CELLULOSE INSULATION

In the January/February issue of Home Energy, Alan Meier, the executive editor of that magazine, reviews the highlights of a study on the fireproof properties of aged cellulose insulation, performed at Tennessee Technological University (TTU) by Nan Chiou and David Yarbrough. This topic was also covered in the Drexel Insulation Report, vol. 9, no.3, May-June 1991.

Cellulose insulation is made from shredded paper, usually newsprint, treated with a fire retardant, usually boric acid or borax. It had been suggested that the fire retardant properties of this insulation could decrease over time due to settling of the retardant to the bottom of the insulation, its sublimation, or its being leached out by water. The TTU researchers determined that cellulose insulation, when properly treated and installed in accordance with existing regulation, will provide safe, fire-resistant insulation for centuries.

They shook a box containing the insulation at a rate representing more than 600 years of vibration in a representative house and found no significant settling of the boric acid toward the bottom. In their sublimation tests, they ventilated the space containing the insulation. Otherwise an equilibrium between the sublimated gas and the solid boric acid would beestablished, inhibiting further sublimation. Under the typical attic conditions, the rate of sublimation was too small to detect. The researchers then increased temperature and ventilation rate far above usual conditions and determined that, even at 158°F and 1 air change per hour, it would take more than 500 years for sublimation to cause a significant decrease in fire resistance. For more information, readers are réferred to the original report "Permanency of Boric Acid Used as a Fire Retardant in Cellulose Insulation", which was published in Energy and Buildings, vol. 14, 1990, pp. 351-361.

Chiou and Yarbrough did not perform leaching tests because other researchers had already collected the pertinent data. Although boric acid is soluble in water and could therefore be carried away if the insulation ever got wet, it so happens that this chemical forms a fairly stable compound with the cellulose polymers, thus resisting separation of the acid. In theory, cellulose insulation should never be exposed to water, but in practice it may become exposed to moisture due to leaky roofs sweating or broken pipes, or condensation. Not only could this leach out the fire retardant, but it also would decrease the insulation properties of the material. Leaching may only become important when the cellulose is exposed to water for prolonged periods of time, say under condensation conditions. The loss of fire resistance, however, would be localized and would not seriously incease the fire danger to the building. It is probable that other serious problems, such as structural damage, would appear first in such cases.

- Drexel Insulation Report
VOLUME 9 NUMBER 5
September-October 1991