Commercial Building Deep Energy Retrofit

Description: To reduce carbon emissions from buildings, the City of New York enacted Local Law 97 (LL97) in 2019 as a part of the Climate Mobilization Act. This leading-edge law places carbon caps on most buildings larger than 25,000 square feet—roughly 50,000 residential and commercial properties across NYC. These caps start in 2024 and will become more stringent over time, eventually reducing emissions 80% by 2050.

At its time of adoption, the law was the most ambitious building emissions legislation enacted by any city in the world. It includes a green power purchase option, a provision for carbon trading between buildings, and future refinement through an advisory board process.


  • Affects buildings greater than 25,000 square feet
  • Sets increasingly stringent limits on carbon emissions per square foot in 2024 and 2030
  • Flexibility to comply through renewable energy credits and/or emissions offsets
  • Allows some affordable housing to choose low-cost energy saving measures instead of emissions limits
  • New Office of Building Energy and Emissions Performance at Department of Buildings
  • Strong advisory board to help refine emissions metrics and limits
  • Carbon trading study and implementation plan
  • Penalties for non-compliance and variances for financial hardship


  • Covers ~50,000 buildings and nearly 60% of the city’s building area: 59% residential and 41% commercial.
  • Requires 40% citywide emissions reductions by 2030 from a 2005 baseline.
  • For covered buildings, that’s a 26% carbon cut (5.3 million metric tons) from 2019 levels, the equivalent of San Francisco’s citywide emissions.
  • Many buildings are significantly above emissions limits and will require comprehensive retrofits or alternate compliance by 2030.

The Empire State Building’s deep retrofit, completed in 2010, served as a successful large-city, large-building example leading to Law 97’s adoption. For more than a decade, Empire State Building owners worked to remake the monument as a model of sustainability. Their collective efforts slashed carbon emissions from operations at the Empire State Building by about 40%, and they aim to cut an additional 40% by 2030. This is a critically important success story as, according to the UN Environment Program, processes commonly used to construct, heat, cool, and electrify big buildings account for 39% of global CO2 emissions. This problem is even greater in densely occupied cities.

The Empire State Building retrofit strategy involved three stages and required paying careful attention to implementing changes in the right order.

  • First, insulation of the building was improved, so energy wasn’t wasted on heating and cooling occupied spaces.
    • Behind each radiator, reflective barriers were installed that send steam heat back into the building
    • Refurbished double-pane glass windows were installed with an extra layer of insulating film
    • Spaces within each double-pane were pumped full of krypton and argon gas, to prevent the transfer of heat
    • An automated system was used to raise and lower blinds in synchrony with the sun
    • By controlling the amount of sunlight streaming through windows, the shade system achieved a balance between lighting spaces and keeping them cool
  • Next, efficiency of electricity usage was increased in the building’s interior
    • Automated LED lights were installed and spaced strategically in working spaces, emitting highly directional light and very little heat
    • An automated system was used to control power use, shutting off power to key power outlets during nights and weekends, preventing drain by items left plugged in
    • Elevators were redesigned to use “regenerative braking” allowing them to store energy each time they slow to a stop and feed that power back into the building
    • With significantly reduced energy demand, equipment providing heat and power was replaced with smaller, more efficient, less costly devices
    • Its multicolored lights flashing across the city were replaced by more energy-efficient LEDs
  • Next, resources already in possession were re-used for the retrofit
    • Instead of buying new chillers, pre-existing machines in the building were gutted and refurbished
    • A system recycling condensate from the building’s steam heating system was installed to warm its tap water

In addition to the Empire State Building retrofit, Law 97 is connected with several other related NYC actions including: the 2007 NY Energy Conservation Requirements, the 2009 Law 84, and the 2019 Climate Mobilization Act (which included Law 97).

  • 2007 NYC Energy Conservation Requirements
    • To provide for a cleaner, more sustainable and energy-efficient New York City, the city’s Buildings Department requires that all New Building or Alteration Type 1, 2 or 3 applications comply with the Energy Conservation Construction Code of New York State (ECCCNYS). The ECCCNYS sets minimum efficiency requirements for buildings. These requirements include an energy statement, a professional analysis, and supporting documentation.
  • 2009 NYC Local Law 84 (also see
    • Some cities require building owners to publicly disclose the annual energy and water used in their buildings. New York City Local Law 84 initially required buildings larger than 50,000 sq. ft. to report this information. It later included buildings with over 25,000 sq. ft. Over a five-year period, emissions declined by 14% in 4000+ monitored buildings.
  • 2019 Climate Mobilization Act
    • The Climate Mobilization Act is the largest climate solution put forth by any city in the world. It consists of a slate of climate laws designed to dramatically cut carbon in New York City, including the following.
      • Local Laws 92 and 94 require all new buildings and buildings undergoing major roof renovations to be covered with solar panels, green roofs, or some combination of the two (also see laws also require all buildings to reduce urban heat hazards.
      • Local Law 95 amends the ranges for how energy efficiency grades are calculated as required by Local Law 33 of 2018. Local Law 33 of 2018 required the display of energy efficiency scores and grades for buildings required to annually benchmark their energy and water consumption. The energy label will be displayed near a public entrance and include both a letter grade and the energy efficiency score.
      • Local Law 96 establishes long-term, low-interest Property-Assessed Clean Energy financing to fund upgrades to building energy and water efficiency.
      • The centerpiece of the Climate Mobilization Act, Local Law 97 requires all buildings larger than 25,000 square feet to meet ambitious carbon reduction targets.

Law 97 is similar to legislation adopted or in-process by other cities and states:

  • Building upon benchmarking standards implemented in 2015, Washington, D.C. employs the DC Building Energy Performance Standards (BEPS) Program, an energy-efficiency standard for big buildings.The BEPS standards are based upon the median Energy Star score of reporting buildings. For projects that are not eligible for an Energy Star score, the standard is based on source energy use intensity (EUI). Starting in 2021, private buildings 50,000 square feet or greater must comply. By the third compliance period, all buildings 10,000 square feet or greater will need to comply. The first compliance cycle starts January 1, 2021, and ends December 31, 2026, for private buildings 50,000 square feet or larger. The second compliance period and the phasing in of buildings 25,000 square feet and larger starts Jan 2027 and the third compliance period, which will include all buildings larger than 10,000 square feet, starts in 2033.
  • The Washington state Clean Buildings Performance Standard (HB 1257), signed into law in May of 2019, set performance targets for the state’s existing structures. The law requires the State Department of Commerce to develop and implement an energy performance standard for commercial buildings greater than 50,000 square feet and provides incentives to encourage energy efficiency improvements. Industrial and agricultural buildings are exempt from the standard.
  • Boston’s Building Energy Reporting and Disclosure (BERDO) 2.0, adopted in 2021, builds upon the original BERDO, which was enacted in 2013 in response to the Boston Climate Action Plan (CAP). The CAP set a goal of reducing greenhouse gas (GHG) emissions 25% by 2020 and 80% by 2050. The Boston Air Pollution Control Commission is tasked with regulation and enforcement of BERDO, which requires buildings subject to BERDO regulations to report energy and water use annually and undertake either an energy assessment or energy reduction action every five years. Until now, BERDO has been primarily a reporting and disclosure ordinance, but BERDO 2.0 includes minimum building emissions performance standards, similar to ones recently passed in New York and Washington, D.C.
  • St. Louis’ buildings are responsible for nearly 80% of St. Louis’ greenhouse gas emissions. The city will not achieve its goal of a 100% reduction in greenhouse gas emissions by 2050 without aggressive action to decarbonize buildings. St. Louis Building Energy Performance Standard (BEPS) Ordinance 71132 applies to municipal, commercial, institutional and multifamily residential buildings 50,000 square feet and larger, which covers roughly 1,000 buildings in the city. The performance metric codified in the standard is energy use intensity — a site’s energy use divided by its gross floor area — as calculated by Energy Star’s Portfolio Manager online tool. Performance standards must be set for each building type by May 4, 2021, with the first compliance deadline coming in May 2025. The standard will be set to ensure that 65% of the buildings in each property type will have to save energy to comply with the law. The standards will be reviewed and updated every four years.

Goal: Commercial Building Deep Energy Retrofit

Net reduction of buildings’ CO2 emissions and energy consumption.

Time to Implement:
The NYC Local Law 97 has a legacy of related efforts that extend from President Clinton’s 1988 Climate Initiative. Its effectiveness was confirmed in part by projects such as the Empire State Building retrofit beginning in 2010, and formalized as Local Law 97 in 2019.


Ordinance: Local Law 97, enacted on May 19, 2019, as part of the City’s Climate Mobilization Act,

2019 Climate Mobilization Act

2019 Climate Mobilization Act press release

2009 NYC Law 84 – Energy Use Reporting

2009 NYC Law 84

2007 NYC Energy Conservation Requirements

2007 NYC Energy Conservation Requirements

Washington D.C. Building Energy Performance Standards (BEPS)

Washington state‘s Clean Buildings Performance Standard

Boston’s Building Energy Reporting and Disclosure (BERDO) 2.0

Boston Passes Ambitious Ordinance Targeting Zero Emissions for Large Buildings by 2050

St. Louis Building Energy Performance Standard (BEPS) Ordinance 71132

Additional Information:

Washington Post article May 27, 2020 “Empire State of Green”:

“2019: A Big Year for Reducing Building Emissions in NYC”

“Local Law 97 of 2019: Understanding the NYC Building Emission Limits”,it%20covers%20nearly%2060%2C000%20buildings

“Local Law 97”

“All About Local Law 97” – Urban Green Council”

“The Department of Buildings (DOB) Greenhouse Gas Emission Reporting”

“DC Building Energy Performance Standards; A high level overview of DC’s BEPS, including FAQs”

“Washington Blazes a Trail for State Action on Energy Efficiency”

“Building Sustainability Highlight: Boston’s BERDO 2.0”

City of Boston website – “Developing Carbon Targets for Existing Large Buildings”

“Boston Will Require All Large Buildings To Get To Zero Carbon Emissions by 2050”

“St. Louis Adopts Midwest’s First Building Performance Standard”

Contact Info:

For feedback, comments, and questions about NYC Local Law 97 please email or

Sectors(s) Buildings, Energy
State(s) , , , ,
Date First Adopted May 19, 2019
Last Updated March 17, 2022
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