How to Prevent Condensation Indoors

What causes condensation indoors?

Condensation forms when warm, moisture-laden air meets a cold surface, such as a window pane or an uninsulated exterior wall, and cools to its dew point. The water vapour in the air then turns into liquid droplets. The main factors are high indoor humidity, poor ventilation, and cold surfaces. Common moisture sources include cooking, showering, drying laundry indoors, breathing, and even houseplants. To prevent condensation indoors, you need to either reduce moisture production, remove moist air through ventilation, or keep surfaces warm enough to stay above the dew point.

Indoor humidity is best kept between 40% and 60% relative humidity (RH). In cold weather, you may need to aim for the lower end of this range to avoid condensation on windows. A simple hygrometer can help you monitor levels.

How to prevent condensation in room by room

Different rooms have different moisture loads. Adapt your approach to each space.

Bathrooms

Bathrooms produce large amounts of steam from showers and baths. The most effective measure is to run an extractor fan during and for at least 15–20 minutes after bathing. If you don't have a fan, open a window slightly during and after showering. Wipe down wet surfaces such as tiles and the bathtub to reduce evaporation into the room. Keep the bathroom door closed to prevent moist air spreading to cooler parts of the house.

Kitchens

Cooking, especially boiling and frying, releases a lot of moisture. Always use a cooker hood that vents to the outside, or open a window. Put lids on pots to reduce steam. Avoid leaving kettles boiling longer than necessary. If you have a dishwasher, only run it when full and open the door only after it has cooled, or let steam escape via an open window.

Bedrooms and living rooms

These rooms usually have less moisture, but condensation can still occur on cold windows in the morning. Air the room by opening windows for 5–10 minutes each day, even in winter. This exchanges humid air for drier outside air. Avoid drying laundry in living spaces; if you must, use a clothes airer in a well-ventilated room with a dehumidifier running. Keep furniture a few inches away from external walls to allow air circulation.

Whole house strategies

Consistent low-level background ventilation helps. Trickle vents on windows or air bricks allow a controlled flow of fresh air. Heat your home evenly; cold rooms are more prone to condensation because surfaces stay below dew point. If you have a loft or basement, ensure they are properly insulated and ventilated.

Step-by-step: preventing condensation indoors

1. Measure humidity: Use a hygrometer to know your starting point. If RH is consistently above 60%, take action.
2. Identify moisture sources: Note when and where condensation appears. Check windows, corners, behind furniture, and in bathrooms/kitchen.
3. Increase ventilation: Open windows briefly each day, use extractor fans in wet rooms, and consider trickle vents.
4. Reduce moisture production: Cover pots, dry clothes outside when possible, and avoid paraffin or unflued gas heaters which produce water vapour.
5. Improve heating and insulation: Keep a low background heat in all rooms, insulate cold walls and lofts, and consider double glazing or secondary glazing for windows.
6. Use a dehumidifier if needed: In persistently damp homes or during cold spells when ventilation is limited, a dehumidifier can effectively remove moisture from the air.

Comparing solutions: ventilation, heating, dehumidifiers

Preventing condensation inside windows: special tips

Window condensation is the most common and visible sign. To reduce it:

• Use double or triple glazing: The inner pane stays warmer, so condensation is less likely.
• Install secondary glazing film: An inexpensive temporary measure for single-glazed windows.
• Wipe condensation away: Use a squeegee or cloth each morning to prevent mould growth and water damage.
• Keep curtains open during the day: This allows warm air to reach the glass. At night, close curtains to reduce heat loss, but ensure there is some airflow.
• Check window seals: Damaged seals can let cold air in and cause localised cold spots.

Adapting to your budget and schedule

Low budget: Focus on free actions: open windows regularly, wipe down wet surfaces, cover pots, and use existing extractor fans. Use a simple hygrometer to monitor. Make your own draught excluders for doors, but never block permanent ventilation points.

Medium budget: Invest in a portable dehumidifier, install basic extractor fans, and add inexpensive secondary glazing film. Use timer plugs for fans or heaters to automate ventilation.

Higher budget: Upgrade to double-glazed windows, add cavity wall or solid wall insulation, install a whole-house mechanical ventilation system with heat recovery (MVHR), or a positive input ventilation (PIV) unit. These provide long-term, low-effort condensation control.

Busy schedule: Automate where possible: set extractor fans to run on timers, use a dehumidifier with a humidistat that switches on when RH is high, and set heating to maintain a minimum temperature.

Weather considerations: In cold weather, you need more heating and less ventilation time but still short bursts. In mild, dry weather, open windows more freely. In humid climates, outdoor air may be too humid, so a dehumidifier becomes more important.

Small details that make a big difference

• Move furniture away from walls: Leave a 5–10 cm gap to allow air circulation behind wardrobes and sofas.
• Use lids on aquariums and cover fish tanks: They evaporate water constantly.
• Vent tumble dryers outside: If not possible, use a condenser dryer and empty the water reservoir, or ensure the room is well ventilated.
• Dry clothes outside whenever possible: If drying indoors, use a room you can close off and ventilate or run a dehumidifier.
• Keep extractor fans clean: Dust and grease reduce their efficiency.
• Address leaks and rising damp: Repair any plumbing leaks or rainwater ingress promptly.

Making it part of your routine without it becoming a chore

Condensation prevention works best as small, consistent habits. Open windows while you make your bed or brush your teeth. Put lids on pots as you cook. Wipe windowsills as part of your morning tidy. If you use a dehumidifier, empty it at a set time each day, like when you take out the rubbish. By integrating these actions into existing routines, you keep your home dry and healthy without extra effort.