Condensation indoors

Why do I have condensation on the inside of my windows, and how can I get rid of it?

In the winter months, condensation on inner windows can be a real problem. Moisture condenses on the cold surface of the glass, which often results in pools of water collecting on windowsills. This accumulated liquid can lead to more serious problems of damp and mould in the home if not addressed.

People often think that condensation on the inside of windows is down to poor quality double glazing or other problems with the windows themselves, but this is very rarely the case. So what causes condensation on inner windows, and what can be done to prevent it?

Condensation on the inside of double glazed windows is mainly linked to the following factors:

  • The external temperature
  • The internal air temperature
  • Humidity within the home
  • Ventilation

External temperature

Condensation is usually a problem during winter months as the cold weather outside results in cold windows. While the rest of your house has layers of insulation to keep out the chill, double glazed windows only have two thin layers of glass, so the surface is often colder than the rest of the building. This is why water condenses here, because the glass temperature is below what is known as the ‘dew point’ – the temperature at which water vapour condenses to liquid.

Unless you’re Storm from X Men there’s very little you can do to affect the temperature outside. The external temperature is not something you can change, but the other factors are.

Internal air temperature

You may notice that you get less condensation when your home is warmer. This is because warm air holds more moisture than cold air. Condensation will most likely form when the internal temperature drops – for example if you turn your heating off at night or during the day when you’re out. One effective way to combat condensation on inner windows is by maintaining a warm temperature within the home. Keep your heating on a low setting for most of the day so it isn’t constantly fluctuating.

Humidity within the home

Even the best double glazing will get a build-up of condensation if there is enough moisture in the air. Cooking, showering, washing and drying clothes all contribute to increase the amount of moisture in the air within your home. To combat condensation, try to prevent the moisture escaping to other parts of the home. Keep doors to the rest of the house closed when showering and cooking, use extractor fans and keep lids on pans.



Circulating air is very important to prevent condensation. Your home will naturally become more humid than the world outside through everyday activities like cooking and showering mentioned above. Just the additional bodies breathing in the house will have an impact on air humidity. Tackle this by ensuring there is a good air flow outside. Open windows when cooking and showering, and use extractor fans.


If you’re still experiencing problems with condensation, there are plenty of products available at a small price that can help. Dehumidifiers and window wipers help to collect excess moisture before it becomes a more serious problem.


If you think that excess condensation is a result of your double glazing, we offer A-rated windows and Thermo Seal Technology with a 10 year insurance guarantee.  Get in touch on 01767 765 440 to discuss your options.