Can We Still Trust NFPA 285 & Professional Engineering Evaluation?

Originally published by the following source: Applied Building Technology GroupMay 7, 2018
by Timothy Ahrenholz with contributions by Jay Crandell, P.E, Kirk Grundahl, P.E. and Larry Wainright

  

Recent building fires have seized the world’s attention with flames leaping up facades and engulfing entire structures in seemingly no time at all.  Tragedies like London’s Grenfell Tower fire (2017) and less deadly conflagrations like the one that occurred at The Torch in Dubai (2015 and 2017) have raised questions regarding the use of combustible materials in cladding assemblies, particularly on high-rise buildings.

In a 2014 research report, the National Fire Protection Agency (NFPA) Research Foundation recognized “that fire spread from floor to floor and over the façade in buildings can be a catastrophic event” and concludes that “full-scale façade tests are currently the only method available for absolutely determining the fire performance of complete assemblies.” One such full-scale test administered in the U.S. is the NFPA 285 standard test.

The test mimics a fire that starts on the interior of the building in a room that reaches flashover, exits a window opening and impinges on the exterior of the building. An interior fire is by far the most common source for exterior fires in at least 95% of reported cases. A successful NFPA 285 test is one where both the vertical and horizontal spread of the fire is limited. The goal is to prevent the spread of fire horizontally to rooms on either side of the room of origin or vertically to the floor above the room of origin as well as along the face of the exterior wall, and inside the wall assembly.

However, a troubling question being raised today is whether wall assemblies that pass NFPA 285 are actually safe enough.

It may seem tricky to determine the “real” effectiveness of a fire test method like the NFPA 285 standard. After all, only fires that aren’t prevented from spreading become media events. Nevertheless, by looking at what kinds of buildings experience fires that involve exterior flame spread, we can make some useful inferences about those that don’t.

In a white paper published last year, FM Global compared several recent high-profile fires going back to 2010, and the resulting table is fascinating (page 5 of the report):

On page 6 of the report, FM Global stated their conclusion:

 

To restate in the affirmative, non-combustible exterior walls combined with fire sprinklers result in the safest high-rise building facades. Sprinkler performance and life safety going together seems obvious.

However, it is also very interesting to note two additional observations. 

  1. There were no fatalities in any of the fires (including those involving combustible exterior construction) where automatic fire sprinklers where employed.
  1. Perhaps of greater relevance is what is not stated: it is commonly understood that none of the reported fires for “combustible exterior construction” involved installations that would pass the NFPA 285 test criteria. This finding also extends to additional exterior fire data reported by NFPA Research. (Please review data and analysis at this link.).

According to the NFPA website, NFPA 285 “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” (emphasis added).

NFPA 285 is the law in the U.S. where the International Building Code (IBC) requires its use for various cladding systems incorporating combustible materials. Since the only fire listed in the FM Global report which occurred in the U.S. (Marco Polo Apartments) had concrete exterior construction, none of the buildings were required by law to pass NFPA 285. If none of these fires took place in NFPA 285-certified buildings, does it make sense to question the effectiveness of the standard?

NFPA 285 testing along with engineering analysis using this test data and additional test data calibrating fire-engineering modeling isn’t the problem; it is the solution! 

The circumstantial evidence supporting the effectiveness of NFPA 285 is very strong. Moreover, history bears out this conclusion as found in the report sponsored by DuPont at this link. Since its introduction in 1988, the NFPA 285 test has remained relatively unchanged and 30 years of use has generated no evidence of any life safety deficiencies.

Here is the history of NFPA 285 per the DuPont report:

It’s only now with high profile international fires (where NFPA 285 does not apply or cladding installations were used that do not comply) that the standard is being questioned.

NFPA 285 testing along with engineering analysis using this test data and additional test data calibrating fire-engineering modeling isn’t the problem; it is the solution! 

In the U.S., NFPA 285 is working, and the available data indicates that if there is any need, it is to ensure compliance with the sections of the IBC which relate to exterior wall assembly fire performance, NFPA 285 and any relevant engineering analysis (also known as “engineering evaluations”). The key to safe construction hasn’t changed: know the code requirements, rely on the value of professional engineering and follow all construction details and product installation requirements.

It seems clear from all the information available that if designers, builders and installers perform in a manner that conforms with the requirements of the IBC, the 30 years of demonstrated effective and safe performance when NFPA 285 and IBC Chapter 26 is used will continue.

For more in-depth information on fire safety and the use of foam sheathing, read this recent document created by the American Chemistry Council’s Foam Sheathing Committee (FSC).

For additional information about this topic, please review:

  1. Understanding Fire Safety and the Use of Foam Sheathing
  2. ICC Provides Perspective on Combustible 'Cladding Systems'
  3. Post Grenfell, Do You Know the Code and Your Cladding Options?
  4. Would Smoke Alarms and Sprinklers Have Saved Grenfell's Installed Cladding?
  5. London's Grenfell Fire: Will Plastics Be Inappropriately Blamed?