You can use the energy performance ratings of windows, doors, and skylights to understand their potential for gaining and losing heat, as well as bringing sunlight into your home.

Dec 31, 2025 · Free window R-value calculator. Determine how well your windows insulate your home and compare different window types for energy efficiency and comfort.

Jun 25, 2025 · What is window R-value? See charts for single, double & triple panes, compare U-value, learn what’s a good R-value, and discover the highest R-value windows & doors.

View our glass performance chart for each of our different types of glass.

Aug 26, 2025 · While a single-pane window with an R-value of 1 does not offer great insulation, you get a much better picture of its performance by comparing it to a double-pane window …

The NFRC label helps you compare between energy-efficient windows, doors, and skylights by providing you with energy performance ratings in multiple categories.

Jan 3, 2021 · R-value measures the performance of a specific material, like insulation, to reduce the transfer of heat. We know that the R-value measures heat resistance, but that implies …