Stop Mice From Eating Your Foam Insulation

Foam insulation is a popular choice for homeowners who want to keep their homes energy-efficient and comfortable. It’s highly effective at sealing out drafts and reducing heating and cooling costs. However, despite its benefits, foam insulation has one potential weakness—mice.

Mice can chew through insulation, causing serious issues like energy loss and contamination. When left unchecked, this damage can lead to costly repairs and even health risks. In severe cases, professional pest control experts need to intervene to permanently eliminate an infestation.

In this blog, we’ll cover why mice eat insulation, how to recognize the signs of damage, and, most importantly, what you can do to stop them from burrowing through your walls.

Why Do Mice Eat Insulation?

Mice are notorious chewers. Their teeth never stop growing, so they constantly gnaw on various materials to keep them from getting too long. Foam insulation is a common target because it’s easy for them to chew through. The material offers little resistance, allowing mice to create tunnels or nests within the insulation.

But mice aren’t just interested in chewing for the sake of it—they’re also drawn to the warmth and shelter insulation provides. Once inside your walls, insulation becomes an ideal nesting spot, protecting them from predators and extreme temperatures. Unfortunately, this behaviour leads to damaged insulation and higher energy bills as the material’s effectiveness declines over time.

Types of Insulation Susceptible to Mice

Mice can chew through almost any type of insulation, but soft and malleable materials like foam are especially appealing. Some insulation types are more vulnerable than others, and knowing which ones mice are likely to target can save you a lot of headaches—and money.

1. Foam Board Insulation. Mice will eat foam board insulation, especially if it’s installed in basements, attics, or foundations, where they commonly seek shelter. Foam boards are denser than spray foam but still have a soft core that mice can chew through. Once they find a weak spot, they’ll dig tunnels through it to create nests or burrow for warmth.
2. Fiberglass Insulation. Although fibreglass might seem less appealing to mice because of its texture, that doesn’t stop them from tunnelling through it. They will shred and move it around to build nests. The loose-fill version of fibreglass is particularly susceptible because it’s easier for rodents to move through compared to batts or rolls.
3. Cellulose Insulation. Made from recycled paper, cellulose insulation can be just as vulnerable. Mice see it as prime nesting material, thanks to its loose-fill texture. Once inside, they’ll shred it to pieces, leaving you with a mess and poor insulation performance.
4. Cotton (Denim) Insulation. Cotton insulation might seem like a natural, eco-friendly choice, but its soft, fibrous texture is essentially an open invitation to rodents. Mice will readily chew through it to make nests, just like they would with cellulose or foam.

Signs of Mice in Your Insulation

You don’t need to see a mouse to know they’re there—sometimes, the signs are all around you. Identifying these early signs will help you prevent further damage.

Visible damage is one of the first red flags. If you notice chewed-up foam, small holes, or tunnels running through your insulation, chances are, mice have moved in.

Then, there’s the unmistakable presence of droppings and tracks. Tiny, dark pellets near your insulation or along baseboards can indicate that mice are scurrying through. You might even spot small footprints or trails where they’ve been dragging dust or debris.

And don’t forget about those unusual sounds. Hearing scratching or scurrying late at night, especially in the walls or attic, usually means you’ve got some uninvited guests. If these noises are becoming a regular thing, it’s a clear sign you need to act before they cause even more damage.

Types of Insulation That Mice Hate

So you’ve spotted the signs and are probably wondering if there’s any insulation out there that mice will actually leave alone. The truth is, there’s no such thing as mouse-proof insulation that can completely stop rodents in their tracks. Mice are persistent creatures, and if they’re determined enough, they can chew through almost anything. That said, some types of insulation are far less appealing to them. 

For those looking for the best insulation for rodent control, the key is opting for materials that are difficult for rodents to chew through. Here are your best bets:

1. Closed-Cell Spray Foam Insulation (Best Overall Choice)

• Why it works: Closed-cell spray foam creates a rigid, dense barrier that is tough for rodents to chew through. When properly installed, it also fills gaps, cracks, and crevices, blocking potential entry points. Even so, will mice eat through spray foam insulation? While it’s possible for mice to chew through spray foam insulation, the dense structure of closed-cell foam makes it far less likely compared to other insulation types.
• Added benefit: It acts as an air and moisture barrier, further reducing the chance of pest entry.

2. Mineral Wool (Rock Wool or Slag Wool)

• Why it works: Mineral wool is made from inorganic materials that rodents typically find unattractive for nesting. Its dense, fibrous structure makes it harder for rodents to tunnel through compared to other types of insulation like fiberglass or cellulose.
• Added benefit: It’s also fire-resistant and mould-resistant, adding extra protection beyond just rodent control.

3. Rigid Foam Board Insulation (Polyiso or XPS)

• Why it works: Rigid foam boards like polyisocyanurate (Polyiso) or extruded polystyrene (XPS) are dense and strong, making them harder for rodents to chew through compared to softer insulations.
• Installation tip: When using rigid foam boards, seal all gaps and edges with caulking or metal flashing to prevent rodents from sneaking behind them.

4. Treated Mouse-Proof Expanding Foam

• Why it works: Expanding foam is often used in DIY projects to seal small gaps, cracks, and openings around windows, doors, and pipes. While technically not as tough as other types of insulation, multiple versions of expanding foam sold in the market are designed with bitter additives and repellent properties that deter rodents from chewing through it.
• Added benefit: When used in conjunction with physical barriers, it’s an effective way to discourage mice from burrowing into your insulation.

5. Bonus Tip: Add Physical Barriers Like Steel Wool, Copper Mesh, or Metal Flashing

• Why it works: Using steel wool or copper mesh to fill any cracks or holes around insulation (especially near pipes, vents, and utility lines) creates a physical barrier that rodents can’t chew through. Metal flashing can also be applied to key areas like the base of walls or around windows and doors.
• Added benefit: Next to prevention, physical barriers are the most effective method for preventing rodents from accessing your insulation or getting inside the home.

How To Prevent Mice From Destroying Your Foam Insulation

You may have chosen the right insulation, but that’s only half the battle. Even the best rodent-resistant insulation can’t do all the work. To keep your insulation intact, you’ll need a combination of smart strategies to keep mice from finding their way into your home. Let’s dive into some practical ways to protect your insulation from mice.

• Seal entry points. Inspect your home for cracks or openings around pipes, vents, and the foundation. Use caulk or concrete to fill the gaps. For larger holes, steel wool or copper mesh works wonders as a physical barrier.

• Remove food sources. Keep kitchen areas clean and store food in airtight containers. Make sure trash cans are securely sealed, and clean up crumbs or spills right away. Reducing their food supply makes your home far less appealing.

• Install ultrasonic repellents. Ultrasonic devices emit high-frequency sounds that irritate rodents but remain undetectable to humans. These can be placed in attics, basements, or areas near your insulation to discourage mice from settling in.

• Use traps around vulnerable areas. Place traps strategically around potential entry points and areas where you’ve seen signs of mice. Whether you choose snap traps or humane alternatives, setting traps near your foam insulation adds an extra layer of protection.

• Maintain your landscaping. Overgrown vegetation provides shelter for mice. Trim back bushes, trees, and shrubs near your home, especially around the foundation.

• Professional rodent control. Sometimes, despite your best efforts, an infestation can become too large to handle on your own. If you notice multiple signs of mice or if they keep returning after you’ve tried various methods, it might be time to call in mouse control professionals. They can assess the severity of the problem and provide targeted solutions to eliminate the infestation.