Case Study

660 Fifth Avenue


High-rise implements heat pumps and outdoor air systems for decarbonization

660 Fifth Avenue, developed by Brookfield Properties, highlights how a building redevelopment can be leveraged by property owners to improve functionality and efficiency of building systems, setting a successful precedent for high-rise offices of the future. The 41-story, 1.4 million square foot commercial property was built in 1957 and is currently completing a full redevelopment to modernize the building.

The decarbonization plan for 660 Fifth Avenue involves a phased approach from 2023-2035 to electrify heating and eliminate steam usage through measures such as expanding the building’s thermal network, installing water-to-water and air-to-water heat pumps, and fine tuning HVAC sequences, with the goal of reducing site EUI by 59.8% and greenhouse gas emissions by over 6,500 metric tons annually.

Brookfield Properties is a fully integrated, global real estate services company that owns and operates 40 million square feet of office, residential, hotel, and retail property in New York.

660 Fifth Avenue

Project Status


Under Construction

Monitoring & Evaluation

Emissions Reductions


Brookfield will achieve net-zero annual carbon emissions by 2035 at 660 Fifth Avenue.


“We’re excited to demonstrate our continued commitment to achieving net zero carbon by partnering with leading industry professionals and NYSERDA to identify scalable, effective solutions to drive meaningful reductions in carbon emissions in our properties. We see immense opportunity in collaborating in these types of initiatives to support the successful transition to a net zero economy.”

Michael Daschle

Senior Vice President, Sustainability

Brookfield Properties

660 Fifth Avenue
Lessons Learned

Modern heat recycling and fresh air systems help Brookfield meet accelerated climate goals.

660 Fifth Avenue

A baseline assessment is key to understanding current systems and performance, then identifying conditions, requirements or events that will trigger a decarbonization effort. The assessment looks across technical systems, asset strategy and sectoral factors.

Building System Conditions
  • System Failure
  • Equipment nearing end-of-life
  • Damage from events
  • Tenant load change
  • Comfort improvements
  • Indoor air quality improvefments
  • Facade maintenance
  • Efficiency improvements
Asset Conditions
  • Repositioning
  • Recapitalization
  • Capital event cycles
  • Tenant turnover/vacancy
  • Carbon emissions limits
  • Tenant sustainability demands
  • Investor sustainability demands
  • Building codes
  • Owner sustainability goals
Market Conditions
  • Technology improves
  • Market demand changes
  • Policy changes
  • Utility prices change
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Brookfield Properties is leveraging the redevelopment of this property to integrate decarbonization solutions that will upgrade its internal systems, reducing its reliance on fossil fuels and positioning it for full decarbonization by 2035. Brookfield Properties acquired its interest in 660 Fifth in 2018 with the intent to redevelop and reposition the property into an iconic, trophy-class office building. The redevelopment plan included a full facade upgrade to create the largest windows in New York City redevelopment history, as well as full upgrades to the property’s mechanical systems resulting in a 60% EUI reduction and 40% water use reduction at the property. In addition to major operating expense savings as result of such improvements, the property will also be able to lease space for significantly more, helping accelerate the return on investment. Further, the redevelopment shifts a majority of the property’s energy usage from steam to electric, positioning it well for performance relative to Local Law 97 requirements and enabling a 97% reduction in greenhouse gas emissions from energy when the property started sourcing 100% renewable electricity in the fall of 2023. 

Effective engineering integrates measures for reducing energy load, recovering wasted heat, and moving towards partial or full electrification. This increases operational efficiencies, optimizes energy peaks, and avoids oversized heating systems, thus alleviating space constraints and minimizing the cost of retrofits to decarbonize the building over time.

Existing Conditions

This diagram illustrates the building prior to the initiation of Strategic Decarbonization planning by the owners and their teams.

Click through the measures under “Building After” to understand the components of the building’s energy transition.

Sequence of Measures





Building System Affected

  • heating
  • cooling
  • ventilation
660 Fifth Avenue Building Before
660 Fifth Avenue Building After
Replace single pane windows and facade without wall insulation with insulated curtain wall. The curtain wall is a larger format with less mullions than a curtain wall with a 4’ to 6’ module
Replace Make up Air Unit (MAU) supplying high pressure perimeter induction units with full airside energy recovery DOAS with heating/cooling coils
Replace high pressure perimeter induction units with fin tube radiators
Replace steam turbine chillers with electric variable speed chillers
Reducing heating hot water supply temperature to 120-130F
Connect retail tenants to main condenser water loop to maximize waterside heat recovery potential
Replace lobby chiller with a heat pump chiller to supply heating and cooling reusing hydronic coils in lobby AHU. The existing cooling coil is converted to a dual purpose cooling or heating coil depending on the season
Install water source VRF condenser with DX coil to provide minimum heating of garage ventilation air, replacing steam coils in the garage MAU
Facilitate additional waterside heat recovery using water to water heat pumps that extract useful heat from the condenser water circuit(s) that would normally be rejected to ambient
Install ASHPs to provide supplemental heat injection to the condenser water and/or hot water circuits
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Reduce Energy Load 

Brookfield is incorporating several measures to immediately reduce the building’s steam demand and enable strategic implementation of low-carbon heating solutions. These include:

  • Replacing single pane windows with an insulated curtain wall.
  • Replacing steam turbine chillers with electric chillers.
  • Installing a full energy recovery dedicated outdoor air system (DOAS), which separates the building’s ventilation system from the heating system and allows each to operate independently.

Next steps include optimizing the existing hydronic system to operate at lower heating hot water supply temperatures and enable integration of air source heat pumps in the future.

Recover Wasted Heat

This project utilizes water source heat pumps in a variety of heat recovery and reuse applications to dramatically reduce steam use throughout the building by applying resource efficient electrification. The team looks to maximize heat recovery by integrating retail and tenant supplemental cooling loops to the main condenser water loop. Heat recovery measures being implemented include:

  • Thermal Network Expansion: connecting retail tenant condenser water loop to main condenser water loop to maximize waterside heat recovery potential
  • Waterside Heat Recovery: recapturing heat from condenser water loop using water source heat pumps (WSHPs) in the building’s lobby, garage, and hot water production 
  • Energy Recovery Dedicated Outdoor Air System (DOAS): recapturing heat from ventilation exhaust to condition make up air and replacing high pressure induction system with energy recovery units

Partial Electrification

After maximizing energy load reductions and recovering rejected heat, electrification solutions will be pursued, including: 

  • Electric Chillers: replacing steam turbine chillers to electric chillers
  • Air Source Heat Pumps (ASHPs): installing ASHPs to provide supplemental heating by injecting hot water to the condenser water or hot water circuits

Making a business case for strategic decarbonization requires thinking beyond a traditional energy audit approach or simple payback analysis. It assesses business-as-usual costs and risks against the costs and added value of phased decarbonization investments in the long-term.

Retrofit Costs

Decarbonization Costs

Capital costs of decarbonization for entire repositioning.

Avoided Risks

Business-as-Usual Costs

Energy cost savings.

Avoided Risks

Business-as-Usual Risks

LL97 fines beginning in 2030. 

Added Value

Decarbonization Value


Net Present Value

Net difference between the present value of cash inflows and outflows over a period of time.

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The business case for the decarbonization project at 660 Fifth Avenue was analyzed by comparing the net present value (NPV) and return on investment (ROI) of the proposed energy conservation measures against the original redevelopment scope and budget. The analysis considered factors such as implementation costs, operational cost savings from reduced steam and electricity consumption, increases in property value, and the impact of potential Empire Building Challenge funding.

Key findings from the business case analysis include:

  • The NPV of the project including Phases 0-2 plus renewable energy credits (RECs), offsets and EBC funding is $99.2 million compared to $99.7 million for the original redevelopment scope, indicating the decarbonization measures are NPV positive.
  • The marginal cost of decarbonization, at $9.72 million for Phases 0-2, represents only about 2.7% of the total $355 million repositioning budget, yet is projected to reduce site EUI by nearly 60% and carbon emissions by over 6,500 tons annually.
  • The proposed measures are estimated to generate an unleveraged 17.9% internal rate of return (IRR) with EBC funding compared to 6.7% without it, showing the important impact of public-private partnerships.
  • Annual ROI is projected to ramp up to 18-19% by 2035, creating significant long-term value.

The decarbonization efforts tie into Brookfield’s broader sustainability goals and ESG strategy across its portfolio. With over 29 million square feet of property potentially impacted, the replicable measures piloted at 660 Fifth Avenue can be a model for achieving cost-effective carbon reductions at scale. The strong business case, boosted by EBC funding, helps justify the capital allocation and paves the way for wider adoption.

While the added costs and complexity compared to business-as-usual upgrades do present risks, the robust returns, replicability, and climate benefits make a compelling case that deep energy retrofits can be a win-win for the owner, tenants, city and environment. The business case will be further bolstered as equipment costs decline, climate regulations tighten, and demand grows for low-carbon buildings.

An emissions decarbonization roadmap helps building owners visualize their future emissions reductions by outlining the CO2 reductions from selected energy conservation measures. This roadmap is designed with a phased approach, considering a 20- or 30-year timeline, and incorporates the evolving benefits of grid decarbonization, ensuring a comprehensive view of long-term environmental impact.

Strategic decarbonization roadmap for 660 Fifth Ave.
Learn More

An emissions decarbonization roadmap helps building owners visualize their future emissions reductions by outlining the CO2 reductions from selected energy conservation measures. This roadmap is designed with a phased approach, considering a 20- or 30-year timeline, and incorporates the evolving benefits of grid decarbonization, ensuring a comprehensive view of long-term environmental impact.

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