The Importance of Engineering Judgments for Perimeter Fire-Containment Systems

[ Page 3 of 5 ]        
Sponsored by Owens Corning
EJ Provider

It is critical to obtain an EJ from a reputable source; after all, it is this evaluation that will confirm or deny that the proposed system will perform as well as a listed and tested system. There are three entities that may provide EJs: independent laboratories such as UL and Intertek; FPEs; and firestop manufacturers. Each of these comes with benefits and limitations, which will be discussed in the next section.

General Contractor

The general contractor manages overall coordination of subcontractors and must also make sure that nothing has been improperly substituted: if a code-approved system is required, it cannot be replaced with something else.

Firestop Manufacturer

Manufacturers are experts on their products and systems, as they have invested millions of dollars in testing and often are at the leading edge of innovation in firestopping applications. Consequently, a manufacturer can and should be a key part of the team that ensures a successful and code-compliant perimeter fire-containment system. Manufacturers usually have technical experts who can consult on projects and help guide the design and installation. Manufactures can also issue EJs. Since mineral wool is the integral component and ultimately provides the fire protection, it is recommended to collaborate with the mineral wool insulation manufacturers to ensure proper installment of the curtain wall and safing insulation. Also, the mineral wool manufacturers have the most knowledge when it comes to selecting the correct mineral wool products and the performance of insulation itself.

Firestop Installer

Firestopping contractors are tasked with installing firestopping correctly so that it performs as designed. When they install a firestop, contractors typically do so to address a construction joint between two rated assemblies, or a penetration through a rated wall. They are also responsible for installing perimeter fire-containment systems. Every situation is different, and more often than not, there is not a tested and approved system that fits the unique elements of the situation. As the professionals who install a firestop, they must trust that the specifications for the system have been tested, that the materials have been approved, and that the solution is code-compliant.

One of the most effective ways for a firestop installer to gain that confidence is to work closely with the firestop manufacturer. This partnership can help ensure that a technical specialist from the manufacturer can draw on past experiences and analyze the data specific to the situation and produce a high-quality EJ.

Building Inspector

The system must be properly installed for the specific space. In the case of a perimeter fire-containment system, even the smallest gap can provide enough space for flame or hot gases to penetrate, which could mean the floor above is not protected. The building inspector must verify that the perimeter fire system has been installed properly, with all design criteria implemented into the assembly and that it meets the requirements of the building code.

There are many critical details to a successful perimeter fire-containment system. Given the important role these systems play in helping to protect buildings and allowing more time for occupants to escape, it should be apparent that the process of designing, procuring, installing, and inspecting these system must be a team effort that includes everyone from the project’s architects and construction team to the component manufacturers, installers, and inspectors. It should also be apparent that a quality EJ can help ensure that the assembly is appropriate for the project, especially when a contractor encounters unanticipated problems, or when the conditions in the field differ from the original design.

Who Can Issue EJs?

You have now learned about the critical elements that a good EJ must possess. Recall that high-quality EJs are project specific, reference a third-party tested system, comprehensively describe the variables from the referenced tested assembly, and clearly identify that they are not a tested and listed system.

Given the stakes of a noncompliant perimeter fire-containment system, it should be obvious why the EJ must be specific to the project in question. In spite of this, some might be tempted to refer to a judgment from a similar project. To avoid this dangerous possibility, be sure to verify that the EJ has been provided by one of the three parties permitted to issue an EJ. The three parties include third-party testing laboratories, FPEs, and manufacturers of firestopping systems. Though there are benefits and drawbacks to each of these, they represent the best option for a quality EJ that will accurately evaluate the proposed system.

Third-Party Fire-Testing Laboratories

Laboratories that conduct the fire testing per ASTM E 2307 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, from firestop design and installation to guidance during inspection.

One of the primary benefits of having a third-party fire-testing laboratory provide the requested EJs is 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; consequently, they have a solid understanding of how specific curtain-wall components and configurations perform when exposed to the fire conditions of ASTM E 2307.

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. As we shall see, 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, which can be a limiting factor on some projects.

Fire-Protection Engineering Firms (FPEs)

FPEs 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 and use this to justify how they expect an assembly or design to perform in the event of a fire.

There are three key benefits that an FPE brings to an EJ. First, as with 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.

There are some drawbacks to utilizing FPEs for EJs, most of which stem from their general lack of testing experience. First, they tend to have a limited knowledge of specific product performance characteristics, and therefore they can only base EJs on interpolation of data from specific listed designs. Second, as mentioned, FPE firms do not 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 be 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 on perimeter fire-containment systems. These companies are often at the leading edge of innovative firestopping solutions, and their work requires working closely with third-party testing laboratories to test designs, materials, and systems in different situations. They employ highly trained technical experts who often have extensive testing experience and are qualified to provide EJs for challenging situations. These experts can also provide detailed technical assistance to architects and building professionals about the manufacturer’s products and how they 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 for how to use 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.

Mineral wool 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 is the key component of penetration, construction joint, and perimeter fire-containment systems. A company that manufacturers mineral wool will be experts on the material and have invested significant financial resources into the development of its firestopping products and systems. Consequently, it will have an extensive test data set (both internal and third-party tested) to reference and support its EJs. Finally, as a manufacturer, it will have detailed knowledge about its products’ durability, performance, and safety as installed in the field.

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 its 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 even past 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 some limitations to consider. First, 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. This 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 FPEs, on behalf of their customers, and the FPEs signs off on the manufacturers’ EJs.

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.

Collaboration Is Key

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 drawn 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.


[ Page 3 of 5 ]        
Originally published in Architectural Record
Originally published in December 2019