Final answer:
A vapor barrier is the application of impervious coatings that prevent water vapor from passing through walls under slight pressure, which is essential for protecting building interiors from moisture-related damage.
Step-by-step explanation:
The application of one or more coatings of impervious compounds that prevent the passage of water vapor through walls under slight pressure is known as a vapor barrier. This is distinct from other building techniques such as insulation, which is used to limit the conduction of heat, or waterproofing, which protects against liquid water.
Vapor barriers are essential in building construction to prevent water vapor from penetrating walls and causing moisture-related problems like mold, mildew, or structural damage. While similar in some respects, these methods serve different purposes: insulation is for maintaining temperature by limiting heat transfer; waterproofing is used to protect against liquid water, and ventilation allows for air flow, which also helps control moisture and temperature.
A vapor barrier, however, specifically targets and prevents water vapor migration under slight pressure differentials, which is critical for maintaining indoor air quality and structural integrity.