Posted By Nathan Pobre, PIMA
Improvements to the building envelope through the use of continuous insulation solutions have played a major role in mainstreaming high-performance construction practices that meet the requirements of commercial building energy codes. To meet the demands of today’s builds, architectural and design professionals must balance energy efficiency with whole building performance considerations, including fire safety. With respect to wall assemblies in Type I-IV Construction, understanding and properly implementing NFPA 285 can be a critical component for designing a compliant, high-performance building envelope.
NFPA 285 is a fire test standard that measures the flammability characteristics of exterior wall assemblies. More specifically, and according to the National Fire Protection Association (NFPA), it “provides a standardized fire test procedure for evaluating the suitability of exterior, non-load bearing wall assemblies and panels used as components of curtain wall assemblies that are constructed using combustible materials or that incorporate combustible components for installation on buildings where the exterior walls are required to be non-combustible.” While the individual products used in the wall assembly carry product-specific fire tests, it is important that entire wall assemblies are tested to meet approved fire performance requirements and ensure the safety of the building occupants.
The NFPA 285 test is performed on both load-bearing and non-load-bearing wall assemblies. It requires a wall assembly mockup spanning two stories (18’ high) with a test room on each floor. A single window opening is provided in the first-story room where a test burner is located. This burner is ignited in order to simulate an interior room fire. A second burner located on the exterior side of the test wall further enhances the flames to the window header. The test simulates a common, real-world interior fire scenario that reaches flashover, breaches a window, and spreads upward along the wall face. The test examines fire performance of the entire wall assembly, including within the wall assembly. It’s important to note also that the test is conducted without any interior fire suppression system.
To pass the NFPA 285 test, flame propagation cannot occur on or within the wall assembly beyond a certain distance either vertically or laterally from the area of flame plume impingement. Thermocouples are placed throughout the wall assembly to measure temperatures. Exceeding defined temperature limits results in a test failure. Additional requirements include:
No flame propagation in second-floor room;
The inside wall assembly thermocouples shall not exceed 1000°F rise during the 30-minute test;
External flames shall not reach 10′ above the top of the window; and
The external flame shall not reach 5′ laterally from the center line of the window.
It is a common misconception that only foam insulation products trigger NFPA 285. While any wall containing foam plastic insulation in Types I-IV Construction must comply with the test requirements, the use of other wall assembly configurations may also need to pass NFPA 285. These assemblies can include those constructed with combustible claddings and weather resistant barriers.
Since 2000, NFPA 285 has been in the International Building Code (IBC) and has gained attention due to the increased diversity in exterior wall systems and greater compliance with building energy efficiency standards. To learn more about NFPA 285, please refer to the National Fire Protection Association.