Aluminium spacer bars are currently the most commonly used in double glazing window. Light but strong, their flexibility means that they can be formed into a wide variety of shapes and sizes. Less expensive than warm edge spacers they are, however, less effective in insulating against heat loss than warm edge spacer bars.
A spacer that reduces heat flow in glazing configurations may also have characteristics for sound dampening where external noise is an issue. Typically, spacers are filled with or contain desiccant to remove moisture trapped in the gas space during manufacturing, thereby lowering the dew point of the gas in that space, and preventing condensation from forming on surface #2 when the outside glass pane temperature falls.