Material Failure–Focus on Cellulose Insulation


This recurring series will discuss various materials, including engineered plastics, woods, metals, polymers, bio-polymers, and other composites, and evaluate real world failure modes and provide practice tips for the recovery professional. The first material discussed is cellulose insulation.

Cellulose is an organic material derived from wood, and commonly used in the building industry to insulate.  Cellulose is commonly seen as blown in insulation in homes and businesses. Blown cellulose insulation is made mostly from shredded newspaper and chemicals to reduce flammability. The composition can vary significantly as to the cellulosic material, and the type and percentage of fire retardant chemicals utilized. Many cellulose companies use a blend of ammonium sulfate and borate. While cellulose manufacturers contend this material is fire safe, even treated cellulose can support combustion and smoldering ignition. 

In the last decade, exactly how cellulose insulation can be ignited has become a growing debate. An older theory claimed that when cellulose was subjected to heat, its ignition temperature was lowered and eventually ignited by that heat source. The current explanation is that through pyrophoric carbonization, where the cellulose first chars and carbonizes, it will self-heat until it ignites. This theory is supported by a 1999 National Institute of Standards and Technology ("NIST") study. Wood chips and whole wood pieces were tested, resulting in a finding that self-heating occurs because of a physical change in the wood which raises its surface temperature and leads to ignition.    

Regardless of the processes, blown in insulation is a competent ignition source. In any fire claim where cellulose insulation may be in the area of origin, steps should be taken to identify the manufacturer, brand/type, and the installer. These parties should be placed on notice if it is suspected the cellulose could have played a role in ignition or fire spread.  If packaging can be obtained, it will typically identify the material type, composition, standards to which the material has been certified, and any warnings.  Samples of cellulose from areas of the home or business that were unaffected by fire should also be taken for future testing.

Decisions should be made whether a chemist or fire spread engineer will be needed. While certain jurisdictions have allowed submission to a jury based merely on cellulose insulation being the most probable fuel for the fire, expert testimony regarding he ignition sequence may be advisable. In circumstances where the fire occurred months or years after installation, having an expert explain the delay in ignition may help the jury to connect the dots.

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