For decades, R-value has been the industry’s default measure of insulation performance, appearing in building codes, specifications, energy models and product literature, according to an Industry Perspectives op-ed published by Daily Commercial News. The op-ed, written by Rockford Boyer, a building science leader at Elastochem Specialty Chemicals, argues that a single material property obscures how complete wall assemblies actually perform.
Building enclosures are more than insulation. Framing, sheathing, air barriers, fasteners, windows, doors and installation quality all affect how a wall performs once it faces weather, pressure differences and temperature fluctuations, the op-ed states. As a result, two wall assemblies with identical insulation values can deliver very different levels of energy efficiency, comfort and durability.
Shift toward assembly-based performance
The building science community is increasingly emphasizing how assemblies perform in real-world conditions. Boyer identifies a metric called Assembly Performance Value, or A-Value, currently being developed by the Spray Polyurethane Foam Alliance. The op-ed says the metric is intended to supplement R-value rather than replace it, by considering both thermal resistance and air leakage within a complete wall assembly.
The concept reflects a broader industry shift toward evaluating the entire enclosure system and how its components work together.
Why R-value tells only part of the story
R-value remains an essential metric because it measures resistance to conductive heat flow under controlled conditions. However, heat moves through buildings in several ways, including conduction, convection and radiation. Air movement can also have a significant impact on energy performance by allowing conditioned air to escape and unconditioned air to enter.
Because R-value measures only one aspect of performance, assemblies with identical insulation values can perform very differently once constructed. Factors such as air leakage, thermal bridging and installation quality often have a significant influence on actual results, according to the op-ed.
Air leakage and thermal bridging
As energy codes become more stringent, airtightness is playing a larger role in building performance. Air leakage can increase heating and cooling loads, reduce occupant comfort and contribute to moisture-related concerns. Boyer notes that a highly insulated wall may underperform if gaps and transitions allow uncontrolled air movement.
Thermal bridging presents another challenge. Heat can bypass insulation through framing members, fasteners, structural components and other materials with lower thermal resistance. These pathways can significantly reduce the effective performance of a wall assembly compared with its nominal insulation value.
Together, air leakage and thermal bridging help explain why real-world performance often differs from theoretical calculations based solely on insulation ratings.
Where spray foam fits into the conversation
The discussion surrounding assembly performance draws attention to spray polyurethane foam because of its ability to contribute to both thermal insulation and air control when installed at appropriate tested thicknesses, the op-ed explains. In many wall assemblies, spray foam can help establish the thermal-control layer while also serving as part of the air-control strategy.
Boyer cautions that spray foam does not automatically guarantee superior assembly performance. Like any enclosure system, successful outcomes depend on proper design, detailing and installation. Gaps, inadequate sealing and poor workmanship can compromise performance regardless of the insulation selected.
When insulation products are compared strictly on published R-values, the benefits associated with air-sealing performance may not always be fully reflected. Evaluating the assembly as a whole can provide a more complete understanding of how different enclosure strategies perform under operating conditions.
Research supports a whole-wall approach
Research conducted by Canada’s National Research Council and other building science organizations has reinforced the importance of evaluating complete wall assemblies rather than individual materials, the op-ed states. Studies examining thermal performance and air leakage have shown increased air movement can reduce the effective thermal performance of a wall, even when insulation levels remain unchanged.
The findings also demonstrate that no single insulation product automatically guarantees superior results. Assembly design, detailing, air sealing, moisture control and installation quality all play important roles in determining performance.
What this means for designers and specifiers
Whether A-Value ultimately becomes a widely adopted metric or simply influences future thinking, the broader message is already resonating across the industry, according to Boyer. For architects, engineers and specifiers, wall performance is increasingly being viewed through the lens of the complete assembly. Air leakage, thermal bridging, moisture management, continuity of control layers and construction quality all influence how a building enclosure performs over time.
R-value will remain an essential design tool, but it represents only one part of the performance picture. As building science continues to evolve, the focus is shifting toward designing wall assemblies that effectively manage heat, air and moisture while delivering long-term energy efficiency, durability and occupant comfort.
Canadian perspective
For Canadian glazing contractors, architects and specifiers, the op-ed’s argument arrives alongside national and provincial codes that treat enclosures as systems rather than collections of rated products. While Canadian window and door standards such as CSA A440 address product-level thermal ratings, the op-ed suggests that product metrics alone cannot predict how windows, curtain wall and wall assemblies will perform together in a finished building.
The National Research Council of Canada research cited in the op-ed reinforces that assembly-level evaluation matters for Canadian climate conditions, where air leakage and thermal bridging can penalize even well-insulated assemblies. The op-ed does not prescribe specific Canadian code changes, nor does it claim A-Value is required under any Canadian standard; rather, it argues that designers should weigh assembly performance before selecting enclosure components.
For the glazing trade specifically, the op-ed’s message points toward asking how window and curtain wall systems contribute to overall enclosure airtightness and thermal continuity, rather than relying only on product-level center-of-glass performance. That question aligns with the assembly-based lens Boyer describes.