R-value on Replacement Windows

The R-value of a window represents its resistance to heat transfer, or thermal resistance. A higher R-value indicates better insulation and less heat transfer. The R-value for most insulated windows will be at least 2.

The R-value is significant because much of the heating and cooling loss in a home occurs through the windows. Windows with higher R-values can help slow this loss, improve your home’s energy efficiency, and reduce your energy costs.