Perimeter Fire Containment and Engineering Judgments

Ensuring system integrity to provide escape time for building occupants
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Sponsored by Owens Corning®
By Rebecca A. Pinkus

Who Can Issue an Engineering Judgment and How to Know if It’s High Quality

In the previous section, we discussed the elements that a quality EJ must have—namely that they are project specific, based on data from third-party testing, comprehensively described, and that they clearly identify that they are not a tested and listed system.

In most senses, the issue that the judgment must be project specific and represent the project conditions under evaluation should be obvious. After all, the repercussions of relying on a judgment that doesn’t consider the precise project could be disastrous; however, it may be a tempting time saver to refer to a judgment for an analogous project. One way to avoid this is to ensure that the judgment is provided by one of the three parties permitted to issue an EJ. The three parties include a third-party testing laboratory, a fire-protection engineering firm, and a manufacturer of the firestopping system.

Third-Party Fire-Testing Laboratories

Laboratories that conduct the fire testing per ASTM E2307 test standard can provide EJs for project conditions based on the performance of the assembly of materials in a specific tested and listed system from the Fire-Resistance Directories. These directories provide critical information for different phases of the project, from firestop design and installation to inspection.

The primary benefits of having a third-party fire-testing laboratory provide the requested EJs are that the labs are independent and objective; their analysis is purely based on the actual test data. The labs witness the fire testing first hand, and so they have a solid understanding of how specific curtain wall components and configurations perform when exposed to the fire conditions of ASTM E2307.

While these labs can offer unbiased, data-based recommendations, they often have limited knowledge about specific product performance characteristics. This means that they can only base their EJs on their interpolation of data from specific tested and listed designs. Labs are aware of this limitation, and they often prefer that the manufacturers provide the EJ for this very reason. The manufacturers have more test data on the fire-performance and mechanical properties of their materials. In addition to the limitations on data, third-party labs charge a fee for their engineering services, and that can be a limiting factor on some projects.

Fire-Protection Engineering Firms

Fire-protection engineering (FPE) firms will employ professional engineers who can address situations where a firestop design does not match the listed assembly or cases where an installation is different from the approved design. Engineers in this field are well versed in the relevant code requirements to help them assess the unique situation and provide a solution that is based on solid, technical evidence to justify how they expect an assembly or design to perform in the event of a fire.

There are three key benefits that a FPE firm brings to an EJ. First, like third-party laboratories, it can offer an independent and objective analysis that is based on the actual tested and listed assemblies. Second, it will look at the entire project from a holistic life-safety perspective rather than just the specific fire-containment system conditions. That is, it will review and evaluate the installation of passive fire-containment features, automatic sprinkler systems, the overall design of the building, and the means of egress for building occupant safety, among many other fire-safety aspects of the project. Third, these firms typically provide EJs based on professional engineering (PE) review and approval for municipalities requiring a PE stamp on EJ letters and drawings.

The four main limitations that FPE firms have in providing an EJ stem from their general lack of testing experience. First, they tend to have a limited knowledge on specific product performance characteristics, and therefore they can only base EJs on interpolation of data from specific listed designs. Second, as we mentioned, FPE firms most often don’t conduct the actual fire testing; this means that they may not have access to the actual fire-performance data of the tested assembly being used as the basis of design. Third, FPE firms may not necessarily be experienced or knowledgeable about evaluating and providing EJs for specialized firestopping applications. Finally, as with third-party laboratories, FPEs charge a fee for their engineering services.

Firestop System Manufacturers

Firestop system manufacturers also can issue EJs about relevant situations. These companies are often the leading designers of innovative solutions, and a primary part of their work involves working closely with third-party testing laboratories to test designs, materials, and systems in different situations. Highly trained technical experts within the company have extensive testing experience and are qualified to provide EJs for challenging situations. They also can provide detailed technical assistance to architects and building professionals in regard to the manufacturer’s products and how various products will perform under certain situations. Perimeter fire-containment manufacturers also work closely with code development and other relevant organizations to ensure that their products—and the information they provide them—are based in the most up-to-date evidence available. Consequently, technical representatives from a manufacturer can provide architects and builders a highly credible judgment about their product in just about any situation.

Firestop manufacturers offer a long list of benefits when it comes to providing EJs. For one, they manufacture the actual products that are the integral components to the fire-containment assemblies. For example, mineral wool, as we discussed earlier, is the preferred material in most penetration, construction joint, and perimeter fire-containment systems. A company that manufacturers mineral wool will know a lot about it, and it will have also invested significant financial resources into the development of its firestopping products and systems. Both of these points mean that they have an extensive test data set (both internal and third-party tested) to reference and support their EJs. A third point is that as a manufacturer, it will have detailed knowledge about its products’ durability, performance, and safety when it comes to actual use.

A somewhat unique benefit that manufacturers who sponsor the tested and listed systems have is that they own and have access to the fire test report. This is particularly important because the actual fire test report, rather than just the listing from the labs’ fire-resistance directory, provides all the details of the assembly and fire performance (including thermocouple data and visual observations) made throughout the duration of the test. With this information, manufacturers can identify points of failure and potential weaknesses that can be applied to project-specific conditions. An EJ provider who knows the failure points of a system can in turn provide safer recommendations for the design and installation of their fire-containment products and systems.

Yet another benefit is that manufacturers also tend to have an extensive archive of test data from past years (and often decades), along with access to third-party and internal tests that they can draw on for the special conditions of existing buildings. And finally, most manufacturers do not charge for EJs.

While the list of benefits for having a firestop manufacturer provide an EJ are many, there are several limitations of which to be aware. The three most pressing challenges are that manufacturers who have promulgated designs based off another manufacturer’s base system will not have access to the fire test report that contains the critical fire-performance data needed to provide a superior quality EJ. A design without the fire test report and included data means that they may know the “what” but not the “why” about a design decision. That missing information can negatively impact an EJ.

Second, most manufacturers do not provide PE-stamped EJs and drawings. However, they can collaborate with FPEs by providing testing and product performance data so that an FPE can develop the EJ. Often, reputable manufacturers simply conduct all the engineering analysis work and submit to the FPE, on behalf of their customers, and the FPE signs off on the manufacturer’s EJ.

Unfortunately, because of a small percentage of manufacturers providing inferior quality EJs, certain municipalities are reluctant to accept manufacturers’ EJs. Therefore, it is critical for designers, curtain wall manufacturers, firestopping contractors, and firestopping inspectors to have a basic understanding of fire containment and how to evaluate and identify manufacturers who produce EJs based on actual testing and sound engineering principles.

A key takeaway from the benefits and limitations of the various EJ providers is that in many cases, the best judgment comes from a team of specialists from two or even three of the above groups. Many of the providers work together to help fill in the gaps in knowledge or experience, and stakeholders requesting an EJ can certainly request the insights of more than one provider in order to ensure that the recommendation results in the safest option for building occupants.

 

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Originally published in Architectural Record

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