Double glazing can develop a misted appearance when double-glazed units fail, also known as a ‘blown unit’ or ‘failed unit’.
Holes in the seal around the double-glazed unit is a common cause of misted double glazing. Such holes need only be small to draw moisture from the atmosphere, which then causes what looks like condensation inside the window unit. Once inside the unit’s cavity, changes in temperature can cause the moisture to condense. As more moisture is drawn in, with nowhere to go, units can end up holding considerable amounts of water.
Replacing misted double glazing
There are a number of repair techniques that some claim will solve the problem of misted double glazing, most of which involve drilling into the unit. We don’t recommend such approaches as they can result in air circulating between the panes of glass, therefore no longer operating as a sealed, energy efficient window. What’s more, those techniques seldom remove any staining that has taken place and are more likely to fail again.
The best solution for a misted double-glazed unit is replacement.