Indoor moisture meets cold glass, collects at edges and can wet seals, frames and nearby finishes.
Failure path
- Step 1: Outdoor temperature falls.
- Step 2: Glass surface temperature drops.
- Step 3: Indoor air reaches its dew point at the glass.
- Step 4: Droplets run toward the sill.
- Step 5: Repeated wetting supports staining or growth at cold edges.
What makes this pathway plausible
The timing, location and operating or weather trigger should repeat. A diagram shows a mechanism; evidence from the actual house determines whether it applies.
Best next observation
Record the trigger and compare the nearest materials, components and routes before opening finishes or choosing a repair.
Verification after repair
Recreate the original trigger when safe, then confirm the symptom does not return and affected materials are stable or drying.
Trigger→Pathway→Symptom→Verification
Simulation boundaryThis pathway explains a plausible mechanism. It does not establish that the mechanism is active in a specific house without matching evidence.
