The U-Value measures how effective a building material is as an insulator. It indicates the rate of heat transfer through a structure, with lower values signifying better insulation. U-Values are commonly used for walls, roofs, windows, and doors, helping to assess energy efficiency in buildings. In construction, materials with low U-Values, such as double-glazed windows or insulated walls, help maintain comfortable indoor temperatures and reduce energy costs. Understanding U-Values is essential for architects and builders to design energy-efficient homes and comply with building regulations.