New York City Local Law 97: Decarbonization and the Challenges of Going Green

With the arrival of the new year, it’s important to remember that our resolutions should be challenging. To paraphrase Stanford School of Medicine neuroscientist, Andrew Huberman, participating in challenging tasks builds resilience to deal with future unknowns. The New York City Department of Buildings’ NYC Sustainable Buildings department was likely not aware of that statement, but it certainly plays a role in the upcoming 2024 greenhouse gas emission limits to be enforced in accordance with Local Law 97 (LL97). Cutting emissions will prove challenging but will undoubtedly aid the city and current building owners to foster resilience to deal with future uncertainties.

For context, Local Law 97, described as “one of the most ambitious plans for reducing emissions in the nation” was introduced in 2019 as the centerpiece of NYC’s Climate Mobilization Act. Its intent is to require most buildings greater than 25,000 square feet to meet energy efficiency goals and cap annual energy use.

What does that have to do with 2024 (and Kermit the Frog’s 1970 smash hit “It’s Not Easy Bein’ Green” for that matter)? This year will be the first time emissions thresholds for buildings will be set based on occupancy type and size with fines imposed for those buildings that exceed the annual emissions limit. In short, LL97 will impose categorical emissions limits on a per square foot basis.


Navigating Local Law 97 Requirements

The natural follow-up questions become:

  1. Is my building subject to the LL97 requirements?
  2. How do I determine the greenhouse gas emissions limit for my building and what happens if I exceed the limit?
  3. How do I determine the actual annual greenhouse gas emissions for my building?

In general, buildings that exceed 25,000 square feet, or two or more buildings on the same tax lot that together exceed 50,000 square feet will be subject to the requirements of LL97. Significant financial penalties may be incurred if actual emissions exceed the allowable limit. Building owners can seek to avoid future penalties by preparing now for capital investments in energy reduction.

Determining a building’s greenhouse gas emissions limit should be a reasonable activity because many buildings are already likely complying with Local Law 84’s yearly benchmarking, which requires “all large buildings… to measure and disclose energy consumption annually.”

Calculating the actual annual emissions for a building requires a little math. Starting on Page 10 of LL97 (or § 28-320.3.1.1), different emissions coefficients are shared based on source. In the simplest sense, those are summarized below.

Energy Source Greenhouse Gas Coefficient
Electricity 0.000288962 tCO2e per kBtu
Natural Gas 0.00005311 tCO2e per kBtu
#2 Fuel Oil 0.0007421 tCO2e per kBtu
#4 Fuel Oil 0.00007529 tCO2e per kBtu
District Steam 0.00004493 tCO2e per kBtu


Table 1. Note that coefficients are shown in metric tons of carbon dioxide equivalent.

The greenhouse gas coefficient is then applied to the actual annual metered energy consumption for each energy source and converted into the respective.

Let’s look at an example sourced from Local Law 84’s public database:

Building Square Footage: 390,878 ft2
Use Type: Office
Year Built: 1961
Natural Gas: 804,271.7 kBtu
Electricity: 4,207,162 kWh or 14,354,838.4 kBtu

Assuming the above to be true, we now factor our greenhouse gas coefficients as follows:

Actual Annual Greenhouse Gas Emissions Calculation

(Electricity kBtu  x 0.000288962 tCO2e/kBtu) + (Natural gas kBtu x 0.00005311 tCO2e/kBtu)

(14,354,838.4 x  0.000288962 tCO2e/kBtu )  + ( 804,271.7 x x 0.00005311 tCO2e/kBtu)

(4148.0 tCO2e) + (42.7 tCO2e) = 4,191 tCO2e calculated annual emissions

For the purpose of LL97, this gives us an annual greenhouse gas emission value of 4,191 metric tons carbon dioxide equivalent. Offices (of building type B) have a 2024 emissions limit of 0.00846 tCO2e per square foot. Recalling the example building to be 390,878 ft2 yields a limit of 3,307 tCO2e.

Annual Greenhouse Gas Emissions Limit Calculation

Building type emissions limit coefficient x building square footage

0.00846 tCO2e/ ft2 x  390,878 ft2 = 3,307 tCO2e annual emissions limit



In this example, the emissions limit of 3,307 tCO2e is cause for concern. We calculated the building to be producing 4,191 tCO2e per year, or 884 tCO2e more than the allowable limit. In the simplest case, the building owner would be required to pay a penalty of $268/ tCO2e or $236,912 for that year. (Kermit was right!). In subsequent years, the building operations team can look to identify ways to reduce energy usage to help reduce or avoid the annual emissions and associated financial penalties.

Potential substantial financial penalties are now a critical factor when considering payback opportunities on energy capital investments. Early efforts to conduct energy audits, refine operational strategies, engage in HVAC retro-commissioning will prove invaluable when developing capital expenditure plans, reducing emissions, and avoiding steep penalties.


Future Penalties and a Path Forward

The emissions limits expressed in tCO2e per square foot only become more stringent after 2024 – dropping from 0.00846 tCO2e/SF to 0.00453 tCO2e/sf – roughly a 47% decrease for the aforementioned office building. Significant creative thinking in operations and capital planning will be required to meet those future emissions limits.

Henderson is available to assist facility owners meet the limits and deadlines set forth by Local Law 97 via a regenerative approach to energy use reduction that creates resilient and equitable integrated systems that make it a little easier being green.


Henderson Knows Sustainability

Our pledge is to lead regenerative and innovative design for a brighter, cleaner future. Henderson’s sustainability mission is to establish a regenerative mindset within our operations and design practice to realize solutions that restore, renew, and replenish sources of energy and materials while benefiting employees, clients, communities, and global ecological systems. Click here to learn more about our sustainable and regenerative design practices.

Written By

Eastern Regional Manager

Written By

Sustainability Director


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