Fogged-up car windows – what causes them and how to get rid of them

It's raining, you get into the car, start the engine, and within seconds all the windows are covered in a thick layer of condensation that the ventilation system can't handle. Sound familiar? If the problem of fogging windows keeps coming back, it's time to understand the possible causes and deal with it once and for all – and in true detailing style!

First, you need to know your enemy well before you can fight it effectively. Why do car windows fog up on the inside in the first place, and where does the moisture inside the car come from?

Why do windows fog up?

Condensation on car windows has several sources. Part of it comes from the weather and the natural humidity of the surrounding air, which partially seeps into the interior. This problem is particularly noticeable during autumn and winter.

A significant amount of moisture is brought in by us as passengers, however. We get in wearing wet clothes, we track in moisture on our shoes, and opening the door on a rainy day exposes the interior to dampness. On top of that, we breathe out warm, moist air. All of this causes water particles to settle deep into the fabrics of the upholstery, headlining, carpet and floor mats, only to evaporate at the first opportunity and settle on the windows.

If your car's interior is thoroughly saturated with moisture and the ventilation system is inefficient or has a fault, that's the most direct path to a fogging problem. So how do you get rid of fogging windows? Here are our tips!

Cleanliness is the foundation

It may not be obvious to everyone, but dirty windows are far more prone to fogging. A layer of grime on the glass surface attracts moisture particles like a magnet. Make sure your windows are perfectly clean.

If you're looking for a reliable glass cleaner for the inside of your car, Glaco De Cleaner will be right up your street – it's a unique "two-in-one" product in the detailing market. How does it help with condensation?

Spray it onto a clean microfibre cloth and thoroughly clean the windows from the inside. The product's formula contains a water and dirt-repelling agent, similar in effect to Glaco's hydrophobic coatings. The result? Moisture finds it significantly harder to settle on the glass. As a bonus, you can also use De Cleaner just as effectively on the outside of your windows!

Other things worth bearing in mind when windows fog up:

Keep it tidy

The state of your car's interior matters just as much. If you're unnecessarily carrying clothing or other items inside the cabin, bear in mind that they can both accumulate moisture and slow down or obstruct air circulation – making fogging windows more likely.

Floor mats make a difference

If you're fond of velour or fabric floor mats, you should know that in winter they can be a contributing cause of fogging windows. These mats absorb moisture from wet shoes, as well as snow and mud tracked in from outside, only to release all that moisture back into the interior and onto the glass. You have two options: you can keep your fabric mats but treat them with a water-repellent product and vacuum them regularly, or swap them for rubber alternatives and regularly remove any water from their surface.

Don't neglect servicing

Do you know when the cabin air filter in your car was last replaced? It's a frequently overlooked component that performs a very important function and is worth remembering – at least once a year. It filters the air drawn into the interior through the ventilation system. A dirty or clogged filter won't do its job properly, and will also reduce the amount of air being pushed through. That's the most straightforward route to fogged-up windows.

Check for leaks

It's possible that the fogging is caused by a fault that's allowing water to enter the interior. This could be a damaged seal or a blocked drainage channel – of which there are at least several in any car. Check carefully whether the carpet is damp anywhere or whether water is collecting in any out-of-the-way spot.

In modern cars this can be increasingly difficult to detect, so it's worth asking your mechanic to check for any potential leaks during routine inspections.

Air conditioning isn't just for summer

Do you only use the air conditioning in summer? That's a mistake! As well as cooling, the air conditioning system also dehumidifies the air – making it an invaluable ally in the fight against fogging windows. Regular use will also keep the system itself in better condition.

"Just the way it is": when nothing seems to work

In some cars, the problem of fogging windows can be very difficult to solve. The efficiency of the ventilation system, the level of moisture in the interior and similar factors can all have a decisive influence, making it impossible to resolve the issue fully. But there's still one more option.

If you've worked through every point on the list above and still can't shake the problem, it's time to bring out the big guns: Anti-Fog Spray, a convenient foam that leaves a coating on the glass to block condensation from settling. One simple step is all it takes to banish fogged-up windows for good.

Unlike typical liquid anti-fog products, Anti-Fog Spray settles on the glass as a thick foam that you spread with a soft microfibre cloth. This makes it easy to see which areas have already been treated, and you avoid getting the product on the upholstery.

Summary

If fogged-up windows are the bane of your driving life, focus first and foremost on two things – cleanliness and tidiness inside the car, and the technical condition and efficiency of the ventilation system.

For the cleaning side of things, products such as Glaco De Cleaner, Wash Mist, Fabric Seat Cleaner, Leather Cleaner and the Super Cloth microfibre will all be a great help – our full range of interior products for both fabric and leather interiors. The tidying and servicing is down to you, of course. And remember: when all else fails, there's always Anti-Fog Spray!