Do mice chew through closed cell spray foam?

Mice can chew through closed cell spray foam, though closed cell foam is harder and more resistant than open cell foam or fiberglass. Mice and rodents can gnaw through almost any soft material including foam, wood, and plastic to create pathways, nests, or access food. Closed cell spray foam is dense and provides some deterrent because it is harder and less appetizing than open cell, but it is not rodent proof. Mice may chew through closed cell foam if it blocks their entry route or if they want to nest behind it, especially if foam is only barrier. To prevent mice chewing through spray foam, it is recommended to combine foam with rodent proof materials like steel wool, hardware cloth, or metal flashing at entry points, and to seal gaps with foam plus metal barrier. Spray foam alone should not be relied on as rodent exclusion. Proper pest control, sealing exterior entry points with metal, and keeping area clean helps prevent mice from chewing foam. So while closed cell is more resistant, mice can still chew through it.