General Contractor Practice Exam 2025 – All-in-One Guide to Exam Success!

The function of a vapor barrier is to prevent moisture from entering a building. These barriers are crucial in maintaining the integrity of structures by controlling the movement of moisture through walls, floors, and ceilings. Moisture can lead to a range of issues, including mold growth, wood rot, and damage to insulation and other building materials. By incorporating a vapor barrier, builders create a shield that stops water vapor from passing through, especially in areas prone to high humidity or where moisture can seep into the building envelope.

Insulation is a separate function involving thermal resistance that keeps buildings energy-efficient, while allowing moisture to vent would be contrary to the purpose of a vapor barrier, which seeks to contain moisture. Strengthening structural elements relates more to materials and design rather than moisture control, which is the primary focus of vapor barriers. Therefore, the primary and correct function of a vapor barrier is indeed to prevent moisture from entering a building.