New Study Confirms Dense-Pack Cellulose Outperforms Fiberglass in Fire Resistance

A Building Science Corporation study comparing fire performance of dense-pack cellulose, fiberglass batts, and open-cell spray foam found that cellulose-insulated wall assemblies maintained structural integrity 40% longer than fiberglass and 25% longer than spray foam in standardized fire testing. The borate fire retardant in cellulose creates a char layer that slows flame spread. The study also noted that cellulose's air-sealing properties when dense-packed reduce oxygen flow through wall cavities, further slowing fire progression.