Insulated Glass (IG): Glazing comprised of two or more glass panes separated by a hermetically sealed airspace. Heat transmission through this type of glass may be as low as half that without such an air space. This space may or may not be filled with an inert gas, such as argon.
A hermetic seal makes the window airtight and minimizes the amount of warm (or cool) air that can pass through. This enables the mechanical ventilation system to recover the heat before discharging the air externally. These windows combine triple-pane insulated glazing with the airtight void between panes filled with argon or krypton gas to reduce thermal conductivity and increase R-value (insulation) efficiency.