Argon-Filled Windows

Ordinary double-glazed windows trap a thin layer of air between two panes of glass. This trapped air already insulates a room better than a single pane alone, since air conducts heat much less than glass does. Manufacturers can improve this insulation further. They replace the air between the panes with argon, a colorless, odorless gas that makes up about one percent of the atmosphere. Argon conducts heat about a third less than air does. This means less heat can pass directly through the gas from one pane to the other. Argon is also about forty percent denser than air. This extra density slows down convection, the slow circulation of gas caused by temperature differences. Normally, convection carries warm gas upward and cool gas downward within the sealed gap. By slowing this circulation, argon further reduces how much heat crosses from one side of the window to the other. This reduction works in both directions. An argon-filled window slows heat from escaping in cold weather just as well as it slows heat from entering in hot weather. This is why the same window can help a room stay warmer in winter and cooler in summer. Compared to a similar air-filled window, a well-sealed argon-filled window can cut heat loss through the glass by up to about thirty percent.