Foggy windows, whether outside or inside, happen due to one reason – different temperatures in the cabin and ambient air. If you live in a cold climate area, you’ll often stay in the car with a heater. And if you are driving on a hot sunny afternoon, you need the air conditioner to stay cool inside the cabin.
When using a car heater or air conditioner to stay calm, the outside and the inside temperature is not the same. This will invariably fog the car windows. Using an air conditioner may cause the windows to fog from the outside while using a car heater will cause fog to blur the windows from the inside.
In this article, you’ll learn what causes car windows fogging up inside when parked and what to do in such situations.
What causes car windows fogging up inside when parked?
As explained earlier, condensation happens due to temperature changes. This doesn’t matter whether you’re driving or parked. Let’s narrow it down to see why car windows fogging up inside winter, whether you’re driving or parked.
Passengers exhaling
If passengers are inside the car, nothing will prevent them from exhaling, whether sleeping or awake. The air they breathe out will turn to condensation once it hits the windows and the outside temperature is far below the cabin temperature. The condensation will fog your car from the inside.
Rainfall
Having car windows fogging up inside when it rains is normal. If you park your car in an open space and it rains, the ambient temperature will be much lower than the cabin temperature. Because of the temperature difference, the car will fog up from the inside.
Using car heater
If you park your vehicle in a cold area where the inside cabin is cold, you’ll likely turn on your car heater if you have one. While turning up the car heater will keep you warm and comfortable, it’ll increase the cabin temperature, causing the windows to fog from inside.
Sweat or heat
If the passengers and the driver are sweating inside the car, the heat from their bodies will form condensation when it reaches the windows. The condensation will cause fog-blurring the windows.
Now that you have seen what causes fog inside car windows let’s see how to stop car windows from fogging up inside.
What to do if my car windows are fogging up inside when parked?
Depending on the root cause, windows fogging from the inside means the inside temperature is higher than the ambient temperature. To keep car windows from fogging up in the morning when parked, you need to ensure the ambient and cabin temperature are the same.
Here are what you should do if your windows are fogging up inside when parked;
Crack the windows
If you want to sleep in the car, crack the windows to allow outside air to enter the cabin. This way, your breath will not reach a dew point when it touches the glass. The dew point is when condensation touches the windows, and the outside temperature is far below cabin temperature.
Alternatively, you can run the air conditioner if you don’t want to crack the windows. But please, do not leave the engine and the air conditioner on while sleeping. It is unsafe to sleep in a car with the engine running. Sleeping in the car with the engine running will let exhaust fumes containing carbon monoxide enter the cabin.
Park your vehicle in a garage
Always park your vehicle in the garage whenever it is raining. Leaving the vehicle in an open space when it’s raining will cause it to fog up from the inside. To prevent this from happening, park the vehicle under a shade.
Turn off the car heater.
If the vehicle is fogging up from the inside when using the car heater, crack the windows or switch on the air conditioner. This will let the ambient air and cabin temperature stay at the same rate. However, remember to turn off the air conditioner once the inside fog is gone. If not, the windows will start fogging from the outside.
Check out this comprehensive article that explains how to stay warm in a car with no heat. Staying warm in a car without heat will prevent your car from fogging inside.
For a more comfortable solution, turn on the car defroster and blow warm air across the windshield and windows to clear off the accumulating moisture on the windows. Check if your vehicle’s climate system has a recirculate feature and turn it off. If the system is on, the vehicle air conditioner or heater reuses the air inside the car instead of drawing ambient air.
You want your car to pull the ambient car into the car to prevent your breath from fogging the car from the inside. This explains why you should turn off the recirculate feature. If you don’t know whether your car has this recirculate feature, look for a button on the dashboard with a circle or semi-circle arrow. Not to escape, some vehicles will have an icon of a car with a circle inside.
Frequently Asked Questions – FAQs
Q: Why do my car windows fog up on the inside overnight?
Generally, cars parked in open space fog overnight since the temperature inside the cabin is higher than the ambient temperature.
Here’s what happens. At night, condensation occurs due to the difference in the outside and inside temperatures. As the warm air from the cabin and the cool ambient air hit the windows simultaneously, the difference in temperature coats the windows with condensation.
Q: How do I stop my car from fogging up inside?
Car fogging up from inside or outside is not unusual though it can be disturbing at times. However, there are a smart ways to prevent your car from fogging at night. These include using a silica dehumidifier, applying an anti-fogging coating, and turning off the recirculate feature when using ac and car heaters.
Q: Is it normal for car windows to have condensation on the inside?
It is absolutely normal for car windows to condense inside. So do not fret when it happens with your car windows. As already mentioned, condensation happens due to temperature changes from the cabin and ambient temperature. However, you can prevent or stop it by following the steps outlined in this article.
Q: Should I be worried about window condensation?
You shouldn’t worry if your car condenses when parked. All you have to do is clean the fog with a clean rag and crack your windows. On the other hand, you should worry if it happens when driving because it can impair your view, invariably increasing the risk of road accidents. If you want to use your heater in cold weather, set the heat setting to the max and turn on the ac to dry the moisture.
Q: Is it heat or cold to defog windows?
Heat is usually better than cold when defrosting windows. According to Road and Track, the best way of defogging your car is to turn on the heater to max settings and then turn on the air conditioner. This way, the heat will hold more moisture, while the ac will pull out the moisture from the air as it passes over the cooling coils.
Q: What can I spray on windows so they don’t fog up?
While fogging is normal, it is so unnerving and frustrating in most cases. For this reason, drivers often look for what to spray on the windshield and windows to discourage fogging. If you don’t want your windows to fog from the inside, thoroughly clean your windows with a soft towel and apply the anti-fog spray. Apply the same step on the exterior glass if you don’t want your windows to fog from the outside.
Q: How much does it cost to fix window condensation?
Fixing car window condensation does not cost a fortune, depending on the root cause. In most cases, all you need to do is to turn on the car heater to max settings and turn on the car ac as well. In other cases, you may need to use a dehumidifier to clear and prevent the windows from fogging. However, if the windows thermal seals are damaged, you may need to spend between $100 and $200 to fix it.
Final Words
Car windows fogging up inside when parked are normal. However, it can be frustrating and unnerving at times. Here at Rx mechanic, we don’t want you to feel frustrated. That’s why this article has answered the question, why are my car windows fogging up when parked and outlined what to do in such a situation. It also suggests preventive measures and implementing those can help you avoid the hassle. But if you fall victim to this uncalled for situation, follow the guidelines religiously to successfully defog your car windows.
