A single pane of glass has very poor thermal resistance. The addition of an airgap increases the insulation value significantly by eliminating heat transfer since air is a very good insulator.
ThermalPlus works to insulate in both winter and summer conditions and reduce the cost of heating and cooling in buildings. The measurement of thermal performance is known as the U-Value, and this can range from 3 down to 1 W/m2k depending on the air space and glass type.