When is condensation on vapor lines a concern?

Condensation on vapor lines is a concern when lines are routed inside a wall because of the potential for moisture buildup that can lead to mold and structural damage. When vapor lines are concealed within walls, it becomes difficult to monitor moisture levels and any resulting condensation can remain trapped within that space. This can create an ideal environment for mold growth, compromise indoor air quality, and potentially damage the building structure itself.

In contrast, vapor lines on rooftops or in other exposed areas have the advantage of airflow and natural drying conditions that help to mitigate the condensation issue. Additionally, while low outside temperatures and heavy system loads can contribute to variations in the operation of heat pumps or temperature differences, they do not inherently lead to the same concerns related to the concealment of vapor lines within walls.