By P.J. Norwood
Attic fires pose many hazards for the fire service. When a fire occurs in an attic, it often will go unnoticed until smoke or flames are visible from the outside of the structure. Because these fires take longer to detect, they are more dangerous for firefighters and residents. A fire in the attic may involve insulation and wood structural members as well as a variety of stored belongings. In a fire situation, the attic ventilation system, which is designed to reduce moisture accumulation by drawing fresh air low from the eaves and exhausting moisture-laden warm air near the peak, create an optimal fire growth and spread situation by supplying oxygen to the fire and exhausting hot gases.
In December 2012, I was invited to be a member of the Underwriters Laboratories Firefighter Safety Research Institute (UL-FSRI) Residential Attic Fire Mitigation Tactics and Exterior Fire Spread Hazards on Fire Fighter Safety Technical panel, commonly referred to as “The Attic Study.” Although attic fires were a big piece of the study, the study was not limited to attic fires. The goal was to increase firefighter safety by providing the fire service with scientific knowledge on the dynamics of attic and exterior fires and the influence of coordinated fire mitigation tactics from full-scale fire testing in realistic residential structures.
The Technical Committee was tasked with the following very specific set of goals and objectives:
· Improve firefighter safety by increasing knowledge of fire behavior.
· Develop an understanding of the impact of new construction materials and techniques and “green” building technologies on fire spread along the building envelope and propagation into and growth within the attic.
· Identify and disseminate standard best practices for mitigating attic fires based on science.
· Provide the knowledge to better understand the fire dynamics and building response factors that cause and contribute to fireground injuries and fatalities during attic fire incidents.
· Disseminate to stakeholders knowledge gained pertaining to the built environment that can impact the code process to improve the safety of the public and the fire service.
· Bring the “science to the streets’ by transferring science-based tactical considerations founded on experimental results that can be incorporated into firefighting standard operating guidelines. Research findings will be communicated to the fire service community through an eLearning training course and class room presentations at major fire department conferences.
An estimated 10,000 residential building attic fires are reported to U.S. fire departments each year and cause an estimated 30 civilian deaths, 125 civilian injuries, and $477 million in property loss. The location of the attic creates several difficulties for the fire service. Firefighters must decide whether to fight the fire from inside the structure, from the outside, or a combination of the two. In these incidents, firefighters have to consider that the ceiling can collapse, creating rapidly deteriorating conditions inside the structure, and that the roof structure can collapse, creating deadly conditions for firefighters operating on and under the roof. Structural collapse accounted for 180 firefighter deaths between 1979 and 2002; one-third occurred in residential structures.
Many of these incidents involved a roof falling on firefighters or firefighters falling through the roof during firefighting operations on attic fires. Compounding these hazards is the speed at which conditions can deteriorate. A piece of gypsum board may fall or be pulled from the ceiling, quickly changing the relatively clear and cool conditions in the living space, endangering firefighters executing a search and rescue operation.
In several fires, rapidly changing conditions occurred during firefighting efforts, resulting in fatalities and injuries. In one incident, Firefighter Kyle Wilson of Prince William County, Virginia, lost his life fighting an attic fire on April 16, 2007. This was an exterior fire that propagated up the exterior into the attic space. Although this fire was aided by the wind, the large attic space allowed a substantial amount of fire to build until the pressure forced the fire downward into the second floor of the residence where Firefighter Wilson was performing search and rescue. The sudden changes in the environment created an unsurvivable atmosphere, even with full personal protective equipment. Firefighter Wilson perished.
A second incident involved an interior chimney fire that originated in the basement. Because of the void spaces within the structure, the fire propagated into the large attic space, where a large amount of air and unchecked fire growth created a high pressure build up that forced the fire downward, explosively by some accounts, onto firefighters operating on the second floor. The rapidly changing environment caused critical injuries to 19 firefighters.
Fires in attics may also be challenging to attack because of specific design and construction features such as half-story Cape Cods or bungalow style homes. These attic spaces are common throughout the United States and present unique challenges to the fire service. The presence of knee walls and collar ties create void spaces for fire to travel around the finished attic space.
Firefighters have been battling fires in attics for many years. In recent times, the fireground has changed for a number of reasons. First, the fire service is encountering larger attic spaces because the average size of a home built in the United States has increased from approximately 1,600 square feet to 2,600 square feet since the 1970s. Fires in these larger attic spaces are grow to a substantial size because of the amount of available air, putting firefighters at risk as they operate unknowingly below the fire.
Second, the construction practices have also changed over this time frame. Older homes tend to have attics that are framed with larger size lumber and are built with one continuous volume. Newer home attics typically are constructed with more complex attic spaces created with smaller-dimension wood member trusses. Fires in these attics can create concealed fires that are more difficult to locate and extinguish. In addition, “green” initiatives to increase energy efficiency use products like foam insulation that have the potential to lead to faster fire propagation and create new challenges such as rapid exterior fire penetration into the attic space.
The number of residential structure fires originating from the building exterior such as an adjacent structure fire, garage fire, deck or porch fire, mulch/vegetation fire, or a wildland fire have been increasing. Exterior fires can transition into attic fires directly through the eave/soffit and wall vents or indirectly by burning through eaves/soffits, exterior walls, or windows.
Changes in residential wall construction over time are thought to play an important role in how exterior fires are initiated and spread. Older homes commonly had brick, wood clapboard, or stucco on the exterior. Construction practices evolved, and vinyl siding over a wood sheathing with a vapor barrier was introduced. Today, it is common to find vinyl siding over a rigid foam sheathing to increase energy efficiency. Residential construction allows architects to use expanded polystyrene and polyisocyanurate foam core sheathings in their designs. The 2012 International Energy Conservation Code wall insulation requirements have become more stringent in several climate zones. For the first time, builders in some climate zones will be required to install exterior rigid foam insulation or use some other comparable wall-insulation strategy.
The data, science, and tactical recommendations that resulted from the UL-FSRI “attic fire” technical committee were presented and discussed in my class at FDIC International
Bibliography
UL-FSRI Final report – Residential Attic Fire Mitigation Tactics and Exterior Fire Spread Hazards on Fire Fighter Safety.
Attic Fires in Residential Buildings. Topical Fire Report Series. U.S. Fire Administration, Vol 11:6, January 2011.
Brassell, LD and Evans, DD., “Trends in Firefighter Fatalities Due to Structural Collapse, 1979-2002,” NISTIR 7069, National Institute of Standards and Technology,
Gaithersburg, MD, November 2003.
Career Fire Fighter Dies in Wind Driven Residential Structure Fire.” Fire Fighter Fatality Investigation Report F2007-12, National Institute for Occupational Safety and Health, May 2008.
“Significant Injury Investigative Report 3380 Soper Road March 19, 2011.” Huntington Volunteer Fire Department and Rescue Squad, Inc., March 2012.
P.J. Norwood is a deputy chief/training officer for the East Haven (CT) Fire Department. He served four years with the Connecticut Army National Guard. He is an FDIC instructor, Fire Engineering educational advisory board member, and a Fire Engineering author. He served on the Underwriters Laboratories Technical Panel for the Study of Residential Attic Fire Mitigation Tactics and Exterior Fire Spread Hazards on Fire Fighter Safety. He is certified to the instructor II, officer III, fire marshal, and EMT-P levels.
