U-Value (Coefficient of Heat Transmission) is the effectiveness of a material as an insulator in buildings that measures the heat transmission through a building part (such as a wall or window) or a given thickness of a material (such as insulation). The lower the number, the greater the heat transfer resistance (insulating) characteristics of the material. The U-Value is the reciprocal of the R-Value (U-Value = 1/R-Value), and the number of Btu that flow through 1 square foot of material, in one hour. (Refer to the Heat Transmission Coefficient (or Heat Transfer Coefficient))

Related Definitions in the Project: The Property and Unit; CSA Engineering