A wall cavity air loop cools one interior strip

Air movement within or through a wall bypasses insulation and creates localized cold surfaces.

Failure path

• Step 1: Pressure drives air through an opening.
• Step 2: Air follows a cavity or service route.
• Step 3: Insulation performance is bypassed.
• Step 4: One strip becomes colder than adjacent areas.
• Step 5: Dust marking or condensation may reveal the route.

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.