Black Mould Season 25/26 Has Begun

Every year, as temperatures drop and homes are sealed up against the cold, the same problem returns. Black mould season is back for 2025/26. Thousands of UK households will already be noticing the first signs. With black mould appearing on walls, ceilings, and window frames.

Condensation builds up quickly once heating goes on and windows stay shut. Without enough ventilation, excess moisture has nowhere to go. 

Cleaning products are simply not enough. The result? Damp corners, musty smells, and spreading mould problems. 

All of which is unpleasant and harmful to your health. Especially those with weakened immune systems.

For landlords and homeowners alike, the time to act is now! Before black mould takes hold causing health risks and long lasting property damage.

Why Black Mould Appears in Autumn and Winter

Black mould thrives in damp air. During the colder months warm indoor air meets cold surfaces like external walls and window panes. This creates condensation, which is the perfect environment for mould to grow.

Even homes that appear clean and well-kept can suffer from black mould. This is because windows are kept closed most of the time in Winter. Bathrooms and kitchens have poor ventilation and that air also gets trapped. Furniture is placed tightly against cold walls and often next to radiators and people use their tumble dryers. 

Left untreated, black mould can damage plaster, wallpaper, paintwork and timber. More worryingly, it can trigger respiratory issues like allergic reactions, skin rashes and asthma. This can be especially serious for children and older people.

Effective Black Mould Treatment

When black mould appears, cleaning it off is only a short-term fix. The key to a lasting black mould treatment is removing the root cause. Which is excessive humidity and poor air circulation.

Professional mould removal products can help kill spores, but if condensation continues, it will come back. The only reliable way to stop it is to improve airflow.

That’s where a Positive Input Ventilation (PIV) system from ClearAIR PIV can make all the difference.

How a PIV Unit Stops Black Mould

A PIV system works by introducing filtered, fresh air into your property. No need to open windows in the cold UK Winter. Its all done at a gentle and continuous rate via the PIV unit. This replaces stale, moisture-laden air with clean, dry air from outside.

By maintaining positive air pressure, a PIV unit prevents condensation from forming on cold surfaces. This removes the conditions mould needs to grow.

Key benefits for landlords and homeowners:

• Stops black mould before it starts.
• Reduces humidity throughout the property.
• Protects walls, ceilings, and fixtures from damage.
• Improves indoor air quality and helps reduce odours.
• Low running costs and minimal maintenance.
  

Once installed, a PIV unit quietly does its job 24 hours a day, keeping your property fresh, dry, and free from damp.

To learn more about how this works, visit our Black Mould Treatment page for full details.

Why Act Now

October to March is the peak black mould season in the UK. By the time visible mould appears, the underlying moisture levels are already high.

Installing a PIV system before winter fully sets in will help you stay ahead of the problem. It will help you to avoid costly repairs and complaints later in the season.

For landlords, this is especially important under new compliance standards like Awaab’s Law. This will require swift action on damp and mould issues from October 2025. Preventing mould now is the easiest way to stay compliant.

Get Help From A Local And Recommended Specialist

Is PIV the right solution for you?

Simply take our 20 second assessment and check your suitability for PIV. Or speak to a professional at ClearAIR PIV

FAQ's About Black Mould Treatments

Here are some of the most frequently asked questions we get about our black mould treatments across the UK.