What is the purpose of a vapor barrier in construction?

The purpose of a vapor barrier in construction is to control moisture transfer. A vapor barrier helps prevent moisture from passing through walls, floors, and ceilings, which can lead to issues such as mold growth, wood rot, and reduced insulation effectiveness. By restricting moisture movement, it protects the structural integrity of the building and improves the overall indoor air quality.

While improving energy efficiency is indeed an important aspect of modern construction, the primary function of a vapor barrier is specifically focused on moisture control rather than energy savings directly. Ensuring that moisture does not infiltrate building materials is essential for maintaining the durability of the structure and for the health of the occupants.