--- title: "How to stop condensation inside your car | Home Comfort Lab" description: "Why car windows mist up and stay wet, and the quick fixes and longer-term ones that stop it." url: https://homecomfortlab.co.uk/damp/condensation-inside-car/ --- # How to stop condensation inside your car Why car windows mist up and stay wet, and the quick fixes and longer-term ones that stop it. By [Pete Harvey](https://homecomfortlab.co.uk/about/), editor. Updated 14 October 2026. ![A misted car windscreen with droplets, dashboard vents blowing air up the glass and a cloth on the dash.](https://homecomfortlab.co.uk/images/scenes/condensation-inside-car.svg) > **The short answer** > > Car windows mist up when warm, moist air from your breath and wet clothes meets glass chilled by the cold outside. To clear them quickly, turn the blower to the windscreen, switch the air conditioning on and use fresh air instead of recirculate. If the glass is wet every morning, there is water inside the car that needs to be found and dried out. ## Why the windows mist up It is the same process as [wet windows at home](https://homecomfortlab.co.uk/damp/why-are-my-windows-wet-every-morning/), in a much smaller space. Every breath adds water vapour to the air in the car, and so do wet coats, umbrellas and shoes. When that air touches glass that is colder than its dew point, the water comes out as a fine mist. A car fills up with moisture quickly because there is so little air inside it. With two or three people in the car on a cold, wet day, the windscreen can mist over within a few minutes of setting off. ## How to clear it quickly 1. **Start the engine and set the blower to the windscreen**, on full fan. 2. **Switch the air conditioning on**, even in winter, with the temperature turned up. The air con dries the air before the heater warms it, so it clears the glass much faster than heat alone. 3. **Turn recirculation off** so the car draws in fresh air from outside. Recirculating keeps the same damp air going round. 4. **Switch on the heated rear window** and heated mirrors, if you have them. 5. **Open a window a little** for the first minute or two if it is still slow to clear, to let the damp air out. 6. **Wait until every window is clear before you drive.** The Highway Code says to make sure the windows are demisted thoroughly before you set off, so don't drive off peering through a small clear patch. Avoid wiping the glass with your hand or a sleeve. It leaves greasy smears that mist up again faster and scatter light from oncoming headlights. Keep a clean microfibre cloth in the glovebox for emergencies. > **Stay with the car** > > The Highway Code for England, Scotland and Wales says you must not leave a parked vehicle unattended with the engine running, or leave the engine running unnecessarily while stationary on a public road. Stay in the car while it demists. ## Why it keeps coming back If the windows are streaming every morning, even when nobody has been in the car overnight, the moisture is coming from inside the car itself. Common causes: - **Wet floor mats**, from rain and snow on your shoes, which slowly dry out into the cabin overnight. - **Wet carpet under the mats**, which can stay damp for weeks once it soaks through. - **A leak** from a worn door or boot seal, a blocked sunroof drain, or blocked drains under the scuttle panel at the base of the windscreen. - **A clogged cabin (pollen) filter**, which cuts the airflow through the vents and slows demisting. - **Dirty glass** on the inside. Condensation forms on the film of grime more easily than on clean glass. ## How to stop it for good 1. **Take the mats out and dry them indoors** after a wet day, and feel the carpet underneath. If it is damp, leave the car somewhere dry with the windows open a little, or dry the carpet with an old towel pressed down hard. 2. **Clean the inside of the glass** with a glass cleaner and a microfibre cloth, then buff it dry with a second cloth. 3. **Don't leave wet things in the car** overnight: coats, umbrellas, gym kit or dog towels. 4. **Run the air con for a few minutes once a week** in winter. It keeps the system working and dries the air in the cabin. 5. **Check when the cabin filter was last changed**, in your service book, and have it replaced if it is overdue. 6. **Use a reusable moisture absorber**, such as a silica gel bag left on the dashboard or under a seat. It soaks up some of the moisture overnight and can be dried out again at home, following its instructions. It helps with everyday damp but can't keep up with a leak. > **Worth knowing** > > To find a leak, press a dry paper towel into the carpet in each footwell and the boot after rain. The corner that comes up wet points you towards the seal or drain at fault. ## When to get it looked at If the carpet is soaked, water collects in a footwell or the boot, or the car smells musty, there is a leak that drying alone won't fix. A garage can check the door and boot seals, the sunroof and scuttle drains, and the heater system. Leaving it risks mould in the carpets and seats, and water getting into wiring that runs under the carpet. If your windows at home are wet every morning too, see [why it happens and how to stop it](https://homecomfortlab.co.uk/damp/why-are-my-windows-wet-every-morning/). ## Sources - [The Highway Code, rule 229: before you set off in adverse weather (gov.uk)](https://www.gov.uk/guidance/the-highway-code/driving-in-adverse-weather-conditions-226-to-237) - [The Highway Code, rule 123: the driver and the environment (gov.uk)](https://www.gov.uk/guidance/the-highway-code/general-rules-techniques-and-advice-for-all-drivers-and-riders-103-to-158) Checked 14 October 2026. ## Read next - [Why are my windows wet every morning?](https://homecomfortlab.co.uk/damp/why-are-my-windows-wet-every-morning/) (How to) Morning condensation means warm, moist air is meeting cold glass. What causes it and how to stop it. - [Humidity and mould risk checker](https://homecomfortlab.co.uk/tools/humidity-mould-risk-checker/) (Calculator) Enter your room temperature and humidity to see your mould risk and the temperature at which walls and windows start to get wet. - [Dehumidifier running costs: popular models compared](https://homecomfortlab.co.uk/damp/dehumidifier-running-costs/) (Running costs) What each popular dehumidifier costs per hour and per month at the current price cap, from its rated power. - [Dehumidifier noise and capacity table](https://homecomfortlab.co.uk/damp/dehumidifier-noise-and-capacity/) (Running costs) Every model we list, with its extraction rate, tank size, noise level and power, in one sortable table. --- As an Amazon Associate I earn from qualifying purchases. Links to shops are marked, and earning from them never decides what we recommend. [How this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). Running costs use 26.32p per kWh for electricity and 7.97p per kWh for gas, the [Ofgem price cap, Direct Debit average for England, Scotland and Wales](https://ofgem.gov.uk/news/changes-energy-price-cap-between-1-october-and-31-december-2026) for 1 October to 31 December 2026.