024). Several environmental justice provisions are incorporated to ensure an equitable energy transition. At least 35% of the benefits from state climate programs are designated for disadvantaged communities (New York’s Climate Leadership and Community Protection Act, 2024).

The relationship between NYC building emissions policies and global health is complex. Even in an ideal scenario of global net carbon neutrality, Earth’s temperature is unlikely to stabilize for decades, underscoring the long-term nature of climate mitigation efforts (Inman, 2008). Therefore, understanding the global health implications of LL97 requires acknowledging that the impacts of modern-day investments against fossil fuel burning may only materialize in future generations—and only if similarly ambitious policies are embraced worldwide. The buildings and construction sector accounts for more than one-third of global energy consumption and GHG emissions. It represents a leading impediment to achieving climate resilience and advancing global health (Global Alliance for Buildings and Construction, International Energy Agency and the United Nations Environment Programme, 2019; Zhong et al., 2021). Efforts like the United Kingdom’s Minimum Energy Efficiency Standard, Germany’s Buildings Energy Act, Montreal’s Building Emissions Bylaw, and Dubai’s Green Building Regulations reflect a growing appreciation for the carbon footprint of our built environment. Compared with these, LL97’s aggressive targets, broad application to existing buildings, and innovative compliance options are notable. Nonetheless, critics question both its rigorousness and flexibility. The strengths and limitations of LL97 offer a compelling case study in how urban centers can implement building emissions legislation to optimize environmental and public health outcomes.

While LL97 has theoretical implications for global health, its local public health impact could be more immediate. Although scant literature has quantified LL97’s health impacts due to its only recent implementation, insights can be drawn from prior decarbonization efforts. For instance, NYC’s Climate Mobilization Act and NYS’s All-Electric Building Law aim to reduce onsite fossil fuel combustion in favor of electrification (Mananga et al., 2023). Gas infrastructure generates harmful air pollutants, such as nitrogen oxides (NO_x), carbon monoxide (CO), and PM_2.5, which are linked to the development of chronic obstructive pulmonary disease (COPD), asthma, and lung cancer (Perera, 2017; Kashtan et al., 2024). Cumulative improvements in NYC’s outdoor air quality over the past two decades illustrate the transformative impact of previous decarbonization efforts. Between 1998 and 2021, ambient PM_2.5 and NO₂ concentrations dropped by 37 and 31%, respectively (Lau et al., 2024). The Climate Mobilization Act also incentivizes the replacement of gas-powered heating systems and stoves with electrical alternatives, resulting in improved indoor air quality. A pilot program replacing gas stoves with induction stoves in NYC public housing found a 56% reduction in mean daily NO₂ concentration exposure. During cooking periods, the median NO₂ concentration in gas homes rose from a baseline 18 ppb to 197 ppb, while the change was negligible in induction homes (Daouda et al., 2024). Long-term exposure to gas stoves increases the odds of respiratory illness in children by 20% (Hasselblad et al., 1992). Likewise, an estimated 18.8% of childhood asthma cases in NYS are attributable to gas stove use (Gruenwald et al., 2022). Based on estimates of pediatric asthma prevalence in NYS, we may extrapolate that the eradication of gas-powered appliances would result in ~60,000 less pediatric asthma cases.

Furthermore, LL97 also incentivizes the adoption of more energy-efficient and reliable HVAC systems, which protect against heat-related morbidity and mortality. Between 2013 and 2022, nearly all heat-stress deaths in NYC occurred among decedents who did not have or use AC at home, in part due to financial constraints (2024 NYC Heat-Related Mortality Report, 2024). Extreme heat exposure poses direct risks such as heat stroke and exhaustion, while also exacerbating chronic health conditions and mental health disorders. Heat waves are linked to increased rates of acute coronary syndrome, myocardial infarction, stroke, congestive heart failure, asthma, COPD exacerbation, acute renal failure, and kidney stones (Bell et al., 2024). Additionally, ED visits for substance use disorders, anxiety, stress-related disorders, mood disorders, schizophrenia, and self-harm spike during periods of elevated ambient temperature (Nori-Sarma et al., 2022). Heat exposure has even been correlated with higher rates of violent crime in urban areas (Heo et al., 2024). Air conditioner use is a well-established safeguard against the harmful effects of extreme heat, including aggression (Sera et al., 2020). By promoting energy-efficient HVAC systems, LL97 will mitigate financial obstacles to AC use, especially during periods of high electrical demand in hot weather.

Lastly, LL97 promotes environmental justice by addressing the disproportionate impact of air pollution and climate change on marginalized communities (Picciano et al., 2023; Tessum et al., 2021; Khan et al., 2024). Over half of households in NYC still use piped gas for heating and cooking, and a disproportionate number are found in low-income public housing (Stack, 2023; Tan & Kresowik, 2021). These residences are often smaller in size and inadequately ventilated, resulting in even greater exposure to the same level of emissions (Daouda et al., 2024). A recent study revealed that communities of color in the NYC metropolitan area face 41% higher exposure to PM_2.5 emissions from residential gas combustion compared to the general population (Tessum et al., 2021). These health inequities are further perpetuated by the fact that 70% of low-income residents in NYC are renters who have limited control over the energy source of home appliances. Under LL97, the NY Housing Authority, which provides homes to around 400,000 low-income residents, has committed to electrifying all of its buildings (Daouda et al., 2024). These mandated upgrades will improve indoor air quality for low-income and minority communities who may otherwise lack the resources to access such protective measures. Additionally, environmental inequities extend to heat-related mortality: black NYers have an age-adjusted heat stress mortality rate twice that of white NYers, and rates are higher in impoverished neighborhoods. Black and low-income NY residents are also less likely to own or use an air conditioner (2024 NYC Heat-Related Mortality Report, 2024). Upgraded energy-efficient HVAC systems can provide relief from these disparate financial and health burdens.

Policy gaps and resistance efforts threaten to undermine the effectiveness of LL97. First, building electrification is unlikely to yield net benefit without a transition to renewable energy sources. Currently, NYC’s carbon-intensive electricity grid contributes disproportionately to GHG emissions, with electricity accounting for 8.9% of building energy usage but 10.7% of emissions (The City of New York Mayor Eric Adams, 2023). Achieving the CLCPA’s goal of emissions-free electricity by 2030 would require installing 20 gigawatts of renewable energy capacity—a 200% increase (Office of the New York State Comptroller, 2023). Given that only 12.9 gigawatts of total electrical energy capacity has been added in the last two decades, this target appears ambitious. Building emissions cuts must be coupled with realistic renewable energy expansion goals to ensure that the burden of emissions is not transferred across sectors.

Financial incentives under LL97 also pose concerns. On the one hand, compliance caps might not be stringent enough with building owners opting to pay fines instead of investing in costly energy upgrades (Urban Green Council, 2019). The equitable implementation of LL97 raises questions, as retrofit or penalty costs could be passed to tenants. Advocates urge NYC to codify rules protecting building occupants from harboring these costs (Align NY, 2023). The Climate Mobilization Act most directly addresses equity concerns by establishing more lenient compliance pathways for buildings with rent-regulated or affordable housing units as well as a low-interest loan program to fund renovations. Still, federal funding may be unsustainable and unreliable in the years to come (Align NY, 2023). Conversely, loopholes intended to promote equity may be widely leveraged, significantly delaying progress (WE ACT for Environmental Justice, 2023).

Lastly, opposition efforts threaten LL97. The gas industry and conservative politicians have challenged the law’s constitutionality and raised concerns over higher utility costs (Stack, 2023; AP News, 2023). Glen Oaks Village Owner, Inc. vs. City of NY (2023) argued that LL97 penalties constitute improper taxes and violate due process rights (Glenn Oaks Village Owners Inc. v. City of New York, 2022). The case was reinstated in May 2024. At the same time, political efforts can undermine LL97. Intro 772 was introduced in the NYC Council. It would exempt thousands of buildings from LL97 changes by establishing loopholes in a building’s gross floor area calculation and adjusting limits based on prior efforts (New York City Council, 2024). These struggles highlight the politically polarizing effect of climate change initiatives and underscore the need for enforceable policies.