How to stop condensation on windows - why it happens in the first place and how to prevent it

There are a number of tips and tricks you can use to help prevent the build-up of condensation on your windows

As we enter the last month of 2022, the days are getting shorter, nights are getting longer and temperatures are falling fast. One of the consequences of the colder weather is steamed up windows for many homes and cars.

Fogged up windows on your car or in your home can be unattractive and can be bad for your health as it can contribute to the growth of black mould. This is everything you need to know about condensation - from why it happens to how to prevent it.

Why do windows steam up on the inside?

Condensation occurs when moisture contained in warm air meets a surface that is cold enough to turn it back into a liquid. Window panes are particularly susceptible to condensation during winter because this is when the difference in temperature between the outside and the inside is at its greatest.

In the winter condensation can form on the inside of your windows because it is warm and humid inside, but cold and dry outside. The heat from your body and your breath also comes into play, as it warms the air and increases moisture levels.

Why do windows steam up on the outside?

In the summer, windows can steam up on the outside because it’s usually warmer and more humid outside than it is inside. It’s normal for droplets to form on the outside of your windows from morning dew in the spring and summer, or even in the autumn when warm days are followed by cool nights.

If you wipe your windows and the condensation doesn’t go away, then you may have moisture trapped between pieces of insulated glass and this points to a bigger problem. You’ll need to call an expert, and may need to get the window pane, or the entire window repaired.

How do I get rid of condensation on my windows?

While of course you can buy something like a window vac to clean the condensation on your windows, you can actually do it without the use of any expensive equipment.

To help with clearing the condensation away, you can make a simple, home-made solution by mixing two cups of water with two cups of white vinegar and a couple drops of washing up liquid.

Pour this mixture into a spray bottle if you have one and spray the solution straight onto your window. Use a soft cleaning cloth to wipe it down and let the glass air dry once you’re finished.

You don’t need to do anything about condensation on the outside of your windows, as when the sun comes out it should dry up, however if you find it annoying you can buy a water repellent.

What about condensation on my car windows?

If you’ve got condensation in your car, you can wipe the windows with a clean cloth or demisting pad, but it’s better to use the ventilation system if you can.

You can do this by making sure the air is directed at your windscreen and windows, and the fan is turned all the way up. Keep the temperature low to begin with, as overloading your car with hot wet air will just make the problem worse.

The cold air from the fans will still be warmer than that of the glass, and will help to dry it out - then you can start to turn up the heat.

Alternatively, if you’ve got air conditioning, use this instead as it will help to dry the air out more quickly.

Avoid using recirculated air as this will warm the car quicker and keep the moisture trapped inside.

If you don’t have air con on climate control, opening a window will help to clear out the screen faster as the cold dry air from outside will help to reduce the moisture inside and then you can start to raise the temperature.

How can I prevent it from happening?

There are a number of steps you can take to prevent condensation building up on your windows.

You can try investing in a dehumidifier or moisture eliminator as they will draw excess moisture from the wait. Another tip is to avoid leaving wet clothes to dry indoors, as the water from your laundry will add moisture to the air.

In the kitchen, you should keep the lids on your pots and pans to lock the steam in, and make sure to have your extractor fan on if you have one.

Additionally, fans in the bathroom should be left running for 15 minutes after you’ve finished with your shower or bath, and opening a window can let the warm, moist air escape.

If you’re struggling with condensation on your car windows, you can:

  • Clean your windows as removing tiny dirt particles will give the water less to cling to
  • Avoid leaving wet items in your car, like wet umbrellas or jackets as they will add moisture to the air 
  • Get a portable dehumidifier pad as this will absorb some of the moisture and help reduce condensation
  • Try the shaving foam hack - as strange as it sounds, wiping the inside of your windscreen/windows with a little bit of shaving foam can help deter condensation as the detergent in the foam stops the water from beading and forming a mist 
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