Are you familiar with NFPA 285? Maybe you know that it’s the standard test method designed to determine the flammability characteristics of exterior, non-load-bearing wall assemblies that contain foam plastic insulation. The test, developed by the National Fire Protection Agency in 1998, is crucial to occupant safety in a multi-story building.
But do you know all the ins and outs of this assessment? Do you know why it’s the gold standard to compare to other, less-stringent test methods? Keep reading for some of the most frequently asked questions and necessary information about NFPA 285.
How is the NFPA 285 test conducted?
The NFPA 285 standard test is for a two-story specimen wall at least 18 feet high and 13 feet, 4 inches wide. The assembly to be tested must contain a window opening at least 78 inches wide in the lower floor wall. There are additional specifics regarding the dimensions of an apparatus to support the wall.
During the test, the assembly is exposed for 30 minutes to intense, gas-fired flames. Two flame sources are used – one inside the lower floor and one outside – directed at the upper edge of the window opening. The inside burner is ignited first, followed by the window burner five minutes later. The intent is to simulate flashover, testing the effect on the exterior wall of a fire within the structure that extends out the window opening.
How does a wall assembly pass the test?
The specific assembly must be shown to limit the spread of the fire both vertically and horizontally from the window. Temperature is monitored during the test with thermocouples, and flame height and width are measured. To pass, flames cannot reach 10 feet above the top of the window or five feet laterally from the window centerline, and the thermocouples cannot exceed 1,000°F during the test.
Acceptance criteria involves five areas: flame propagation on the exterior face of the wall assembly; flame propagation through combustible components and insulation; temperatures in the second story; flame propagation to the second story; and flame propagation to adjacent horizontal spaces.
If a particular assembly has passed the NFPA 285 test, can I substitute a similar component (such as one type of exterior insulation for another, for example) and still be compliant?
Material and construction substitutions can sometimes be made, but they must be analyzed and approved through an engineering judgement provided by an approved third party. New tests are often required when changes are made to an assembly. Even changes in the wall system geometry (for example, addition of air cavities) can have a significant effect on overall performance. And, although specific components may show testing compliance with NFPA 285, that does not always indicate that when combined into a wall assembly, the assembly will also meet NFPA 285 standards.
When is NFPA 285 compliance required?
In the IBC, NFPA 285 compliance is required in Type I, II, III and IV construction, for those with limited combustibility. NFPA 285 compliance is not currently required in Type V construction. In most buildings of Type I, II, III and IV construction, foam plastic triggers NFPA 285 testing (with limited exceptions). Other triggers include combustible claddings and combustible weather resistive barriers when the building is over 40 feet tall.
It is in the best interests of contractors and architects to verify NFPA 285 compliance of each assembly in their projects so as to limit the risk to life safety, property damage and liability. With decades worth of test data, there is a vast database of information about how various combinations of wall components perform when introduced to fire. These insights and expertise are quite valuable when considering what materials to use in a project, especially when substitutions are considered.