Do mice hate cellulose insulation?

Mice do not hate cellulose insulation, but cellulose is significantly more resistant to nesting than fiberglass, and it can deter mice to some degree. Cellulose insulation is made from recycled newspaper treated with boric acid and borate for fire resistance. Borate is a natural mineral that irritates the digestive system of insects and rodents and has low toxicity to humans. Because cellulose is dense-packed and treated with borate, it is less attractive for nesting than fluffy fiberglass, which mice love to burrow into and use for bedding. Mice can still tunnel through cellulose, especially if it is loosely blown in an attic, but they are less likely to make long-term nests in it compared to fiberglass. Studies and pest control professionals report that dense-pack cellulose in walls at 3.5 pounds per cubic foot is very difficult for mice to move through. However, no insulation is truly rodent-proof. Mice will chew through almost any insulation to reach warmth or food if there are entry points. The best approach is to combine cellulose with thorough air sealing and rodent exclusion. Seal all holes larger than a quarter inch with steel wool and caulk, cover vents with hardware cloth, and keep food sources away. Some companies add extra pest deterrents to cellulose, but standard borate-treated cellulose already offers better pest resistance than fiberglass or mineral wool, though Rockwool mineral wool is also highly resistant because its fibers are irritating.