What is the primary purpose of a vapor retarder?

The primary purpose of a vapor retarder is to prevent moisture from escaping from a building or structure. This is crucial in areas where high humidity levels can lead to condensation and moisture accumulation within walls, ceilings, or floors. By limiting the movement of moisture vapor, vapor retarders help maintain a controlled environment, reducing the risk of mold growth, rot, and deterioration of building materials.

In addition to its role in protecting structural integrity, using a vapor retarder is essential for preserving insulation effectiveness. When moisture infiltrates insulation, it can lose its thermal performance, leading to increased energy costs and decreased comfort levels within the building.

While other options may involve aspects of moisture management or thermal performance, they do not accurately capture the primary function of a vapor retarder. The emphasis is on restricting moisture vapor movement, which aligns with the correct answer.