Carpenter ants in Pacific Northwest homes exploit moisture-damaged wood caused by the region's persistent rain, and homeowners unknowingly make the problem worse by insulating their crawl spaces per energy code requirements

Carpenter ants (Camponotus modoc and C. vicinus) in the Pacific Northwest — Seattle, Portland, Eugene, Vancouver WA — do not eat wood like termites but excavate galleries for nesting, preferentially targeting wood with >15% moisture content. So what? The Pacific Northwest receives 37-44 inches of rain annually spread across 150+ rain days, and residential construction in the region features wood framing, wood sheathing, and wood siding that is perpetually exposed to moisture intrusion through roof flashing failures, window sill deterioration, and siding penetrations — conditions that create exactly the >15% moisture wood that carpenter ants require. So what? Washington and Oregon energy codes (following IECC 2018+) require crawl space insulation and vapor barriers, and when these are improperly installed (which field surveys show in 40-60% of retrofits), they trap moisture against floor joists and sill plates rather than keeping it out, creating hidden pockets of 20-30% moisture content wood that are ideal carpenter ant habitat and completely invisible to the homeowner above. So what? Carpenter ant parent colonies (with the queen) can be located 100+ feet from satellite colonies inside the home — often in a dead tree, stump, or woodpile in the yard — and the satellite colony inside the home's wall can contain 3,000+ workers causing active structural damage while the parent colony is never found or treated. So what? Pest control operators typically bait or spray the visible ant trails inside the home, which may suppress the satellite colony but does not eliminate the parent colony outdoors, resulting in re-establishment of the satellite colony within one season when parent colony workers re-discover the moisture-damaged wood entry point. So what? The problem persists structurally because the Pacific Northwest's climate ensures continuous wood moisture, energy code requirements inadvertently create hidden moisture traps, carpenter ant colony biology (parent/satellite structure with colonies split across indoor/outdoor locations) defeats single-location treatment, and the construction industry's separation of trades means the energy auditor insulating the crawl space, the roofer maintaining the building envelope, and the pest control operator treating ants never communicate — each addresses their scope without understanding they are interacting facets of the same moisture-ant cycle.