U-value

First off you need to use the U-value (reciprical of R) to determine heat transfer, so that drops us down to 22%.

Greener Building Codes: Cool But Costly « PubliCola 2010

The city of Seattle has recently adopted the 2006 energy code which requires a U-value of .34 making it nearly impossible to use the prescriptive approach for aluminum windows.

Build Blog » Mid-Century Modern Remodel 2009

Brian – The energy efficiency is good for aluminum windows and doors, the U-value is between 0.35 and 0.40 depending on the manufacturer and whether it is a fixed pane, operable pane or door.

Build Blog » Mid-Century Modern Remodel 2009

This U-value met the prescriptive energy code at the time of permit submittal and for years prior to then.

Build Blog » Mid-Century Modern Remodel 2009

The lower the U-value, the more energy-efficient a material is.

Test Your Energy IQ 2008

Remember you won't have to worry about air infiltration and U-value performance (heat loss) at Lakeside.

Custom made windows in Guadalajara or Colima? 2005

Remember you won't have to worry about air infiltration and U-value performance (heat loss) at Lakeside.

Custom made windows in Guadalajara or Colima? 2005

Remember you won't have to worry about air infiltration and U-value performance (heat loss) at Lakeside.

Custom made windows in Guadalajara or Colima? 2005

Remember you won't have to worry about air infiltration and U-value performance (heat loss) at Lakeside.

Custom made windows in Guadalajara or Colima? 2005

Remember you won't have to worry about air infiltration and U-value performance (heat loss) at Lakeside.

Custom made windows in Guadalajara or Colima? 2005