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New Changes are Coming to an Old Fire Test

Andy Williams, Director of Codes and Standards, Metal Construction Association, Posted 07/05/2017

Andy WilliamsFor as long as there has been construction, one of the major considerations has been fire performance. While many construction products have not changed greatly over the years, concerns over how buildings burn, if anything, have increased.

As far back as the early 1980s, there has been a need for better understanding of how walls burn when combustible elements are introduced. This led to the development of large-scale testing, which has remained generally unchanged for over 20 years. The standard, NFPA 285: Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components, is developed by the National Fire Protection Association (NFPA). Recent concerns have led to modifications to NFPA 285 that were approved by NFPA membership in early June.

In the United States, some version of the International Building Code (IBC) is generally used to regulate construction. The IBC requires compliance to NFPA 285 criteria for many different types of construction when a wall assembly contains combustible materials. The test shows flame spread on a vertical wall assembly, which is the closest reproduction we have to real-world construction. The wall tested in NFPA 285 is a minimum of 13 feet, 6 inches wide by 17 feet, 6 inches tall.

Recent changes in NFPA 285 have led to a great deal of concern by many different groups. Discussion on these changes began in 2015 at the NFPA Technical Committee on Fire Tests meeting. These discussions centered on the location of joints or seams created during the construction of the test wall. The guidance provided in the original standard stated that the "test specimen contain(s) vertical or horizontal joints or seams, joints or seams representative of standard construction practices shall be incorporated into the test specimen."

It seems that these instructions have led to confusion within the testing community. Several inquiries have been made from both companies wanting to test their products and building officials asking about the acceptability of test reports where joints in the test wall do not match the actual building construction. With the many design options used in normal construction, it is easy to see where joint locations can vary from the test wall to real-world construction.

Throughout 2015 and 2016, the Technical Committee heard testimony from a number of groups on what a panel joint is and where these joints should be located on the test wall if a fixed location was to be defined. The problem was that each group had a different idea on where to locate the joints. Testing laboratories were looking for more direction so that the test wall assemblies could be more standardized. Material manufacturers, recognizing product size and use limits, were looking to optimize panel sizes based on material capabilities. Building designers and architects wanted to simulate real-world designs. Finally, from a fire and code perspective, the groups wanted to make sure that a worst-case scenario was tested that would truly define the expected performance of the wall assembly.

There seemed to be no single answer on where the panel joints should be placed, so a proposal was made by the committee to have one vertical joint located above the window opening and one horizontal joint located within a fixed distance above the window opening. There could be additional joints as required for the construction of the test sample, but joints would be required in these specific locations.

After significant discussion and debate, the initial committee proposal was made more specific. Mandatory locations were defined as a vertical joint extending upward from plus or minus 13 inches of the center of the window opening width and at least one horizontal joint located not more than 36 inches above the window opening. The location of the vertical joint was chosen because this is also generally the center of the flame plume that is created during the test procedure. The distance of 36 inches or less above the window head locates the mandatory horizontal joint in the general area where the flame plume comes into contact with the wall assembly. During fire testing, joints are often considered to be the weakest area of the system because the flame does not have to penetrate the wall cladding to attack the unexposed cavity and any combustible elements that may make up the remainder of the wall assembly.

On the surface, this makes some sense. The new requirements more clearly define and standardize the construction of the wall assemblies to be tested. However, the results of this change will most definitely have a significant impact on the construction industry.

The NFPA 285 test standard has been around since before the development of the IBC in 2000. Prior to that, similar test standards were recognized by the Uniform Building Code (UBC) as far back as 1988, and before those, the test standard used was the UBC 17-6: Method of Test for the Evaluation of Flammability Characteristics of Exterior, Nonload-Bearing Wall Panel Assemblies. That test involved an even larger test wall assembly exposed to a very large wood crib fire. It wasn't until 1998 that NFPA 285 was developed and adopted. The results of the change were a decrease in the size of the wall sample (decreasing cost and time to construct), relocating the test from outdoors to indoors (taking away variability due to weather) and changing the fire source from wood to gas (decreasing the variability of the fire itself).

Since the adoption of NFPA 285, many hundreds of wall assemblies have been tested with no specific guidance regarding joint placement. These tests have provided the design professional a broad range of test reports covering assemblies with anything from no vertical joints to the-now mandatory-vertical joint in the center of the window opening and with horizontal joints located practically anywhere on the wall assembly. Out of the hundreds of tests run over the past 20-plus years, only a small fraction have been done with joints in the newly defined locations. Each of these wall assemblies have met the test criteria at a test cost in the neighborhood of $25,000 or more when combining lab fees plus material and labor costs to construct the wall.

When the new NFPA 285 standard is published, most existing tests will no longer meet the requirements due to the new joint requirements, and a new test will need to be run on a wall assembly that has been accepted for decades. With only three or four recognized test facilities in North America, there will be a considerable backlog for new wall design tests, and to retest walls that were once considered acceptable. While the IBC may not reference the new test version of NFPA 285 until the 2021 code is published, architectural specifications can begin requiring these new test results almost as soon as the test standard is published.

This change has been discussed within the Metal Construction Association (MCA) and many other organizations for some time now, and a number of companies have already started testing wall assemblies to the new criteria. However, there are still many wall assemblies that will need to be retested. With new construction demanding new systems, the time delay for testing may be quite long.

This change in NFPA 285 impacts more than just the manufacturers of cladding material and system designers. Other products that are part of the combustible wall assembly, principally insulation material, will also need to provide test reports showing compliance with the revised test standard. Testing previously completed that did not use the newly prescribed joint layout will at the very least need to be reevaluated and quite possibly retested to show compliance with the updated standard.

Fire code consultants will also need to determine the impact of these changes on the performance of the materials being tested. They will most likely have to review previous equivalency reports that have been issued based on the old criteria. This review process will surely lead to additional testing, increased costs and, more importantly, lead times for projects that will be constructed in the future.

While these changes have now been voted on by the membership, there remains one final appeal that will most likely be submitted to the Secretary of the Standards Council in late June. The appeal could possibly reverse the recent ballot; however, there will be no resolution prior to sometime in late July. Assuming that the membership vote is upheld, this decision will have an impact throughout the construction community.

While these changes to NFPA 285 will help provide performance information on a more standardized wall assembly, there will be a significant impact on material suppliers and system designers resulting in a significant amount of new testing and retesting to provide approved systems. The high number of tests to be run at a limited number of test facilities will most likely lead to significant added cost and longer lead times for companies to provide combustible exterior wall cladding assemblies that fully comply with the new standard and ultimately the IBC.

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Andy Williams is the director of codes and standards for the Metal Construction Association. He is a professional engineer who began his career in the wall cladding industry in 1982. For more information about MCA, go to www.metalconstruction.org

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