Pushing the Envelope

Improving the performance of existing buildings is one of the most critical actions states can take to meet their climate goals — in tandem with increasing housing affordability, resilience, and energy efficiency jobs. Envelope retrofits, which seal and insulate a building’s exterior barrier, are at the heart of that effort. They lower the heating and cooling loads of a building, which reduces the electricity demand on the grid and makes electrification more cost-effective. They also extend the life of aging buildings and improve comfort, helping people stay safely in their homes longer during extreme weather or power outages. Many envelope retrofit strategies already exist to make buildings more energy-efficient, however, they vary in market maturity and remain difficult to implement at scale.

Sponsored by the New York State Energy Research and Development Authority (NYSERDA) and prepared by RMI, this report is primarily directed at project delivery stakeholders, including building owners, project team members, and manufacturers. It provides a granular assessment of envelope solutions for New York’s building stock (with a focus on multifamily buildings and some applicability to office buildings), key suitability considerations for decision-making, and resources to guide project teams, while also touching on the current market, key challenges, and recommendations to promote affordable, scalable solutions that accelerate market growth. Although focused on New York, many of the challenges and lessons are not unique to this state and can inform efforts in other cold climate regions.

Envelope Retrofit Strategies

New York’s diverse building stock calls for a range of retrofit pathways, as no single solution applies universally across building types, conditions, and ownership structures. Most approaches fall into three primary categories:

• Light-touch interventions (targeted weatherization)
• Full retrofits from the interior
• Full retrofit from the exterior (over-cladding), including site-built and prefabricated approaches

The report outlines how each approach performs across key considerations such as cost, constructability, disruption, durability, and operational impact. It also highlights where each strategy is most appropriate and how building-specific constraints, including structural capacity, occupancy, site conditions, and regulatory requirements, influence feasibility and selection.

Scaling Envelope Retrofits

Despite growing solution development and deployment, persistent barriers make envelope retrofit projects difficult to advance and repeat. Getting projects off the ground remains challenging; costs are high, uncertain, and poorly understood; retrofit value is not fully recognized; demand is too fragmented to support investment; and workforce and delivery capabilities need to mature alongside solutions.

Scaling deployment requires more than continued technical innovation. It will also require more streamlined delivery conditions and stronger market organization, so that both proven and emerging solutions are easier to select, finance, install, verify, and repeat.

Repeatable Project Delivery

A consistent indicator of retrofit success is whether an owner would pursue the same strategy again. Lessons from early projects suggest that repeatability depends less on peak performance and more on predictability, manageable disruption, and alignment with long-term asset planning. Projects that deliver durable improvements, minimize tenant disruption, and remain predictable in cost and schedule are more likely to be replicated. Integrated design and delivery, contingency planning, standardized approaches, alignment with capital cycles, and tenant management strategies can support more reliable outcomes and deployment at scale.

Creating Market Conditions for Scale

Building-specific conditions will continue to shape individual retrofit projects, but scaling requires solutions to be delivered more consistently and repeatedly across buildings and portfolios. Achieving this depends on broader market conditions that support sustained demand and industry investment. A durable retrofit market requires coordinated progress across the industry beyond addressing individual challenges in policy, financing, or workforce. The three improvement areas can be summarized as follows:

• Create a favorable landscape: Align policy, incentives, financing, and risk allocation to enable investment and reduce barriers to entry.
• Simplify the retrofit process: Reduce complexity across planning, decision-making, and delivery to improve project clarity and predictability.
• Build market capacity: Expand workforce capability, manufacturing readiness, and supply-chain coordination to support scalable deployment.

The current and future opportunity is to better align these elements to support repeatability, reduce costs and uncertainty, and build confidence across the market. Together, these efforts can enable a shift from fragmented, project-by-project implementation toward more standardized and scalable delivery, positioning envelope retrofits as a core pathway for decarbonizing New York’s and other states’ existing building stocks.

Additional Contributors:

Ella Mure, Ellie White, Nina Prescott, and Owen Woolcock and Alyssa Watson (ADL Ventures)