Did you know that any cavity wall assembly with rigid foam insulation is required by the International Building Code (IBC) to have passed the National Fire Protect Agency (NFPA) code 285 assembly test? If you’re like most architects, contractors, and code officials — the answer is no. Incredibly, NFPA 285 has been in the code books since 1988 (although under different names).
There are two reasons that our industry is becoming increasingly aware of this significant code requirement:
- Rigid foam insulations are now more common in our exterior building assemblies as an effective strategy to achieve better energy-efficiency and to adhere to the new 2012 International Energy Conservation Code (IECC) requirements for continuous insulation.
- Manufacturers have recognized the marketing potential of being the first in the industry with products and assemblies that have passed the NFPA 285 test (NFPA 285 is an assembly test – approved individual products do not exist) and these manufacturers are actively increasing awareness while simultaneously selling their products.
The NFPA 285 test is meant to evaluate the potential for vertical and lateral flame propagation in exterior wall assemblies that contain combustible components. For an NFPA 285 test to take place, the test building must be two-stories in height, contain a window, and simulate a flashover fire with gas burners both on the interior and exterior of the exterior wall/window assembly. The test has been criticized as apocalyptic and without evidence that foam plastics or other combustible materials within a cavity wall system could lead to a significant fire hazard. A single NFPA 285 test could easily exceed $50,000. If any materials, geometries, or details are changed at all, the NFPA 285 test is no longer valid due to changes in the assembly. It is not realistic for manufacturers to test every single assembly combination, since the design process can evolve rapidly. It is therefore quite rare that actual conditions as designed will accurately match one of the few tested assemblies.
These are the 2012 IBC triggers requiring the NFPA 285 test:
- IBC 2603.5 – if any foam plastics are used in exterior walls
- IBC 1407 – if MCMs are used as exterior veneer, >40’ height
- IBC 1409 – if high-pressure decorative laminates are used on exterior walls, >40’ height
- IBC 2612 – if fiber-reinforced plastics are used on exterior walls, >40’ height
- IBC 1403.5 – if a combustible weather-resistive barrier (WRB) is used in exterior wall, >40’ height, regardless of insulation or cladding type
Did you catch that? The NFPA 285 test is required if a combustible WRB is used regardless of cladding type! That requirement only slipped its way into the code book in 2012. Fortunately, the national Building Enclosure Councils (BECs) teamed up with other industry groups and petitioned for the following exceptions that are likely to be included in the 2015 IBC:
- WRBs will be acceptable if they are the only combustible component in the assembly
- All window flashings are to be exempted
- Foam plastics will be exempted (if 1” or more of concrete/masonry is used, there is no air cavity in the assembly, and the lame spread is < 25)
Another solution to avoid the NFPA 285 requirement is to use non-combustible insulations, such as mineral wool. While mineral wool has some great characteristics (non-combustible, moisture-resistant, termite-resistant, semi-rigid), it has a lower R-value per inch than foam plastics, cannot be used as an air barrier (foam plastics must be taped to act as an air barrier), and has a reduced R-value when wet.
Many experts believe that sprinkled buildings should be exempt entirely from NFPA 285 testing. In the meantime, architects are left with a decision: Do we continue to bury our heads in the sand and ignore this code requirement? While a common strategy, the burying-our-heads-in-the-sand strategy is tenuous from both a legal and liability standpoint — especially as more and more industry professionals become aware of the NFPA 285 code requirements. As a community, we should proactively meet with code officials and policy decision makers, and submit commonsense exemption recommendations to our governing bodies and jurisdictions.