Mould: Prevention Is Better than Removal or Renovation

January 7, 2021
  1. Causes of mould in living spaces
  2. How to detect mould in living spaces
  3. Structural causes of mould
  4. Anthropogenic causes of mould
  5. How to prevent mould
  6. How to remove mould
  7. Is mould dangerous to health?
  8. Are mould measurements useful?

Mould is a natural thing, and it, for example, helps in the formation of humus with other organic substances in the soil. Outside, mould does not bother anyone. However, mould spores can enter houses and flats through the air. They are invisible to the human eye and fly around until they find a damp spot. There the mould spores find fertile ground, multiply and become visible and smelly. Experts estimate that mould occurs in one in four or five family homes. It only appears in old buildings, but also in new ones, if the ventilation system does not work as intended.

Causes of mould in living spaces

In nature, there are more than 100,000 species of mould. But there are only two ways that mould can develop in living spaces: occupants ventilate incorrectly or ventilate the space too little, or the mould growth is due to construction defects. There is often more than one cause of mould growth. A crack in the wall or water damage can be the trigger, but ventilation in the bathroom or the extractor fan in the kitchen can also be responsible if they do not extract humidity properly. If you ventilate incorrectly or too little, the mould spores multiply uncontrollably.

How to detect mould in living spaces

Mould growth depends on humidity, nutrient supply and temperature. A relative humidity of 40-60% is ideal for humans; we feel more comfortable than in a drier or more humid environment. However, at a humidity of over 70%, it is the mould spores that feel at home. For this reason, the indoor climate in the home should be checked regularly as follows:

  • Observe walls and ceilings carefully, especially in corners.
  • Measure the air temperature and relative humidity with a hygrometer.
  • Measure the temperatures on the ceilings and walls and look for large differences.

A hygrometer is a measuring instrument and determines the humidity of the air. Simple hygrometers are available from 10 francs or can be obtained easily from our partner Condair. It is best to hang or position the hygrometer and check the values regularly. If the humidity is constantly high, you should check your home. If you smell mould, it is already too late.

Mould: A hygrometer is a measuring instrument and determines the humidity of the air. Simple hygrometers are available from 20 francs.
Check the relative humidity regularly. A value between 40 and 50% is ideal to avoid mould.

Structural causes of mould

  • So-called cold bridges, which occur e.g. in balconies, at the ends of ceilings, window parapets, window frames, radiator niches or roller shutter boxes, conduct cold inwards more quickly and cool the inner surfaces of walls considerably. Especially if they are insufficiently insulated or not insulated at all. In this case, the risk of surface humidity increases as soon as the temperature on the inside surface of the wall falls below the dew point.
  • Poorly or insufficiently insulated houses lose a lot of heat because they dissipate it more quickly to the outside.
  • There are indoor surfaces that absorb and release humidity better than others. For example, mineral building materials such as gypsum plasters and smooth plasters, gypsum boards or clay plasters coated with vapour diffusing mineral paints are very useful. They can compensate for high humidity by absorbing it to a certain extent.
  • Defects or damage to the building structure can be the cause of mould growth. If this is the reason, the damage or defects should be investigated by a specialist, e.g. a building physicist, and the building should then be brought up to standard.

Anthropogenic causes of mould

  • Ventilation is the easiest way to regulate indoor air humidity. If you ventilate too little or not at all, you risk high humidity of more than 60% and thus the risk of mould growth, especially in winter.
  • A family of three produces an average of six to twelve litres of moisture per day. This amount is produced when you breathe, when you shower, when you cook. Aquariums, humidifiers, clothes dryers or house plants can further increase the relative humidity.
  • Radiators covered by furniture or curtains and underfloor heating systems covered by carpets distribute heat unevenly. Incorrect heating promotes the formation of mould and can lead to higher electricity consumption and thus higher electricity costs.
  • Walls behind furniture or curtains are colder than open interior wall surfaces. This is why condensation or dew can form there - a paradise for mould spores.

Mould often forms behind large pieces of furniture such as cupboards.
Mould tends to form behind large pieces of furniture, such as cupboards, if the walls are not well insulated and if air cannot circulate.

How to prevent mould

  • Pay attention to a relative humidity of 40-50%. If it is very cold outside, the humidity should be around 40%.
  • Ventilate briefly but intensively. This means opening and ventilating the windows for five to ten minutes three times a day instead of simply tilting them, even in winter.
  • Ventilate after showering, when humidity is particularly high.
  • After the shower, dry the tiles and joints in the bathroom or the glass wall of the shower cubicle with a cloth or rubber scraper.
  • Clean or replace bathroom ventilation filters regularly.
  • Do not place large pieces of furniture directly against an outside wall, leave enough space between the furniture and the wall to allow air to circulate.
  • Close the bedroom door if the air is cooler there than in other rooms.

How to remove mould

Experts distinguish three stages of mould formation:

  1. Mould appears in the corners of walls, at panel joints or on windows. If it appears on the walls and is no bigger than one hand, you can take action. Put on rubber gloves and remove the mould with water, a detergent or mildew remover or water and bleach. For smaller areas, high-grade alcohol is usually sufficient. However, care must be taken not to damage the surfaces.
  2. Mould occurs in a single room. Perhaps it is only one spot and the area is smaller than half a square metre. It may be due to a defect in the building, such as water damage to the ceiling or a crack in the wall. Remove the stain as in step 1 and wear a respirator. However, consult a specialist to examine the mould more closely and clarify the cause. If necessary, the ceiling or wall should be renovated.
  3. Mould appears in several places over a large area (larger than half a square metre), the stains quickly become larger - and you can smell the mould. In this case, only a specialist can intervene, first clarifying all the causes and then removing the mould professionally. Moisture and mould can cause lasting damage to a building in a short space of time, so you need to act quickly. Failure to do so will result in serious damage that will require costly renovations or reduce the value of your home.

Houzy Advice

Good to know

Further information can be found in the brochures "Attention mould" and "Mould in living spaces" of the Federal Office of Public Health FOPH.

Prevent Mould with the Right Ventilation System

Prevent Mould with the Right Ventilation System

Get free offers from our certified regional experts.
Request Offers for Climate Now

Is mould dangerous to health?

Mould spores are always in the air. In normal concentrations they are harmless to humans. However, the more severe the mould formation, the greater the health risks. Mould spores can irritate the eyes, respiratory tract or skin and trigger allergies, asthma or bronchitis. People with a weakened immune system or a pre-existing condition such as cystic fibrosis or chronic asthma should avoid contact with mould at all costs. Mould also affects the well-being of healthy people.

Are mould measurements useful?

Mould measurements such as those made on room air, house dust or swab analyses are time-consuming. They are not suitable for assessing health risks in living spaces and are of limited use in selecting appropriate measures. Mould measurements are snapshots that depict situations that can vary considerably over the course of a day and even more so over the course of a year. For this reason it makes more sense to hire a specialist in building damage or building physics to assess the damage on site and document it photographically. In general, we recommend saving money for a mould measurement.

Plasterers and painters are familiar with mould. In our craftsmen catalogue you can find painters and plasterers in your area who we can recommend and who can help. Requesting a free and non-binding offer is quick and easy.

Find Plasterer and Painters

Read more about

No items found.

Share article

Was this article helpful?

Related articles

No items found.