Why Is There Mould Around My Windows? Causes and Solutions

Mould around windows is a common problem that can affect homes of all ages. Whether you're living in a modern property or an older one, the presence of mould can quickly escalate from minor inconvenience to a major issue, damaging window frames and even posing health risks. Fortunately, there are practical steps you can take to prevent mould from forming and address the root causes. Here’s everything you need to know to keep your windows mould-free.

Is Mould Around Windows Normal?

Yes, it is relatively common to see mould around windows, especially during the colder months. Mould tends to form when condensation accumulates on the glass and drips down onto the window frame, creating a damp environment where mould can thrive. This is particularly true during winter when the temperature difference between the inside and outside is at its highest.

Even in newer homes, mould can become a problem. Modern airtight designs often trap moisture, and without proper ventilation, condensation can accumulate, leading to mould growth. Household activities like cooking, showering, and even drying clothes indoors can increase humidity levels, further exacerbating the issue.

Common Causes of Mould Around Windows

Mould doesn’t just appear out of nowhere—several factors contribute to its growth. Identifying the root cause is key to preventing future mould outbreaks. Here’s what might be happening around your windows:

1. Excess Humidity

Moist air is the main culprit behind condensation, which in turn fuels mould growth. When the humidity levels inside your home are too high (above 60%), moisture collects on cooler surfaces like window panes. To prevent this, aim to keep the humidity levels between 30-50%. You can monitor this with a hygrometer and, if needed, use a dehumidifier to help control moisture in the air.

2. Poor Insulation

Windows, especially those with poor insulation, are more likely to attract moisture. Cold air from outside meets the warm, moist air inside, causing condensation. If your home has single-glazed windows or poorly sealed frames, condensation is more likely to build up. Consider upgrading to double-glazed windows or improving insulation to reduce moisture accumulation.

3. Leaky Seals and Frames

A broken seal or gap in the window frame can let water in, increasing the risk of mould growth. If you notice drafts, foggy windows, or water stains around the frames, it’s essential to check for leaks and repair or replace damaged seals promptly.

Types of Mould Around Windows

Not all mould is the same, and it can vary in appearance and potential health effects. Here are the common types of mould you might find around your windows:

Black Mould (Stachybotrys chartarum): Black or dark green patches that can appear on damp window sills or frames. It is the most harmful and can lead to respiratory problems, skin irritation, and headaches.
Yellow Mould (Aspergillus): Appears as yellow, green, or black spots. It thrives in humid conditions and can trigger allergic reactions or worsen asthma.
Green Mould (Cladosporium): Dark green or black patches found on wooden frames, particularly in cool, damp conditions. It can irritate the skin and respiratory system, though it’s generally less dangerous than black mould.
Blue Mould (Penicillium): Bright blue or green patches found on water-damaged surfaces. The spores it releases can cause allergic reactions.
Woolly Mould (Alternaria): Often dark and fluffy, this mould thrives on damp surfaces like window frames and can cause symptoms such as sneezing, coughing, and itchy eyes.

How to Prevent Mould Around Your Windows

Now that you know the causes and types of mould, here’s how you can tackle the problem and prevent mould from recurring:

1. Control Humidity Levels

Maintaining the right humidity levels is essential in stopping mould before it starts. A dehumidifier can help keep moisture levels between 30-50%. This is particularly useful in high-humidity areas like kitchens, bathrooms, and bedrooms. Be mindful of drying laundry indoors, as it can add excess moisture to the air.

2. Improve Ventilation

Proper ventilation plays a crucial role in preventing mould growth. Open windows when possible to allow fresh air to circulate, especially during dry and sunny weather. In colder months, try to open windows for short periods to let moisture escape without letting the warmth out.

If you’re in a high-humidity area, use exhaust fans in bathrooms and kitchens. You can also invest in an air purifier with a HEPA filter to help remove mould spores from the air, improving overall air quality.

3. Upgrade Insulation and Windows

If your windows are the primary source of mould, it might be time to upgrade to double-glazed or triple-glazed windows. These types of windows provide better insulation, reducing condensation on the glass. Additionally, consider opting for uPVC frames, which are more resistant to moisture and mould.

4. Repainting with Anti-Mould Paint

Repainting your window frames with anti-mould paint can help prevent mould growth in the future. These paints contain fungicides that form a protective barrier. However, before repainting, make sure to clean the mould thoroughly and address the underlying causes like poor ventilation or insulation.

How to Clean Mould Around Windows

If you already have mould, cleaning it as soon as possible will help prevent it from spreading and causing further damage. Here are some effective cleaning methods:

DIY Cleaning Solutions

Vinegar: Fill a spray bottle with undiluted white vinegar and spray it directly onto the mould. Let it sit for about an hour, then scrub with a brush or sponge.
Bleach: Mix one part bleach with three parts water. Apply it to the affected area with a cloth or sponge, then rinse thoroughly with water.
Baking Soda: Make a paste with baking soda and water, apply it to the mouldy areas, and scrub gently.

For tougher mould problems, consider using a commercial mould remover designed for windows. Always wear gloves and a mask when cleaning mould to protect your health, and ensure proper ventilation while you clean.

When to Call Professionals

If the mould problem is extensive, affecting more than one square metre or spreading to surrounding walls or ceilings, it might be time to call in the experts. Mould that keeps returning despite your cleaning efforts could indicate hidden leaks or structural issues. Additionally, if you or your family members experience health symptoms like respiratory problems, it’s crucial to get professional help.

Final Thoughts

Mould around windows is a common issue, but with the right preventive measures and maintenance, you can minimise the risk of mould growth and keep your windows clean and healthy. From controlling humidity and improving ventilation to upgrading your windows and cleaning effectively, these strategies will help keep your home free from mould. If the problem persists, don’t hesitate to seek professional mould removal services to ensure your home remains safe and healthy.