UK households are being warned that opening the window after a shower could be the reason for bathroom mould growth.
According to specialists at Shutter Store, opening the window after a shower, especially when the air outside is cooler than it is indoors, allows the cold outdoor air to mix with the warm, damp air from the bathroom. This causes water vapour to condense quickly on surfaces, creating the perfect breeding ground for mould.
The World Health Organisation (WHO) identifies persistent dampness as the leading factor in mould development. Making the bathroom the ideal environment. It’s estimated that the likelihood of finding mould in a bathroom is 2 to 3 times higher than in bedrooms or living rooms.
After a hot shower, humidity levels in a bathroom can increase by up to 90%, especially in small or poorly ventilated spaces. This moisture clings to tiles, mirrors, ceilings, and windows, and if not properly managed, mould can begin to grow within 24 to 48 hours.
Opening a window after a shower may seem helpful, but it can disrupt the airflow created by extractor fans and introduce cold air that accelerates condensation. This leads to more moisture settling on surfaces, exactly what mould needs to thrive.
Experts recommend the following mould-prevention tips that don’t involve opening the window:
Apply shaving foam on mirrors
By applying a small amount of shaving foam to the mirror’s surface and wiping it clean with a towel or microfiber cloth, a barrier is created between the steam and the glass. This method can keep your mirror steam-free for several weeks.
Underfloor heating
Cold surfaces like ceramic or stone tiles are magnets for condensation. When warm, moist air hits these cold surfaces, it turns into water droplets, creating a moist, damp environment. Keeping the floor temperature above the dew point helps prevent condensation.
Wipe down surfaces after use
After a hot shower, moisture clings to walls, mirrors, windows, and even ceilings. If left to sit, this moisture can feed mould growth. To prevent this, use a towel or squeegee to wipe down tiles, glass, and countertops. Focus on corners and grout lines, where mould tends to settle.
Turn on the extractor fan
Extractor fans are designed to remove moist air from the bathroom and vent it outside. Turn the fan on before your shower starts and leave it running for at least 30 minutes after you finish. It’s also important to clean the fan every few months to remove dust and lint buildup.
Place moisture absorbers
Moisture absorbers like silica gel, calcium chloride crystals, or desiccant containers are passive tools that draw excess humidity from the air. They’re especially useful in smaller bathrooms without windows or with poor ventilation.
Sam Tamlyn, Managing Director at Shutter Store, commented: “Opening the bathroom window after a shower can reduce the effectiveness of your extractor fan and create cross-drafts that spread moisture. Instead, focus on wiping down surfaces and letting your fan do its job. Understanding how ventilation works is key to keeping mould at bay.”
