California General Contractor B Practice Exam 2025 – All-In-One Guide to Master Your Contractor Certification!

The primary purpose of using a vapor barrier in insulation is to prevent moisture accumulation. Vapor barriers are materials that resist the diffusion of moisture through walls, ceilings, and floors. In construction, managing moisture is crucial because excess humidity can lead to mold growth, deterioration of insulation efficiency, and damage to structural components. By installing a vapor barrier, builders help maintain a dry environment within the insulated spaces, improving overall building durability and occupant health.

Thermal resistance is provided primarily by insulation materials themselves, while aesthetics refer to the visual appeal which is not a function of a vapor barrier. Similarly, although insect infiltration is an essential consideration in building design, it is not the role of a vapor barrier. Thus, the emphasis on controlling moisture is the key reason for incorporating vapor barriers into construction practices.