Mould around windows is almost always caused by excess indoor humidity. When warm air hits the cold glass, moisture forms and settles on the frame where mould can grow.
Step one: reduce condensation
- Open bedroom windows for a few minutes each morning.
- Keep trickle vents open.
- Use a dehumidifier for one to two hours after waking.
Step two: clean existing mould safely
Use a mould spray or a diluted bleach solution. Wipe the frame and silicone, then dry the area thoroughly. Wear gloves and ensure good ventilation.
Step three: prevent mould returning
- Keep rooms between forty and sixty percent humidity.
- Avoid drying laundry in bedrooms.
- Run a dehumidifier in winter to stop condensation forming.
Why mould appears even in new homes
Newer windows are very airtight which traps moisture inside. Even with double glazing, condensation forms when humidity rises above sixty percent.
Once moisture is controlled, mould usually disappears and windows stay clear for the rest of winter.