What does a vapor retarder do?

A vapor retarder plays a crucial role in managing moisture within building assemblies. Its primary function is to limit the movement of water vapor through materials by diffusion, thereby reducing the chances of moisture accumulating in places where it can cause damage, such as within walls, ceilings, or attics. By impeding vapor diffusion, the vapor retarder helps to maintain the desired humidity levels and prevents issues like mold growth and material degradation, which can result from moisture buildup.

In contrast, choices that suggest the retarder enhances moisture movement or encourages evaporation fail to recognize its primary purpose. A vapor retarder is specifically designed to restrict the flow of vapor, not facilitate it. Additionally, the option stating that it has no impact on water movement overlooks the essential functionality of vapor retarders in preventing excessive moisture transmission, which can lead to structural issues and health concerns.