Use location and timing to separate thermal bridges, insulation voids and airflow around roof deck, insulation, ducts and ceiling penetrations.
What the timing tells you
The phrase during a cold snap is diagnostic context. Compare the symptom before, during and after that trigger.
What is special about this location
Roof deck, insulation, ducts and ceiling penetrations create pathways that are not visible from the finished room.
Start with competing explanations
Compare thermal bridges, insulation voids and airflow. Do not select a cause from appearance alone.
First useful check
Use the linked check to create a timeline or pattern, then follow the strongest cause family to its full dossier.
Repair decision
Avoid cosmetic work until the source or mechanism is controlled and the original trigger no longer reproduces the symptom.
Observe→Compare triggers→Repair source→Verify outcome
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