Unfaced insulation installed in wall cavities will do all of the following EXCEPT?

Unfaced insulation installed in wall cavities indeed provides thermal insulation, helps reduce noise transmission, and can contribute to air sealing, but it does not act as a vapor barrier.

Thermal insulation is the primary function of unfaced insulation, as it effectively reduces heat flow, keeping spaces warm in the winter and cool in the summer. Additionally, unfaced insulation can help dampen sound transmission, providing some acoustic benefits between rooms.

In terms of air sealing, while unfaced insulation can contribute to minimizing air leaks around walls, it is not primarily designed for that purpose. Specialized materials or methods are typically needed to achieve effective air sealing.

However, vapor barriers are specifically designed to resist the passage of moisture. Unfaced insulation lacks the material attributes required to serve as a vapor barrier, which is crucial in preventing moisture problems in wall assemblies. Therefore, it cannot fulfill that role effectively.