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|FPE Extra Issue 5, May 2016|
The Importance of Exterior Wall Fire Testing and Certification for Fire Protection
By Karl Houser, P.E.
Public safety has been increasingly scrutinized by the media, the public and government agencies. The building and construction industry is no exception. In fact, the safety of the buildings we live and work in has drawn particular attention at a time when everything can be photographed, recorded and shared with millions in the blink of an eye. Cellphone recordings of recent dramatic exterior building fires around the globe were shared instantly on social media and news websites alike, receiving hundreds of thousands of views. The dangerous, soaring flames in these videos captured the attention of those who may not have ever seriously considered fire protection otherwise. Such visual and highly publicized occurrences have created an increased awareness of fire safety. The efficacy of automatic fire sprinklers inside of a building—although virtually indisputable for interior fire control—may have varying effect on fires spreading vertically outside the building.
The comprehensive process of codes, standards and product testing is designed to keep dangerous events like building fires from occurring. Various fire safety tests are required by the International Building Code (IBC) to ensure that building products, including the exterior wall assemblies involved in recent fires, meet stringent testing criteria. As more combustible materials are being used in building facades, fire testing standards such as NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load–Bearing Wall Assemblies Containing Combustible Components, are playing a significant role in mitigating the risks of fires in tall buildings. NFPA 285 outlines a standardized fire test method for evaluating exterior, non-load–bearing wall assemblies that include combustible components.
Major building fires in places such as Australia, China, Korea and Dubai in the United Arab Emirates over the past 18 months have brought building exteriors to the forefront of the fire protection engineering conversation. This gives the industry a unique opportunity to review one of the most widely used fire protection standards and to reevaluate the most effective way to help ensure the safety of building occupants.
NFPA 285 was developed after the use of foam plastics in or on exterior walls emerged in the 1970s. Energy conservation had become a focus due to recent energy shortages. This focus on energy efficiency served as the foundation for our current International Energy Conservation Code and the U.S. Green Building Council’s LEED rating system. Using foam plastics as part of the exterior building envelope, including exterior insulation and finish systems, increased the energy efficiency of a building and helped to meet new energy regulations.
The growing use of these materials resulted in some concern from the code community because certain plastic products had a history of poor fire performance and issues with fire propagation. The Society of the Plastics Industry (SPI) was aware of these issues and, desiring inclusion in the model codes, partnered with the Southwest Research Institute (SwRI) around 1980 to develop a rigorous fire test program. The aim was to develop a new full-scale fire test standard for exterior wall systems that included foam plastics. A new test method was developed and evolved from a UBC Standard over the next few decades. The final result was the current 2012 edition of NFPA 285.
This current test standard outlines a 30-minute procedure (typically performed inside the test laboratory building) designed to simulate a fire that starts on one floor of a building and spreads to an adjacent floor. The basic idea of the test is to ensure that a fire that starts on the lower floor won’t travel up the side of the building (or at the edge of the floor slab) to reach the adjacent floor. In real-world scenarios, fire propagation issues in certain exterior wall assemblies can cause these flames to spread vertically up dozens of floors. The two-story Intermediate-Scale, Multi-Story Test Apparatus (ISMA) uses a two-burner, gas-fired system to simulate a fire that starts on the lower floor. The first burner is in the middle of the lower level, with a gas flow that provides temperatures relational to ASTM E119. After an initial five minutes, the second burner, located at a simulated wall opening, is ignited (simulating flashover of the lower compartment) and follows a predetermined heat release regimen. Gas flows are adjusted at five-minute intervals to follow the ASTM E119 curve. As the test fire grows, flames travel outside the window opening and can continue up the side of the test apparatus and specimen. Visual, thermocouple and calorimeter data determine pass/fail. There are several other test standards similar to NFPA 285 used internationally—for instance, the CAN/ULC S-134 test is available in Canada and the U.S., and the BS 8414 is available in the U.K. This kind of fire safety engineering is of increasing importance worldwide. Recent building fires overseas (as well as in the U.S.) have shown firsthand the kind of damage that can occur when a fire spreads vertically on an exterior wall.
This standard fire test is essential to help ensure the safety of exterior building components by requiring that they meet criteria for low fire and flame propagation and other dangers. However, testing is only one part of the larger integrated system of fire safety. There is a second important step that can increase the safety of these building products in the field and can help to prevent the kinds of dramatic fires we have seen abroad. Certification, while not required by NFPA 285, is crucially important. The certification and labeling of a product or system components help to provide the vital link between the fire test report and the actual products installed in the field. Even the most minor change in the final building materials can result in significant differences in fire test results. Certification serves as a check-and-balance system to verify that materials being installed and inspected in the field will continue to pass the fire tests conducted in a lab. Field inspection of the products and systems for comparison to NFPA 285-tested system performance and use of certified products closes the loop.
Once the NFPA 285 test is conducted and a fire testing report is generated, an accredited outside agency can certify and label the products being used on a new project by architects, specifiers and contractors. The certification process is demanding and requires that the agency make regular plant inspections and audits—typically at least quarterly—for quality assurance and validation. This helps ensure traceability for approved products and systems so that the products that were tested are the exact same (or with approved modifications) as those being manufactured. It is a necessary, methodical and highly scrutinized process to ensure confidence in the manufacturing and delivery chain. Above all, certification enables architects, specifiers, building officials, fire marshals and contractors to quickly and easily verify that their building products meet germane fire protection standards. These professionals can conveniently search an online directory provided by an independent, third-party certification agency. All of the information that verifies that the wall assembly being installed in the field is representative of what was tested is easily accessible in the listing report and the design listing.
There are three certification agencies in the U.S. that are currently accredited to test and certify assemblies to the NFPA 285 fire test: Intertek (with two testing facilities in San Antonio, Texas, and York, Pennsylvania), Southwest Research Institute in San Antonio and UL LLC in Northbrook, Illinois.
By coupling fire performance testing with certification and comprehensive field inspections, building owners and manufacturers alike can mitigate the risks of exterior wall fires that may quickly endanger lives. This process has been successful in the U.S., whereas recent occurrences overseas exemplify the risks that poor fire performance poses. Any breakdown in the chain from product certification through field inspection and post-occupancy system integrity can be disastrous.
Fire safety and fire protection engineering have improved over several decades and have only become more meaningful over time as public safety continues to be a national priority. The system of manufacturing quality assurance, certification labeling, workmanlike installation and field inspection/code enforcement works to decrease risk and help keep building occupants safe.
Karl Houser, P.E., is with Intertek-Building & Construction