Over the cold and damp days, it’s only a matter of time
until you come across the dreaded foggy windscreen. Nothing is more frustrating
than jumping in your car, only to find a strong mist has taken away your
ability to see straight.
So what’s the science behind it all? The cause of your
windscreen fogging up comes down to the water vapour in the atmosphere that
occurs when your body heats the air inside the cabin (as does your breath)
increasing the amount of moisture it can hold. This means when it comes into
contact with your windscreen it cools and condenses, forming a mist.
Here are some tips and tricks on how to combat the mist to
ensure maximum visibility.
1. If your car has air conditioning, make sure it is
switched on. Whether it be in the dead of winter when it’s cold outside or in
the heat of the summer, your car’s air conditioner does more than just cool the
interior air. Not only does it act as a method of cooling the passenger cabin,
but it doubles as a dehumidifier.
2. If you want to be more comfortable, use the heater -
Start the heater off cold, then slowly increase the temperature as the air
dries out, rather than overloading the cabin with hot, ‘wet’ air. Make sure the
heater’s blast is directed at the windscreen.
3. If you don’t have air conditioning, then you’re going to
have to use your windows. Wind the windows down fully. This helps because the
dry, cold air from outside can help reduce the amount of water vapour inside
the car, stopping the screen misting up.
If you're concerned about fuel economy and you're already
warmly dressed, don't forget to reduce the heat and turn off the
air-conditioning when you and the windscreen are dry. Air-conditioners increase
your fuel consumption, and producing warm, dry air uses a little more fuel than
producing cold, dry air on a cold morning.
What NOT to do
The typical response in the old days was to furiously rub
the screen with your sleeve or cloth to remove some of the condensed water
vapour. Does it work? Sure, but it’s more of a short-term gain as the windscreen
can mist straight back up again. Also, using your hand on the glass can smear
the natural oil from your skin on to the windscreen making it even worse.
Some people think winding down the window an inch will do
the trick… not the case. You’ll only let in more cold, moist air into the cabin
making that mist impossible to clear. For the windows down trick, you’ll need
to prepare for the cold and wind those windows right the way down for a strong