Single glass itself insulates poorly. When we use the glass to achieve more than two sheets of glass up to insulating glass thermal insulation, possibly supplemented with a heat reflective coating and a cavity, any gas-filled. We speak of HR high-performance glass.
The coating ensures that heat radiation from the heating remains within, while outdoor sunlight is admitted to the same extent as in white insulation. A coating consists of several extremely thin layers of metal or metal oxides, which are applied to the glass surface. Because of this coating on the glass surface, to change the properties of the glass. For example, can be an important part of the heat radiation or solar radiation, and reflected by a coating.
Broadening the cavity gives to some extent improved. Now, when the cavity is too wide creates an airflow on both windows and is therefore just the reverse. Addition of gases in the air cavity may also provide an improvement of the insulation values. We distinguish 2 types of gas: Argon and SF6, where SF6 is mainly used for soundproofing results.