Condensation on glass window panes is a natural phenomenon that cannot be completely avoided, no matter how well insulated your house or how efficient your double glazing windows are.

Condensation occurs when warm, moisture-laden air meets a cool surface such as glass – the change in temperature causes the moisture to condense onto that surface in the form of water droplets. Colder external temperatures during winter months combined with heated internal temperatures will result in larger amounts of condensation.

The link below explains how and why condensation occurs, and what you can do to control it: Condensation explanation