Hearth & Lawn

How to stop condensation on windows

Last updated: · By the Hearth & Lawn team

About this guide: This is general information, not professional or medical advice. It's based on UK government guidance on damp and mould, NHS inform, and manufacturer information. We haven't tested the products mentioned. If you have a lot of mould, a damp problem that keeps coming back, or health worries, get help from a qualified professional, your landlord or your GP. Prices were checked on 18 October 2026.

On a cold morning, the inside of many UK windows is running with water. That's condensation: warm, moist air inside the home hits cold glass, cools, and can't hold its water any more, so the water forms droplets.

A bit on the glass first thing isn't unusual. But if it happens every day, pools on the sills, or you're seeing black spots on frames, seals, walls or behind furniture, the moisture is staying in your home too long. Over time that leads to mould, which UK government guidance says mainly affects the airways and lungs and can also affect the eyes and skin.

Is it condensation, or something else?

The UK government's damp and mould guidance describes four main kinds of damp:

Type What it looks like Typical cause
Condensation damp (most common) Water on windows; black spots on cold corners, window reveals, behind wardrobes and sofas Moisture from cooking, showers, drying washing and breathing, with too little ventilation or heat
Penetrating damp Damp patches that get worse after rain, often on one wall Rain getting in through roofs, walls, gutters or window seals
Rising damp A tide mark low on ground-floor walls Failed damp-proof course. Often misdiagnosed; it needs a proper survey
Traumatic damp Damp near pipes, under baths or below a neighbour's flat Leaks, burst pipes, overflows

Misting between the two panes of a double-glazed unit isn't condensation you can fix. It means the seal has failed and the unit needs replacing.

Only the first kind is mostly about everyday moisture. The others need repairs. If you rent, report them to your landlord.

How to stop condensation: the daily habits that work

These are the measures recommended in UK government guidance on damp and mould, in the order we'd tackle them.

  1. Wipe the windows every morning. Use a cloth, a squeegee or a window vac, and wring the water into the sink rather than letting it soak back into the frames and sills.
  2. Use your extractor fans. Run the bathroom fan during and for 15–20 minutes after a shower, and the cooker hood while cooking. If a fan doesn't work or barely moves a tissue, get it repaired.
  3. Keep doors shut while cooking, showering or drying washing, so the moisture doesn't spread to colder rooms.
  4. Put lids on pans.
  5. Open trickle vents (the slots at the top of many modern windows) and keep them clear. If you have none, opening a window slightly for a few minutes each morning swaps the moist air out quickly.
  6. Dry washing outside when you can. Indoors, dry it in one room with the door shut and a window ajar, an extractor running or a dehumidifier on. A typical wash load puts about 2 litres of water into the air. See the cheapest way to dry clothes indoors.
  7. Leave a gap of a few centimetres between furniture and outside walls, so air can circulate.
  8. Keep the home steadily warm if you can. Cold walls and windows attract condensation. Heating rooms to a low, steady temperature is usually better than letting them go very cold and then blasting them. We know that isn't affordable for everyone. If you're struggling, see our guide to the cheapest way to heat one room and the support listed at the end of this page.

Measure it: a cheap hygrometer

A digital thermo-hygrometer shows the humidity in a room. Around 40–60% is the range commonly recommended. If a room sits above about 60–70% for long periods, especially overnight, condensation and mould are likely.

  • ThermoPro TP50 thermo-hygrometer. About £8.49 on Amazon UK (Amazon listing seen via search on 18 October 2026; check before buying). Small, battery-powered, shows humidity and records the highs and lows. It's a basic consumer gadget, so treat its reading as a guide rather than a precise measurement.

When a dehumidifier helps

If you've done the basics and the windows still stream, or you have to dry washing indoors, a dehumidifier is the most direct fix. A compressor model costs about 4–6p an hour to run at 26.32p/kWh; check your own figures with our running-cost calculator. See our best dehumidifiers, including picks for bedrooms and cold rooms.

A window vac makes the morning wipe much quicker:

  • Kärcher WV 6 Plus window vac. From about £79.99 across UK retailers on a price comparison site (idealo, 18 October 2026). A battery squeegee that sucks the water into a small tank.

Longer-term fixes

  • Secondary glazing or new double glazing on single-glazed windows keeps the inner pane warmer.
  • Insulation. UK government guidance notes that well-insulated homes are less prone to condensation, as long as ventilation is adequate. Loft insulation of at least 270mm is a particularly effective measure.
  • Humidity-controlled extractor fans, which switch on automatically.

Window work, new ventilation and heating changes are building work, so use a competent, registered installer. Grants may be available; GOV.UK's "Find energy grants for your home" service is a good starting point.

How to get rid of black mould safely

Small patches you can clean yourself

UK government guidance says it's reasonable for most people to remove condensation and very small amounts of mould themselves. NHS inform says the same for small amounts. For larger areas, get a professional. Follow these precautions, taken from the government guidance:

  1. Protect yourself. Wear gloves, a mask and goggles.
  2. Shut the door to the room so spores don't spread, and open the window.
  3. Use a mould and mildew cleaner, following the label. The government guidance recommends these in preference to bleach for health and safety reasons. If you do use a bleach product, NHS inform advises always opening a window.
  4. Let the area dry completely afterwards.
  5. Bag and bin the cloth or sponge, or wash it straight away, and wash your clothes afterwards.
  6. Throw away badly affected soft items such as carpet, curtains or soft furnishings if they can't be cleaned. Government guidance warns it may be impossible to remove mould from absorbent materials completely.

Our own advice on top: never mix cleaning products, especially bleach with other cleaners, and don't dry-brush mould, which can spread spores.

Some people should not clean mould themselves. NHS inform says babies, children, older people, people with asthma, allergies or other breathing problems, people with skin conditions such as eczema, and people with weakened immune systems are more sensitive to damp and mould, and should stay away from it as much as possible. Ask someone else to do it, or get professional help.

If you have symptoms such as a persistent cough, wheezing or worsening asthma, speak to your GP or pharmacist.

Cleaning mould won't fix the cause

Mould comes back unless the moisture problem is solved. Government guidance is clear that simply removing surface mould will not stop it reappearing. If it returns within weeks despite ventilating and wiping, or there's a musty smell without visible mould, there may be a hidden leak, penetrating damp or a building defect. Get it looked at.

If you rent: your landlord's responsibilities

In England, landlords have legal duties to deal with serious damp and mould. These come from several laws, including the Housing Act 2004 and the Homes (Fitness for Human Habitation) Act 2018. UK government guidance says it is "totally unreasonable" to blame damp and mould on tenants' "lifestyle choices", and that landlords should tackle the underlying causes.

  • Report it in writing, with photos and dates, and keep copies.
  • Social housing (council or housing association) in England: under Awaab's Law, in force since 27 October 2025, landlords must investigate significant damp and mould hazards within 10 working days, make the home safe within 5 working days of the investigation, and send you a written summary within 3 working days. Emergency hazards must be made safe within 24 hours. If they can't make your home safe in time, they must offer you somewhere else suitable to stay. If you're not happy, use their complaints process, then the Housing Ombudsman.
  • Private renters in England: Awaab's Law doesn't apply yet. The government is consulting on how and when to extend it to private renting; the consultation closes on 18 December 2026, and no start date had been set when we checked. Your landlord still has legal duties, and your council's environmental health or private housing team can inspect and take action.
  • Scotland, Wales and Northern Ireland have different rules. Shelter Scotland, Shelter Cymru and Housing Advice NI can help.

Shelter and Citizens Advice give free advice to renters everywhere in the UK.

Help with heating costs

Cold homes are more prone to condensation. GOV.UK's guidance lists support including the Warm Home Discount, Cold Weather Payments, Winter Fuel Payment, and advice from Citizens Advice and National Energy Action. Your energy supplier may also have hardship funds.

See also: best mould removers and cheap draught-proofing fixes, including what you must never block.

FAQs

Why do my windows have condensation on the inside every morning? Overnight, moisture from breathing, plus anything left over from cooking, showers and washing, builds up in a closed room. The glass is the coldest surface, so water condenses there first. Open the trickle vents, keep bedroom doors shut while drying washing elsewhere, and wipe the windows each morning.

Is condensation on windows bad? A little on cold mornings is common. Daily streaming, pooling on sills and black spots on seals or walls are signs the home is too humid, which can lead to mould.

Does opening a window stop condensation? It helps. A few minutes with a window wide open, or trickle vents left open, swaps moist air for drier outside air. In winter, short bursts lose less heat than leaving a window open all day.

What gets rid of black mould permanently? Only fixing the cause: less moisture, more ventilation, warmer surfaces, or repairing leaks and defects. Cleaning removes what you can see; it doesn't stop it returning.

Should I use bleach on black mould? UK government guidance recommends mould and mildew products in preference to bleach. Whatever you use, follow the label, wear gloves, a mask and goggles, open a window, and never mix products.

Will a dehumidifier stop condensation? It usually reduces it a lot, especially in bedrooms and rooms where washing is dried. It's a fix for condensation, not for leaks or rising damp.

Does a heated airer cause condensation? The airer itself doesn't, but the water from the washing has to go somewhere. Ventilate or use a dehumidifier. See our heated airer guide.

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