Fire Safety

Second only to structural performance, fire performance is of utmost importance. A key life safety focus is the NFPA (National Fire Protection Agency) 285 fire-test requirement for multi-story, noncombustible construction. Recent developments in ASHRAE, IECC, and LEED have increased interest in high-performance building envelope designs with continuous insulation, which commonly involve combustible plastic foam. In the U.S., fire regulations are issued by government agencies and reference codes such as a building code, which in turn reference fire test methods and acceptance criteria. Fire safety is regulated by a combination of active and passive fire protection measures. Passive fire protection involves the use of products that are unlikely to generate a serious fire under their expected use. Active fire protection involves the use of methods to reduce or prevent the spread and effects of fire, heat, or smoke by means of detection and/or suppression of the fire.

US codes typically require that composite assemblies be fire tested, both as individual combustible components and in addition to as a complete assembly. With the increased use of thick foam insulation in sustainable, energy-efficient designs, architects should be aware that all foam plastic insulations used in exterior wall assemblies are required to pass all seven elements of Chapter 26 of the IBC, including Section 2603.5.5, which requires compliance with NFPA 285. Foam plastic insulation manufacturers should provide verification that products are part of an approved NFPA 285 assembly. It is important to note that the NFPA 285 standard fire test is an assembly test, not a component test. The details of the test assembly and application materials should be strictly followed in practice.

Other requirements for NFPA 285 fire test exist, such as the use of a combustible cladding material such as Metal Composite Material or High-Pressure Laminate. Additionally, FRP products may require NFPA 285 in their own right depending on configuration and size. In addition to the possibility of requiring an NFPA 285 tested assembly, Section 2613 requires the FRP product to bear the label of an approved agency, indicating the end use will comply with code requirements. The label and identification applied on an FRP product by the manufacturer need to contain the name of the manufacturer, the function and performance characteristics of the product or material, and the name of the identification of an approved agency that indicates that the representative sample of product or material has been tested and evaluated by an approved agency. Because FRP may include hundreds of different combinations of fiber, polymer, and processes, FRP products have very specific code requirements that must be met to be an acceptable and approved system. Additionally, currently, no ASTM standard exists for governing FRP products in an attachment application.

Combining fire with strength of materials is another consideration. The epoxy used in an FRP can soften or possibly melt in temperatures as low as a few hundred degrees, whereas the fibers themselves can stand temperatures well within the range of a typical fire. However, the strength of an FRP is a combination of both the epoxy and fibrous strand, so the loss of one can be catastrophic since the component in the context of this article would be supporting the weight of the cladding through a fire event.

Steel and Fire Codes

Steel is noncombustible, so the material does not contribute to the ignition of fires, the spread of fires, or the size and severity of fires, thereby reducing risks to occupants, firefighters, and property and business owners. In fact, no fire codes or listing requirements exist within the IBC related to steel. In a fire, the resilient steel element and its connection to the structure will not melt or become disconnected, which would result in a catastrophic failure. This can be referred to as a continuous noncombustible structural connection, which describes the preservation of the connection in the event of a fire.

CONCLUSION

Rainscreen systems superpower the exterior wall. One of the most important elements of this superpower, the cladding support system, can magnify this by using steel with its inherent properties of strength, resilience and fire resistance. Thermally isolated and improved steel rainscreen attachment systems enable a project to conform to building and energy codes quite easily. These types of systems, when properly designed and implemented, will easily meet, and even surpass stringent performance requirements. The intrinsic capabilities of steel also allow rainscreen systems to satisfy building code requirements that directly impact the design and construction of buildings and their cladding support system. The familiar is something not to lose.

RESOURCES

“Sustainability”. Build Using Steel, American Iron and Steel Institute. 2023. Accessed June 27, 2023.
“Emission Omissions: Carbon accounting gaps in the built environment.”. International Institute for Sustainable Development. 2019. . Accessed June 27, 2023.
“Sustainability.”. American Institute of Steel Construction. https://www.aisc.org/why-steel/sustainability/. Accessed June 27, 2023.

Brian Nelson is a graduate of Oregon State University with 15 years of rainscreen facade experience and has secured multiple patents. He currently serves as the General and Technical Manager at Knight Wall Systems as well as the Building Codes Committee Co-Chair for the Rainscreen Association in North America. He consistently collaborates with project teams, providing solutions to challenges in rainscreen facade design.