How To Handle Fires In Buildings With Cellulose Insulation
Cellulose insulation is an easily misunderstood building material. It is made from paper fibers, so it is an organic material. Left untreated, organic materials are combustible. Some other common insulation materials – fiber glass and mineral wool, for instance – are inorganic and are noncombustible. That however does not mean cellulose insulation is less fire-safe than noncombustible materials. As the National Fire Academy, a service of the Federal Emergency Management Agency, wrote in a training manual issued as early as the 1970s: “It is critical to recall that noncombustible does not mean ‘safe,’ and it certainly does not mean ‘fireproof.’ The concept of fire resistance goes beyond that of noncombustibility. It refers to the capacity of a material or construction to withstand fire or give protection from it.” By this standard, cellulose insulation is one of the most fire resistant building materials in common use today.
Cellulose insulation is one of the few building insulation products that has a Class 1 Fire Rating. It has a flame spread of 25 or less. Walls with cellulose insulation are one-hour (or greater) fire walls. This allows the product to help control the spread of fire in homes and buildings where it is used to insulate attics, walls and other spaces. It also has a very low smoke development index level.
By design, the fire retardant in cellulose insulation slows the spread of flames through insulated assemblies to help localize the fire in structures. This allows occupants more time to escape to safety when a fire is detected and gives the fire company more time to reach the scene and limit damage.
The fire retardant in cellulose insulation suppresses flaming combustion and the dense fiber structure of the material resists passage of fire and hot gases. Unlike some insulation materials cellulose does not melt, but retains its structural integrity when exposed to fire. In an open attic, the surface of cellulose insulation chars, creating an intumescent coating that resists incursion of fire deeper into the insulation blanket. These factors help protect highly flammable wood and other materials in attic and wall assemblies from igniting and further spreading the flames from the original source of the fire. The cellulose insulation may smolder when in contact with fire, also limiting the amount of smoke released by the blaze, which is often the most deadly aspect of home fires for residents.
Special Considerations For Fire Officials and Firefighters
These inherent characteristics also require special considerations for firefighters responding to fires in homes and buildings containing cellulose insulation. Firefighters must remove the affected cellulose insulation from the home or building once the fire is brought under control. Again, by design, the cellulose insulation,or framing members covered and therefore protected by the cellulose insulation, may continue to smolder after the fire is effectively extinguished, particularly inside walls or attics where water or other flame retardants used by occupants or firefighters have not actually reached the affected cellulose insulation or smoldering lumber.
Where possible, homeowners and building owners should tell fire official responding to a fire when they are aware of cellulose insulation in the attic or walls. Fire departments should also help to make their firefighters aware of how cellulose insulation slows flames by creating smolder, rather than fire and smoke, and for the need to evaluate areas of the structure for smoldering insulation.
The critical step to ensure the fire is fully extinguished: any cellulose insulation that is smoldering must be removed from the building to completely contain the fire.
With the correct knowledge of how cellulose insulation is designed to control fires homeowners, building owners and professional firefighters can help the product to effectively limit property damage and injuries.