Massachusetts Unrestricted Construction Supervisor License Practice Test

When installing insulation, where does the vapor barrier go?

1. On the exterior side of the space

2. On the heated side of the space

3. On the unheated side of the space

4. Vapor barriers are not necessary

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

The vapor barrier is placed on the heated side of the space primarily to prevent moisture from entering the insulation and the wall assembly where it can condense and lead to mold, rot, or structural damage. This placement is crucial in climates that experience cold winters, as warm, moist air from the interior can move toward the colder exterior surfaces. By having the vapor barrier positioned on the heated side, it helps to keep that moist air from reaching the insulation and other building components where it could cause issues. Additionally, choosing not to install a vapor barrier or placing it on the exterior or unheated side would not effectively manage moisture control. If placed incorrectly, the risk of moisture accumulation within the insulated assembly increases, potentially leading to significant long-term damage and decreased energy efficiency. Thus, ensuring proper placement of the vapor barrier on the heated side is key to maintaining the integrity of the building and the effectiveness of the insulation.