How to stop condensation on my windows?

If you have ever experienced condensation on the inside or outside of your windows, you’ll know how frustrating it can be.  Not only can it be unsightly, but it can also damage finishes and timber, cause mould and even be detrimental to your health.  But what exactly causes condensation and what can you do to prevent it?

In this article, we’ll cover:

  • What is condensation?
  • Why do I have condensation on the inside of my windows?
  • Can condensation damage my windows?
  • How do I stop condensation on the inside of my windows?
  • How do I stop condensation on the outside of my windows?


How to stop condensation on my windows?

What is condensation?

Put simply, condensation is water which collects as droplets on a cold surface when the surface comes in to contact with warm air.  If you think back to your school science lessons, you will remember learning about evaporation – when a liquid is heated to a point where it then becomes a gas.  Condensation is this process in reverse when water vapour cools and becomes liquid again.  It may be a natural process but when it starts to cause damage to our homes (and health), then it’s time to do something about it.


Why do I have condensation on the inside of my windows?

How to stop condensation on my windows?

Condensation on the inside of windows can be a common problem, especially if you have excess water vapour in your home.  Water vapour comes from a number of sources.  From cooking and boiling the kettle to taking showers and drying and ironing laundry, even breathing produces water vapour.  Did you know, that the average person will contribute four pints of water per day to the atmosphere, through these activities?  All this water vapour must go somewhere!

As we strive to make our homes more energy efficient, we reduce the natural escape routes for humid air that builds up in our homes. And if it hits a cold surface the vapour becomes liquid again and condensation forms.

Can condensation damage my windows?

External condensation is unlikely to cause any damage to windows, as it is dried off by the warmth of the sun.  Condensation on the inside of your windows, however, can over time be detrimental to surfaces.  Seals can crack from the constant expansion and contraction, as they dry and paint and varnish can peel.

Persistent condensation can also lead to mould which, if left untreated, will damage and discolour uPVC and wood.  Mould is also exceptionally bad for our health.

How to stop condensation on my windows?


How do I stop condensation on the inside of my windows?

To stop condensation forming on the inside of your windows, you need to allow the water vapour to escape from your house.  There are a number of ways you can do this.

  1. Open a window

One of the easiest ways to prevent condensation forming is to open your windows.  Even opening a window for just a few minutes can decrease the humidity in a room sufficiently enough to reduce condensation.  It’s good practice to open a window whilst cooking, bathing/showering or drying washing and even opening the windows for just 20 minutes a day can drastically reduce the effects of condensation.

  1. Install air extractor units

Air extractor fans remove moisture from the air before it has chance to come into contact with a cool surface and form condensation. Installing air extractor fans in bathrooms and kitchens, where the majority of moisture is expelled, will help prevent condensation forming on the inside of your windows and on walls.

To be truly effective, it’s important to leave extractor fans on for a short period of time, after cooking or taking a bath/shower.  For safety though, don’t leave your extractor fan on for long periods of time as this could cause a fire. Regularly cleaning your extractor fans will prevent a build-up of dust and keep them running efficiently.

  1. Open trickle vents/air inlets on windows

The majority of windows these days come with trickle vents which naturally allow air to transfer outside, even when the window is closed. These vents are designed to help prevent or minimise problems associated with poor ventilation, such as condensation.

Some windows, such as FAKRO pine roof windows, have automatic controlled ventilation which is activated by changes in atmospheric pressure, reducing the air inlet in windy or cold weather.  This system provides the optimum balance of fresh air regardless of weather conditions, while avoiding heat loss.

How to stop condensation on my windows?

  1. Don’t dry clothes indoors

A major cause of condensation is drying clothes on radiators. When clothes dry, they omit water vapour and this water vapour has to go somewhere.  If you do have to dry clothes indoors, ensure that there is good ventilation – open windows or invest in a dehumidifier to help remove the moisture from the air and reduce the condensation from forming.

  1. Keep your home’s temperature consistent

Condensation forms when warm air, filled with moisture, meets with colder objects, such as windows or cold walls.  Keeping your home at a constant temperature prevents surfaces from getting cold enough to cause condensation. Using a thermostat can help maintain a constant temperature but, of course, with energy bills increasing, this might not be a cost-effective solution.

  1. Install windows that improve ventilation and reduce condensation

The types of windows fitted to your property can have an impact on the amount of condensation produced, as some windows are more prone to condensation than others.

Single glazed windows are not able to keep warm so you will, inevitably, get condensation forming over the colder months when the warm air in the house comes into contact with the cold window pain.

Ironically, new double or triple glazing can result in increased condensation, as the increased energy efficiency of the window, can mean that it is more difficult for moisture in the air to escape.

Some windows, such as FAKRO’s roof windows, have a unique draining system that allows condensation to escape to the outside - preventing moisture from entering into the timber and resulting in greater durability.

How to stop condensation on my windows?

Many roof windows use metallic spacers to separate panes of glass and these can encourage condensation to form by forming a cold ‘bridge’ between them. By contrast, FAKRO uses only warm spacers in order to ensure that this otherwise common problem does not affect its windows. 

How do I stop condensation on the outside of my windows?

Condensation on the inside of the windows forms when the air outside is colder than the air inside a building.  In contrast, when warm humid air outside comes into contact with a cold window, condensation can form on the external side of the window.  This is usually seen first thing in the morning, especially after a clear, cool night.  Condensation on the outside of the window usually means your windows are doing their job of preventing heat from escaping – ensuring energy efficiency.

Condensation on the outside of your windows, is usually nothing to worry about and the water soon evaporates as the outside temperate rises.


The tips in this guide cover what condensation is, why you might have it on your windows and how to stop it. At FAKRO, all of our roof windows are supplied with automatic air vents and a unique draining system as standard to help prevent damage from moisture and mould! For more information contact the team here.

How to stop condensation on my windows?  Download our FREE guide to preventing condensation