Dealing with condensation in double glazing

Double glazed windows are generally designed to alleviate the sort of problems that affected older-style alternatives, such as keeping out the cold and stopping condensation, which can lead to mould forming in the corners. However, if double glazing starts to malfunction, the latter can still be an issue.

To deal with it, the tactics can generally be about prevention, ensuring that rooms are not left humid, letting moisture cool on the cold windows and get between the panes.

Difficulty rating

Level of difficulty: beginner

Things you’ll need

Window seals
Window cleaning solution
Measuring tape

The steps to follow

Replacing the seals

If you do find condensation between the panes of your double glazed windows, the problem will usually be the seals around the edges. These can prematurely crack or split, and this allows condensation to get in.

    1. Start by checking the state of the seals. Go around the edges of the seal with your hand slowly, feeling carefully for any splits in the rubber. If they need to be replaced, you can buy the correct seals for your window types from the company that fitted them in the first place. This is important, as simply buying some from a hardware store can mean they do not quite fit, and the problem will only get worse.
      Note: Seals should be replaced one at a time rather than all at once to make sure you do not further compromise the windows.
    2. Remove a seal and measure it accurately. Using scissors, cut the replacement length to the same size and hold it against the window to make sure it fits exactly in place. Start at one end and simply press the seal carefully into the groove with your thumbs. Make sure it goes fully in all the way along and that it reaches perfectly into each corner. Once all are done, you need to ensure that there are no gaps at all where each seal meets.
    3. Repeat this for all four sides of the window. It can be a good idea to make sure that you go around the window again with your thumbs to check that the seal is sitting in the guide grooves perfectly, or else the window will remain compromised.
      Note: If you are having problems with getting the rubber seals into the grooves on the window, use window cleaning solution to give yourself a little bit of lubrication – this can help to make the whole process much easier.


Once you have replaced the seals, it’s important to check periodically to make sure the issue does not return. If you have done the job properly and condensation seems to still be getting between the panes, the best thing to do is replace the whole unit. This is a job better done by professionals, however, and it is always pertinent to call in experts rather than trying it yourself.

Preventing condensation

Prevent is better than cure. The best way to ensure it does not make its way into windows, and this mostly comes down to making sure your home is generally dry and warm. There are a number of ways to do this.

      1. When cooking, always cover pots and pans with a lid to stop steam from getting into the air. This will cool onto the coldest surfaces in the room, which are invariably the windows. You should also always use an extractor fan.
      2. When using the shower or running a bath, make use of the bathroom’s extractor fan to stop steam gathering. Alternatively, leave the window open a little to allow steam to escape.
      3. Make use of your central heating. Even in rooms you are not using, it can help to keep the heating on, even at a low temperature – it helps remove moisture in the air and prevents the windows from getting condensation.

Please note that all our DIY guides and ‘Expert answers’ advice have been written strictly for reference only. Rated People do not accept any liability for any damage caused to an individual, property or anything else as a result of following our DIY guides and using our ‘Expert answers’ advice.

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