Insulating glass units, or IGUs, were designed to keep buildings/homes warmer in the winter and cooler in the summer. Two or more lites of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between each lite. Heat transfer and sound transmission are reduced through the glass unit. Many decorative glass types, including Restoration Glass®, can be installed in IGUs to achieve the desired thermal performance and create or maintain the desired aesthetic.