What areas of my house are most vulnerable to pest entry this winter?

Three pages in this cluster answer closely related questions, and it's worth being clear about which one this is. This page ranks physical locations on a house by how vulnerable each one is — it's the map. Our winter-proofing overview turns that map into a full action plan, including storage and monitoring steps that aren't physical locations at all. Our DIY-steps page narrows that plan down to only what a homeowner can do without hiring anyone. If you're trying to figure out where to look first, you're in the right place; if you want the full to-do list, the winter-proofing page is next.

Mice enter overwhelmingly at ground level, and the ranking above reflects that directly: the top two positions are both ground-level categories, together accounting for the large majority of practical entry incidents according to extension and CDC exclusion guidance. That's not because ground-level gaps are individually more dangerous than a chimney or an attic vent — it's that there are simply far more of them on an average house, and homeowners are far less likely to inspect a sill plate or a utility penetration than they are to notice something at eye level or above.

A chimney feels like the obvious winter pest risk — it's a hole straight to the outside, and it's easy to picture something climbing down it. The chimney is real, but it's a narrow entry compared to the sheer number of ground-level gaps a typical foundation and sill plate combination presents, which is exactly why it sits at rank six rather than rank one. The lesson generalizes: rank by how many pests actually use a given entry point and how directly sealing it reduces that traffic, not by which location is easiest to imagine an animal using.