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.

	Frame Type	Suspended Film	R-Value full frame	U-Factor full frame	Gas Fill	Glass	UV Blockage
1125 Series	Fiberglass	Triple	6.7 - 11.1	0.15 - 0.09	Xenon or Krypton	Low-E	99.5%
925 Series		Dual	5.9 - 9.1	0.17 - 0.11	Krypton
725 Series		Single	4.2 - 7.1	0.24 - 0.14