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What is Causing Mould in Your Home

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What is Causing Mould in Your Home

By Ruth MacEachern

Product Manager

Nov 24, 2023

Seeing a patch of dark mould growing on a wall in your otherwise pristine home can be unsettling.  Aside from looking unpleasant, the presence of mould can result in serious health problems for you and your family.  If inhaled, mould spores can cause allergic reactions in healthy people and affect the wellbeing of young children, older people, and those with underlying medical conditions.

Finding and cleaning mould before it can affect your health is important, but you also need to remove the conditions that allow the mould to grow in the first place to stop it from coming back.  Mould thrives in moist conditions and can grow quickly from spores. Damp patches on walls and ceilings are the perfect environment for mould to grow.  If it is not dealt with, the mould will consume the material it is growing on, causing damage to the fabric of your home.

Why mould grows in homes

The spores that mould grows from are microscopic and present almost everywhere.  Unless the spores fall onto surfaces where they can activate and grow, they remain inert and are simply moved around by the air.

Domestic mould is mainly caused by excess moisture in the air. Moisture can come from various sources, such as:

  • Leaking pipes, roofs, or gutters
  • Rising damp in basements or ground floors
  • Rain seeping in through damaged windows or walls
  • Condensation on walls from cooking, showering, or drying clothes indoors

An often-overlooked source of moisture in the air in a home is from people breathing.  This is more noticeable during the winter months when we spend more time indoors.

When the temperature drops, the air can hold less moisture. This means that the excess moisture in the air condenses on cold surfaces, such as walls, windows, or mirrors. This is called condensation. Condensation creates a wet and warm environment that is ideal for mould to grow.  In the winter, colder weather outside creates a bigger temperature difference and makes condensation more likely to form on windows and exterior walls.

Without regularly opening windows and doors to bring fresh air into the home, the air becomes increasingly moist and stale, and the concentration of mould spores in the air rises, making the chances of growth more likely.

Cleaning domestic mould

If you have discovered mould in your home, the first step should be to clean away the surface growth.  This will temporarily stop the mould from spreading by removing the fruiting bodies that release more spores into the air.

If you have an underlying medical condition, an allergy to mould, or suspect that the mould growing in your home is toxic black mould (Stachybotrys Chartarum), you should have the mould removed professionally to protect your health.

Domestic mould can be cleaned with some household products and a bit of elbow grease. However, you should take some precautions before tackling the mould, such as wearing rubber gloves, a face mask, and goggles to protect yourself from the spores. You should also cover the furniture and carpets with dust sheets and open the windows to ventilate the room.

Start by using a soft brush or a vacuum cleaner to remove any loose mould from the surface.

Using a mould cleaner (fungicide), or dilute bleach is recommended for cleaning mould as it will kill off the surface mould.  Other cleaning products such as white vinegar or baking soda will also work but are less effective.

Spray the fungicide onto the surface where the mould is growing and leave it for 15 minutes to take effect.  Once sufficient time has elapsed, you can wipe the remaining mould away with a cloth.  If you have more persistent mould, or a textured surface, you may need to scrub to remove the growth, but if you do, try to avoid allowing droplets of water to fall onto other surfaces where the mould could also grow.

Once you have finished cleaning the mould away, dispose of any cloths you have used and wash your clothes immediately to prevent spreading spores elsewhere in your home.

Unfortunately, cleaning the mould away is only temporary.  Unless you remove the conditions that allowed the mould to grow in the first place, it will soon return.

How to improve ventilation to prevent domestic mould?

The best way to prevent domestic mould is to reduce the moisture and improve the ventilation in the home.

Ensure that you have extractor fans installed in wet rooms such as bathrooms, kitchens, and utility rooms, and switch them on when the room is in use – modern extractor fans such as the EnviroVent Cyclone 7 feature humidity sensors that detect the amount of water vapour in the air and adjust their power levels accordingly to reduce humidity more quickly.

If you have found mould growing away from an obvious source of moisture, the overall airflow in your home may be poor.  Whole house ventilation such as a positive input ventilation (PIV) system like EnviroVent ATMOS will help to improve the air quality and circulation in your home.

A PIV system is a device that draws fresh and filtered air from outside and distributes it throughout the home. The system creates a slight positive pressure in the home, which pushes the stale and moist air out of the gaps and cracks in the building. This prevents condensation and mould from forming.  PIV systems are energy efficient and low maintenance.  They are installed in your loft and can be combined with extractor fans to create much better ventilation.

Find out more

We can help you stop mould in your home permanently.  Enter your postcode below to find a ventilation specialist near you.  EnviroVent offer a free home survey that identifies the sources of condensation, and our local expert will provide you with advice about how you can stop condensation from developing into a more serious problem.


Need help with condensation, mould or damp problems?

One of our local experts will contact you to learn more about your problems, offer free expert advice and make recommendations for a permanent solution.

During the free survey we will

  • check Assess any condensation, damp or mould problems in your property
  • check Take readings of the relative humidity levels
  • check Identify any underlying problems and make recommendations for a permanent solution

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