Implement complete testing of fire-stopping systems now to avoid potential catastrophe later
by David Flaherty | 8 August 2024 12:42 pm
Passive fire containment in high-rise commercial buildings helps support a precious commodity: time. By slowing down the spread of flames and smoke, all components of the perimeter fire containment system, including the mineral wool insulation components, which are the workhorse of the assembly, must be included if PFC systems are to extend the amount of time for occupants to exit and for firefighters to access the building to extinguish the fire.
However, there are some troubling trends. Today’s U.S. building codes require that fire-stopping materials, including the mineral wool insulation components, installed in PFC systems be tested and certified to ASTM E2307, Standard Test Method for Determining Fire Resistance of Perimeter Fire Barriers Using Intermediate Scale, Multi-story Test Apparatus. The test subjects the PFC system to intensive and rigorous fire exposure and could, potentially, be one factor contributing to U.S. building’s impressive safety track record.
In the absence of any large-scale fire catastrophes, a sense of complacency may be influencing the substitution of E2307-compliant mineral wool with noncompliant mineral wool components in the PFC System. In recent years, North America seems to have seen a relaxed attitude toward fire-stopping standards. Another trend also merits concern when it comes to supporting life safety in high-rise buildings. Pre-insulated curtain wall panels produced by overseas manufacturers include mineral wool insulation that is sold for fire-stopping purposes but contains mineral wool that has not been tested in a system in accordance with ASTM E2307. Aside from failing to comply with U.S. building codes, mineral wool components, being used in a PFC assembly while not tested as a system to ASTM E2307, could present an elevated life safety threat. Such mineral wool insulation materials have not demonstrated their ability to withstand the extreme fire conditions of ASTM E2307 where it simultaneously exposes the test specimen to direct fire impingement on both sides of the assembly. As ASTM E2307 is designed to closely replicate the conditions of an actual high-rise fire, fire-stopping material manufacturers invest millions of dollars annually to ensure their PFC systems stand up to these conditions.
PFC systems, including foreign mineral wool manufacturer’s materials within the system, must be certified to ASTM E2307. ASTM E2307 testing is conducted by independent third-party organizations such as Intertek or UL. The ASTM E2307 listing attests to the third party’s assessment of the system’s (including the individual components) performance under intense testing conditions. Installing an ASTM E2307-tested and -listed PFC system, and assuring that the mineral wool has the ASTM E2307 certification marking, is the best practice for passive life safety systems in commercial high-rise buildings. Because the PFC approach relies on a “system,” all the fire-stopping parts—mineral wool insulation, hangers, mullion covers, and firestop sealants—are designed and tested to work together when providing a barrier at the perimeter of the building.
Mineral wool purpose and performance design
The purpose materials serve in a building, as well as the process used to design it must be given the utmost consideration. Simply put, parts are not parts when it comes to the performance of fire-stopping systems. Mineral wool insulation is a good example.
Renowned for its fire resistance, mineral wool insulation can deliver many different performance properties in a commercial building enclosure. The manufacturing process used to make the material informs the properties it delivers in the enclosure. Depending on the desired performance attribute, this versatile material may be produced to reduce noise in mechanical rooms, repel water in rainscreen applications, or provide thermal comfort. Installed in PFC systems, the purpose of mineral wool is to leverage its fire-resistant properties. Therefore, the correct mineral wool products, the ones designed for PFC systems and tested in large-scale E2307 testing, must be used for those same systems.
To reiterate, depending on the intended application, mineral wool can be specifically engineered for the intended function. For example, mineral wool in an ASTM E2307-compliant system is designed to withstand extreme heat and maintain its structural integrity under intense fire conditions, while demonstrating its ability to withstand direct flame impingement and temperatures exceeding 923 C (1,800 F). The mineral wool insulation’s ability to resist deterioration and maintain integrity is essential, considering that the relatively lightweight components in the curtainwall—such as aluminum and various components—may start to deflect, melt, or show signs of failure as early as nine minutes into a fire. With all these performance requirements in mind, ASTM E2307 subjects the entire PFC system with its mineral wool components to similar conditions that it would see in a commercial high-rise fire.
Testing has shown that various types of mineral wool do not perform the same. The testing found that a standard mineral wool industrial or acoustical board at 101 mm (4 in.) thick and with a density of 64 kg/m3 (4 pcf) does not provide the same level of fire protection as a certified curtainwall or safing insulation in a UL or Intertek ASTM E2307-tested and -classified system. Firestopping materials, including mineral wool and other components, should be tested to ASTM E2307.
Appreciating the role manufacturing plays in supporting mineral wool’s performance in PFC systems makes it clear why the specific mineral wool insulation used in these systems—including pre-insulated panels—needs the testing and verification of ASTM E2307. These certified E2307 systems provide contractors, as well as building owners and occupants, with an independent measure of assurance that the fire-stopping components of the assembly are designed to provide the necessary protection in a high-rise fire condition.
Complete PFC system testing
ASTM E2307 assesses the entire system’s performance including how all of the system components work together to support performance. Every fire is unique, but as the comprehensive design of ASTM E2307 considers the whole system, this test provides a holistic approach to vetting the system compared to small-scale testing that evaluates components individually to less fire exposure.
Despite the rigorous design of ASTM E2307 and the robust safety record of America’s buildings, some manufacturers are advocating for a reduced, smaller-scale test as a substitute or replacement test. Proponents of a smaller-scale test are seeking one that would evaluate components individually without considering how the individual parts function to support system performance. Imagine a situation where mineral wool stands up to fire but lacks the mechanical integrity to stay securely in place as curtainwall components begin to fail. This approach could potentially lead to the “normalization of deviance,” coined by Dr. Diane Vaughan of Columbia University. This term refers to the gradual acceptance of exceptions. Or, in the case of testing, acceptance of reduced, smaller-scale testing becomes normal until a catastrophic event occurs.
The Grenfell Tower in the UK provides an example of the risk inherent in installing untested components and façade systems. Although the risks of untested facade assemblies are well known, little concern was given to the potential for disaster until the 2017 Grenfell fire illustrated just how quickly a fire can spread vertically up an enclosure’s facade.
Conclusion
Delivering the highest level of life safety is a timeless responsibility for those who design and construct commercial buildings. Efforts to shorten or simplify the testing standard by validating individual components instead of the system as a whole should be stopped. Industry stakeholders as well as the North American Insulation Manufacturers Association urge the industry to support ASTM E2307 for evaluating firestopping mineral wool used in PFC systems.
As Owens Corning’s senior engineering leader, Angie Ogino has more than 26 years of experience in the mineral wool and firestopping industry. She is also responsible for all Owens Corning third-party fire containment testing and provides engineering evaluations and technical support on fire-stopping for the design community. Ogino is the vice president of the International Firestop Council (IFC), where she is also the task group chair of the perimeter fire containment educational program. Ogino is also the vice president of Fire Safe North America.
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