How to Stop Car Windows from Fogging Up

13 March 2025

Fogged up car windows aren’t just a nuisance; they can be a serious safety risk. Even a few extra minutes to clear the steam can make all the difference when your vision is compromised. Knowing how to quickly clear and prevent fogging can keep you safe on the road. This blog explains why fog happens and shares practical hacks to keep your windows crystal clear.

Why do car windows fog up?

Fog forms when warm, moist air inside your vehicle meets cold glass. This temperature difference causes the moisture to condense into tiny water droplets on the windows.

• Temperature Contrast: A warm car interior in cold weather or a chilled interior on a humid day can cause fogging.
• Ventilation Issues: It's important to know how your air con works. In general, air-conditioning systems can help clear condensation by removing moisture from the air. However, if your air conditioning system draws in cold or moist outside air, it might struggle to control humidity effectively, which could worsen condensation problems indoors.
• Excess Humidity: Having damp clothes or even a wet umbrella adds moisture to the air, making condensation more likely to happen.

How to clear the fog from car windows

• Gradually increase the heat setting - Start with a low setting, then slowly increase it to avoid saturating the air with additional moisture.
• Put on your air conditioning - Air conditioning helps reduce indoor humidity and clears condensation quickly by removing moisture from the air. This is especially useful in warmer, more humid environments.
• Open the windows - Briefly crack open the windows to reduce humidity and balance the temperature inside the cabin with the temperature outside.
• Use a microfibre cloth - Wipe down the windows with a clean, soft cloth to remove existing fog without leaving streaks.
• Switch to defog mode - Engage your car’s defrost setting to direct warm, dry air onto the windows.

How to prevent your car windows from fogging up

• Park in a garage or sheltered spot. A temperature-stable environment can significantly reduce condensation.
• Remove damp items from your vehicle. Don’t leave wet coats, umbrellas, or towels in your car, which will add moisture to the atmosphere.
• Keep your windows clean: Dirt and grime attract moisture, so clean windows regularly to help prevent fogging.
• Use moisture-absorbing products: Consider using a small dehumidifier or placing a moisture-absorbing pouch inside your car.
• Apply an anti-fog treatment to your windows. A commercial anti-fog solution can create a barrier against condensation.

Demisting your windscreen quickly can save you crucial time, especially on those dark, early winter mornings.

Is it illegal to drive with fogged-up windows in the UK?

Yes it is illegal! According to the UK Highway Code and Road Vehicles (Construction & Use) Regulations, drivers must have full visibility through the front windscreen and windows. Driving with misted or fogged up glass can result in a police warning, fines, or penalty points if it is considered to compromise your control of the vehicle. Ensuring your windscreen is fully clear before moving off is a legal requirement, not just a safety recommendation.

What causes persistent fogging even after demisting?

If your windows continue to fog despite normal demisting methods, it may indicate:

1. A blocked pollen cabin filter, which can reduce air flow and increase moisture buildup.
2. A faulty air-conditioning system, which may no longer remove moisture from the air effectively.
3. A leak allowing water into the vehicle, such as through door seals, boot seals, or the windscreen.

In these cases, having your vehicle checked by our qualified technicians at Setyres, can help identify the root cause/resolve any issues.

Should I use recirculation mode when windows fog up?

No, don’t use air recirculation mode. Recirculation mode keeps moist air trapped inside the vehicle, which can make fogging worse. For the quickest results, switch recirculation off and allow fresh, dry air from outside to enter the car.

Visit Setyres for Expert Advice

If you’ve tried clearing and preventing fog without success, or if you need further advice on other vehicle safety issues, visit your local branch. We provide professional guidance to ensure your overall vehicle safety.

Our experienced team is ready to assist with practical tips and professional advice, ensuring that your car is safe and reliable for every journey. For more motoring advice, visit our website at www.setyres.com or go to your local setyres garage today!