Why does the condensation occur?

Condensation is a natural phenomenon which hapens as a result of temperature drop below the dew point. Usually there is  always some water vapor in the air. When the temperature of the objects and the air is lower then the dew point, condensation occurs.

External condensation is caused by cooling of the external glass pane. Condensation occurs in the middle area of the glazing. Mostly it happens during spring and autumn when the air humidity is higher and the air temperature lower. In some extreme situations during winter it may happen that external surface of the glazing is covered with ice for a short period. Although it may seem unpleasant external condensation is actually an indication of high energy efficiency - internal heat does not warm the external glass pane.

Illustration of external condensation: internal heat does not reach the external pane of glass	Illustration of internal condensation: internal air humidity is too high

New windows and doors

While planning new house, we recommend following: 3-glazing ensures better energy efficiency compared to 2-glazing. Thus 3-glazed windows are less likely to form internal condensation (but higher probabilty for external condensation). To reduce internal condensation risks significantly, we recommend warm edge spacer solutions (e.g. Swisspacer; Chromatech), which have better insulation properties compared to aluminium spacers. In 3-glazing 2 glasses with LowE coating are used by default.

Existing windows and doors

Before you decide that something (really bad) has happened with your windows and/or doors because there's condensation, you should consider air humidity inside the house. During heating season the relative internal air humidity should be Rh = 25...45%. It is important that rooms have proper ventilation to ensure quality of internal air. Even with the windows with best available thermal insulation one may end up with the condensation if the internal climate conditions meet certain levels. 

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