Can pest-made holes in homes let in cold air or drafts?

A drafty spot near a baseboard and a mouse problem in the same general area of the house read, to most homeowners, as two unrelated complaints — one goes to a home-improvement task list, the other goes to a pest-control task list. The physical reality doesn't respect that split: an opening a rodent gnawed or enlarged doesn't stop being an opening once the rodent moves on, and it keeps leaking air for as long as it stays unsealed. The insulation compression that often comes with an active nest compounds this, because compressed fiberglass or cellulose loses much of its rated insulating value even where the vapor barrier or surface still looks intact.

The scale here isn't marginal. ENERGY STAR's air-sealing guidance puts air leakage at roughly twenty-five to forty percent of a typical home's heating and cooling energy use, and separately estimates an average fifteen percent savings on heating and cooling costs from a combination of air sealing and adding insulation. Rodent-made and rodent-enlarged gaps are a subset of the air-leakage sources that guidance addresses — not a separate category — which is why the same sealing work that stops pest entry also contributes directly to that documented savings range.

The most common incomplete fix is sealing the visible opening while leaving compressed or shredded insulation behind it untouched. That closes the pest entry but leaves the energy-loss problem partially unresolved, since damaged insulation continues to underperform even once the hole itself is sealed. The complete version of this job checks the insulation immediately around any pest-related opening and repairs or replaces it where it's been compressed, soiled, or torn, not just the gap in the wall or soffit. For the broader question of what pest damage does to insulation and wiring performance specifically, and what repair scope that implies, our sibling Damage Ledger hub covers the materials-science depth this page doesn't rebuild.