U-value and R-value

What do U-value and R-value mean?

High-performance windows are designed to insulate homes against heat gain or heat loss. Homeowners prefer windows that insulate extremely well and improve the overall comfort of a home and room. How well a window insulates is measured as the U-value.

The U-value measures how much heat will transfer through a window. The lower the U-value, the better a window insulates by means of reducing heat flow and maintaining comfortable temperatures. However, the temperature difference in the calculation according to EN673 is assumed to be ∆T = 15 ° С.

The R-value is the opposite of the U-value; it depicts a windows total resistance to heat loss. The R-value is used mainly to compare windows with walls, insulation, and other home fixtures. The higher the R-value, the greater resistance a window has to heat loss. At the same time, the temperature difference is taken into account relative to the city where the glazing is installed, as for the city of Moscow, ∆T = 45 ° С. Calculated according to GOST EN 673-2016.