Duct Work, Insulation, and Wiring
Small SpacesRats, mice and other animals such as raccoons, opossums and skunks will sometimes get into duct work. Rodents are especially notorious for chewing holes in light flex duct work which contains no metal.
Comfortable PlacesHot and cool air then blow through these holes, which then drives up heating and cooling costs. It is not uncommon for holes to become so large that they completely stop the flow of air to their designated rooms. Cable, telephone and security wiring are often the targets of animals in the attic or under the floor.