Cellulose Makes Home Safer
All residential structures contain large amounts of wood. Cellulose insulation is the only wood-based building material that is always treated for fire retardancy. This makes cellulose insulation one of the safest materials used in home construction.
If a fire occurs, the dense structure of cellulose and its fire retardants slow its spread through the building by blocking flames and hot gases and restricting the availability of oxygen in insulated walls and ceilings. Scientists at the National Research Council Canada report that "cellulose in the wall cavity provided an increase in the fire resistance performance of 22% to 55%." Fire roars right through fiber glass. The NRCC study showed that "the fire resistance of fiber-glass insulation was slightly lower than that of a non-insulated assembly."
Tests at Omega Point Laboratories indicated that cellulose in a wall increased fire resistance 26% to 77%, as compared with an uninsulated wall.
Several fire demonstrations have been conducted in which cellulose-insulated structures have remained virtually intact while uninsulated and fiber glass insulated structures burned to the ground.
The Highest Standards of Any Insulation Material
Today's cellulose insulation is covered by American Society for Testing and Materials Standard Specifications C-739 for loose-fill insulation, C-1149 for spray-applied self-supporting insulation, and C-1497 for stabilized cellulose insulation. Developed and refined over many years through the consensus standard development process of ASTM, the cellulose insulation standards cover several material properties, including:
Heat transfer resistance (R-value)
Settled (or design) density
Critical radiant flux (a measure of surface burning characteristics)
Smoldering combustion (an assessment of fire resistance within the insulation layer)
Moisture vapor absorption
Adhesive/cohesive strength (spray-on only)
This industry standard is more comprehensive than the Consumer Products Safety Commission regulation, which has strict requirements for flammability and corrosiveness, but does not address other important charachteristics that are not safety-related.
Approved Under All Codes
Cellulose insulation is subject to the strict flammability and corrosiveness standards established by the Consumer Products Safety Commision. Federal law prohibits states and local jurisdictions from adopting less stringent requirements for cellulose insulation, but communities can empower building officials to enforce the CPSC standard by placing identical requirements in local building codes.
The International Code Council codes, which have replaced the model codes of Building Officials and Code Administrators (BOCA), the Southern Building Code Congress International, and the International Conference of Building Officials (ICBO), require that cellulose insulation must conform with the CPSC standard.
The ICC codes also recognize the fire safety advantages of cellulose by permitting insulation of electrical boxes on opposite sides of fire rated walls if the boxes are on opposite sides of fire rated walls if the boxes are seprated by as little 3.5 inches of cellulose insulation. In walls with fiber glass the required separation is 24 inches.
Some local codes may not yet specify that cellulose insulation must conform with the CPSC standard, but a building inspector who insists on conformance with the federal standard is acting responsibly and legally.