HEAT FROM THE SUN
Infrared rays of the sun coming through a window will create additional heat above the heat that is blocked out by the dual-pane windows. So where you have a southern or westerly exposure you may need a tinting to block out this heat. This measurement (SHGC) is different than the U-value (as explained under insulation).
QUANTIFYING
WINDOW INSULATION
SHGC – (Solar Heat Gain Coefficient). The measurement of blocking heat from the sun. Lower Values = Better blockage.U-Value – the measurement of heat flowing through a window. Lower values = better insulation