The g-value is the total solar energy transmittance in the wavelength range from 300 nm up to 2500 nm. This is an important aspect for the climate-technical calculations. The factor is composed of the direct transmission of solar radiation as well as the heat transfer of the parts absorbed in the glass, like heat radiation and convection towards the interior.

A lower g-value in summer and during the transition periods is advantageous and helps to prevent the overheating of a building. This is especially important for industrial and administrative buildings with secondary heat sources (e.g. computer).

A lower g-value can reduce the passive using of solar energy in winter. The correlations however are relatively complex. A lower g-value in combination with a low U-value can be very useful.

LIF can reduce the g-value of the insulating glass and therefore the heat transfer by about 30%:

In summer the lower g-value protects from solar heat impact and reduces the energy consumption of the air conditioning systems.

The lower energy transfer in winter will be compensated by U-value reduced of 30%.