(U-value) - A value indicating the rate of heat flow through a building construction, expressed in units of 'Btuh per square foot of surface per degree F. difference between indoor and outdoor air temperature.' This is numerically equal to the 'inverse of the sum of H-values' for the construction.
any one of a number of coefficients used in calculating heat flow by through various materials and structures (total, conductive, and radiative heat transfer coeff.), , [W/m2K] Wärmeübergangs- zahl (Gesamt- bzw.für Konvektion und Strahlung
The quantity of heat transferred through a unit area of a material in a unit time per unit of temperature difference between the two sides of the material.