Foggy windows in the car: reasons and solutions

Increased humidity levels inside the car, strong temperature changes and high levels of moisture in the air inside the car lead to fogging of the windshield , side and sometimes rear windows. High concentrations of moisture in the air inside the car can be caused by natural causes, i.e. weather, or the condition of the car. For example, in winter the temperature outside is much lower than inside the car, as a result the glass cools from the outside, and the warm and humid air inside settles on the glass in small droplets – condensation.

And it turns out that the windows in the car sweat, because the moisture in the cabin has nowhere to evaporate, and it accumulates on its internal surfaces – the windows. In summer, this situation often happens due to rain and damp weather, fog, moisture in the cabin accumulates due to wet clothes and shoes, wet rugs. Heavy fog is the same rain, only very fine, together with the air it gets into the cabin and collects in the most hidden corners of the cabin. At the same time, the windshield in the car sweats, as well as the side, even the rear, which seriously impairs visibility and leads to the emergence of dangerous situations on the road.

If there are too many passengers in a cool cabin, this will also lead to fogging, as they exhale warm air in large volumes, which does not have time to cool down. But the culprit of fogged windows is not only weather conditions.

Unfavorable microclimatic conditions are formed under the influence of the following factors:

1. The presence of objects saturated with moisture in the passenger compartment or luggage compartment . Wet clothes, towels, mats soaked with water – all this will lead to the fact that the humidity level will increase significantly, even good ventilation may not cope with it. Do not be surprised why the windshield sweats from the inside of the car, if the trunk after another trip to the countryside, beach, fishing or visiting the pool is filled with wet things.
2. Traveling with a large group . The air exhaled by a person is saturated with tiny droplets of water, this is easy to understand by the steam from the mouth in cool, frosty weather. Of course, in the car interior, all this water will very quickly begin to accumulate on the internal surfaces, primarily on the glass, due to the significant temperature difference between their internal and external surfaces.
3. Activating the recirculation mode . Why do the windows inside the car fog up in this case? This happens because of the peculiarities of the mode. It assumes that the air conditioner cools not the outside air, but the air that is already in the car. The function allows you to protect yourself from external unpleasant odors, which is important when driving in close proximity to treatment facilities, a large oil refinery. If the internal air is saturated with moisture, however, recirculation will lead to serious problems with visibility, because the windows will not dry out.
4. Incorrect direction of heater deflectors . From school physics, everyone knows that warm air rises upward, and therefore the optimal direction for heater deflectors is the bottom, so that the heated flows first go to the feet, and then are evenly distributed throughout the entire volume. It sounds reasonable and logical, but in order to prevent the windows in the car from fogging up, it is correct to direct the air streams directly at them, to quickly remove condensation.
5. Contamination of the cabin filter . Its cleanliness is often not given enough attention, because the condition of the element does not affect the dynamic characteristics, driving performance of the vehicle, which is why it is simply forgotten. Meanwhile, a decrease in the filter’s throughput leads to insufficiently effective ventilation of the cabin and, consequently, the rapid formation of large volumes of condensate.
6. Design flaws . This situation is extremely rare, modern cars are equipped with reliable and effective ventilation systems, but on some models from the 70s and 80s, the windows in the car really fog up almost constantly. Owners can only be advised one thing – use additional accessories, make changes to the operation of the equipment, replace standard components with more productive and powerful ones.

Fogging for the reasons listed above can occur at any time of the year. Another reason why the glass in the car fogs up from the inside in the summer and not only is the evaporation of alcohol from people inside. Ethyl alcohol, released during a hangover, attracts water vapor, the moisture in the air becomes more concentrated and dense, and settles on the surface of the glass. The answer to the question of why the windshield fogs up from the inside in the car can also be an unnoticeable leak, for example, a radiator or pipes, antifreeze or antifreeze can leak, which also evaporate, these evaporations condense and stick to the glass from the inside of the car.

It happens that the windows in the car fog up in the rain, while in clear or, at least, dry weather such a problem is not observed. Its main reason is the general increase in the humidity level. If on a sunny day it is low, and on a cloudy day it only slightly exceeds the comfortable norm for a person, then on a rainy day it approaches 100%. Of course, this is reflected in the amount of condensation.

The problem is aggravated by the following:

• • Wet clothes of the driver and passengers .

• Reduction of air temperature . In bad weather it becomes noticeably cooler, the glass does not heat up, which is why moisture actively condenses on it.
• Insufficient sealing of the body . If the doors and other enclosing elements do not fit tightly to the pillars and supporting body structures, the rubber and silicone seals are worn out, there are through holes, then precipitation begins to penetrate into the interior, so do not be surprised why the windows in the car sweat in the rain. The only way to cope with the problem is to eliminate the listed defects.

Since the main reason is humidity, you need to prevent the very fact of moisture getting into the interior. What to do if the windows fog up in the rain: try not to get into the car wet, watch whether the mats and seats are wet or not, dry them regularly.

So, if the windows in the car fog up in the summer or in another season, first of all, you need to ensure effective ventilation of the air in the cabin. You should also follow a number of fairly simple recommendations:

• Maintaining the cabin filter clean . Are the windows fogging up in your car? You need to make sure that the element is not dirty. In most cases, everything can be eliminated by simple washing, only in the most difficult cases is replacement necessary.
• Activation of windshield blowing . If the configuration includes a full electric heating function, it should be activated as well.
• Turning on the air conditioner . This is a universal piece of advice that is relevant at any time of year. In winter, turning on the air conditioner seems like a strange solution, but it can really help if the windshield in the car is fogging up. The reason is the wide functionality of the climate control system, which not only cools the air, but also removes excess moisture from it.
• No wet things in the cabin! In winter, it is not a bad idea to shake snow off your boots. This is not only a matter of cleanliness, but also of maintaining a comfortable microclimate. If you cannot do without loading wet things, for example, after swimming, visiting the beach, spending the night in a tent, rafting on a river or fishing, then it is worth packing them in a sealed plastic bag.

To avoid having to urgently search for why the windows in your car are fogging up, you should follow a number of rules:

1. 1. Regular checks of the efficiency of the ventilation system, the serviceability of the air conditioner, heater, and the cleanliness of the cabin filter.
   2. Periodic treatment of glass surfaces with anti-fogging compounds. Yes, this measure may seem excessive to someone, but forewarned is forearmed! Such prevention will definitely eliminate the unpleasant question of why the windows in the car fog up.
   3. Keeping small bags or jars of silica gel in the car. This is the same substance that you can see in shoe boxes, its task is to absorb excess moisture from the air. Small containers of gel in the glove compartment, under the seat will allow you to forget about the problem of why the glass in the car fogs up from the inside.
   4. Maintaining the tightness of the passenger compartment, monitoring the condition and efficiency of rubber and silicone seals in the area of ​​the doors and luggage compartment. Every crack is a path for moisture, which causes the windows in the car to fog up during rain.