Which of the following types of glass usually has better thermal performance?

Insulated glass typically offers superior thermal performance due to its design, which includes two or more panes of glass separated by a spacer and an insulating gas, such as argon or krypton, within the sealed unit. This construction reduces heat transfer between the inside and outside environments, making it effective in minimizing energy loss and improving overall building efficiency.

The use of multiple panes creates an insulating barrier that enhances the resistance to heat flow, reducing the need for heating and cooling in buildings. This not only leads to energy savings but also contributes to maintaining a more comfortable indoor climate. Insulated glass is commonly used in energy-efficient windows and is rated using the U-factor, which indicates the rate of heat transfer; lower values signify better insulating properties.

In contrast, the other types of glass listed do not provide the same level of thermal insulation. Float glass, laminated glass, and low-iron glass each have their respective benefits but do not incorporate an insulating gas layer as part of their standard construction, which limits their thermal performance compared to insulated glass.