How to prevent the inside of your windshield fogging or freezing

Fogging within a windshield occurs when vapor water from inside warm automobile condenses on the windshield cold. The air in the car absorbs moisture from the exhaled breath of the passengers or any wet clothing with. If the heating is turned on, the air in the car is heated, leaving absorb more water vapor.

When moist air that touches the windshield cold, cooled and supersaturated, and the water vapor condenses. If the windshield is sufficiently cold, condensation can become ice. This creates a potentially dangerous situation because fogging or freezing on the windshield limited driver visibility. There are several steps you can take to limit the effects of condensation on the windshield.


  1. Directs warm air windows using the defrost setting. As the windshield is heated, there is less temperature difference between it and the air in the car, so it is less likely that condensation occurs.
  2. Deactivates the air recirculation control. Causing air to circulate helps quickly heat the car again, but also increases the humidity inside the car, passing air through it and again, absorbing more moisture occupant while doing so. Since cold air support less moisture than warm air coming from outside will be less humid than hot inside, even if it rains or snows.
  3. Turn on the air conditioning. The compressor removes moisture from the air inside the vehicle, so that the air strikes the inside.
  4. Remove the rain or snow before entering the car. The additional water in the car humidity increases, so do everything you can to limit the amount of water entering the car. Do not leave open containers of liquids in the car. If the seats are wet, damp clean as soon as possible. Do not leave wet rags or other items in the car.
  5. Clean windows with ammonia based cleaner or shampoo. There are also liquid treatments and towels available commercially that are specifically designed to deal with fogging the windshield.