While all of New York’s buildings must play an essential role in effective climate action, its tall residential buildings present one of the biggest challenges. Representing approximately 15% of all of New York City greenhouse gas (GHG) emissions in 2022, New York’s tall residential buildings have a predominance of natural gas and oil-powered domestic hot water and steam heating systems. Coupled with extremely low vacancy rates, the transition away from fossil fuels will be a significant and daunting challenge.

As we reach the first compliance period of NYC’s groundbreaking 2019 legislation to curb carbon emissions, Local Law 97 (LL97), and look, just ahead, to the law’s second compliance period, in 2030, when over 60% of covered multifamily buildings will need to reduce their emissions to avoid an annual penalty, this report explored several key retrofit questions, including: what GHG reductions are achievable; what building systems were upgraded; what technology was implemented; what were the challenges and opportunities; and what are the lessons learned?

Having previously explored tall office building deep retrofit case studies, in 2020 (High Rise Low Carbon Office Deep Retrofit Profiles, August 2020), this research team turned its focus to a global search for deep retrofits of existing high-rise residential buildings that resulted in annual operational carbon emissions at or below LL97’s 2030 carbon cap, limiting the search to climate zones similar to New York and only including projects with verified pre- and post-retrofit energy data.

Building Profiles

This survey profiles eighteen projects that undertook a deep retrofit that resulted in often dramatic energy reduction. A complete facade reclad, a Midtown tenant repositioning, a Chicago upgrade and densification, a midwestern energy model calibration, a Japanese climate policy demonstration project, the comprehensive repositioning of NYC’s most iconic tower, and many more, this diverse set of retrofit projects was able to achieve an average of a 36% reduction in their site energy intensity, with several projects cutting their energy use in half.

Above: excerpts from the Building Profiles. Find the complete summary list in the full report here.

As the devastating effects of the climate crisis become increasingly clear, cities around the globe are adopting building performance policies similar to New York’s LL97 designed to drive emissions reductions in existing buildings. For these aggressive regulations to succeed, building stakeholders need concrete models of how to achieve compliance, as well as the right tools and resources. These case studies show examples of how New York’s existing tall residential buildings can significantly reduce emissions and play an essential role in effective climate action.

Ken Soble Tower: Energy Conservation Measures - Overview

The Ken Soble Tower project in Hamilton, Ontario truly sets out a template for implementing a Passive House retrofit alongside electrification.

Built in 1967, the building was in need of either a complete renovation or demolition. The owner, City-Housing Hamilton (CHH), decided to maintain the structure and invest in an entirely new exterior envelope and building HVAC systems. This was undertaken in an unoccupied building; all CHH tenants had been relocated to other properties in advance of the project.

Being one of the first Passive House retrofits in the Toronto region, the design team, client, and contractor addressed numerous challenges, including quality-control on site, construction methods for air tightness, product availability, and conflicts with the building code. They managed through their issues and now have a demonstration project for site tours and a model approach for decarbonizing tall residential buildings.

Above: excerpts from the case study for Ken Soble Tower. Read more and explore the other thirteen buildings in the full report here.

Technical Solutions

As detailed in the report’s Technical Solutions Matrix, almost all projects include an upgrade to their lighting systems; most observed significant carbon emissions reductions by making improvements to their building envelopes through air sealing, adding insulation, or window replacement projects; and many implemented improvements or replacements to their heating and domestic hot water systems.

Above: excerpt from the technical solutions matrix. Read the full report here.

Each retrofit had various motivating factors, from complete repositioning of the property, to equipment reaching the end of useful life. Implementation approaches ranged from incremental improvements over many years to major renovations as singular projects.

Key Findings

It was surprisingly difficult to find 14 tall residential buildings that had completed a deep retrofit delivering more than 20% energy savings
During our research, most typical retrofits showed less than 20% savings or were low-rise residential.

Most retrofits were not part of a long-term capital plan, rather they were a reaction to building systems at end of useful life requiring immediate or urgent attention
The cost of doing nothing is not nothing.

Deep retrofits tend to be invasive and require major system replacements, which is very challenging to do in an occupied building
It is much easier to renovate an empty building, but those are very rare in the residential sector.

Residential deep retrofits completed prior to 2023 were mostly boiler replacements and facade improvements
Electrification is in early innings.

Electrification is key to deep decarbonization, but the economics of electrification need to evolve before we see conversions at scale
The cost of natural gas relative to electricity makes it hard for full load electrification to make economic sense as a standalone measure.

Verified post-retrofit data is scarce
Validated, metered, whole building energy data is what makes this compendium unique, but proved to be one of the biggest challenges in finding case studies.

Project Team

Byron Stigge, Level Infrastructure
Richard Yancey, Building Energy Exchange
Adam Hinge, Sustainable Energy Partnerships

This report made possible with the generous support of New York State Energy Research and Development Authority.