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How to Prevent Car Windows from Fogging Up

By Kathleen Burgess


Published on

Finally losing patience when there’s fog covering your car windows?

Well, you should be scared, too.

Fog sounds harmless since it’s pretty common, but low visibility can cause fatal accidents. That’s why you should learn how to prevent car windows from fogging up.

Before we proceed to the tips, let’s understand first why fogging occurs. This is important so you can easily understand the logic behind some strange solutions we’ll discuss later.

Car windows experience fog due to condensation

In general, condensation happens when moisture from warm air comes into contact with a cold surface. Now, what exactly happens when we talk about car windows?

According to Cars.com, when warm air inside the passenger compartment meets cold glass, the windows get blurry. That’s why fogging is common during cold weather.

A perfect way to prove this concept is by breathing close to the window inside the car when it’s really cold outside. Since your breath is naturally warm and full of moisture, it will instantly create a mark on the window.

Aside from breathing, there are other instances where people unconsciously enhance moisture or warmth inside a vehicle. Here are five common examples:

  • Wet clothes
  • Snow (which will eventually melt) dragged by boots
  • Damp car flooring
  • Hot food
  • Couples getting intimate (we’re surprised, too!)

Sometimes, the concept of condensation can be reversed as well, especially if car windows are concerned. If it’s hot outside while it’s cold inside your car, fogging may also occur. However, it’s not as intense as the original idea since cold air contains less moisture.

Next, we’re going to discuss what you should do when it starts to fog. This will be the consequence if you won’t make some preventive measures. Don’t worry; we’ll talk about prevention later.

The solution to fogging car windows depends on the weather

We prepared two sets of instructions because – let’s face it – it’s not always cold outside. If it’s a sunny day, you need to use another method.

  • Cold Weather

    Of course, if it’s a cold day, you would prefer to activate the heater. Unfortunately, that will lead to fogging. In case you experience that, do the following steps:

    1. Adjust the heater to its highest setting.
    2. Activate the air conditioner.
    3. Turn off recirculation mode.
    4. Slightly open the car windows for a few minutes.

    The reason why you have to max out the heater is to produce more moisture inside the car. That doesn’t make sense for now, but wait until we explain the next step.

    Once you activate the AC, it will absorb a big amount of moisture inside the car in an efficient manner. Then, when you turn off recirculation, dry air finally enters your area.

    The last step is for a more thorough defogging. When you crack a window, the colder air outside will completely eliminate humid air inside the vehicle.

  • Hot Weather

    Just like the first method, you also have to regulate the temperature inside the car when it’s sunny outside. So, you clearly have to make the interior warm, too.

    The tricky part is this: condensation is on the exterior surface of the car window. You have to wipe the window clean from outside. At least with windshields, you just have to use the wipers.

    To defog the outer part of the windows, you have no choice but to make a little sacrifice by dealing with hot weather for a while.

    What you need to do is simply adjust the AC to its lowest setting. You might even have to turn it off if the fog keeps on appearing. You should also turn off recirculation mode.

    If you don’t mind the wind, just open the car windows. It can be uncomfortable to deal with hot weather if the AC is low and the windows are closed.

How to Prevent Car Windows from Fogging Up

You can avoid the hassle of defogging if you know how to maintain clean car windows. Nobody wants to shiver or sweat inside the car just to eliminate condensation.

Before we get to the weird stuff, here are the basic preventive measures:

  • Clean your car windows regularly so they can resist moisture (remove adhesives carefully – if ever – to avoid permanent white streaks on the glass).
  • Park with two open windows if it’s safe (especially if you have an adult present inside).
  • If you’re alone, crack the second-row windows (one inch) when you park your car.
  • Open the front windows if your car is in a garage.

Finally, we’re now going to discuss two strange methods that are surprisingly effective for defogging.

  • The Potato Method

    For some reason, moisture from potatoes makes fogging less likely to happen. After cleaning your windows, here’s what you should do:

    1. Slice a potato in half.
    2. Wipe the potato’s flesh all over the window (cut a small portion of the potato if there’s dirt buildup on it).
    3. Remove streaks of the potato’s starch, if any.
    4. Wipe the flesh again to the surfaces where you removed starch streaks (be careful not to create more streaks).
    5. Leave the windows untouched for five minutes.

    Don’t hesitate to use more than one potato if it’s not enough for covering all car windows. You may also use spoiled potatoes to avoid using ones that are still fresh for consumption.

  • The Cat Litter Method

    We saved the most interesting one for last. According to Bustle, cat litter is excellent at absorbing moisture.

    So, should you also put cat litter on car windows? Here are the steps:

    1. Position a big roll of tape across one sock.
    2. Pour cat litter into the roll which serves as a funnel.
    3. Wrap the sock with another sock.
    4. Place the bundle of cat litter anywhere in the passenger compartment.

    Don’t expect this method to work instantly. It will need days for completely absorbing moisture in your car. Remember, it is a long-term solution, not an emergency defogging option.

In Conclusion

To avoid the tricky defogging techniques, learn how to prevent car windows from fogging up. The long-term solutions will keep you comfortable inside the car no matter how hot or cold the weather is.

Clean car windows aren’t only important for resisting moisture. Find out how important they are in case you sell your vehicle.

If you’re looking for car essentials, we have a list of things you should keep in your vehicle. The list includes products designed for car windows.

About Kathleen Burgess

Kathleen started her career in journalism writing about cars during her Journalism degree at CUNY and even though she didn't like it at first, she quickly became an ace, writing news, reviews and comparisons like one of the best car writers out there. Today she writes content focusing on the latest trends in the car industry, looking at sales, policies and green alternatives. Learn more about GCB's Editorial Process.

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