Does Drying Clothes Indoors Cause Mould?

How Much Moisture Do Wet Clothes Release?

A typical load of wet laundry adds several litres of water vapour to indoor air.

When wet clothes are hung out to dry indoors, the water evaporates into the surrounding air. A single load washed in a standard washing machine can release approximately 4 to 5 litres of moisture, depending on the fabric type and spin speed [S1].

This is a significant amount of water vapour for an enclosed room. In an average UK living room, this can push relative humidity from a comfortable 50% to well above 70% if there is no ventilation or heating [S1].

Higher spin speeds extract more water in the machine, reducing the amount that needs to evaporate indoors. Using the highest spin cycle your clothes can tolerate is one simple way to reduce indoor moisture.

• One load of washing can add 4 to 5 litres of water vapour to the air
• This is equivalent to boiling several kettles of water continuously
• Higher spin speeds reduce the moisture content of clothes before drying
• Synthetic fabrics dry faster and release less moisture than heavy cotton or towels

When Does Indoor Drying Cause Mould?

Mould risk is highest in closed, unventilated, unheated rooms.

Indoor clothes drying becomes a mould problem when the moisture cannot disperse or escape. This is most likely in a closed room with no ventilation and no heating, such as a spare bedroom or a poorly ventilated utility room [S1].

Mould spores are naturally present in most homes and begin to colonise surfaces when relative humidity remains above 60% for extended periods. Wet clothes left in a closed room can sustain this level of humidity for hours or even days [S1].

The risk is greater in winter when windows are less likely to be opened and external temperatures keep walls and windows cold, making condensation more likely.

• Closed room with no windows or extractor fan
• No heating running while clothes dry
• Clothes left for extended periods without airflow
• Winter conditions with cold walls and closed windows
• Already high background humidity from other sources

How to Dry Clothes Indoors Without Causing Mould

Ventilation, heating, and dehumidifiers are the most effective measures.

The most effective way to prevent mould when drying clothes indoors is to ensure that the moisture has somewhere to go. Opening a window, even a small amount, allows humid air to escape and drier outside air to enter [S2].

Running an extractor fan in the room while clothes are drying, or placing the airer in a room with a trickle vent or open window, helps move moist air out of the home [S2].

A dehumidifier is particularly effective because it actively removes moisture from the air, keeping humidity below the 60% threshold even in a closed room. Running a dehumidifier alongside a heated airer is one of the most efficient indoor drying methods [S2].

• Open a window, even a crack, to allow moist air to escape
• Use an extractor fan during and after drying
• Run a dehumidifier in the drying room
• Heat the room to help moisture evaporate and disperse
• Avoid drying clothes in bedrooms or rooms with poor ventilation

Best Rooms for Indoor Drying

Choose a room with good ventilation and the ability to heat and close the door.

The best room for drying clothes indoors is one where you can close the door to contain the moisture, while still providing ventilation. A kitchen or utility room with an extractor fan and a window is ideal [S2].

Avoid drying clothes in bedrooms, particularly children's rooms, as mould spores can affect air quality and trigger respiratory issues. If you must dry clothes in a bedroom, ensure there is an open window and use a dehumidifier [S1].

If you have a bathroom with an extractor fan and a window, it can work well for drying, but be aware that steam from showers can add to the moisture load.

• Kitchen or utility room with extractor fan and window
• Bathroom with extractor fan and window (be aware of shower steam)
• Avoid bedrooms, especially children's rooms
• Choose a room where you can close the door to contain moisture

Alternatives to Indoor Drying

When weather permits, outdoor drying is always the cheapest and most effective option.

Drying clothes outdoors on a washing line or airer costs nothing and allows moisture to disperse naturally. Even on cool days, wind and airflow make outdoor drying effective [S1].

If outdoor drying is not possible, a tumble dryer is an alternative, but it generates heat and moisture that must be vented outside. A condenser or heat pump dryer does not require external venting but still adds heat to the room [S1].

For frequent indoor drying, investing in a dedicated heated airer and dehumidifier combination provides the best balance of cost and moisture control.

• Outdoor drying: free, effective, and zero indoor moisture
• Vented tumble dryer: requires external vent, effective but energy-intensive
• Heat pump dryer: no external vent needed, lower energy use, moderate cost
• Heated airer + dehumidifier: good balance of cost and moisture control

Frequently asked questions

Bottom line

Drying clothes indoors does release significant moisture into your home, and without adequate ventilation and heating, this can lead to condensation and mould. The risk can be managed by opening windows, using extractor fans, running a dehumidifier, and heating the room. Outdoor drying remains the cheapest and most effective option when weather permits.