How to Remove Window Mould, Naturally (and Keep It Away)

Why Window Mould Happens — and Why It’s Worth Dealing With

It’s winter again and that means cold mornings, condensation on the windows… and then, mould. Yuck. Is it normal for windows to get mouldy? Sadly, while it shouldn't be normal, it is common because a great number of Kiwi homes can lack the ventilation needed to remove excess moisture. 

Mould spores float around in the air inside our homes – this is perfectly normal – but when they land on a surface that’s damp, cool, low in light, and lacking airflow, they’ll start to grow. Our homes in winter can be the perfect environment for mould, especially on and around windows. It’s very common in bathrooms and bedrooms where steam, breathing and closed windows add to the humidity.

Mould on bedroom windows is especially concerning because we spend 6–9 hours in there sleeping, often with the door closed or only slightly ajar, which reduces airflow and increases condensation.

But the good thing is, when you keep an eye on the humidity levels in your home and focus on adequate ventilation - mould will stop growing. Cleaning mould off windows might be a chore, but using the Figgy & Co natural cleaning method means window cleaning becomes easy and straight forward, without any harsh chemicals adding to the problem.

Why mould on windows is bad for your health

Mould on your windows isn’t just an eyesore – it’s a health risk. Mould releases mycotoxins, which are tiny invisible toxins that float into the air and can trigger symptoms like rashes, headaches, sore eyes, breathing problems, chest infections, and even disrupt your immune system. For people with asthma, allergies, or other immune function issues, mould can be particularly harmful. Over time, exposure to indoor mould can make symptoms worse and lead to long-term respiratory irritation.

What causes mould on windows

Window mould is directly related to high humidity in your home. It’s not just about how you clean – it’s about managing moisture in the air. Everyday living activities like showering, cooking, and even breathing release moisture. Without good ventilation, this moisture condenses on cold window glass and frames, creating the perfect damp environment mould needs to thrive. That’s why south-facing rooms, bathrooms, and unventilated bedrooms are most at risk.

The best way to clean mould off windows, naturally

If you’ve been asking yourself “What is the best cleaner for black mould on windows?” the answer is soap! You definitely don't need any harsh chemical waffle to do this job well. Hot soapy water is ideal because it makes the glass slippery so the mould and the spores are literally washed away. Simple as that! And the great thing about castile soap is it’s safe, effective, and completely non-toxic.

Step 1 – Dust the area

Use your vacuum with a brush attachment to dust the window frames, sills, and tracks. Mould grows best when it has dust and grime to feed on, so removing this food source makes a difference.

Step 2 – Wash with hot soapy water

In a bucket of hot water, add Figgy Home Cleaning Castile Soap - use 1 tablespoon per litre of water. Wash the glass, frames, and sills to physically remove mould and spores. Use a cloth with a bit of texture or an old towel cut into smaller squares. For stubborn spots on rubber seals of aluminium or uPVC windows, apply undiluted castile soap to a damp cloth, wipe over the area, and then follow with a clean, rinsed cloth. Rinsing your cloth in a separate bucket will keep you soapy water fresher for longer. Be sure to change your water as it gets dirty

Tip: Add a few drops of tea tree essential oil to your soapy water – tea tree is recognised as being effective against a range of household moulds.

Step 3 – Treat with vinegar

Mix a 50/50 solution of Figgy Strong White Vinegar and water in a spray bottle. Spray generously over the cleaned area, let it sit for five minutes, then buff dry with a lint-free cloth. You can also add tea tree oil to your vinegar spray for extra mould-fighting power.

Step 4 – Safety first

Mould is best handled with care. Wear gloves if you have sensitive skin or respiratory issues, and wash your hands thoroughly after cleaning mould.

How do you stop mould on windows?

Prevention is key. If you can make your home so the mould can't easily grow, it won't. And that will be good for your windows, but also for the wellbeing of your home.

here’s your mould free action plan:

• Wipe down windows to remove condensation every morning in winter. Use a Figgy eco cleaning cloth because it holds 17x its weight in water and will leave the windows almost dry just from wiping them down. Take a bucket with you and simply wring out your cloth as you go from window to window. Now drying your windows is quick and easy and the bonus is no big piles of wet towels to deal with!

• Open two or more windows daily to flush out damp air and bring in fresh air. Use a cross ventilation method of having opposite windows open, this way, the air has a path to follow and damp air is ushered out

• Keep window frames and sills dust-free. Dust is partly dried flaked off skin which makes it a food source for mould to grow. Keep on top of the dusting and you'll stave the mould of the snack it loves.

• Wash your windows monthly, especially in colder south-facing rooms. This will be 30minutes well spent for the health of your home - once you get into the swing of it, you will be surprise how quickly you can clean multiple windows - read this blog on window cleaning to get more time saving tips

• Reduce indoor humidity by being conscious of it. Open windows daily for at lease 10 minutes, utilise extractor fans in your kitchen and bathroom, cook with lids on pots, ensure your dryer is vented outside, and drying laundry outside when possible. It is worth investing in a humidity meter and aiming to keep your home under 60% humidity.

• If you have a heat pump, use the dehumidify function. This looks like water drops and works to remove excess moisture from the air. While it won't blow warm air in this mode, a dryer home is cheaper to heat and feels warmer to be in. 

Why not bleach?

If you’re wondering, “Is bleach or vinegar better for mould on windows?” here’s the truth: you don’t need bleach at all. Bleach doesn’t physically remove mould; it just works on superficial growth & changes the colour. The official advice about effectively cleaning mould from the CDC is to physically wash mould away by cleaning the surface – and that’s exactly what soap does.

Bleach also negatively affects indoor air quality, releasing chlorine gas which is harmful to your lungs. It can damage painted surfaces, corrode metal fixtures, and cause colour damage to textiles. In short, bleach is overkill and unsafe indoors.

FAQ – Window Mould Questions Answered

Q: Is window mould harmful?
A: Yes – window mould can release mycotoxins into the air which can affect your health, especially if you have asthma, allergies, or immune system concerns.

Q: How do you clean mould off aluminium window frames?
A: Dust with a vacuum first, then wash with soapy water (castile soap works best). For rubber seals, use undiluted castile soap on a cloth, then rinse. Treat with a vinegar spray to target any lingering spores.

Q: Is bleach or vinegar better for mould on windows?
A: Vinegar – because it’s safe, effective, and works without damaging surfaces or affecting your air quality. Soap physically removes the mould, and vinegar treats the spores.

Q: What is the best cleaner for black mould on windows?
A: A combination of castile soap for washing and strong white vinegar for treating is the safest and most effective method.

Q: How do you stop mould on windows?
A: Control moisture. Wipe away condensation daily, ventilate well, and keep window frames clean and dust-free.

Q: Is it normal for windows to get mouldy?
A: It is common, especially in winter or in rooms with high humidity and poor airflow. The trick is to catch it early and manage moisture levels.

Q: Why do windows get mould?
A: Because of condensation and damp conditions – mould spores in the air will grow when the environment is right.

Q: How do I stop mould on window sills?
A: Keep sills dry, clean regularly, and wipe away any condensation that forms.

Q: How do you get rid of mould on windows?
A: Dust, wash with soapy water, treat with vinegar, and keep the area dry and well-ventilated.

Q: What’s the best window mould cleaner?
A: A natural castile soap and vinegar combo.

Q: What’s the best window mould spray?
A: A 50/50 vinegar and water mix with a few drops of tea tree oil works brilliantly.

A mould free home is a healthy home

Mouldy windows don’t have to be “just part of winter.” With a little know-how, a few natural cleaning staples, and some healthy daily habits, you can keep your windows fresh, your air clean, and your home feeling good to live in. 

Tackling mould isn’t just about keeping things looking nice—it’s about protecting your family’s health and creating a space where everyone can breathe easier. The bonus? Once you start, you’ll see how quick and doable it really is. A few minutes a day now means fewer problems (and less scrubbing) later. Here’s to clear windows, healthy air, and a home you’re proud of.

Get natural cleaning tips from our blog!

We want you to have everything you need to clean your home healthier while avoiding unwanted chemicals – and looking out for the planet too! Take a browse through our blog and learn more about natural cleaning, safe ingredients and so much more!