Mice Are Living in the Fiberglass Insulation of My Attic

Mice are often the most unwelcome visitors in homes. These little rodents can enter your home through tiny openings around plumbing fixtures and vents or gain entrance under doors and windows. Once inside your home, mice can move into your walls and attic, often using the insulation for nesting material.


Mice can damage your home, including the insulation.

Mouse droppings are often the first sign of these furry inhabitants. The droppings look like long pellets and range in size from one-eighth to one-half an inch in length. You may not see the mice, since they are nocturnal animals and rarely come out during the day. Mice reproduce at a rapid rate, often having up to 10 litters in a single year.


Mice gather and pile up soft materials to create nests. Insulation in the attic is an ideal material for nesting. These small rodents gnaw and tunnel through the insulating materials, reducing the effectiveness of the insulation by creating holes and air spaces that conduct heat. This may result in an increase in heating and cooling costs. Mouse urine can damage the vapor barrier on some types of insulation and cause condensation inside the attic and walls, depending on the level of infestation. The permanent damage may require insulation removal and replacement.

Other Damage

Although mice may target your attic insulation for its superior nesting qualities, their presence can cause serious damage to other structures within your home. Their constant gnawing can ruin furniture, books, clothes and food. Mice can transmit salmonellosis, a type of bacteria that causes food poisoning. Some of the most destructive damage they can cause occurs when they chew through electrical wires, sometimes causing appliance failure or electrical fires.

Methods of Control

The best way to keep mice out of your house and attic is to close off their point of entry. They can squeeze through gaps as small as a quarter-inch. Removing or sealing off their food supply helps reduce the mouse population. Glue boards, traps and rodenticides are products designed to kill mice. Place these in the attic, close to their nests, since mice forage as close to their nests as possible. Setting the traps beside mouse droppings will ensure the traps are along their regular route of travel. Rodenticides work best for large infestations, but the poison may also pose a risk to children and pets. Use caution when using rodent poisons and check traps regularly.

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