What is the primary function of a vapour barrier in construction?

The primary function of a vapour barrier in construction is to prevent moisture from passing through walls and ceilings. This is essential for maintaining the integrity of the building and preventing issues such as mold growth, wood rot, and damage to insulation. By creating a barrier that limits the passage of moisture, vapour barriers help manage the indoor climate, ensuring that humidity levels remain stable and that the structural elements of the building are protected from moisture-related problems. This function is crucial in areas where there is a significant temperature difference between the inside and outside, which can lead to condensation if not properly managed.

Other options do not accurately represent the primary purpose of a vapour barrier. For example, while airflow within walls is important for ventilation, it is not the function of a vapour barrier. Similarly, vapour barriers do not serve as structural components or primarily enhance aesthetic value; rather, their main goal is to control moisture transfer.