How To Clean Mould Off Windows and Aluminium Window Frames

To clean mould off aluminium window frames, spray a 50:50 mix of white vinegar and water onto the mould, leave it for up to an hour, wipe it away with a soft non-abrasive cloth, then rinse and dry the frame thoroughly. To stop it returning, reduce condensation with better ventilation and keep sills and drainage holes clean and dry. Mould problems around windows are very common but often go unnoticed. While it's common for aluminium window frames to gather dirt and grime over time and lose some of their shine, they can be vulnerable to mould growth.

Mould on your windows is not something you want to see. The good news is this can be overcome with good cleaning and maintenance!

This guide explains how to clean mould from your aluminium window frames and how to prevent mould growth in future.

What Does Mould on Windows Look Like?

Window mould usually appears as black, grey or green spots on seals, sills and the corners of frames, often alongside condensation or a musty smell. Because it only grows where moisture sits for long periods, finding it usually means you also have a condensation or leak problem to fix.

The mould you find in your home is an airborne spore that thrives in humid, damp conditions. Mould can look like spots and is often black, grey or greenish. But it can also be brown, purple, white, pink, yellow and orange. The humidity level can influence the colour of mould.

Generally, mould infestations are higher in winter, as we tend to keep our windows and doors closed. In closed-up homes, poor ventilation can make condensation and mould issues worse over the days.

If you spot mould on your aluminium window sill and frames, there's a chance the window has condensation buildup or is leaking. Identifying the potential leaks and condensation buildup can help you find the root cause before you remove the mould.

Why Does Mould Grow on Aluminium Windows?

Mould grows when warm, moist indoor air condenses on cold glass and frames and the water is left to sit. Older aluminium frames without a thermal break get very cold, so they collect more condensation, and water trapped where the glass meets the frame gives spores the damp conditions they need. Our guide to preventing condensation on aluminium window frames tackles the root cause.

Unfortunately, aluminium windows are a proverbial magnet for mould. To see why you must understand condensation comes about and how this leads to mould on aluminium windows.

Generally, condensation forms due to a buildup of excess moisture. The warmer the air, the more moisture it can hold.

Condensation happens when moist (warm) air hits cold glass or the aluminium frame. Moisture buildup in your home can come from many sources, and other factors can worsen condensation. Everyday processes like breathing, cooking, showering, and washing dishes increase condensation. Other water sources inside your home, like fish tanks, can also worsen moisture buildup.

This problem worsens during winter when the outside temperature is lower and cold air increases the temperature difference between indoors and out, making condensation more likely. At the same time, ventilation within your home is reduced due to closed windows and doors.

Older aluminium windows without a thermal break are particularly vulnerable to condensation, and single glazing is especially prone to it. These windows have a high u-value, meaning they transfer heat and cold well. uPVC and wooden window frames have less thermal transfer and are less likely to have a buildup of condensation.

Often, condensation buildup gets trapped between the meeting spot of the glass and frame. Mould then sees this as an ideal home and quickly takes hold.

Be sure to inspect the top, bottom and side of the window for cracked or missing sealant that could be letting moisture in. Also, check your windows during and after rainy weather, as it will be easier to spot potential leaks.

Is Mould on Windows Dangerous?

Mould can be harmful to health, particularly for people with asthma, allergies or weakened immune systems, because its spores irritate the airways. Left untreated it spreads, stains seals and plaster and causes musty odours, so remove it promptly and fix the moisture source behind it.

Mould can pose a health problem, especially for people with an existing respiratory problem. People with allergies, asthma or weakened immune systems are also vulnerable. High levels of condensation cause mould spores to grow and lead to poor air quality, nasal and sinus congestion, and other serious health problems.

It's essential that you don't ignore even the slightest sign of mould around your window sills and frames, or anywhere in your home for that matter. If mould is not removed, mould spreads by releasing microscopic spores to the rest of your home. This damage can lead to additional mould remediation expenses as well as leave stains and cause musty odours.

While in most cases, mould around windows doesn't become a major problem. It is best to perform due diligence and prevent growth on your windows from the get-go to avoid costly and time-consuming tasks if the mould worsens.

What Should You Check Before Cleaning Mould?

Check how large the affected area is, test your chosen cleaner on a hidden part of the frame, and use a pH-neutral or mildly acidic cleaner rather than anything strongly alkaline, which can dull or stain aluminium. Large or recurring outbreaks are a job for a damp specialist.

Before you begin cleaning the mould from your window frames, here are a few suggestions:

• If the mould in question covers a large area of your window(s) or you suspect it's black mould, it may be time to call in an expert. Mould remediation and water mitigation professionals can determine how extensive the mould is and the appropriate solutions for removing the problem.

• If you're using commercial or homemade cleaning products, be sure to test them on a small part before applying them to the whole frame. This is important to check for any reaction that could potentially damage the aluminium, such as discolouration.

• Ensure your cleaning detergents are non-alkaline and have a PH level of 7 or less to avoid damaging the aluminium.

How Do You Stay Safe When Cleaning Mould?

Wear rubber gloves, goggles and a mask, keep the room well ventilated, and avoid touching or dry-brushing the mould, which releases spores. Never mix bleach with ammonia or acidic cleaners, and keep children and pets away until the area is clean and dry.

Before tackling the mould, the most important thing to remember is your health and safety. Exposure to damp and mouldy environments may cause health problems. Some people are sensitive to mould, so it's best to protect yourself.

Consider all these safety measures before you begin cleaning mould from your windows.

• Wear appropriate protective clothing, including rubber gloves, a mask and goggles, to protect your eyes, nose, mouth and skin.

• Avoid touching the mould with your bare hands or breathing in mould spores, and take proper precautions when removing black mould.

• Do not clean the windows on a rainy, windy or very hot day.

• Open all doors and windows when you are working, and leave as many open as you safely can when you leave.

Cleaning can disturb invisible dust from mould, so wear gloves throughout the job.

What Is the Best Way to Clean Mould Off Aluminium Window Frames?

For most frames, white vinegar diluted 50:50 with water is the best first option: spray it on, leave it for up to an hour, wipe it away with a soft cloth and dry thoroughly. Use mild washing-up liquid for light marks and diluted bleach only for stubborn mould on seals, rinsing well afterwards.

Some of the best methods for cleaning mould from aluminium frames utilise the power of everyday household products.

Here are four effective methods for cleaning mould off your aluminium windows. After this section is the step-by-step process of using your chosen cleaner to remove the mould.

Method 1: Vinegar and water

The natural acids in white vinegar have been proven effective in removing 82% of different mould species. Vinegar is often used as a natural, non-toxic way of killing household mould.

Cleaning vinegar is the best type for killing mould as it contains 6% acetic acid. White vinegar will also work just fine as it has 5% acidity.

Before cleaning the mould, remove any dirt or dust on your window frames.

1. Mix equal parts vinegar and water in a spray bottle and spray it onto the mould.

2. Let it sit for about an hour.

3. Use a clean cloth or sponge to gently scrub the mould.

4. Rinse the frames with water and dry them with a drying cloth.

Method 2: Mild detergent

A versatile cleaning option for most aluminium forms is warm, soapy water made with mild detergent. Mix two cups of warm water with two tablespoons of mild detergent, such as a dish detergent, to create a cleaner.

You can pour your homemade solution into a spray bottle for easier application.

Mild detergents cannot kill mould but can be used to remove visible mould. When added to water, dish detergent acts as a surfactant that helps detach mould and mould spores from surfaces, making them easier to loosen and wipe away with a damp cloth.

Method 3: Lemon juice and baking soda

Lemon juice and baking soda are other natural household cleaners that can be used to clean mould, dirt and grime off aluminium. Lemons are high in citric acid and have natural antibacterial properties. Baking soda is an alkaline substance with pH levels between 8 to 9, which is higher than most moulds can tolerate.

As a result, a mixture of the two can be considered a safe and natural mould killer.

1. Mix 1⁄2 cup (120 ml) of lemon juice and ¼ cup (45 g) of baking soda to make a paste.

2. Apply to the mouldy area and scrub off the mould with the help of a cloth or sponge.

3. Let the paste dry completely.

4. Once the paste is dry, remove it with a damp sponge on the inside and a water hose on the outside for easier cleaning.

Method 4: Water and bleach

Chlorine bleach is a potent biocide commonly used to kill mould spores. Once diluted with water, it is safe to use on aluminium surfaces.

Before applying this mixture to the whole frame, test a small part that's not directly visible. This is important to check for any reaction that could potentially damage the aluminium, such as discolouration. For stubborn mould, hydrogen peroxide can also be used as a targeted alternative.

Never mix bleach with ammonia-based or acidic cleaners, including vinegar, as this releases toxic gases. Rinse thoroughly afterwards, as bleach left on aluminium can cause pitting. Also, wear gloves when using bleach.

1. Mix one part household bleach with ten parts cold water (for example, 100ml of bleach to 1 litre of water).

2. Apply the diluted bleach solution to the mouldy surface.

3. Let it sit for 15 minutes.

4. Gently scrub off the mould, especially any remaining patches, with a soft cloth or sponge.

5. Rinse with water and dry the surface thoroughly.

How Do You Remove Mould From Aluminium Window Frames Step by Step?

Wet the mould to stop spores spreading, spray on your chosen cleaner and leave it to work, wipe gently with a non-abrasive sponge, repeat on stubborn patches, then rinse and dry the frame, seals and tracks completely.

Follow this step-by-step guide to thoroughly and safely remove the mould from your aluminium window frame.

Things you'll need:

• Cleaner of choice (vinegar, lemon juice and baking soda, mild detergent or bleach)

• Bucket/Garden Hose

• Spray Bottle

• Sponge

• Microfibre cloths

• Washing up liquid

Step 1: Wet the affected area

With all your protective gear on, it's time to start cleaning your aluminium window frames. For the inside, use washing-up liquid to remove any dirt and grime before tackling the mould. Use a wet cloth to wipe down the frames.

Once done, fill the empty spray bottle with room-temperature water and saturate the affected areas. Wetting the mould helps stop windows mould spores spreading while you clean. Be sure to spray the area around each spot of mould growth.

To clean the outside, use a hose or bucket of water to remove dirt and grime and to wet the mouldy area.

Step 2: Gently wipe away the mould

Allow the water to saturate the mouldy area, and spray on your prepared cleaning solution. Spray in an even layer if you're using a homemade product such as water and white vinegar. Give your cleaner time to work to get rid of the mould thoroughly before you begin to rub it.

Using a sponge or cloth, gently but thoroughly clean the affected area. It is best to use a non-abrasive sponge or soft cloth when cleaning, as aluminium can scratch easily during the cleaning process.

You may need to repeat this step twice as mould may appear to fade at first and then dark spots can remain after the first pass. Don't worry: a second round will often solve the problem.

A second application can help rid of mould that is clinging to the surface.

With a second round of cleaning the area, be prepared to wipe it a little more thoroughly. Be sure to use a fresh cloth for each application.

Once the physical mould growth is removed, it becomes a little easier to control.

Step 3: Clean and dry the area you've treated

After the cleaning, you will need a final scrubbing down of all surfaces using a fresh cloth to remove any leftover debris. Clean all affected areas, including the window panes, tracks, joints and grooves.

The aim is to leave the area dry after cleaning. Use a clean, dry cloth and remove any lingering hints of moisture. If you're treating tight spots, open your window and allow sunshine and wind to aid the drying process.

Once you've completed your clean, place all used cloths and sponges in a bin bag, seal the bag tightly and throw it away in the outside bin. Any tools can be immersed in a mixture of bleach and water to kill any remaining mould spores.

If your aluminium window frames still appear dull, you can use a polish to make them shine.

How Do You Stop Mould Coming Back on Windows?

Control moisture: ventilate daily, use extractor fans when cooking and showering, run a dehumidifier in damp rooms, wipe condensation off glass and sills each morning, and keep drainage holes in window tracks clear. Fix any leaks too, as mould will keep returning if the frame or wall stays damp.

Mould is quite fragile and can easily be killed by most acidic and abrasive chemicals. However, these often don't get to the root of the problem. A small area left untreated can cause another infestation.

The good news is that prevention is much easier (and better) than dealing with the problem.

To prevent recurrence and keep mould growth at bay, here are some steps you should take:

How Can You Reduce Humidity Around Windows?

To prevent window sweating and stop mould growth, reduce your home's humidity levels, increase ventilation, and ensure proper ventilation throughout the home.

This is especially important for damp areas such as the bathroom and kitchen. These are rooms prone to condensation and mould. Hot showers, boiling pans and steaming food all release moisture and contribute to condensation. If the air can move freely through these spaces, there's less chance of moisture settling on the windows and causing mould growth.

You can use a dehumidifier or a fan to decrease humidity in a space. Dehumidifiers help with removing excess moisture, making your home less hospitable to mould and mildew. In kitchens and bathrooms, use extractor fans or exhaust fans, and if needed install extractor fans for adequate ventilation. Bringing in fresh air also helps lower humidity and improve airflow.

How Often Should You Clean Your Windows?

Weekly window cleaning should be included as part of your regular cleaning routine. Cleaning includes dusting and vacuuming to stop mould from growing back.

As you know, aluminium is particularly bad at preventing moisture buildup, so it's essential you clean your window sills, frames and tracks.

Window tracks can accumulate dust and moisture more easily. Many window tracks have small holes to drain water out, but these holes can become blocked by dust and cause mould.

Routinely wipe down wet areas with a dry cloth to prevent moisture buildup from turning into mould.

Our guide to removing scratches from aluminium window frames also explains how to clean them without damaging the finish.

How Do You Find and Fix Window Leaks?

Locate and seal any gaps between the window frame or any small points of separation around the framework that may be causing a leak.

It's also wise to inspect your roof and gutters for proper drainage. Any leaks from these can lead to mould production, as well as more serious structural and insulation problems. Leaks or other drainage problems typically occur after a heavy storm.

After a storm, take a moment to wipe down the aluminium window framework, including the window sill, tracks and panes. For the most part, sunlight will help dry out the moisture, but some tight spots can harbour moisture.

You may need a professional to make more extensive repairs, but the money is well worth it.

These methods can also be applied to aluminium doors and door frames, and our guide to condensation on aluminium bifold doors covers the causes and fixes for doors specifically.

When Should You Repair or Replace Mouldy Windows?

If a leaky window frame is the culprit, you may need to repair or replace your aluminium window. Damaged sealant is often to blame.

If your aluminium windows or doors are in poor condition or you've noticed mould growing, it may be worth replacing the window altogether. Upgrading old windows can also help reduce condensation. Stronger, high-quality window frames insulate better, and triple glazing can further reduce condensation by keeping indoor surfaces warmer, resulting in less condensation and mould.

If you're comparing materials, a wooden window frame or painted wood still needs regular maintenance because trapped moisture can support mould grow.

Remember, mould can also grow around your doors. If you've also been experiencing this problem and cleaning doesn't seem to solve it, it may be time to replace your doors. If replacement is not immediate, mould resistant paint can help protect nearby damp surfaces.

Modern thermally broken aluminium bifold doors and sliding doors from Aluminium Living are designed for thermal efficiency and weatherproofing, which greatly reduces the risk of leaks, condensation and mould.

Window Mould FAQs

What causes black mould around windows?

Black mould around windows is caused by condensation or leaks keeping the frame, seals and surrounding plaster damp. Cold spots on older single-glazed or non-thermally broken frames, poor ventilation and drying clothes indoors all make it worse. Treat the mould, then deal with the moisture, or it will return within weeks.

Should I open windows in winter to prevent mould?

Yes. Opening windows for 10 to 15 minutes a day, or using trickle vents, lets moist air escape and noticeably reduces condensation and mould, even in cold weather. Short bursts of ventilation lose far less heat than leaving windows ajar all day.

Can you use bleach on aluminium window frames?

Diluted bleach can be used sparingly on stubborn mould, but it should be rinsed off thoroughly because it can pit and discolour aluminium and damage some coatings. Vinegar or a pH-neutral cleaner is the safer first choice for frames, with bleach reserved for rubber seals.

Why does mould keep coming back on my window seals?

Mould returns when the cause is not fixed: persistent condensation, blocked drainage holes or failed sealant letting water in. If the seals themselves are stained deep into the rubber, replacing them is often easier than cleaning. Our guides on sealing aluminium doors and windows and stopping water leaking from aluminium windows explain the fixes.