There are certain weather conditions throughout the year - usually during autumn and spring - that leads to condensation forming on the outside of certain windows. This can cause people to believe their windows are faulty, but more often than not it’s a transitory effect that clears within a couple of hours.
Condensation appears on a surface when it’s cold, due to factors such as outdoor weather, and then water is released into the air. Single glazed windows and bathroom mirrors are often exposed to condensation because of the warm, moist air created when running baths and showers, and your kitchen windows may experience temporary condensation when cooking.
When a window drops below its “dew point,” condensation will appear on the surface. As a rule, the warmer the window, the less likely it is to attract condensation. This means windows that are made-to-measure, and units that boast double or triple glazing, suffer far less from condensation as they retain more heat.
However, in the case of Pilkington-K low emissivity glass, which provides particularly great insulation and allows less heat through it, the pane feels cooler from the outside. Therefore, if cold overnight temperatures are followed by a sudden temperature rise or moisture in the air, condensation may appear externally until the window temperature exceeds the dew point, when it will completely disappear.
Click here for further tips on how to stop condensation on windows.