Dealing with a Foggy Windscreen

Dealing with a Foggy Windscreen

Dealing with a Foggy Windscreen

In the cooler Canterbury months it’s not uncommon for your cars windscreen to steam or fog up on the interior. As I’m sure you’ve experienced this obstructs visibility making it difficult if not impossible to drive.

The fog is basically tiny droplets of water that condense on the cold surface of the windscreen. The air inside your car contains moisture from your breath, pets, and any wet items you may have. When this warmer moist air comes into contact with the cold glass of your windscreen, it cools down releasing some of its water vapor which sticks to the glass forming a fog. This is because the cooler air can’t hold as much moister as the warm air.


In winter, with the sun lower in the sky and shorter daylight hours, coupled with rush hour traffic, frosty and/or foggy windscreens can all combine to create a dangerous driving cocktail.


So, how can you prevent this from happening? There are a few things you can do:

1 Keep your car dry. One of the best ways to avoid interior windscreen fogging is to keep your car dry. Ideally storing it under cover or in a garage.
2 Applying an anti-fog spray to the windscreen interior. This works by lowering the water's surface tension so it spreads out rather then forming droplets. There are a number of different products available that can be purchased from any auto-part store, garage, or hardware stores


Of course prevention is all very good and well, but what’s the best approach if you do have a foggy windscreen?

1 Use your air conditioner. This may sound counterintuitive, but using your AC can actually help reduce fogging. That's because your AC dehumidifies the air inside your car, removing some of the moisture that causes fogging. Remember to make sure you set it to fresh air mode, not recirculate mode, otherwise you'll just be blowing the same moist air around.
2 If your car has a demist function then use this. Even it it starts off by blasting cold air this is drying out the air reducing the moisture level similar to using the AC and it's directing this flow onto the windscreen.
3 Using your heater. This reduces fogging by warming up the air inside your car. This will increase the capacity of the air to hold moisture, so less of it will condense on your windscreen.
4 In contrast to the heating option another way to deal with a foggy windscreen is to wind the windows fully down. This works by reducing the amount of water vapour in the vehicle, although in the winter months you'll need to be well wrapped up.

Try to avoid using your hand or sleeve. While this may give an immediate improvement the windscreen will soon re-fog as the moisture level and windscreen temperature haven’t changed. There also has the potential to mark the windscreen with oils, smears, and dirt causing reduced visibility.

I hope these tips help you avoid interior windscreen fogging and enjoy a safer and more comfortable driving experience.

The team at Fast Autoglass wish you happy and safe driving.