Wood Destroying Organism (WDO) Home Inspection Practice Exam

Which material is commonly used for vapor barriers in construction?

1. Wood panels

2. Polyethylene sheeting

3. Plywood sheets

4. Fiberglass insulation

The correct answer is: Polyethylene sheeting

Polyethylene sheeting is commonly used for vapor barriers in construction due to its effectiveness in preventing moisture from passing through walls, floors, and ceilings. The primary purpose of a vapor barrier is to control the amount of moisture that can infiltrate or escape a building, thereby reducing the risk of mold growth, wood rot, and damage to insulation. Polyethylene is chosen for this purpose because it is highly resistant to water vapor transmission, making it an ideal material for maintaining the desired humidity levels within a building structure. In contrast, wood panels, plywood sheets, and fiberglass insulation do not serve the same function. Wood and plywood are porous materials that can absorb moisture, potentially leading to deterioration over time. While fiberglass insulation is important for thermal performance, it does not function as a vapor barrier on its own and can actually promote moisture retention if not properly managed. Therefore, polyethylene sheeting stands out as the appropriate material for vapor barriers in construction applications.