How does foundation type in homes affect pest entry in winter?

It would be convenient if foundation type didn't matter, but it genuinely does — a vented crawl-space foundation simply has more physical openings by design than a poured slab, and older masonry has material properties (softening mortar) that a newer poured foundation doesn't share. This isn't superstition; it's construction. A house with a rubble or fieldstone foundation, common in older New Hampshire housing stock, has irregular joints that were never airtight to begin with and that loosen further with decades of freeze-thaw cycling.

The counter-mistake is assuming a poured concrete slab solves the problem entirely. It doesn't. A slab foundation has dramatically fewer natural gaps than a crawl space or an old rubble basement, but it still has a sill plate where the wood framing meets the concrete, a door threshold at every exterior entry, and utility penetrations for water, gas, electrical and HVAC lines — every one of which is exactly as functional an entry point on a slab home as on any other foundation type. 'Slab' reduces the count of vulnerabilities; it does not reduce any single vulnerability to zero.

The honest answer to whether you can change your foundation type is no — nobody replaces a foundation to solve a pest problem. But that's a narrower question than it sounds, because changing the foundation was never the fix. Every opening a foundation type creates, from a crawl-space vent to a crumbling mortar joint, is independently sealable with ordinary materials: hydraulic cement and mortar for masonry cracks, hardware cloth for vents, metal mesh and sealant for penetrations. The practical takeaway is that foundation type tells you where to concentrate your inspection and sealing effort, not that you need a structural remedy.