Can I Use Spray Foam for Mice and Rodent Problems?

Many homeowners think insulation alone will stop pests, but the real issue is the pathways rodents use. Research shows that even if you use high-R materials, gaps around utility penetrations, rim joists and attic bypasses remain major entry points. For example, a recent study found that in homes insulated with spray foam, rodent sightings dropped by 50 % compared with homes using traditional insulation. 

What that tells us is: spray foam for mice problems can be part of the solution when the entry routes are sealed and the environment is made unattractive to pests. 

What Spray Foam Does – And What It Doesn’t 

Spray foam insulation expands to fill cracks, reduces airflow and raises the barrier for pest entry — especially closed-cell foam, which is denser.  

But here’s the catch: pests may still chew through or bypass foam if it’s improperly installed or if gaps remain. Primarily, spray foam insulation isn’t a pest control product; it’s an insulating and sealing product that helps reduce the conditions that rodents exploit. 

Best Approach for Pest Resistance Using Spray Foam Insulation 

Inspect all entry points — Look for gaps at the foundation, sill plates, plumbing/wiring penetrations, attic top plates, and rim joist joints. 

Perform exclusion work — Use steel wool, copper mesh, sheet-metal flashing and sealants to block rodent highways before any insulation. 

Install spray foam insulation — Preferably closed-cell where rodent pressure is highest (basements, crawl spaces, rim joists). Use open-cell in less critical areas if appropriate. 

Follow up with remediation and monitoring — Because excess moisture, hidden voids or failed seals can allow pests to take advantage again. 

Site-specific Concerns in Indiana & Michigan climates 

In our region, humid summers followed by cold winters mean high vapor drive and thermal cycling. If foam is applied without first controlling moisture or sealing bypasses, the insulation envelope may still allow rodent access or degrade faster. A case study of attic mold noted that when humid air enters and the sheathing stays above 60% RH, mold and pest activity both increase. 

Thus for homes in northern Indiana and southwest Michigan, our approach includes: verifying crawl-space ventilation and ground barriers, checking for attic exhaust fans dumping into attic, and ensuring foam seals both infiltration and exfiltration paths. 

Using Spray Foam for Mice Eradication is a Very Careful Art 

There are situations where spray foam insulation alone won’t solve a pest or comfort problem. If rodent populations are already high and damage is extensive, exclusion and cleanup must come before any insulation work. Spray foam cannot correct an active infestation; that stage requires a licensed pest-control firm to eliminate the source first. 

In homes where pest inspection is required for warranty or resale, such as properties under termite protection, spray foam may not be appropriate for certain areas.  

There are also structural limitations to consider. When gaps exist behind finished walls or in sealed cavities where foam cannot safely reach, removal or partial demolition may be necessary to access the problem. Spraying over an unknown void can trap moisture or fail to adhere properly, reducing the foam’s lifespan. The best results come from inspecting each section, ensuring accessibility, and applying spray foam insulation only where it can form a complete, continuous seal. 

Get a Spray Foam Insulation Quote from M.Y. Insulation 

M.Y. Insulation serves homes and businesses in Fort Wayne, Elkhart, South Bend and Kalamazoo, providing rodent-resistant insulation solutions that last. 

Get a quote today!