Can fall invaders survive inside sealed homes?

'Can they survive inside a sealed home' actually asks two separate things, and the answer flips depending on which one you mean. Question one: if I seal my house before fall invaders show up, will it keep them out? Yes — this is exclusion working exactly as intended, and it's the single best-evidenced intervention in this hub. Question two: if insects are already inside and I seal the house up tight, will that finish them off? No — and this is the part that trips people up, because it seems like it should work and doesn't.

The insects already in a wall void when sealing happens are in diapause, and diapause specifically includes resistance to the conditions people hope will kill them off. They aren't relying on outside air to survive; they're running on stored body fat with metabolism and water loss both sharply reduced.

It's intuitive to think a tightly sealed house, especially a dry one in a New Hampshire winter, would desiccate any insects trapped inside. Research doesn't support that intuition for the adults that make it into a void. A study in the Journal of Insect Physiology measured diapausing brown marmorated stink bugs tolerating desiccating conditions three to four times longer than non-diapausing individuals, through mechanisms that reduce water loss through both the respiratory system and the outer cuticle. A separate peer-reviewed study in Environmental Entomology found that low humidity is really lethal to newly hatched BMSB nymphs — but adults and eggs showed little to no effect from humidity at all.

That distinction matters because the insects overwintering in your walls are adults, not newly hatched nymphs. The life stage that's vulnerable to drying out isn't the one present in an overwintering void. Sealing a house tight doesn't create a hostile enough environment to finish off the population that's already settled in.

This is the real limit that separates good advice from bad. Extension guidance frames exclusion explicitly as a pre-entry action — done in late summer, before insects arrive, it prevents entry entirely. Done in November, after insects have already worked their way behind siding and into voids, the same caulk gun and screening close off routes those insects would otherwise use to move and eventually exit in spring. The result isn't a solved problem; it's a redirected one. Insects that would have found their own way back outside in spring instead find a sealed exterior and are more likely to push inward, into living space, when diapause ends and they reactivate.

This is why 'just seal it airtight' is truly good advice at one point in the calendar and actually counterproductive advice a few months later. The real answer depends entirely on which side of that line you're on, and being told that distinction clearly is worth more than being told 'seal your house' without it.