How to demist a car windscreen

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Why?
Using AC
Using a heater
Other tactics
How to avoid it

When it's wet and cold out, there's nothing worse than getting into a car to be met with a fogged up windscreen.

It adds time to the morning commute, can leave your car damp or even mouldy, and can waste fuel.

Here's a step-by-step guide on how to demist it easily, so you can hit the road quickly and safely 👇

Why do windscreens steam up?

Windscreens steam up due to the moisture and temperature differences inside and outside the vehicle, and they can be especially troublesome when driving in the rain.

The air inside the car often contains moisture from many sources - breath from the occupants, wet clothing, or even residual moisture from the air outside.

When this warmer, moist air inside the car comes into contact with the cold windscreen or windows, it cools down quickly.

The contrast in temperature is most significant in colder months, exacerbating this effect in autumn and winter.

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Using AC to demist your windscreen

Both air conditioning (AC) and standard heating systems can be effectively used to demist your windows. Here's a step-by-step guide on how to use the AC.

1. Start your car: Turn on the engine and allow it to warm up for a few moments, especially in cold weather

2. Set the AC to fresh air mode: Recirculating the air already inside the car might make it more humid. Fresh air mode brings in outside air, which is typically less humid

3. Turn on the AC: Activate the air conditioner, which removes moisture from the air as it operates, thus reducing the humidity within the car

4. Adjust temperature and fan settings: While the cool air from the AC helps dehumidify, it's more effective at demisting when it's warm. Set the temperature to a warm setting and increase the fan speed to help move the air

5. Direct the air: Use the dashboard controls to direct the airflow towards your car windows

6. Wait: It may take a few minutes, but the mist on your windows should clear up as the AC system continues to pull moisture from the air

Cars are more likely to steam up in wet or cold conditions
Cars are more likely to steam up in wet or cold conditions
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How to use the heater to demist your car

And here’s a step-by-step guide on how to demist your car without AC:

1. Start your car: Begin by starting your engine. During colder months, it might take a minute or two for the heater to produce warm air

2. Turn on the heater: Set your car’s heating system to a low temperature to start with - starting with hot air could increase the humidity, so it’s better to take it slow

3. Fan setting: Set the fan to a high setting to increase the airflow over the windows

4. Direct the air: Use your car’s controls to direct the hot air towards the windows that are misted

5. Slowly increase the heat. Slowly increase the temperature of the heater. Warm air will absorb more moisture from the air, but it’s best to increase it in stages rather than all at once

6. Open your windows slightly: If it's not too cold outside, crack your windows for a moment, which helps exchange the humid interior air with the drier outside air

6. Wait: After a few minutes, the mist should start disappearing as the warm, dry air blows over the windows

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How to demist your windscreen without AC or a heater

Driving without a functional AC or heater can be challenging, especially when car windows fog. Here are some practical tips for demisting your windows without these systems:

  • Use a dry cloth or sponge: Keep a clean, dry microfibre cloth or sponge in your car. You can wipe the mist from the inside of your windows before driving and during your trip

  • Open the windows: Letting in the outside air can help, especially since the exterior air is often less humid than the air inside your car. Even a small crack will allow the drier air to circulate and help reduce the moisture inside that's causing the misting

  • Remove excess snow or water from your clothing before entering the car: If it's raining or snowing, shake off your coat, hat, umbrella, and any other items before getting into the car as wet things contribute to the interior humidity

You can use AC or your car's heater to demist your windscreen in cold or wet conditions
You can use AC or your car's heater to demist your windscreen in cold or wet conditions

How to avoid your car misting up

Taking some preventive steps can also reduce the chances of your car windows misting, saving you time and ensuring a safer, more comfortable driving experience.

Use a dehumidifier

Portable car dehumidifiers absorb excess moisture from the air inside your vehicle. Place one of these in your car overnight or while driving to help keep the interior dry and fog-free. If you're on a budget, filling an old sock with absorbent cat litter and tying off the end can help remove moisture.

Use a windscreen cover

Windscreen covers aren't just for stopping driving in snow and ice. They can also help regulate the temperature of your car's interior compared to the outside, reducing the likelihood of mist forming inside your windows, and are particularly useful when parked overnight.

Keep the windscreen clean

Regularly clean the inside of your windows with a good glass cleaner. Dirt, dust, and other residues can attract moisture, encouraging misting.

Use anti-fogging products

Various sprays, wipes, and gels are available that you can apply directly to the inside of your car windows to prevent fogging. These products leave a thin film that prevents moisture from settling.

Believe it or not, shaving foam can prevent fogging. Spread the foam over the windscreen using a clean, dry microfibre cloth. Then, with another clean towel, wipe off the shaving foam completely. You’ll need to reapply the foam regularly to be effective.

Check your car’s seals

Moisture can enter your car through damaged or worn seals around the windows and doors, contributing to fogging. Make sure these seals are intact and replace them if necessary.

Improve air circulation

Leave a gap in your windows when parked, if it's safe to do so, to allow for air circulation, or ensure your car's ventilation system is set to bring in fresh air rather than recirculating interior air when you're driving.

Avoid wet clothing and items

Wet coats, shoes, umbrellas, and the like contribute to the moisture level inside your car. If possible, store them in the boot or a sealed container to keep excess moisture out of the cabin.

Use a portable fan

If your car's ventilation system isn't effective, use a portable fan to help circulate air and reduce moisture in your car's interior.

Regular maintenance

Ensure that your air conditioning and heating system are functioning correctly by conducting regular car maintenance. They are integral in regulating the vehicle's humidity levels and temperature, which prevents misting.

Park your car in a garage or covered area

If possible, parking indoors or under cover can help reduce the temperature difference between the inside of your car and the outside environment, minimising the fogging effect.

Check your car's air vents

Ensure that your car's air vents are open and are set to bring in outside air. Even without the AC or heater, the movement of outside air into the car can help reduce misting.

Before even thinking about demisting a windscreen, however, you should focus on the most important part of hitting the road: making sure you’re insured. With Cuvva, you can borrow any car, with policies from 1 hour to 28 days. It only takes a few minutes to get a quote.

Updated on 1st November 2023