BIFORIUM / GUIDE
UW, UG AND UF WITHOUT CONFUSION
A low Uf does not guarantee the same Uw. Frame fraction, IGU, spacer, dimensions and opening scheme all change whole-element performance.
Ug describes the central IGU area, Uf the frame and Uw the complete window. Compare the same metric at an equivalent size.
Ug is the IGU
It describes heat transfer through the central glass area without the full edge effect.
Uf is the frame
It characterises the profile section and follows its geometry and thermal break.
Uw is the complete window
It combines glass, frame and edge zone for a particular size.