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Local Law 97- Sustainable Building NYC - Forum BuildIng Design Experts

Local Law 97- Sustainable Building NYC

1 year ago
Local Law 97NYC greenhouse gas emissions interactive map developed by Jill Hubley, 2015

As part of the realisation of the Climate Mobilization Act, the largest climate solution set forth by any city in the world, the enactment of Local Law 97 in May 2020 requires buildings in NYC over 25,000 square feet to reduce their carbon emissions by at least 40% by 2030. This interim requirement is part of the projected goal of carbon neutrality by 2050 (as outlined in the Paris Agreement).

Law coverage and implementation

Local Law 97 encapsulates nearly 60% (3.15 billion SF) of NYC building area. The emissions limit that property owners must comply to is determined by the Intensity Limit (metric tons of CO2e per square foot) multiplied by its gross floor area per occupancy group (LL97 § 28-320.3.1). The emissions limit will be implemented starting January 2024. Property owners need to evaluate their buildings and take appropriate action to meet this requirement by submitting a compliance report, due May 1, 2025 (and yearly after the first report). Failure to comply will result in penalties (§ 28-320.6)

Definition of building emissions

What does Building Emissions actually mean? Local Law 97 defines the term as “greenhouse gas emissions as expressed in metric tons of carbon dioxide equivalent emitted as a result of operating a covered building and calculated in accordance with rules promulgated by the department in consultation with the mayor’s office of long term planning and sustainability”. The law also outlines some extenuating circumstances where CO2e emissions need not be calculated such as “greenhouse gas emissions emitted during a local state of emergency declared by the mayor…”  or “a state of emergency declared by the governor pursuant to sections 28 of the executive law, where such local or state emergency has an impact on building emissions.” (LL97 § 28-320.1)

An Office of Building Energy and Emissions Performance was established in NYC Department of Buildings in 2019 to oversee the implementation of the law and work with the advisory board to develop rules, guidelines, benchmarking, metrics and a roadmap to varied circumstances. As designers we need to quickly develop tools and develop processes that effectively assess new builds and retrofits within this context.

Alternative approaches 

As an alternative to minimizing emissions and following  prescriptive limits, three alternative approaches to compliance are provided:

  • A Carbon Trading Program (report developed by Urban Green) which allows the exchange of credit between properties in the case of under-qualification or over-qualification of the emission cap (§ 28-320.11 ). Carbon trading is still under research and was scheduled to be published January 2021.

  • Owners may purchase Renewable Energy Credits (RECs) to deduct their carbon emissions by delivering renewable energy generated to the NYC electric grid (§ 28-320.6.1). This has led to owners incorporating renewable energy sources to new designs and retrofitting existing buildings.  This page from Environmental Protection Agency defines and outlines the attributes of RECs and its difference with the next approach – Offsets.

  • An option for owners to purchase Greenhouse Gas Emissions Offset (§ 28-320.1) allows deduction of up to 10% of the prescriptive emissions limit. The offset is defined as “a credit representing one metric ton of carbon dioxide equivalent emissions reduced, avoided, or sequestered by a project from a measured baseline of emissions and which has been verified by an independent, qualified third party in accordance with offset standards referenced by rules of the department”. Details of the verification process and criterias in the emissions offset can be found in LL97 § 28-320.3.6.2.

Image via NYC Department of Citywide Administrative Services

Special Circumstances

Adjustment to the applicable annual building emissions limit was made possible for buildings of varied circumstances such as hospitals, healthcare facilities, and other buildings based on density or other factors (§ 28-320.7). The adjustment will be in a percentage reduction.

Calculate building emissions 

Greenhouse gas coefficient of energy consumption is defined in sections 28-320.3.1.1 and 28-320.3.1.2 of the law for respective calendar years (up to 2030 at this time). This also shows the proportion of greenhouse gas contributed per energy source (electricity, fuel oil, natural gas, steam). A calculation tool developed by BE-Ex helps those looking to start evaluation to quickly calculate the current emissions and compare with the emissions limit described above.


Although the first compliance report is due May 2025, we encourage early action by property owners to start thinking and planning in terms of sustainable development and management. The implementation timeline developed by Urban Green gives an overview of local law 97 agenda. 

In our article on Sustainable Building Design we have outlined the multiple changes upcoming in the AEC industry in response to the climate emergency. Design and construction professionals can work with clients to achieve the best result considering diverse factors involved in the lifecycle of a building. You can also learn more about the different strategies and performance indicators that have been implemented in the US driven by the Environmental Protection Agency and the LEED certification system in our Green Building Design article.

Below is a short video by Carbon Visuals supported by Environmental Defense Fund which visualizes the greenhouse gas volume in sphere in real time on the street. At standard pressure and 59 °F a metric ton of carbon dioxide gas would fill a sphere 33 feet across (density of CO₂ = 1.87 kg/m³). One sphere is released every 0.58 seconds. The diameter coincides the width of streets in NYC (each standard block in NYC is 200 ft x 800 ft).

Find more articles about sustainable building design in our blog!

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