After all, this fire test method has hidden in plain sight in building codes dating back to the early 1980s. Fire safety officials have long understood the risk of blending combustible materials, starting with foam plastic insulation and air/water barriers, in non-combustible exterior wall construction. NFPA 285 measures that risk.
So why all the noise now? What happened?
ASHRAE 90.1 Happened
To be more precise, the requirement under ASHRE 90.1 for continuous insulation (ci) and an air/water-resistive barrier (AWB) happened, through successive energy code updates beginning in earnest in 2007.
The ASHRAE 90.1 requirement put architects and building engineers in a pickle. How can they deliver a code-compliant building with limited flame propagation potential in the “noncombustible” exterior wall while using often combustible ci and/or AWB wraps or coatings to meet energy code? Waiting in the wings was a test that was originally devised to assess that point and could demonstrate that an ASHRAE 90.1-compliant wall assembly can also be IBC complaint.
NFPA 285 to the Rescue
The once-languishing NFPA 285 fire test standard, self-described as the Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components, now plays a prominent role in modern building code enforcement by helping identify assemblies that meet the 30-minute limited fire propagation criteria.
Few know the realities of this new normal better than registered architect Herbert Slone, the chief architect and senior manager, commercial building systems, of Owens Corning.
Slone understands the architect’s predicament at a peer level. “For architects, the need to comply with NFPA 285 seems to have suddenly fallen from the sky,” Slone says. “I know how frustrating it can be to specify a compliant wall assembly.”
The pain can come from several directions, Slone says. Start with the variety of combustible materials used in non-combustible wall construction that are subject to the test. Foam plastics, certainly, but the list also includes a growing family of ci and AWB materials, plus cladding such as high-pressure laminates, metal composites, and fiber-reinforced polymer panels. Even rooftop mechanical equipment screens and rooms may be subject to an NFPA 285 rating, Slone advises.
“The other thing people sometimes forget is this is an assembly test,” Slone says. “It’s not a test of individual components, as some product manufactures might have you believe. Change one element in a compliant assembly and it could be rendered non-compliant. There really is no such thing as a stand-alone ‘NFPA 285-compliant product.’ ”
The plot thickens even more when you compare the differences between the 2012 and 2015 International Building Code (IBC). Code compliance requirements are “a little less burdensome” in jurisdictions subject to the 2015 IBC according to Slone. “Building science is better understood and the 2015 code reflects somewhat less stringent requirements in some situations,” Slone says.
What’s right for your project? Slone says the best approach for designers is to specify a tested wall system. To identify tested candidates, Slone recommends any of a few sources including NFPA 285 test reports, manufacturers’ literature, and the UL online certifications directory, using FWFO for the UL Category Code. It is also important to note that the IBC acceptance criteria accepts NFPA 285 engineering analysis from an independent third party to demonstrate compliance.
To learn more about designing to NFPA 285 standards, click here.