Black mould on windows: Causes, removal, and prevention

Black mould on windows is a common issue that many homeowners face, particularly in damp and poorly ventilated spaces.

If left untreated, it can not only damage your window sills and window frames but also lead to mould growth in other parts of your home. In this guide, we’ll explore the causes of black mould around windows, how to remove it effectively, and the best strategies to prevent it from returning. 

Whether you’re dealing with mould on window sills or trying to prevent black mould from forming, this article will equip you with practical solutions.

What causes black mould on windows?

Black mould around windows is often caused by excessive moisture, which can be attributed to condensation on windows, poor ventilation, and leaks from windows.

Mould tends to grow when warm indoor air comes into contact with cold glass surfaces, creating the perfect conditions for spores to develop. Black mould often develops due to common issues such as:

• Condensation: It occurs when humid indoor air cools down upon contact with the cold window surface, forming moisture that provides an ideal breeding ground for mould spores. Persistent condensation on windows, especially in winter months, can rapidly escalate the problem.
• Poor ventilation: Can lead to trapped moisture inside your home, creating a damp atmosphere where mould can easily grow. Areas such as bathrooms and kitchens are particularly prone to mould due to high humidity levels, and insufficient ventilation can trap moisture inside, further encouraging mould growth.
• Leaks: Gaps in the window frame and sealant can introduce moisture. Cracked or worn-out sealant allows rainwater and damp air to seep in, which, if left unaddressed, can exacerbate black mould formation. Checking and maintaining window sealant regularly can help keep moisture from seeping in and causing mould.

How to spot mould on your windows

If you suspect black mould from window condensation, inspect the following areas:

• Window sills and corners: These areas are most susceptible to mould growth due to the accumulation of condensation and limited airflow. Regularly check for dark patches and musty odours.
• Wooden window frame: Wooden materials can retain moisture and develop black mould, especially if the paint or finish is deteriorating. Inspect for discolouration and softness, which may indicate mould presence.
• Sealant: Mould around the window seal is another sign of an underlying issue. Cracks and gaps in the sealant can allow moisture infiltration, creating a breeding ground for mould spores. Ensure all seals are intact and regularly maintained.

Is black mould dangerous?

Too much time in a mouldy environment can cause serious issues, particularly for those with breathing difficulties. 

Mould spores can cause:

• Allergies and respiratory issues: These include coughing, sneezing, nasal congestion, and throat irritation, often exacerbating existing conditions like hay fever.
• Skin irritation: Touching mould can cause skin irritation, leading to rashes, itching, and redness, especially in individuals with sensitive skin.
• Aggravation of asthma symptoms: Mould spores can worsen asthma, causing symptoms like shortness of breath, wheezing, and chest tightness.
• Serious infections: Individuals with weakened immune systems, such as the elderly or those with underlying health conditions, are at a higher risk of developing respiratory infections.
• Chronic health conditions: Long-term exposure to black mould can lead to chronic respiratory issues such as bronchitis and other lasting breathing problems.
• Mental and neurological effects: Studies suggest that long-term exposure to mould spores can impact cognitive function, leading to symptoms like memory loss, difficulty concentrating, and mood changes.

Taking care of black mould as soon as possible can help reduce health risks and create a safer home environment. If symptoms persist after mould removal, seeking medical advice is recommended.

Ways to get rid of black mould on windows (Clean it)

To remove black mould effectively, follow these steps:

1. Start cleaning mould by wiping down windows with a damp cloth to remove surface moisture and visible spores.
2. Use a specialised mould cleaner or white vinegar to clean the affected areas. Vinegar is a natural antifungal solution that can help eliminate mould spores effectively.
3. Clean mould patches quickly by mixing water with a mild detergent and applying it to the affected areas. Scrub gently using a soft brush to avoid damaging the window frame.
4. For your safety, it’s best to wear gloves and a mask to prevent exposure to mould and harsh cleaning chemicals.
5. Clean the mould thoroughly and let the area dry completely. Using a dehumidifier speeds up drying and keeps moisture levels in check, helping to prevent mould growth.
6. Inspect the window sealant and frames for any damage that may have contributed to the mould problem, and reseal if necessary.
7. Regularly maintain and wipe down windows to prevent black mould from returning.

Tips to stop mould from growing on your windows (Permanent solutions)

Keeping mould at bay requires regular upkeep and awareness. Key prevention strategies include:

Improve ventilation: A good start is improving ventilation by opening windows frequently to boost airflow. Proper ventilation helps reduce indoor humidity levels and prevents moisture from accumulating on window surfaces.

Use dehumidifiers: To reduce indoor moisture levels. In rooms with high humidity, such as kitchens and bathrooms, using a dehumidifier can prevent excess moisture that encourages mould.

Upgrade your windows or just glazing to more efficient: Installing energy-efficient windows/ glazing like vacuum glazing can create a better thermal barrier, reducing the chances of condensation forming on window surfaces.

Sealant maintenance: Ensure all gaps and cracks are properly sealed. Regularly check window frames and seals for any signs of wear or damage, as leaks can introduce moisture and create an environment conducive to mould growth.

Manage indoor humidity: Use exhaust fans in damp areas such as kitchens and bathrooms helps get rid of excess moisture.

Monitor room temperature: Sudden temperature changes can lead to condensation. Keeping indoor temperatures stable can help prevent moisture buildup on windows.

Reduce condensation by installing more efficient glazing. Consider reglazing your single-glazed windows with double-glazing units. You don’t need to change the frames, as we can fit vacuum double glazing into the existing frames.

Addressing leaks and structural issues: Professionals can identify hidden leaks in window frames, walls, or roofs that contribute to persistent moisture problems and recommend effective repairs to seal these sources of water intrusion.

When to consider changing your windows

In some cases, replacing your windows might be the best option to prevent mould growth. Consider a change of windows if:

Your wooden windows need frequent repairs: If you find yourself constantly fixing minor issues such as cracks, leaks, or warping, it may be more cost-effective to invest in new windows or properly refurbish window frames with our sash window repair service 🙂

The window frame is beyond repair: Severe mould infestations can weaken the structural integrity of wooden window frames, making replacement the only viable solution.

Persistent leaks continue despite resealing efforts: If water continues to seep through the frame even after resealing, the underlying materials might be too damaged to hold new sealant effectively.

Energy efficiency concerns: Older windows with poor insulation can contribute to condensation buildup, which encourages mould growth. Installing energy-efficient windows can help regulate indoor temperatures and reduce moisture buildup, which lowers the risk of mould growth.

Visible structural damage: Warped frames, rotting wood, or signs of extensive mould damage indicate that the current windows are no longer effective in preventing moisture intrusion.

Conclusion

Black mould on windows can be a stubborn problem that, if ignored, may lead to health risks and damage to your home.

Understanding the causes, such as condensation and poor ventilation, helps you take control and prevent mould from returning.

Regular maintenance, including wiping down windows, improving ventilation, and using effective cleaning solutions, can help keep mould at bay. In more serious cases, seeking professional help may be the best way to fully remove the mould and stop it from coming back.

FAQ

Is black mould on windows harmful?

Yes, black mould on windows can be harmful. Being exposed to mould over a long period can trigger breathing issues, allergies, and skin irritation, particularly in people with asthma or weakened immune systems.

What’s the best way to prevent black mould from coming back on windows?

To stop black mould on windows, improve ventilation by opening windows regularly, use a dehumidifier to reduce moisture levels, wipe down condensation daily, and check for leaks or gaps in the window frame that could introduce moisture.

What kills black mould on windowsills?

Black mould on windowsills can be effectively removed using white vinegar, hydrogen peroxide, or a specialised mould cleaner. Simply apply the solution, let it soak for an hour, scrub lightly, and wipe it clean with a cloth.

Does not having the heating on cause mould?

Yes, keeping the heating off can lead to mould growth. When the temperature inside drops, condensation builds up on cold surfaces like windows, creating an ideal breeding ground for mould spores.

VIEW ALL QUESTIONS