why do car windows steam up

Why do car windows steam up?

Car windows can steam up for several reasons. In my view the most common reason is due to a difference in temperature between the inside and outside of the car. When the inside of the car is warmer than the outside, the warm, moist air inside the car will condense on the colder window surfaces, forming water droplets or fog.

This is also known as fogging.

This can happen if the car has been parked in a cold place, or if the heater is on and the windows are closed.

Another reason car windows may steam up is if there is high humidity in the air. Humidity refers to the amount of moisture or water vapor in the air. If the air is already saturated with moisture, it will be more likely to condense on the windows when it comes into contact with the colder glass.

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How do I stop my car windows from steaming up?

There are several ways to prevent car windows from steaming up. One way is to use the air conditioning (AC) or ventilation system to circulate the air and keep the inside of the car at a consistent temperature.

How do I stop my car windows from steaming up

Another simpler way and pretty much the only way if you don’t have AC, is to crack open a window to allow some of the moist air to escape. Using a dehumidifier or placing a small container of silica gel in the car can also help to absorb excess moisture in the air and prevent the windows from steaming up.

What is silica gel?

Silica gel is a type of porous, granular material that is made from silicon dioxide, a naturally occurring mineral. It is often used as a desiccant, which means that it can absorb moisture from the air to help keep the surrounding environment dry.

Silica gel is often used in products that need to be kept dry, such as medications, electronic devices, and food products. It is also commonly used to help prevent condensation and moisture build-up in closed containers, such as cameras, musical instruments, and even shoes.

I recently bought myself a new PC and when I opened it there were several little packets inside the box and they had silica gel in them to stop the PC screen from getting condensation on it during transit.

Silica gel inside the in small packets is usually white or blue in colour. The blue beads contain a moisture indicator that changes colour when the gel has reached its absorption capacity, indicating that it needs to be replaced. Silica gel can be regenerated by heating it to a high temperature, which causes the absorbed moisture to be released.

In the context of preventing car windows from steaming up, silica gel can be placed in a small container in the car to absorb excess moisture from the air and help keep the windows from fogging up.

Why do my car windows steam up at night?

You will probably find that this problem occurs more often at night and can me a real pain. I get it a lot in my Jaguar x-Type. Read my Jaguar X-Type review here.

There are a few reasons why car windows might steam up more at night. One reason is that the temperature differences between the inside and outside the car is more pronounced at night.

The temperature inside the car will cool down more quickly. This can cause the warm, moist air inside the car to condense on the colder window surfaces, leading to steamed-up windows.

Humidity tends to be higher at night also, causing the windows to steam up more easily.

Finally, it’s also possible that the windows may steam up more at night simply because the car is being used less. If the car is not being driven, the windows may not be opened as frequently, allowing the moist air inside the car to build up and condense on the windows.

Same methods can be used to clear the problem open the window, (not so much fun at night if it’s cold) or using the AC.


It’s a bit annoying when this happens, especially if like me you are sometimes late when you jump in the car and the last thing you want to do is spend 5 minutes clearing the windscreen.

Open the windows a touch and if you are lucky enough to have a heated front screen use it and get the blower on.

Happy motoring.

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