What type of barrier is polyethylene sheeting categorized as?

Polyethylene sheeting is categorized as a Class I vapor retarder due to its effective moisture control properties. A Class I vapor retarder is defined by its ability to limit the flow of moisture through materials, which is essential in preventing condensation and mold growth within building assemblies. This material has a low permeability rating, making it highly effective in minimizing moisture transmission.

In building construction, using a Class I vapor retarder like polyethylene sheeting helps create a barrier that protects structures from moisture-related issues, thereby contributing to the energy efficiency and longevity of the building. It's commonly employed in areas where moisture is a significant concern, such as under slabs, in walls, and under roofs.