What kind of material is typically used for a vapor barrier in a construction project?

The typical material used for a vapor barrier in a construction project is plastic sheeting. This is due to its effectively low permeability, which prevents moisture migration from one area to another. Plastic sheeting, often made of polyethylene, is designed specifically to block water vapor from entering or leaving spaces, thus helping to control humidity levels and prevent mold growth.

In contrast, materials like fiberglass, metal, and wood composites do not possess the same vapor-blocking characteristics. Fiberglass is more often used for insulation rather than as a vapor barrier, and while metal is durable, it does not act as a vapor barrier due to the potential for condensation on its surface. Wood composites can absorb moisture, which makes them unsuitable for use as vapor barriers. Therefore, plastic sheeting is the optimal choice for effective moisture control in building applications.