Opening bedroom and bathroom windows for 10 to 15 minutes each morning is the most effective way to prevent mould from taking hold in homes during autumn and winter, according to window expert Colin Greenslade, founder of Colin's Slash Windows.
Mould thrives in damp environments, and as temperatures drop in October, humid air can become trapped indoors when windows are kept closed. Daily activities such as showering, cooking, or hanging laundry indoors can cause condensation, where water vapour in the air turns into liquid near cold surfaces. This often results in wet windows and creates conditions that allow mould to spread onto walls or nearby furniture.
Why Short Ventilation Works
Greenslade said: "Opening windows for 10–15 minutes twice a day clears humid air without losing too much heat." Although many people avoid opening windows in autumn due to the cold air entering the home, short periods of ventilation are the most effective way to reduce indoor humidity.
Opening windows for just a few minutes allows humid air to escape and fresh air to enter, reducing condensation and the risk of mould. While the home may feel slightly colder, walls, furniture, and other surfaces retain much of their heat and will not cool significantly during a short ventilation period.
Alternatives and Practical Tips
Other methods to prevent condensation include placing bowls of salt, chalk, or cat litter next to windows, as these materials can absorb moisture from the air. However, these methods only work temporarily for a few hours and are mainly effective in small rooms, making daily window opening quicker and easier.
To prevent mould, open bedroom and bathroom windows for 10 to 15 minutes in the morning, ideally upon waking, as breathing releases water vapour and creates moisture during sleep. If possible, open windows on opposite sides of the home to create a cross-breeze, which helps air flow out quickly and removes humidity. It also helps to open windows after showering or cooking to prevent steam buildup, and to keep rooms reasonably warm to prevent condensation. Wiping windows when they become steamy or wet is also recommended.
