When and where condensation forms depends on the humidity and temperature of a surface. In the colder autumn and winter months, condensation is increasingly noticeable on window surfaces. This can affect both the glass pane on the room side and the outside. While the former indicates a thermal bridge in the edge area, the fogging of the window outside is a sign of excellent thermal insulation of the glazing. There are ways and means to reduce unwanted condensation on glass surfaces. Fogged windows do not only disturb the appearance, the dripping condensation water can also cause damage to walls or floors and promote mould infestation.