What is one common sign of inadequate ventilation in an attic?

A common sign of inadequate ventilation in an attic is stained roof decking. This staining often occurs due to condensation forming on the underside of the roof, which happens when warm, moisture-laden air rises from the living space below and gets trapped in the attic. When this moisture comes into contact with the cooler roof decking, it can lead to water condensation, which eventually causes staining and potential damage over time. This indicator signals that the attic is not properly ventilated, allowing moisture to accumulate rather than dissipate, which could lead to further issues like mold growth or structural damage if not addressed.

While the other options can indicate various problems, they do not specifically point to inadequate ventilation with the same clarity as stained roof decking. For instance, excessive insulation thickness can impede airflow, but it is not a direct symptom of poor ventilation. Cold air drafts may suggest leaks that need sealing rather than ventilation issues, and visible pests could imply a different set of problems related to insulation or entry points rather than airflow.