WINDOWS: Convert from European U-factor to Imperial U-value for Americans
Corbett Lunsford
It’s simple- divide the European U-factor by 5.555
The Euro value is in different units- W/m2·K, and in American software modeling we need U-value that’s simply 1/R-value, aka Btu/h·ft2·F.
So for example a European window U-factor of 0.5 means:
U-0.5 divided by 5.555 = U-0.09 in Imperial. Or an R-11 window, which is amazing. A U-0.5 window in the U.S. means R-2, which is a standard terrible air-filled double pane window.