By The Numbers

Measure Window Performance With Full Frame R-Value 
R-Value is a standard measure of heat loss through a partition, such as a wall, window or door. In the past, while the insulating performance of walls has been measured in R-Value, windows have been measured by U-Value (U-value is the reciprocal of R-Value, so an R-Value of 10.0 equals a U-Value of 0.10). The use of U-value makes it harder for builders and homeowners to see the poor R-Value performance of major brand windows. As high technology insulating windows such as Serious Windows come to market, the Department of Energy and others are using Full Frame R-Value to measure window performance instead of the older U-Value metric.

It's pretty simple. This chart details the amount of money you can save replacing your home’s old single pane windows (an R-value of 1.0) with other windows on the market. Super-insulating windows of higher R-values can help you save the highest percentage of heating and cooling costs when compared to other “energy-saving” windows available today. Even compared to typical Energy Star windows (they are usually dual pane low-e windows with an insulating value of R-2.5 to R-2.8 depending on geography).

The data for this chart is based on the U.S. Department of Energy’s RESFEN model and is an average taken from 5 typical cities across the U.S.