To reduce condensation and mould, produce less moisture indoors, get the moist air out quickly with extractor fans and open windows, and keep rooms reasonably and evenly warm. If damp keeps coming back, look for a cause such as a leak, rising damp or rain getting in, because habits alone cannot fix a problem with the building.
Most of us see water on the windows on a cold morning, and that is not always a problem if it clears quickly. Trouble starts when moisture builds up day after day, soaking into walls, window frames and furnishings until black mould appears. This guide pulls together advice from the Energy Saving Trust, GOV.UK and the NHS so you can tackle the problem in the right order.
What causes condensation and mould?
Air always holds some water vapour. When warm, moist air meets a cold surface, such as a window, an outside wall or a cold corner, it cools and the water turns back into droplets. That is condensation. Where surfaces stay wet, mould can grow.
The Energy Saving Trust says a typical household produces up to 100 litres of moisture a week through cooking, boiling kettles, showering and even breathing. If that moisture is not removed through ventilation, it settles on surfaces or stays in the air.
Condensation is not the only kind of damp. Government guidance on damp and mould describes several types:
- Condensation damp: the most common type, from everyday moisture meeting cold surfaces.
- Penetrating damp: water coming in from outside through defects in walls, roofs, windows or floors.
- Rising damp: moisture from the ground, usually in older properties, often linked to a faulty damp-proof course.
- Traumatic damp: leaks from pipes and overflows, or flood damage.
The Energy Saving Trust notes that if you have no leaks or rising damp, the problem is almost certainly condensation.
Is damp and mould bad for your health?
It can be. GOV.UK guidance explains that damp and mould mainly affect the airways and lungs, and can also cause eye irritation, skin problems and harm to mental health. The NHS lists mould among the allergens that can trigger asthma symptoms and allergic rhinitis.
The government guidance says some people are at greater risk, including:
- people with existing health conditions such as asthma, COPD or heart disease
- people with weakened immune systems
- pregnant women and new mothers
- children and young people, and older people
- people with mental health conditions
- people who are bedbound, housebound or have limited mobility
If you or someone in your home has symptoms you think are linked to damp or mould, speak to your GP or a pharmacist.
What can you do every day to reduce condensation?
Small habits make a real difference because they tackle moisture at the source. This checklist brings together the Energy Saving Trust's and GOV.UK's practical advice.
| Where | What to do | Why it helps |
|---|---|---|
| Kitchen | Cover pans with lids; use the cooker extractor while cooking and leave it running for at least 15 minutes afterwards | Less steam escapes into the room and more is removed at source |
| Bathroom | Run the extractor fan for at least 15 minutes after a bath or shower; wipe down walls and the screen with a squeegee or towel | Removes moisture before it soaks into surfaces |
| No extractor? | Open a window while cooking or bathing and leave it open for at least 15 minutes afterwards | Lets moist air escape instead of spreading through the home |
| Kitchen and bathroom doors | Keep them shut while cooking or bathing | Stops steam drifting into colder rooms where it condenses |
| Laundry | Dry clothes outdoors when the weather allows; consider a dehumidifier if you must dry indoors | Wet washing releases a lot of moisture into the room |
| Whole home | Open windows several times a day for at least five minutes, and keep trickle vents open and clear | Swaps moist indoor air for drier outdoor air |
| Windows | Wipe off condensation in the morning | Prevents water soaking into frames and sills |
How do ventilation and heating affect condensation?
Ventilation and warmth work together. Ventilation removes moist air, and warmer surfaces are less likely to attract condensation in the first place.
The Energy Saving Trust recommends:
- leaving internal doors open where possible at other times, so air can circulate
- keeping a gap of at least 10 mm between the floor covering and the bottom of internal doors, so air can move between rooms when doors are closed
- leaving gaps between furniture and outside walls
- not leaving the heating off or very low in some rooms during colder months, as these rooms are prone to damp
- getting insulation defects fixed, such as gaps at the top of cavity wall insulation, because cold spots attract condensation
Be careful with draught-proofing. The Energy Saving Trust advises against fitting new draught-proofing in a room that lacks ventilation or already has a condensation problem. If you are having insulation, draught-proofing or new windows fitted, ask the installer how they will keep the home properly ventilated.
How do you remove mould safely?
The Energy Saving Trust advises removing mould as soon as possible, and suggests these steps:
- Use an antifungal cleaning product or one designed to kill mould, and follow the label.
- Wear gloves and a mask, plus any other protective equipment the manufacturer recommends. Never touch mould with bare hands.
- Only wipe mould when it is wet, not dry, to avoid spreading spores into the air.
- Use a disposable cloth and throw it away afterwards.
- Ventilate the room with an extractor fan or open window, and keep doors to other rooms closed.
Cleaning only removes the symptom. If the mould returns, the moisture is still there, and you need to find out why.
When is damp a problem for a landlord or a professional?
If you see a tidemark at the bottom of a wall, a damp patch that gets worse when it rains, or damage from a leak, the cause is probably not condensation. The Energy Saving Trust recommends getting professional advice and comparing quotes from three TrustMark-registered firms.
If you rent, report damp and mould to your landlord in writing. Government guidance for landlords is clear that it is "totally unreasonable" to blame damp and mould on tenants' lifestyle choices, and that landlords are responsible for tackling the underlying causes. It also states that tenants cannot be expected to reduce moisture if their home does not let them do so, for example because of poor ventilation or heating. If problems are not fixed, organisations such as Citizens Advice, Shelter and your local council can help.
Frequently asked questions
Is condensation on windows every morning normal?
A little condensation on a cold morning is common and is not necessarily a problem if it clears quickly. If it is heavy every day, pools on sills, or comes with black mould or musty smells, you need more ventilation, less moisture indoors, or both.
Does a dehumidifier help with condensation?
It can. The Energy Saving Trust suggests a dehumidifier for dealing with excess moisture or helping to dry washing indoors. It works best alongside ventilation and good habits, not instead of them.
Should I keep the heating on all the time to stop damp?
No. The Energy Saving Trust says leaving the heating on constantly just to avoid damp is not a sensible solution because of the energy and cost. Aim for rooms that are not left cold for long periods, with efficient heating and good controls.
Will insulation cause damp?
Insulation that suits the home and is properly installed should not cause damp, and a warmer home is less prone to condensation. However, insulation can expose an existing problem such as a leak, so fix the root cause first and make sure ventilation is considered.
Sources
- Energy Saving Trust: How to get rid of damp
- GOV.UK: Understanding and addressing the health risks of damp and mould in the home
- NHS: Allergic rhinitis
- NHS: Asthma causes and triggers
General information only. It is not medical, legal or building advice. If you are worried about your health, speak to your GP. For persistent damp, get advice from a qualified professional, and if you rent, contact your landlord first.