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

Engineering Judgments and the Design Community

We have looked at the role a quality EJ for a perimeter fire-barrier system plays in the design and construction process, but how does it affect the day-to-day practice of key stakeholders such as architects, curtain wall manufacturers, firestop installers, or firestop inspectors? Each stakeholder has critical roles in ensuring that building occupants are safe in the event of fire and that their health and welfare are considered in the project design.

Trends have shown that building and fire safety professionals are increasingly aware of a building’s fire performance and the potential liability for the design community given the unfortunate event of a fire. No one wants a repeat of the Grenfell Tower fire. Therefore, it is critical to understand that an EJ does not necessarily mean that one is indemnified from any liability. However, taking steps to understand how to identify a quality EJ, as well as partnering with manufacturers who have the testing and experience to provide engineering analysis and recommendations, are two steps that can equip the designer or installer with a solution that provides the highest level of fire safety to the occupants of a building. In this section, we will discuss how a good judgment can help stakeholders feel more confident in their decision-making process as well as in terms of liability.

In the event of a high-rise fire, one of the first questions is “who was responsible?” By their very nature, high-rise projects will include more than just one person or architecture firm responsible for the design, and other stakeholders have a duty to warn building occupants about potential fire hazards. If we go back to the case of the Grenfell Tower tragedy (as of late 2018, it is still under investigation and may take years to complete), we are reminded of how complex this kind of situation is and of how long it can take to conclusively determine what went wrong. Simply put, the more complex the system, the more challenging the investigation. And no one wants to be responsible, especially if lives were lost in a fire. Quality EJs for perimeter fire barriers can help all stakeholders avoid landing in such a position by helping ensure that a system is designed for the specific project and installed according to code requirements.

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Architects

This role of the architect is highly important in the case of fire safety, where it is critical that all of the specified materials in the building are fit for their intended purpose and are actually installed on the job, not value-engineered out or substituted during construction. As we have discussed throughout this course, perimeter fire-barrier systems are in and of themselves complex, as is their installation into an already challenging building design. Where an alternative product might be acceptable for another element of the project, it most certainly is not when it comes to anything related to fire protection. Joint insulation needs to be made of mineral wool, and smoke sealants need to maintain their seal when exposed to extreme heat, and thus should be specifically designed for this purpose. More importantly, it is absolutely critical that the safing insulation and the curtain wall insulation are made from the same material and that they have equal densities; otherwise the fire will find a path through the weakest part of the system. Alternative materials and last-minute substitutions are not acceptable.

An EJ concerning the barrier from a trusted provider can help the architect and associated firm be sure that their design and structure is protected in the best possible and most project-specific way—and they will have the documentation to prove it.

Curtain Wall Manufacturers

Curtain walls are vulnerable in fires in part because of their lightweight design; often, the aluminum framing, the attachment materials, or both will fail in the event of a high-rise fire. Moreover, the lack of proper protection of the joint and the spandrel area can act as a chimney for smoke, gases, and fire. With these issues in mind, it is understandable that curtain wall manufacturers want to be confident that their products (and their liability) are protected by project-appropriate firestop systems. And quality EJs are an important part of this process.

In the previous section, we outlined the benefits and limitations of the three parties authorized to provide EJs. As a key stakeholder, curtain wall manufacturers need to become an integral part of the complex process of determining an appropriate firestopping system for projects where their products are used. Curtain wall manufacturers can help inform the decision-making process by verifying fire test data for their own products when they work closely with firestop manufacturers, third-party fire-testing labs, and FPE firms—or any feasible combination of the three.

Curtain wall manufacturers need to know that when their wall systems are installed, any fire risks have been properly addressed with tested and approved fire-containment systems. They also need to be consulted when something unexpected comes up during installation to help ensure that the materials and products used for the firestop are appropriate for their curtain wall systems. There are a lot of variables to consider, and firestopping in general is a highly challenging task. However, by being an active part of the process, curtain wall manufacturers can help whoever issues the EJ make sure that the perimeter fire-barrier systems are as safe as possible. In turn, they can be more confident about the overall fire safety of the building and thus their liability after having done the due diligence of working closely with the firestop team.

Firestop Installers

Firestop installers have a tricky task. When they install a firestop, they typically do so to address a new penetration that has been made through a fire-rated assembly or the application of the fire safing, mullion covers, and firestopping sealant. 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, the materials have been approved, and 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.

Installers often consult EJs for projects where stick wall assemblies are used. In these cases, when the curtain wall frame (mullions) and panels are installed piece by piece, the installers benefit significantly from knowing that the materials they install are code compliant.

Firestop Inspectors

Firestop inspectors go through extensive training through the IFC and often do additional training with independent testing laboratories. Still, they rely heavily on having high-quality EJs available to ensure that everything is up to code and safe. In addition to high-rise projects, firestops are now required in health-care facilities, so inspectors need to understand the nuances of the EJ and know what to look for to ensure that buildings are code compliant.

Inspectors do far more than a just physical field inspection of the building and containment system; they also closely review the associated reports and other paperwork concerning the structure, and that includes any EJs. This level of document review is typically the first step of the inspection. In addition to consulting the International Firestop Council Recommended Guidelines for Evaluating Firestop Systems in Engineering Judgments (see sidebar), they will also verify that the system used as the basis of design was tested with a nationally recognized laboratory before it was installed. These documents will help during the field-inspection process, where inspectors will be required to make their own expert judgments about the systems and installation based on the sample sites that they can review. (There is simply no way that an inspector can visually inspect every single penetration or the length of every joint and ventilation duct.)

ASTM provides additional guidance that also addresses documentation issues. For example, construction documents detailing the firestop locations and systems must be kept on-site and made available for the inspection. ASTM also recommends that empty containers, wrappings, or boxes of specified materials are also kept on-site as a reference and that the materials are labeled with the approved testing agency marks.

 

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Originally published in Architectural Record

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