← Insulating glass units

Gas fill

Also called argon fill, gas space

The gas trapped in the gap between the panes.

The gap in an insulating glass unit is filled with dry air or a heavier gas. Argon is the usual choice, and krypton is used in thin gaps. These conduct heat less than air, and the still gas resists convection.

Some gas leaks out over the years, which is why the seals matter.

Edge of a double-glazed unit in section

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Insulating glass unit, edge in section

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