Fire, life safety, and smoke control in mixed-use buildings
Engineering mixed-use buildings is a fine art—specifiers must combine multiple engineered systems for several business and residence types into one structure. Fire protection engineers focus on these diverse structures with various fire and life safety techniques.
Robbie Chung, PE, LEED AP, Senior associate, Environmental Systems Design Inc., Chicago
Raymond Holdener, PE, Senior associate, Dewberry, Fairfax, Va.
Andrew Lasse, PE, LEED AP, Associate principal/senior mechanical engineer, Interface Engineering, Portland, Ore.
Gary Pomerantz, PE, LEED AP, Executive vice president, building systems, WSP, New York City
John Sauer, PE, LEED AP, Senior director, BSA LifeStructures, Indianapolis
LeJay Slocum, Assistant director, Atlanta regional office, Aon Fire Protection Engineering Corp., Suwanee, Ga.
CSE: What trends, systems, or products have affected changes in life safety systems? Please include mass notification systems (MNS), emergency communication systems (ECS), etc.
Slocum: Changes to building codes and standards are resulting in more and more mixed-use projects including an emergency voice communication system to serve as the fire alarm occupant notification systems. While not specifically intended to serve as MNS, these voice systems do allow for easier integration with campus or community MNS as they are installed. Additionally, many of the fire alarm and emergency voice systems include the ability to incorporate multiple colors of strobes or beacons to provide the necessary visual notification to serve as MNS.
Holdener: Historically in our market, most high-rise building have had manual pull stations and firefighter telephone systems installed throughout, but more recently many projects have been moving away from providing these systems. A single manual pull station is located in the fire command station or another central location, and a distributed antenna system (DAS) is provided for first responders to communicate. Fire alarm survivability continues to be a critical requirement.
CSE: What fire/life safety lessons have you learned on past building mixed-use building projects?
Lasse: I think chlorinated polyvinyl chloride (CPVC) sprinkler systems need careful consideration on mixed-use projects. While this piping is much less expensive to install, it carries with it a higher level of risk for the building owner, due to the complications that can arise with its use in combination with steel piping and corresponding cutting oils, which can eat away at the CPVC. In the past, even fire-stopping has been known to degrade CPVC. Ultimately, the product certainly has a place but needs to be implemented deliberately within the design as a whole.
Slocum: We’ve learned to adequately size or assess the base building infrastructure. Flexibility costs money and every project faces budget constraints. The constraints can lead to the temptation to provide the bare minimum infrastructure during the initial construction of the building shell or core. Learning not to fall prey to this temptation can be a time-consuming and expensive proposition for engineers and owners. Many mixed-use projects contain retail components, which often represent the greatest fire protection water demand, beside a standpipe system, if required. Typical retail stores with shelving and racking less than 12 ft high will typically require a sprinkler system designed for an Ordinary Hazard Group II occupancy with a resulting water flow demand of 600 to 750 gpm. However, if the retail space is instead occupied by a tenant that uses sales racking to 14 or 15 ft or uses a rack storage arrangement within their stock room, the required water flow demand can very easily exceed 1,000 gpm. If the project infrastructure, including water mains, fire pumps, and distribution piping, has not been designed to accommodate the increased water flow, these modifications can be challenging to both the project schedule and budget.
The same issues can also arise for fire alarm and emergency voice communication systems. Most major manufacturers of fire alarm and voice communication systems produce systems that are highly flexible and scalable to increase in size as necessary through the use of additional panels, amplifiers, and power supplies. However, many of these systems require customized programming, which must include all of these components. If not accounted for early in the design, adding components late in the project to increase the capacity of the fire alarm or voice communication systems can be both expensive and time-consuming. Additionally, all of the new equipment and any impacted circuit must be tested.
Holdener: As with all projects but particularly with mixed-use facilities, the design team must thoroughly review and be aware of not only national and international building codes but also local buildings codes and regulations. The jurisdiction and associated local code authorities of the project can play a significant role in the design and the preparation of your associated documents. The fire/life safety system designer needs to pay particular attention to confirming the specific local jurisdictional requirements regarding fire alarm device layouts within standard dwelling units and dwelling units specifically designated for individuals with disabilities. Atrium smoke control also must be well planned with respect to code-compliance for exhaust, makeup, and control, but also for testing methodologies by each project’s AHJ, which may differ from the code-prescribed operation of the system in an actual event.