Beyond the Wall: Decoding the 2024 International Building Code® and NFPA 285 Fire Safety Evolution

As performance demands placed on building enclosures continue to rise, so too does the complexity of the materials and systems used to meet them. Exterior walls today are  multilayered systems. They provide critical building science control functions, integrating thermal insulation, water management, vapor control, air-leakage control and, increasingly, incorporate combustible components. The 2024 International Building Code (IBC) reflects continuous improvements in regulating the fire safety of these assemblies as their design, construction, and composition continue to evolve and innovate with recent revisions regarding NFPA 285 testing and compliance providing one example. 

Since the inaugural 2000 Edition of the International Building Code® (IBC®), NFPA 285 has served as the industry benchmark for evaluating vertical and lateral flame propagation in exterior wall assemblies employed in Type I, II, III, and IV construction. Since 2000, IBC provisions that require testing and compliance with NFPA 285 have expanded from the original use in regulating certain exterior wall assemblies containing foam plastic insulation, to its use today, for assemblies that contain combustible water resistive barriers, laminated veneers, and an increasing array of lightweight combustible cladding systems.  

The 2024 IBC clarifies how compliance can be demonstrated where the IBC requires NFPA 285, offering practitioners new flexibility backed by clearer criteria. 

NFPA 285: A Systems Approach to Fire Testing 

It bears repeating that NFPA 285 is an assembly test; it is not a test of individual materials. The test evaluates how an entire wall system performs when exposed to the prescribed fire test conditions; performance that is influenced by the interactions between the assembly components and by the configuration of the wall assembly. Flame propagation is assessed, both vertically and horizontally, across the exterior surface, within the assembly layers, through air gaps and cavities, and from floor to floor. The test is pass/fail. However, the data it generates is extensive through the placement of dozens of thermocouples positioned throughout the assembly test specimen to capture heat movement in multiple dimensions. 

Over the past two decades, NFPA 285 has become the backbone for evaluating the fire performance and fire safety of modern exterior wall assemblies. The test’s ability to produce granular temperature data enables experts to understand how specific construction details may influence performance. The data is increasingly being leveraged through rational analysis to address design variations that cannot feasibly be tested in every possible permutation. 

A Codified Path to Engineering Judgments 

One of the most consequential updates in the 2024 IBC may be Section 1402.8, which prescribes three (3) compliance methods for assemblies required to be tested and comply with NFPA 285. These include direct testing of the specific wall assembly, third-party listed assemblies, or an approved analysis based on the test results of a similar assembly or condition meeting the acceptance criteria of NFPA 285.  

Direct testing is of course ideal, but due in large part to the costs of associated testing, often impractical. As a result, use of third party listed assemblies, provided by approved agencies, present a more scalable solution with more design flexibility. But it is the third method — an approved analysis based on a tested assembly or condition that meets NFPA 285 — that presents a meaningful improvement in clarity regarding the recognition and use of data analysis for compliance. 

Now, in the 2024 Ed., the IBC explicitly acknowledges what has become a common and useful practice: that subject-matter experts are able to evaluate modifications to tested assemblies. Through data-driven analysis, experts can demonstrate compliance with NFPA 285 for submission to, and review and approval by, the Authority Having Jurisdiction (AHJ). These analyses — colloquially known as “engineering judgements” or “EJs” — rely on a deep understanding of fire science, material properties, and the NFPA 285 test method itself.  

Additionally, the 2023 edition of NFPA 285 introduced Annex B, a comprehensive informational guide for topics and considerations while performing analyses to extend compliant test results to similar, alternative configurations. This guidance is grounded in decades of expertise. 

More Tools for Authorities Having Jurisdiction (AHJs) 

The authority of building officials to determine and approve compliance is central to the effective enforcement of the building code. To that end, the 2024 IBC also significantly overhauled Section 104, clarifying the building official’s authority to interpret, enforce and determine compliance with the provisions of the code.  

It also provides the building official with new tools through language granting authority to require technical assistance, technical reports, peer review and other information. This is particularly helpful when determining compliance of alternative materials, designs, and methods of construction and equipment.  

Designing for the Modern Age: Implications for Practice 

Design teams now have clarity and greater flexibility to explore and qualify different or innovative wall assemblies, provided that the required performance of those designs can be substantiated through one of the recognized compliance paths for NFPA 285. Yet this flexibility demands rigor. Manufacturers, consultants, and design professionals must collaborate earlier in the design process to determine whether proposed assemblies can be matched to a third-party listing, qualified through an analysis, or if they must be tested anew. Assemblies containing multiple combustible layers, complex fenestration conditions, or multiple material or product combinations will very likely require some level of data extension analysis. 

This dynamic increases the value of NFPA 285 test data itself, not just as a compliance tool but as a resource for performance benchmarking. Manufacturers generally test worst-case scenarios, from a fire performance perspective, configurations (e.g., minimal closure details, high combustible loading, or thin-gauge metal framing) to develop baseline performance that will justify more robust variations in actual design.  

Materials in Focus: Laminates, IMPs and Plastic Insulations 

Several material-specific provisions underscore the IBC’s continuous evolution to keep up with changing technologies. Section 1402.7 introduces a new requirement for NFPA 285 testing of metal-faced panels with veneers laminated to noncombustible cores with combustible adhesives when installed on buildings over 40 feet. This addresses a previously unregulated fire performance characteristic of an innovative building product that has gained traction in proposed high-rise projects.  

Similarly, insulated metal panel (IMPs) systems are now specifically recognized by the IBC, with a newly defined term and a dedicated Section 1409. This section outlines all applicable requirements for these systems, including distinctions between assemblies that incorporate panels with combustible versus noncombustible cores, as well as defined structural, labeling, and fire safety requirements.  

Chapter 26 has also been updated to clarify the application of certain exemptions to IMPs. This update closes a potential loophole that could previously be interpreted as allowing non-IMP systems or uses of foam plastic insulation to bypass critical fire performance testing.  

Looking Ahead: The Integration of Testing and Design 

The 2024 IBC represents another iterative, yet decisive, step in both the integration and clarification of fire performance testing requirements for modern facade and exterior wall design. The expanded compliance options, clearer administrative authority, and improved material-specific and system-specific provisions continue to support a robust framework for ensuring safety in an era of rapid innovation. But as always, proactive engagement is the key to success. 

Designers must determine NFPA 285 considerations and engagement with manufacturers early in project design and development. Manufacturers should continue investing in strategic testing that anticipates downstream analysis and future innovation. 

At the end of the day, fire safety is an important subject throughout the construction value chain and a building’s lifecycle. For those working in building enclosure design, the 2024 IBC is not just a regulatory update — it’s an invitation to elevate practice. The tools are in place, now it’s a matter of using them well.