Insulating glass units consist of two or more glass panes kept apart by a spacer and permanently sealed at the edges. The cavity is filled with desiccant and charged with noble gases such as argon or krypton to reduce thermal conductivity. Metal oxide coatings applied to one pane surface — so-called low-emissivity (Low-E) coatings — reflect long-wave heat radiation back and significantly improve the Ug-value. Double-pane insulating glass achieves Ug-values around 1.0 W/(m²·K), while triple glazing falls below 0.6 W/(m²·K). Manufacturing and testing are carried out in accordance with EN 1279.