Massachusetts Construction Supervisor License (CSL) Practice Test

When installing insulation, where should the vapor barrier be placed?

1. On the cold side of the space

2. On the heated side of the space

3. In the middle of the insulation

4. On the exterior of the wall

The correct answer is: On the heated side of the space

The vapor barrier should be placed on the heated side of the space to effectively prevent moisture from entering the insulation and the structural components of the building. By placing the barrier on the heated side, it helps to keep warm, moist air from entering and condensing within the insulation material, which can lead to mold growth, decay, or reduced insulation performance. In climates where the interior space is heated, the vapor barrier protects the building structure by reducing moisture migration from the living environment into the wall assembly. This is essential for maintaining the integrity and longevity of both the insulation and the building materials. Placing the vapor barrier on the cold side, in the middle of the insulation, or on the exterior of the wall would not be effective at controlling moisture movement and can contribute to issues such as condensation or structural damage. Therefore, positioning the vapor barrier correctly is vital for ensuring a healthy and energy-efficient living space.