“The tried and true 40 mil modified asphalt air barrier sheets and similar spray applied products, unfortunately, are some of the less likely products to be included in NFPA compliant assemblies as they add a substantial fuel load,” says Altenhofen.

While a lot of EIFS have passed NFPA 285, Altenhofen points out that there are some coated foam plastic trim and accent products that look like EIFS, but may not comply with NFPA 285.

As for FRPs and HPLs, he recommends carefully evaluating the plastic panel products because they are often organic based, making them more prone to combustion.

Altenhofen has also observed polyisocyanurate insulation as typically being less flammable than extruded or expanded polystyrene, but the product has some other performance issues that require evaluation.

Designing Without NFPA 285

As noted earlier, if a wall assembly is designed without foam plastics and is less than 40 feet above grade, then NFPA 285 testing is not required. In addition, NFPA 285 compliance is not required for Type V Combustible Wall construction as the IBC gives prescriptive requirements instead. Previously, NFPA 285 compliance was not required for a wall of any height, comprised entirely of noncombustible materials, but the recent addition of the WRB trigger to the 2012 IBC has put a logistical hold on this option.

In terms of the WRB exceptions coming up in the 2015 IBC, although this code version won't be adopted for some time—in fact, as late as 2018 in some jurisdictions—the document is available for reference at this time and some local authorities may choose to implement it, particularly those who are approached by the National Institute of Building Science and the Building Enclosure Technology and Environment Council—with support from the American Institute of Architects—who are actively lobbying the IBC and local AHJs that wall assemblies can be built to acceptable life safety standards without the full requirements of NFPA 285.

In particular, the group proposed changes to the foam insulation and WRB sections of NFPA 285 for the 2015 IBC. Although the foam proposals were rejected, the group achieved partial success with WRBs.

The specific claim made by NIBS/BETEC in the WRB proposal reads as follows:

There are materials that are available, tried and tested by long-term proven history of performance as weather barriers that are not able to meet the standards in this test. Section 1403.2 of the IBC requires weather-resistive barriers while Section 1403.5 requires them to be tested to a standard if they contain a combustible water resistive barrier that many materials that are traditionally used and have proven their value can't meet.

Section 2603.5 establishes requirements for protection and testing of combustible water resistive barriers that include foam plastic insulation, so Section 1403.5 is not necessary for those products. Given that 75% of construction litigation relates to water leakage suggests that this paragraph should be deleted or we are likely to face significant problems in the future with the failure of exterior water barriers.

Although the IBC was not willing to fully exempt WRBs from NFPA 285, the following exceptions were included in the 2015 IBC:

• If the WRB is the only combustible wall component and the wall has a noncombustible covering.
• Windows and doors, and flashing around windows and doors are excluded.
• If the WRB is the only combustible wall component and the following test parameters are met:
•ASTM E84 Product Test:
• Flame spread index of 25 or less
• Smoke-developed index of 450
• ASTM E1354 (Cone Calorimeter) Product Test:
• Incident radiant heat flux of 50 kW/m²
• Effective Heat of Combustion of less than 18 MJ/kg
• Peak Heat Release Rate less than 150 kW/m²
• Total Heat Release of less than 20 MJ/m²