Insulating Glass (IG) units are hermetically sealed combinations of two or more lites of glass separated by a dry airspace. IG units improve thermal performance, significantly reducing heating and air conditioning costs. Sound control is another property that makes IG units popular.

By combining Low-E coatings, tinted glass, reflective coatings, silk-screened patterns, and laminated glass, IG units can be designed to reduce solar heat gain entering the building. The glass lites of an IG unit can be annealed, tempered or laminated, and they can be flat or bent.