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January 9, 2024
Many modern building designs are complex, making it challenging to determine if the occupants will be safe in the event of a fire. This is where fire and egress modeling comes into play. In this blog, we examine the advantages of using these tools.
Fire and egress modeling are valuable tools in fire safety and building design, helping architects, fire protection engineers, and safety professionals create safer environments and improve emergency response strategies. Through computer-based simulations and mathematical models, fire and egress modeling allows experts to assess and predict fire behavior and the movement of people during emergency evacuations within buildings.
Fire and egress modeling are part of a holistic fire protection and life safety approach for designing modern buildings. To understand the full potential of these tools, it helps to know the benefits. Let’s explore them now.
Building codes prescribe minimum requirements and generalized standards for fire protection and life safety. Due to their prescriptive nature, they tend to group similar buildings together in the application of the code and may not account for unique conditions.
For example, in the case of natural smoke venting or heat vents in industrial complexes, the code prescribes specific square footage of openings. However, under certain environmental conditions, such as extreme winter temperatures, the negative stack effect caused air to be drawn into the building rather than vented out – the exact opposite of their intent. Through fire modeling, a more effective and cost-efficient alternative arrangement can be determined.
Fire and egress modeling ensures that a facility meets, and often exceeds, the minimum life safety requirements of the code. Unlike prescriptive code, which relies on if-that, then-this logic without specific consideration of the unique space, fire and egress modeling provides a customized analysis. It allows fire protection engineers to consider the realistic use of a building and see the actual impact of various fire protection systems – such as fire alarms, fire sprinklers, means of egress, etc. – on safety and evacuation rather than blindly complying with the word of the code, highlighting the value of using fire and egress modeling for more precise safety evaluations.
Fire and egress modeling are tools often used in performance-based designs. As part of this process, the actual performance of the systems is evaluated against criteria to demonstrate compliance with the code. Since the overall system performance is key, fire protection and life safety design can be optimized for functionality, aesthetics, cost, or resiliency, depending on the stakeholder objectives.
Consider a smoke control system, for example. During the fire and egress modeling process, fire protection engineers determine optimal locations for makeup air and exhaust systems, which help to control smoke and maintain tenable conditions within a building during a fire emergency.
The National Fire Protection Association (NFPA) 92 guidelines for smoke control systems allow for a few different design approaches for determining makeup air and exhaust systems. The most common is based on algebraic hand calculations, and due to the generic nature of the approach, fans are often oversized, resulting in less efficient systems and wasted resources. In addition, the real-world behavior of smoke and fire events in a structure can significantly differ from what these simplified calculations suggest.
Fire and egress modeling allows fire protection engineers insights into how smoke will actually behave during a fire event. This often leads to more practical solutions, like concentrating all exhaust on one side of the building or spreading it out over a defined lateral distance, or strategically providing makeup air that can serve as an air curtain, limiting occupants’ direct exposure to toxic smoke where queuing conditions occur during evacuation.
Through fire and egress modeling tools, engineers receive a dynamic, real-time view of how conditions will likely unfold within the actual building, which isn't typically offered by prescriptive code methods.
Fire and egress models are tools that can be leveraged as part of an overall approach to code compliance. They provide flexibility within the prescriptive code's framework and offer an alternative to the standard building design process. Prescriptive codes prescribe specific requirements for things like means of egress, fire suppression systems, smoke control systems, minimum setback distances, and construction type, where fire and egress modeling provide a more holistic evaluation of how these systems actually perform in the event of a fire. This ensures compliance and a higher level of safety, often leading to benefits like cost savings and improved flexibility in achieving overall project goals.
Codes typically encourage innovation and adaptability by allowing different approaches to demonstrate compliance. This allows for realistic compliance with regulations, which is especially valuable when a project presents unique challenges that don't align directly with the code's standard requirements. How the request for approval is formally documented and submitted depends on the specific jurisdiction and overall scope of the analysis; sometimes it may take the form of a performance-based design, other times it may be part of a variance request, alternative means and methods request (AMMR), or code modification.
However, one challenge in the implementation of modeling approaches is the lack of education regarding the use of fire and egress modeling tools. Building and fire code officials vary in knowledge and receptiveness to alternative approaches. Some are open to innovation but require educational support, while others rigidly adhere to the code without considering alternative solutions. Therefore, efforts are ongoing within fire protection engineering to educate regulatory officials and promote a more accepting and adaptive industry standard.
Cost savings might be the greatest appeal of fire and egress modeling approaches for developers, builders, and owners. There are many ways to achieve acceptable levels of fire protection and life safety in building design. Fire and egress modeling allows fire protection engineers to compare various strategies for fire protection and life safety by simulating different fire scenarios and comparing the results. Each approach may include different fire protection systems, but more than one could be considered acceptable so long as the established performance criteria are satisfied for each approach. Each of the acceptable methods can be evaluated based on constructability, lead-times of equipment, initial construction cost, lifetime cost of maintenance, etc. Depending on the project objectives and limitations, the most appropriate fire protection and life safety strategy can be selected.
Smoke control systems are one of the best opportunities to realize the cost-saving benefits of fire and egress modeling. Leveraging fire modeling for large volume spaces, such as arenas and theaters, allows fire protection engineers to effectively utilize smoke reservoir areas and layering combined with egress modeling to significantly reduce the required exhaust capacity. Traditional hand calculation methods for smoke control in atriums often require an enormous amount of exhaust air, sometimes reaching hundreds of thousands or over a million cubic feet per minute (CFM). To handle this, a significant volume of makeup air is also needed.
For these types of large projects, fire modeling can help reduce mechanical system demands by more than 50%. This reduction cascades through various aspects of the project, leading to the following:
Another element of cost savings comes in the form of confidence during special inspections and system commissioning. Many design professionals use the testing period of smoke control systems as a time for troubleshooting design challenges. This translates into costly delays and disruptive solutions. If a fire and egress modeling approach is employed from the onset, the testing period primarily ensures that the specified equipment was installed as notated on the design documents. Fire and egress modeling inherently addresses multiple aspects from design through construction, benefiting the design team and contractors throughout the process.
Smoke control is just one of the potential cost-saving opportunities of fire and egress modeling. Items like set-back distances, fire-rated construction, smoke detector spacing, number of exit stairs necessary, and allowable building size can also be evaluated, leading to potential cost savings.
To incorporate fire and egress modeling into your building project, start by reaching out to a fire protection engineer who specializes in fire and egress modeling. They can help you navigate the approach and methodology and talk with the authority having jurisdiction (AHJ) and the stakeholders to explain the performance-based design process.
There are three main stages of the performance-based design process:
Through this process, the fire protection engineer can help you overcome design challenges and find a path forward.
In a world where building designs continue to evolve and become more intricate, fire and egress modeling emerge as indispensable tools that address the complex safety challenges presented by modern architecture. Their benefits extend beyond conventional safety standards, making them a valuable asset in creating safer environments and improving emergency response strategies. Ultimately, understanding and harnessing the potential of fire and egress modeling can lead to safer, more cost-effective and efficiently designed buildings for the future.
When you want fire and egress modeling performed for your project, trust the experts at Performance Based Fire to get it done right. Contact us to learn how we can help.
