Core Thermal Insulation Principle
Insulating glass creates a "thermal barrier" using a cavity filled with dry air or inert gas between two or more panes of glass. Since the thermal conductivity of air is far lower than that of glass, it directly blocks heat transfer between the indoors and outdoors, offering significantly better thermal insulation than single-pane glass.
Thermal Insulation Performance by Configuration
Standard double-pane insulating glass with aluminum spacers: The U-value ranges from 2.8 to 3.2 W/(m²·K). Thermal insulation performance is average; heat transfers quickly, resulting in a noticeable temperature difference near the window in both winter and summer.
Domestic triple-pane insulating glass with warm-edge spacers: The U-value ranges from 2.2 to 2.5 W/(m²·K). Thermal insulation performance is moderate; significant heat penetration still occurs during hot weather.
High-performance triple-pane insulating glass (4SG) with dual cavities: Featuring warm-edge sealing systems and Low-E coatings, the U-value can be as low as ≤1.8 W/(m²·K). It blocks over 90% of solar radiant heat, with thermal insulation performance far exceeding the industry average.
General range for standard insulating glass: Mainstream insulating glass products on the market typically have U-values between 1.4 and 2.8 W/(m²·K). Overall thermal insulation performance is comparable to that of a 20mm-thick wooden board or a 240mm-thick brick wall.