What is used to prevent condensation when cold air meets warm air?

A vapor barrier or retarder is specifically designed to prevent moisture from passing through walls and ceilings, which is essential when dealing with the issue of condensation. When warm, moist air comes into contact with cold surfaces, it can lead to condensation forming. The vapor barrier helps to interrupt this process by providing a barrier to moisture migration.

These barriers are typically made of materials like polyethylene sheeting and are installed on the warm side of insulation in building assemblies to keep moisture from infiltrating colder areas where it can condense. Such moisture control is crucial in maintaining the integrity of structures, preventing mold growth, and preserving indoor air quality.

The other choices address different aspects of building and weatherization but do not directly prevent condensation created by the interaction of warm and cold air. Insulation plays a role in temperature regulation, a moisture barrier serves to protect against water infiltration but not specifically vapor control, and sealants are used for sealing gaps and joints but do not provide a significant moisture management role compared to a vapor barrier.