Recommendations

How mould grows in the home

Mould growth typically occurs for two reasons:

damage or defects in the building itself; or
high levels of moisture in the home, due to the occupants' activities.

An expert can determine the origin and cause of mould growth.

Recommendations to prevent the growth of mould

If there are no defects in the building, the following tips can help to regulate moisture levels in the home and prevent the growth of mould:

Ventilation

To prevent the growth of mould, the home should be ventilated regularly and effectively. Ventilate all rooms at least twice a day. In general, it is recommended to avoid leaving windows slightly ajar (especially in cold weather), and instead to leave them – and doors – wide open for a short time. In winter, doing this for 5-10 minutes is enough to renew the air and reduce humidity. When windows and doors are left open for a short time only, the walls do not have enough time to lose the heat that they have accumulated, so there will be no noticeable drop in room temperature.

Ventilation guide (from least to most effective)

Temperature, humidity

The recommended relative humidity level is between 30 and 70 %. For ambient air, the ideal relative humidity level is between 30 and 60 %.

Above 70 % air humidity, a large number of mould species can develop. Above 80 % humidity, practically all mould species can grow.

The relative humidity of the ambient air can be checked easily using a hygrometer. Low-cost hygrometers, or devices that measure both temperature and relative humidity, are readily available on the market.

Different species of mould grow at widely variable temperatures. In general, it is recommended to avoid significant drops in temperature, which could cause condensation.

Last update 07.01.2026