How to determine if a building’s wall assembly is fire-safe

by David Flaherty | 21 July 2024 3:27 pm

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Being code-compliant is a simplified response to a highly intricate issue. How does one choose the appropriate products for a project’s cladding? The external wall assembly comprises numerous components. The substrate, air-water barrier, attachment system, insulation, and cladding material each play into the evaluation of a wall system’s fire performance. Even something as simple as the depth of the air cavity behind the cladding can play a critical role in how the wall performs in a fire. Building construction professionals turn to the experts to help them navigate the seemingly infinite configurations to stay fire-safe.

In the world of code compliance, the name Art Parker is well known. Principal fire protection engineer and licensed professional engineer (PE), Parker has a career spanning three decades, and his contributions from his tenure at the firm of Jensen Hughes have shaped the discourse on fire safety standards. He is active in the committees that help write the code and has conducted countless tests, analyses, and investigations in fire safety. Parker knows what it takes to be code-compliant.

What is the role of a fire protection engineer?

Parker describes the model building code as a construction roadmap to prevent people from getting hurt. It details the minimum requirements for a building assembly. Often, defining that standard with testing requirements. “The role of a fire protection engineer is to evaluate and potentially test an assembly to confirm that we’ve achieved compliance with the building code requirements, that we meet the life safety requirements in the built environment, and to keep people safe.”

Part of an independent consulting firm, fire protection engineers like Parker review each specific component in a proposed wall assembly. They work with building owners, code officials, commercial laboratories, manufacturers, and the design team. “Our experience and expertise in the testing and the materials in the assembly performance allows us to help the design team to make changes that will result in the assembly complying with the requirements,” says Parker.

Letters of equivalency and engineering judgments

While the possible combinations of products and construction configurations are nearly infinite, limited resources create a significant constraint for cladding professionals. “It’s costly and time-consuming to conduct a test,” says Parker. “It’s simply not practical to test every exterior wall permutation that’s out there. So, we utilize engineering judgments.”

Parker describes the section of the model building code that enables an evaluation of alternative materials and methods. Fire protection engineers review a tested assembly and compare it to a proposed project assembly, systematically evaluating the differences in construction to determine their impact and the ability to meet the code requirements. “It’s a tool that allows me to bridge the gap between a limited number of tested and qualified systems and the near limitless number of proposed wall assembly constructions.”

NFPA 285 is the key to dependable wall performance

NFPA 285 is the Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components. It is a large-scale wall assembly test conducted in a controlled laboratory environment. This test simulates an event where a fire, originating from either inside the building or an external source adjacent to the building, starts to spread up the wall assembly.

Parker describes the NFPA 285 test as the worst-case scenario where there is no mitigation factors to control the fire. “By ensuring I test to a very worst case, the expected performance in the built environment is going to be much better.”

Since its inception in 1998, there have been notable changes made to the fire test standard over the years. In the 2023 Edition, the test standard most notably included the addition of Annex B, “Guide for Extensions of Results from Assemblies that Meet NFPA 285 Test Requirements.”

Understanding the importance of NFPA 285 Annex B

“We’ve been performing engineering evaluations for many, many years. Over that time, we’ve developed these guidelines,” says Parker. He’s excited to see the addition of Annex B because it was created through an industry consensus process and codified many of the best practices for conducting the engineering analysis for exterior walls.

“The NFPA Fire Test Committee documented many of those engineering guidelines, sort of rules, if you will. So, the benefit of that is, it’s now down on paper. Everybody can look at that and understand what the process should be to ensure that we are evaluating a wall assembly correctly.” Most importantly, Parker adds, it can be used by the design team and building officials to ensure that what they receive from a fire protection engineer demonstrates compliance. “It’s another double-check to ensure we’ve achieved compliance. We’ve built in consistency amongst the fire protection community to ensure that we’re all evaluating in the same manner.”

Finding partners one can trust

Parker stresses this process, which has been around for decades, has continued to evolve. “I think we’ve tried to improve that process with the entire team, from the manufacturers all the way through to the installers and all the approvals and evaluations in between to ensure that we’re reducing the risk.” He feels a unique aspect of the U.S. code is that we have a multi-layered system of testing, evaluation, approval, and inspection. “Especially with exterior wall assemblies, we’ve done a really good job of ensuring that what we specify, and actually build, is what we all thought should be there.”

While the architectural community exercises its creativity, there will continue to be new, untested systems that will need to be evaluated. Choosing an independent licensed fire protection engineer and the right building material manufacturer can help give peace of mind. “We’re working closely with the material manufacturers. Everybody is doing their due diligence in testing, evaluation, and analysis to ensure that we have a compliant system at the end of the day,” says Parker.

Safe and beautiful metal composite materials (MCM) are versatile, sustainable, and redefining skylines the world over. “MCM panels that have been incorporated in a wall assembly tested in accordance with NFPA 285 are safe to be used on buildings,” says Parker. When it comes to specifications, for him it’s as simple as requiring an MCM cladded wall assembly that has fully met the requirements of NFPA 285. “That’s key, and then we’ll meet those life safety code requirements.”

Michael Bowie is the technical services manager in the ALPOLIC Division of Mitsubishi Chemical America. After a decade of hands-on experience with the production and quality assurance of MCM, he stands ready to answer your technical questions. Learn more about how MCM can fit into your next project by scheduling an AIA-accredited continuation education course today.

Source URL: https://www.metalconstructionnews.com/articles/building-wall-assembly-fire-safe/

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