Total energy transmittance (g value)

The total energy transmittance (g in%) of insulating glass indicates
what proportion of the total sun irradiation (300 - 2500 nm) is energetically usable behind the glazing. It is the sum of direct and indirect radiation transmission.

The g-value depends essentially on the thickness of the individual panes used. This applies in particular to the thickness of the outer pane. There are building regulations in Germany for the determination of the total energy transmittance of multi-pane insulating glass depending on the glass thickness. The data for the total energy transmittance of ISOLAR glass given in the tables refer to individual glass thicknesses of 4 mm each (thermal insulating glass, sound insulating glass) and 6 or 4 mm (solar protection glass), in each case in conjunction with the building regulations. The percentages include a tolerance of ± 2 percentage points.