condensation inside the car

How do you fix condensation inside a car?

Condensation inside the car is something that affects all vehicles. We’ve put together a quick primer on what causes car condensation and how to reduce its effects.

What is condensation?

Condensation forms when warm air containing moisture comes into contact with a cold surface, such as your car window. When the warm air meets the cold air, the moisture in that warm air condenses onto that cold surface.

Read more: Should you fit winter tyres in cold weather?

On a car windscreen, this moisture takes the form of hundreds of tiny water droplets that, from a driver’s perspective, looks like a fog.

condensation inside the car

What causes condensation inside a vehicle?

One or a number of the following things could cause condensation inside the car:

  • Wet clothes/shoes/pets – water on these items will slowly evaporate into the cabin air or, if heavily soaked, cause the seats and carpet to become wet.
  • Breath – when you or your pets breathe, that exhaled air contains a large amount of water vapour which is released into the cabin.
  • A water leak.
  • No circulation of fresh air.

condensation inside the car

Are new cars more prone to condensation build up?

Modern cars have much better seals, meaning they tend to be more water tight. This means that it’s more difficult for any air inside the vehicle to get out.

If movement is created with a fresh air source, moisture levels will decrease. Well-sealed and insulated newer cars means this movement cannot happen.

Read more: Driving in winter? Our top tips show you how.

Increased insulation also allows modern cars to stay warmer longer after being parked; the longer the air inside the vehicle is warmer than the air outside, the more condensation will appear on the cold windows of the vehicle.

condensation inside the car

How can I reduce condensation in my car?

As condensation collects in the air inside the cabin, the level of moisture will increase; if this air is not vented to the outside then the condensation problem will increase.

The most efficient way to remove moisture from the air is to use the vehicle’s air conditioning system. This system draws air from the cabin through an evaporator, which causes moisture in the air to condensate in a controlled way and drain out of the vehicle.

If the cabin air is not regularly refreshed then condensation will accumulate, as the moisture-filled air will not be removed. However, you can force this by changing the re-circulation feature from internal to fresh air.

Don’t forget the demister function, either. That’s designed to clear the windscreen of condensation. This works by directing fresh air onto the windscreen, which has the effect of drying the inside of the glass.

condensation inside the car

If the features of the heater and air conditioning system are used as above, then the amount of condensation inside the vehicle will be reduced. However, it will never be removed – moisture will always be present inside the vehicle.

Believe it or not, one of the key ways to keep condensation at bay is by simply keeping the insides of windows, particularly the windscreen, as clean as possible. A thorough clean of the windscreen will lessen the likelihood of condensation forming, and ensures that any that does form is removed quicker by the demisters.

You can also buy a car dehumidifier bag. This is a small bean bag full of silicone balls that sits on the top of your dashboard and soaks up moisture from the air inside of your car at all times.


Comments (5)

  1. I have a 65 plate Aygo & regularly suffer condensation after the car has been left on the car park at work for 12 hours. I return to the car & the inside front screen is soaking wet & when its below freezing I have to scrape the inside as well as the outside.

    I also find that the demist is very poor on the drivers side of the windscreen leaving about a quarter of the screen misted over when the rest has cleared (with air con switched on), never use the re circulation setting so its not that.

  2. I sincerely hope this article wasn’t hastily published in response to the number of owners complaining about TSS unreliability!

    1. Hi Ian,
      No, we didn’t make this in response to Toyota Safety Sense. This is just a general winter driving tips article. Many thanks.

  3. Easily the most important tip above, is to switch off recirculation mode. So long as there is sufficient through flow, condensation will mostly be kept at bay, even without the use of aircon.

    btw ‘condensate’ is the liquid that builds up after moisture has condensed, it isn’t a verb!

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