Respuesta :
U-value is generally used to rate door or window units. The lower the U-Value, the more energy efficient the system in question will be. A U-value is typically a low number because it is a rating of how much heat energy is lost or gained. If we look at the two values mathematically, U-value is the reciprocal of R-value; that is, U = 1/R and R = 1/U.
Adversely, U-value measures the rate of heat transfer. This means that products with a lower U-value will be more energy efficient. It is tempting to think that these two values are direct opposites of each other, but there are some important differences to note.
