In summer heat radiation emitting through the insulating glass unit will increase internal temperature and solar UV-radiation may damage the room interior. In order to avoid this and to regulate heat radiation special glass panes blocking solar energy may be used in the insulating glass unit.
Glass transmits solar energy in three ways: by reflecting, transmitting and absorbing. Mostly body tinted glass panes are used. These have excellent solar-energy absorbing properties but low reflection capacity. These glass panes are entirely tinted with some colour shade. An important advantage of these glass panes is their price. Their solar energy control properties and intensity of the colour shade depend on the thickness of the glass pane. A body tinted glass pane in combination with a selective glass pane in a double insulating glass unit may increase solar energy control and also insulation properties of the insulating glass unit. In this case the glass pane covered with low emissivity coating (for instance selective glass) reflects the heat radiation absorbed in the body tinted glass and partially transmitted inside from inside back (partially) and in this way increases the general solar energy control of the insulating glass unit.
Glass panes with reflective surface coating offer more protection. Here glass panes are covered with a metal oxide layer applied by means of pyrolysis during the manufacturing process. This process may be used to treat a float glass pane or body tinted glass pane. There are also combined glasses, which reflect back radiation caused by solar energy and at the same time prevent heat radiation loss through windows. As the glass panes are made on the base of float or tinted glass and treated with thin, soft emissivity coating, they can only be used in the insulating glass unit so that the coated surface is placed inside in the insulating glass unit.