The core idea
Windows need layered flashing that drains incidental water outward even when outer sealant ages.
How the mechanism works
Head flashing, jamb membranes and sill pans form a drainage path behind cladding.
When it becomes relevant
Typical trigger: Wind-driven rain or sealant failure.
Evidence that supports this interpretation
- Water appears at lower corners
- Symptoms depend on wind direction
- Exterior joints or flashing terminations are suspect
Evidence that weakens it
- Interior condensation forms uniformly
- Water is between panes
- A pipe above reproduces the leak
What this concept cannot prove alone
A single observation, image or meter reading cannot confirm the complete failure pathway. Use this concept to form better questions, compare alternatives and decide which safe observation would be most informative next.
Safety and professional boundary
Window removal or cladding opening should be planned to preserve the drainage sequence.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
US Department of Energy · government homeowner guidanceConsumer Guide to Air Sealing the HomeAir leakage, durability, comfort and ventilation coordination.Verified 2026-07-20 · review due 2027-01-20Open source ↗US Environmental Protection Agency · government guidanceMoisture Control Guidance for Building Design, Construction and MaintenanceMoisture sources, transport, design, construction and maintenance controls.Verified 2026-07-20 · review due 2027-01-20Open source ↗US Department of Energy · government research libraryBuilding America Publications and Solution CenterBuilding enclosure, HVAC, windows, indoor air and high-performance housing research.Verified 2026-07-20 · review due 2027-01-20Open source ↗
Observe→Compare triggers→Repair source→Verify outcome
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