What does R-value and U-value mean?
R-Value is a term that measures the insulation properties of a material. For example, fiberglass insulation is measured by its “R-Value.” The energy efficiency of windows is measured by “U-values.” Because windows are not insulators by design, they cannot be measured in “R-Values.” However, windows obviously have insulating properties, so there needs to be a measurement that allows comparison of styles and window packages. There is a relationship between R-values and U-values. Whereas the higher the R-value, the greater its insulating ability, the lower a U-value, the better that product’s insulating efficiency is. To find a U-value, divide the number ‘1’ by the R-value. For example, an R-value of “4” is equal to a U-value of .25.
