Lessons from the London Fire

The general consensus in the media is that the London fire catastrophe in the Grenfell Tower couldn't happen in the US because of our stricter fire codes which don't allow highly flammable insulation material on facades without fire retardents and certainly no high-rise building with a single exit stairway. While it is true that US standards are stricter on both of those counts, there remain troublesome aspects of the London fire that should give architects, engineers, and building managers involved in multi-family housing pause as they deal with egress and flame spread .

Grenfell Tower fire, London

There has been a slew of sometimes spectacular facade fires on highrises which may not have had the terrible death toll of the London fire, but certainly caused very hazardous conditions and large property damage. Those fires happened mostly abroad, but not always: The huge fire on the Marina Torch, Dubai, February 21, 2015, the fire on the Grozny-City Tower Hotel, Grozny, Chechnya, April 3, 2013, and the Tamweel Tower fire in  Dubai, November 18, 2012. There were also prominent facade fires caused by foam insulation in the US, both in casinos that were found to have used non code compliant construction.  (The Monte Carlo casino façade fire in Las Vegas, NV, in 2008 and the  the Water Club Tower fire at the Borgata Casino in Atlantic City, NJ, in 2007. Source).

Atlantic City Casino Fire

Overall, the IBC identifies each major category of combustible component in an exterior wall, and provides detailed limitations and allowances for each type. For each such combustible component, there are typically individual component requirements, such as ASTM E84 flame spread index limits and ASTM E1354 cone calorimeter heat release limits. Making compliance easier, each section also includes several exceptions and exemptions. For example, NFPA 285 compliance is exempted for combustible exterior cladding that is installed not higher than 40 feet above grade. (Source)

1. The Insulation

The London highrise had been subject to a insulation retrofit which is not uncommon in the US either, notably because of the increased insulation requirements of the 2007 edition of ASHRAE 90.1 “Energy Standard for Buildings Except Low-Rise Residential Buildings,” as well as the 2006 and 2009 editions of ICC’s International Energy Conservation Code. Both require significantly increased R-values for exterior walls in almost all states of the country.

The most typical method of increasing the R value of the extreior wall is the use of “continuous insulation across all structural members without thermal bridges other than fasteners and service openings. The easiest way to accomplish this is to install continuous insulation on the exterior side of the exterior walls by using noncombustible mineral wool or combustible foam plastic insulation such as extruded polystyrene foam, expanded polystyrene foam, polyisocyanurate foam or spray-applied polyurethane foam.

Grozny Towers hotel fire

This is where the International Building Code (IBC) and the National Fire Protection Code (NFPA) come in. IBC does allow the use of those principally flammable materials even where a non combustible exterior wall construction is required, but there are strict rules about fire resistance and flammability for all major building types regardless whether it is a high-rise or a lowrise (only Type V and one story buildings are exempt). IBC Chapter 6 and 26 spell out the specifics; in Chapter 26 reference is made to NFPA 285 “Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components.” NFPA 285 tests assemblies, not individual materials and may require testing for a specific application if it deviates from available test results for typical assemblies. Chapter 26 exempts assemblies with thermal barriers in concrete, stucco, metal and fiber cement with specific thicknesses (see image). After IBC 2009 EIFS systems are addressed in Section 1408 IBC, which requires compliance with ASTM E 2586, Standard Specification for PB Exterior Insulation and Finish Systems. ASTM E 2586 requires EIFS to pass NFPA 285, and essentially replaces the foam insulation requirements of Chapter 26 for EIFS.

Chapter 26 exceptions

The Torch fire, Dubai

Like practically all organic building materials polystyrene foam is combustible. However in practice its burning behaviour depends on the conditions under which it is used, as well as the inherent properties of the material. These inherent properties differ depending on whether the cellular material is made from EPS with or without a fire retardant additive. The bonding of other materials to cellular polystyrene also considerably affects its burning behaviour. For example, foil-faced products have an improved surface spread of flame performance. When installed correctly, expanded polystyrene products do not present an undue fire hazard. It is strongly recommended that expanded polystyrene should always be protected by a facing material, or by complete encapsulation. When burning, expanded polystyrene behaves like other hydrocarbons such as wood, paper etc. The products of combustion are basically carbon monoxide and styrene: during a fire, the styrene may be further decomposed, giving off oxides of carbon, water and a certain amount of soot (smoke). (Foam Industry organ EUMEPS)

The following lessons and questions apply:

The NFPA 285 test is done with a perfect assembly executed to the specifications. Especially for EIFS construction one has to consider the fact that surface damage is easily inflicted on those assemblies in which the synthetic stucco that form the exterior face and protect the foam insulation from exposure to the flame during the test may well be exposed in a real life condition where a dumpster placed closed to the wall may catch fire, for example. 

• Have modified assemblies really been tested and have the agencies supervising construction sufficient control over the building progress to assure that a particular assembly meets the NFPA 285 requirement? (The Atlantic City fire showed that actual panels deviated from the test assembly)

• Certain prefabricated aluminum panels are exempted from flame spread requirements of chapter 26. The panels in the London fire were aluminum panels. Although the same panels are not sold in the US, it is still a concern that aluminum panels disintegrate. The contractor for the London insulation project had allegedly suggested zinc panels instead of the cheaper aluminum panels but the recommendation was reportedly rejected by the local council that had authority for cost reasons. A strong fire fuel source can be sufficient to cause the aluminum to deform and the polystyrene to liquefy and delaminate from the aluminum facing.

• Any panel construction that uses rain screen technology creates a void space between the panels and the building which can create a chimney effect, allowing fire to rapidly move up the facade.

• Some jurisdictions have made exceptions to specific requirements of IBC. For example Washington DC in their 2013 Building Code did away with the IBC requirement for NFPA 285 testing for walls with a combustible core. Similarly Massachusetts, Indiana, and Minnesota modified the applicability of NFPA 285. In DC tThe requirements for the acceptable use of foam plastic insulation (IBC 2603.5) have been waived if the building is provided with an automatic sprinkler system complying with either NFPA 13 or NFPA13R.

• There has been considerable pressure of the insulation industry to weaken the IBC requirements. Those attempts have been averted in the most recent IBC code modifications, but the next challenge is probably already scheduled.

  

  Washington Post US fire spread graphic

In summary, the risk of a fire spreading as quickly over over as many floors solely through the insulation material is vastly smaller in code compliant US construction than in the London case. Some spread may still be possible in real life conditions that deviate from the NFPA 285 test conditions or where the requirement has been deleted from the locally applicable code or where the fire source exceeds the one in the test conditions of NFPA 285.  Fire vertically jumping from one floor to another on the facade will not be prevented by interior sprinklers, even though the sprinklers will effectively prevent fire to spread inside the apartments or other floor uses should they have breached the facade, for example through a window. Nevertheless, even fires isolated to the facade will impede fire rescue operations, can spread noxious fumes and can induce panic among building residents.

2. The exit stairways

While the problems in the stairway of the London highrise were exacerbated by the fact that there was only one egress stairway, the conditions in the stairway could also occur where there are two egress stairways with one or several of the below conditions:

While the cladding on Grenfell Tower helped spread the flames, shocking new evidence reveals the stairwell was a deathtrap, sucking in thick smoke and toxic gases, which sealed the fate of many residents. The Times

• Crowded conditions when hundreds of fleeing residents heading downstairs meet with fire personal that is trying to go up (This was also a condition in the initial WTC fire).

• Lack of clarity whether the building should be evacuated or residents should shelter in place

• The fluestack effect of fire on one or several lower floors combined with residents opening the stair-tower doors on several levels for extended periods to flee. The London stairway was reported to be extremely smoky, hot and acting like a smokestack making orderly egress all but impossible

More than 83% of fire deaths in building fires in the United States occur in fires that have become very large so that they extend beyond the room of origin, and thus generate too much toxic smoke (Gann et al. 1994)

Fire death risk in the US

Many older US highrises built before modern codes have stairways that are below 44" wide and may not include proper stairway pressurization. Those buildings likely aren't sprinklered either and only have standpipes in the stairway requiring the presence of the fire department for fire suppression. A prominent highrise fire of a modern skyscraper without an automatic sprinkler system throughout was the Meridian One fire in in Philadelphia that raced from the 22nd to the 30th floor and only stopped after it encountered a floor that was equipped with automatic sprinklers. Three firefighters died in that fire. Codes for standpipes were revised after the Meridian One fire.

While historic tall buildings typically predate the use of EIFS and have truly non combustible often bearing masonry exterior walls, some of the conditions present in the London Tower could easily happen in those narrow old stairways as well. Risks of fire spread from floor to floor would vastly increase if partial rehabilitation would add flammable insulation on the exterior facades, even if it is compliant with US codes.

The London fire should serve as a caution to all involved in fire safety issues that energy efficiency, affordability and fire safety can easily be on a collision course. In doubt, life, safety and health must come first.

Klaus Philipsen, FAIA

Source materials:

Fireengineering
Building Safety
Slate
The missing three hours: The Times, London


The 2000 IBC and legacy codes initially addressed only the potential hazards of foam plastic insulation (IBC 2015 §2603.5.5) and EIFS (2015 IBC §1408.2). Fire safety requirements for Metal Composite Materials (MCM) were added to the 2013 IBC (2015 IBC §1407.10). Fiber Reinforced Plastic (FRP) was added to the 2009 IBC (2015 IBC §2612.5). The 2012 IBC included the addition of fire safety requirements for the use of High Pressure Laminates (HPL) (IBC 2015 §1409.10) and Water Resistive Barriers (WRB) (IBC 2015 1403.5).

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