What is the difference between “R-Value” and “U-Factor.”?
R-values are calculations of resistance to heat flow based on the conductivity and thickness of material while U-factors are measurements of heat flow of an assembled door or window based on testing and/or simulation. R-values are common to the insulation industry, but U-factors are recognized as a much more accurate method of determining energy performance of doors and windows since they consider all elements of construction as well as environmental factors.
“R-Value” is used to measure the thermal resistance of thermal insulation. The higher the R-value, the greater the resistance. “U-Value” is used to measure the rate of heat flow through a glazing system, the lower the U-Value, the better the insulating quality of the window. U-Value can be compared to R-Value, which is the resistance of a material to heat flow by dividing 1 by the U-Value.
