2024 International Building Code® Updates – Fire Safety Provisions for Exterior Wall Assemblies, Foam Plastic Insulations, Section 104
“INSULATED VINYL SIDING. A continuous insulation cladding product, with manufacturer-installed foam plastic insulating material as an integral part of the cladding product, having a thermal resistance not less than R-2.”
“PEER REVIEW. An independent and objective technical review conducted by an approved third-party.”
“RAINSCREEN SYSTEM. An assembly applied to the exterior side of an exterior wall and consisting of, at minimum, an outer layer, an inner layer and a cavity between them sufficient for the passive removal of liquid water and water vapor.”
“RESPONSIVE VAPOR RETARDER. A vapor retarder material complying with a vapor retarder class of Class I or II, but that also has a vapor permeance of 1 perm or greater in accordance with ASTM E96, water method (Procedure B).”
Turning to existing terms, there are some notable revisions. The EXTERIOR WALL ENVELOPE term is now EXTERIOR WALL ASSEMBLY along with some further substantive modifications enhancing clarity:
2021 IBC text:
“EXTERIOR WALL ENVELOPE. A system or assembly of exterior wall components, including exterior wall covering materials, that provides protection of the building structural members, including framing and sheathing materials, and conditioned interior space, from the detrimental effects of the exterior environment.”
2024 IBC text (revisions in bold):
“EXTERIOR WALL ASSEMBLY.
“Envelope” when used in reference to buildings is much more a term of building science and energy efficiency. In the context of IBC requirements, however, the “exterior wall envelope” term and its definition were somewhat confusing. The term seemed to present more focus on the concept of what an exterior wall “does” (i.e., its function) vs. what an exterior wall “is” (i.e., its composition). Such a distinction is important given the scope and purpose of the IBC and its structural and fire performance provisions that include requirements referencing test methods that evaluate assemblies. To this point, revision to the EXTERIOR WALL ENVELOPE term is accompanied by multiple associated revisions to its use throughout the code(s).
The EXTERIOR WALL COVERING term was revised to include the new RAINSCREEN SYSTEM term.
2024 IBC text (revisions in bold):
“EXTERIOR WALL COVERING. A material or assembly of materials applied on the exterior side of exterior walls for the purpose of providing a weather-resisting barrier, insulation or for aesthetics, including but not limited to, veneers, siding, exterior insulation and finish systems, rainscreen systems, architectural trim and embellishments such as cornices, soffits, fascias, gutters and leaders.”
This revision clarifies for code users that rainscreen systems are a type of exterior wall covering where the new definition of rainscreen system further clarifies for the code user more precisely what comprises a rainscreen system.
LISTED was revised to include several examples of common industry/marketplace terminology used to identify equipment, products, or materials that are listed by third-party listing agencies (2024 IBC text [revisions in bold]):
LISTED. Equipment, materials, products or services included in a list published by an organization acceptable to the building official and concerned with evaluation of products or services that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services and whose listing states either that the equipment, material, product or service meets identified standards or has been tested and found suitable for a specified purpose. Terms that are used to identify listed equipment, products or materials include “listed”, “certified", “classified” or other terms as determined appropriate by the listing organization.
The net, collected effect of these terminology updates is the continuation of the IBC’s iterative evolution that allows for the recognition of new building product technologies, changes to design and construction practices, and industry vernacular to ensure not only the clarity of code requirements but also consistency in their application. Said simply, the words are important.
Photo courtesy of EIFS Industry Members Association (EIMA)
IBC Section 705 provides for fire and smoke protection features applicable to exterior walls of buildings.
IBC CHAPTER 7
IBC Section 705 provides for fire and smoke protection features applicable to exterior walls of buildings. This Section was minimally revised for 2024.
Revisions to Section 705 provisions for exterior walls and exterior wall assemblies include a new Section 705.6 that requires that a fire-resistance rating for an exterior wall must extend from the top of the foundation or floor/ceiling assembly to the underside of either (1) The underside of the floor sheathing, roof sheathing, deck or slab above, or (2) the underside of a floor/ceiling or roof/ceiling assembly above that has a fire-resistance rating equal to or greater than the exterior wall and the fire separation distance is greater than 10 feet.
A second new section was added for the condition where floor assemblies in Type III construction support gravity loads of an exterior wall. The requirement is essentially that the portion of the floor assembly supporting the exterior wall assembly must have a fire-resistance-rating that is equal or greater than that required for the exterior wall assembly in Section 601. The net effect of this new provision is to help ensure continuity of the fire-resistance-rating of the exterior wall from the top of the foundation to the top of the exterior wall.
Photo courtesy of Polyisocyanurate Insulation Manufacturers Association (PIMA)
Chapter 14 of the 2024 IBC contains several useful and important updates for various provisions related to fire safety of exterior walls. The addition of exterior wall assemblies effectively removes any ambiguity around “how much” of the exterior wall is subject to the reach of Chapter 14.
IBC CHAPTER 14
Chapter 14 of the 2024 IBC contains several useful and important updates for various provisions related to fire safety of exterior walls. Revisions range from clarifying the Chapter’s Scope, to provisions regarding vertical and lateral flame propagation, to the addition of three new sections containing requirements for different building products and systems.
Scope
Although a simple revision, Section 1401.1 was revised to include “exterior wall assemblies,” and “exterior soffits and fascias” to the scope of Chapter 14. The addition of exterior wall assemblies effectively removes any ambiguity around “how much” of the exterior wall is subject to the reach of Chapter 14. Use of the updated-for-2024 exterior wall assembly defined term throughout Chapter 14 and the rest of the 2024 IBC also confirms (through the defined term) that exterior wall coverings and water-resistive barriers are components of the exterior wall assembly.
Vertical and Lateral Flame Propagation (NFPA 285)
NFPA 285 testing is a critical component of fire safety in buildings where combustible components are used in exterior wall assemblies of Type I, II, III, and IV construction. The 2024 IBC introduces new sections that collect references to provisions where NFPA 285 testing is required, that add new requirements for NFPA 285 testing, and that prescribe methods for demonstrating compliance. Since the inaugural 2000 edition, reference to and use of NFPA 285 in the IBC has expanded as specific recognition of water-resistive barriers, new lightweight energy-efficient cladding materials and systems, and other building envelope materials, claddings, and design practices have been added to the code. Requirements for NFPA 285 testing are a key contributor to the IBC’s overall approach to fire safety of exterior wall assemblies that also includes, where applicable, provisions regarding ignition resistance and fire-resistance-ratings. The IBC approach has been demonstrably successful at preventing catastrophic fires code-compliant exterior walls of high-rise buildings with combustible claddings. For 2024, a new Section 1402.5 was inserted into the performance requirements for exterior walls to collect the references that has the cumulative effect of:
- Establishing a specific requirement within Section 1402 for vertical and lateral flame propagation of exterior walls on buildings of Type I, II, III, and IV construction that contain certain combustible components: specifically combustible exterior wall coverings, combustible insulation, or combustible water-resistive barrier (WRB)s.
- Provides references to other sections of Chapter 14 and 26 where the existing provisions and more specific requirements are located, specifically:
- Section 1402.6 for combustible WRBs (Note: renumbered from 2021 IBC Section1402.5)
- Section 1406 for Metal Composite Material (MCM) systems
- Section 1407 for Exterior Insulation and Insulation (EIFS) systems
- Section 1408 for High-pressure Decorative Exterior-grade Compact Laminate (HPL) systems
- Section 2603 for foam plastic insulation
- Clarifies that where provisions require compliance with NFPA 285, the exterior wall assembly shall be tested in accordance and comply with the acceptance criteria of NFPA 285.
Section 1402 also includes a new Section 1402.7 with a fire safety provision for a type of exterior wall veneer that is manufactured using combustible adhesives on exterior walls of Type I, II, III, and IV construction that are greater than 40 feet in height above grade plane. The veneers subject to this provision are those where a combustible adhesive is used to laminate a metal core (typically in the form of a honeycomb structure) to noncombustible facings (typically in the form a metal skin). The new provision requires that exterior wall assemblies containing this type of veneer are tested in accordance with, and meet the acceptance criteria of, NFPA 285. (It should be noted that a proposal to add reference to Section 1402.7 to Section 1402.5 was submitted for Group A of the 2024-2026 ICC Code Development Cycle.) This new provision is another example of how the code development process allows IBC to address new building materials, systems, and approaches; in this case ensuring exterior wall assemblies containing combustible cladding components are rigorously tested to prevent fire propagation.
