What Causes Fogging on Car Windows?
3 Answers
The fogging on car windows is caused by high interior temperature, unheated glass, or low interior temperature. The specific reasons are as follows: High interior temperature: When the interior temperature is high and the outside is cold, moisture inside the car condenses on the cooler glass, forming fog. In this case, turning on the air conditioning to direct warm air toward the windows can help clear the fog. Unheated glass: Before the glass is heated, warm air can temporarily cause more fogging. Using cold air to blow on the windows or slightly opening the windows to equalize the temperature inside and outside can prevent fogging. Low interior temperature: When the interior is cold and the outside is humid, moisture will condense on the cooler outer surface of the windows. This can only be removed with wipers. Adjusting the air conditioning settings to prevent cold air from blowing directly onto the windows can also avoid external fogging.
Every time I drive, especially in autumn and winter, fogged-up windows are always a headache. It's mainly due to the temperature difference between the inside and outside of the car—cold outside and warm inside—plus the moisture from our breath condensing into water droplets on the glass. For example, on rainy days or when there are many people in the car, the humidity is higher, and the fog forms more quickly. This not only blocks the view, making it hard to see the road while driving, but it's also particularly dangerous. I often have to turn on the air conditioning's defogging function, set to blow on the front windshield, or crack the window a bit to improve air circulation and reduce moisture buildup. Additionally, it's good practice to keep the interior dry—don't leave wet clothes or umbrellas inside for too long. Regularly checking the air conditioning system to ensure the heater and fans are working properly can also prevent problems before they arise. In short, small issues left unresolved can lead to bigger troubles down the road.
I have a deep understanding of window fogging in cars. When the weather gets cold, as soon as people get into the car, increased breathing, along with possibly bringing wet umbrellas or clothes, causes the windows to fog up. The key issue is the large temperature difference between the inside and outside of the car, making it easy for moisture to condense. This is extremely annoying, especially for parents who are always on edge when picking up or dropping off their kids. I recommend immediately using the car's defrost button to blow hot air onto the glass or opening the external circulation a bit for ventilation. Never keep the internal circulation on for too long, as that traps all the humidity. Additionally, placing a small desiccant in the car or regularly cleaning the windows can reduce fogging. Safety should always come first—poor visibility can easily lead to accidents, so don't ignore it.
