The challenge of retrofitting existing multifamily buildings to achieve carbon-neutral performance has long seemed insurmountable. Yet the Contechtrio podcast discussions on construction technology highlight how innovative approaches are reshaping the industry. One of the most ambitious efforts comes from New York State, where James Geppner, the RetrofitNY project manager for the New York State Energy Research and Development Authority (NYSERDA), has been leading a program that uses Passive House standards as the benchmark for deep energy retrofits. In an October 2020 presentation during the Global Passive House Happy Hour, Geppner shared critical lessons on accelerating and scaling the retrofit industry. This article examines RetrofitNY’s framework, the strategies it employs, and what building professionals can learn from its journey so far. For context on how these standards work in practice, the PHIUS Passive House certification system provides the underlying technical framework that many of these projects follow.
What Is RetrofitNY and Why It Matters
RetrofitNY is a NYSERDA initiative that funds carbon-neutral retrofit and building electrification pilot projects across New York’s affordable multifamily housing stock. The program’s central objective is to develop standardized, scalable solutions that dramatically improve the energy performance of existing buildings while also enhancing their aesthetic quality and occupant comfort. This focus on standardization rather than one-off custom solutions is what sets RetrofitNY apart from conventional retrofit programs. The full catalog of NYSERDA RetrofitNY research resources provides in-depth reports on findings and lessons learned from the initiative.
The program targets a critical segment of the building stock. Multifamily buildings, particularly those serving low- and moderate-income tenants, are often the most energy-inefficient and the hardest to upgrade. Tenants bear the burden of high utility costs while building owners face thin margins that make capital-intensive retrofits difficult to justify. E5 James Dose Web Exclusive features from renovation-focused media demonstrate how deep retrofits are gaining attention across the housing sector, yet the scale of need remains enormous.
RetrofitNY addresses this gap by subsidizing demonstration projects that prove the technical and economic feasibility of deep energy retrofits. The goal is not merely to complete a handful of showcase buildings but to create a replicable model that can be deployed across thousands of similar structures statewide.
Passive House Principles Applied to Existing Buildings
At the heart of RetrofitNY’s technical approach lies the Passive House concept, a rigorous building performance standard that prioritizes five key principles: continuous insulation, airtight construction, high-performance windows, thermal bridge-free detailing, and mechanical ventilation with heat recovery. While these principles are well-established for new construction, applying them to existing buildings presents unique challenges.
Existing multifamily buildings were never designed with these performance targets in mind. Common challenges include:
- Envelope irregularities – Older masonry and concrete structures often have uneven surfaces, protruding balconies, and complex roof geometries that make continuous insulation difficult to install.
- Occupied construction – Unlike new builds, retrofits must be carried out while residents remain in the building, requiring careful phasing and dust control.
- Existing mechanical systems – Replacing HVAC systems in occupied buildings requires careful coordination to avoid prolonged service interruptions.
- Window replacement logistics – Installing Passive House-certified windows in existing openings often requires custom sizing and careful waterproofing details.
Geppner’s presentation emphasized that overcoming these challenges requires not just technical expertise but also a shift in how project teams are assembled and managed. Integrated design processes where architects, engineers, and contractors collaborate from the earliest stages are essential for identifying and resolving conflicts before they become costly field problems.
The Energiesprong Model and Its Adaptation to New York
A major influence on RetrofitNY is the Energiesprong approach from the Netherlands, which has achieved remarkable success in scaling deep energy retrofits through industrialized methods. Energiesprong retrofit packages use prefabricated wall and roof panels that are manufactured off-site and installed rapidly over existing building surfaces, minimizing disruption to occupants and reducing on-site labor costs.
NYSERDA commissioned a dedicated study titled “Energiesprong: A Dutch Approach to Deep Energy Retrofits and Its Applicability to the New York Market” to evaluate how this model could be adapted to the U.S. context. The study identified several critical differences between the Dutch and New York markets:
| Factor | Netherlands | New York State |
|---|---|---|
| Building typology | Uniform row houses | Diverse multifamily configurations |
| Regulatory environment | National energy standards | State and local code variations |
| Supply chain maturity | Established prefab retrofit industry | Emerging market with few suppliers |
| Financing models | Energy Performance Contracts | Mix of grants, tax credits, and loans |
| Labor costs | Higher on-site labor costs favoring prefab | Variable across regions |
Despite these differences, Geppner and the RetrofitNY team concluded that the core principles of Energiesprong – prefabrication, performance guarantees, and streamlined installation – remain highly relevant to New York’s building stock. The key was to develop flexible panel systems that could accommodate the greater diversity of building geometries found across New York’s multifamily sector.
Pilot Projects and Real-World Results
RetrofitNY has funded multiple pilot projects that demonstrate what is achievable when Passive House standards are applied to existing affordable housing. Among the most notable is RiseBoro’s Casa Pasiva project in the Bronx, a four-story building that has become a flagship example of what deep energy retrofits can accomplish.
Early results from RetrofitNY pilots show significant energy reductions compared to pre-retrofit baselines:
- Energy use intensity (EUI) reductions of 60 to 75 percent have been achieved in completed pilot buildings.
- Heating load reductions of over 80 percent through combined envelope improvements and high-efficiency heat pump systems.
- Tenant comfort improvements measured through reduced draft complaints and more stable indoor temperatures during extreme weather.
- Operational cost savings of 50 to 70 percent on energy bills, with savings passing through to tenants in most cases.
The energy-saving technologies applied to these buildings include exterior insulation systems, triple-glazed windows, heat recovery ventilators, and air-source heat pumps. These components work together as an integrated system rather than as standalone upgrades, which is why the Passive House framework is essential – it ensures that each measure is sized and coordinated with the others to deliver maximum performance.
However, Geppner was candid about the challenges encountered during Round 1 pilot projects. Cost overruns, supply chain delays for specialized Passive House components, and the difficulty of finding contractors experienced in high-performance construction were all significant obstacles. These challenges informed the program’s evolution and its increasing emphasis on workforce development and supply chain building. The Passive House Accelerator platform continues to document these projects through case studies and expert interviews.
Cost Compression Strategies for Scaling Retrofits
Perhaps the most critical insight from Geppner’s presentation was the focus on cost compression. The current cost of deep energy retrofits remains too high for market-rate adoption without subsidies. RetrofitNY commissioned a dedicated Cost Compression Study (Phases I and II) to identify pathways for reducing costs by 40 to 50 percent over time.
Key strategies identified include:
- Industrialized prefabrication – Moving from custom-built on-site assemblies to factory-manufactured wall and roof panels reduces labor costs and improves quality control. Scaling production volume is the primary driver of cost reduction.
- Streamlined design and permitting – Developing standard detail libraries and expedited permitting pathways for certified Passive House retrofits can reduce soft costs that currently account for 20 to 30 percent of total project budgets.
- Aggregated project pipelines – Bundling multiple buildings into single procurement packages allows contractors and manufacturers to achieve economies of scale that are impossible with one-off projects.
- Financing innovations – Energy Performance Contracts that tie repayment to measured savings reduce financial risk for building owners and attract private capital alongside public subsidies.
The broader movement toward green building practices provides the market context for these cost compression efforts. As more jurisdictions adopt ambitious climate targets, demand for deep retrofit services will grow, creating the market conditions necessary for industrialized approaches to become cost-competitive with conventional renovations.
Lessons for Practitioners and Policymakers
Geppner’s RetrofitNY experience yields actionable lessons for anyone working in building retrofits, whether as a contractor, designer, building owner, or policymaker:
- Start with airtightness. The single most impactful measure in any Passive House retrofit is achieving a continuous air barrier. All other envelope measures underperform if the building leaks air.
- Plan for occupied construction. Retrofits of occupied affordable housing require dedicated tenant communication plans, temporary relocation strategies for the most intrusive work phases, and strict indoor air quality monitoring.
- Invest in training. The shortage of qualified Passive House tradespeople is the most frequently cited bottleneck in the RetrofitNY pilot reports. Programs that train existing construction workers in high-performance techniques are essential.
- Measure and verify. Blower door tests, infrared thermography, and ongoing energy monitoring must be built into project budgets from the start. You cannot manage what you do not measure.
- Think in portfolios, not projects. The greatest efficiency gains come from repeating the same solution across multiple buildings rather than re-engineering every project from scratch.
The challenge of tackling embodied carbon adds another dimension to this work. While operational energy reductions are the primary focus of RetrofitNY, the embodied carbon impact of adding thick insulation layers, new windows, and cladding systems must also be considered in a truly carbon-neutral approach. Combining deep energy retrofits with material selection that minimizes embodied carbon represents the next frontier for this field.
Geppner’s message to the Passive House community was clear: the demonstration phase has proven that deep energy retrofits to Passive House standards are technically achievable in existing multifamily buildings. The work now shifts from proving that it can be done to figuring out how to do it affordably, repeatedly, and at scale. Programs like RetrofitNY provide the template, but the construction industry as a whole must embrace industrialized processes, integrated design, and rigorous performance verification to make carbon-neutral retrofits the norm rather than the exception.