Why do windows fog?
Fog is considered as an intense collection of water drops which is same as the cloud. If the night is very cold, the heat that is absorbed by the ground from the sun during the day will be released by the ground in the night. The combination of hot and cold near the ground will give rise to the condensation of water that is called as dew. This dew will cover plants in the early morning. When the temperature increases in the day again, the air takes in moisture and the dew will evaporate.
If the temperature in the air outside the car is cooler and the air inside is warmer the warm air loses water drops when it touches the car glass which is cool. The variation in temperature between the air inside the car and that of outside the car results in the formation of fog. The Air conditioners will help in cooling the air inside the car to about 20 0 F, lower than the temperature that is present outside. Usually, glass has the tendency to transmit small amount of heat.
The air conditioning will make the glass of the car still cooler. The outside air that is warm will touch the glass that is cool and concentrate to form water drops. The natural water vapor will condense on the windows and form a layer of fog which is difficult for the person inside to see through. The same process also happens even in the case of windows of the house.
In the houses, when the outside air is cooler than inside, the windows will become cool and the air inside will touch the windows and get condensed as there will be variation in temperatures. This happens when the air inside gets cooler after it reaches cool windows. The air now shall not be able to hold moisture anymore. The moisture in the air will be left on the windows as condensation or otherwise called as fog. The windows of the house will have fog on the outside during the night when there is reduction in temperature and when the dew falls.