Humidity and mold growth / In residential areas

The pleasant climate in the room is the basis for a good feeling in the home. Humidity in the rooms primarily affects the quality of the climate in the room. Relative humidity between 40% and 65% is considered a pleasant and healthy room climate, and it largely depends on the following factors:

  • Daily activities at home
  • The use of showers and bathtubs, as well as the natural breathing of people, animals and plants
  • Temperature and weather conditions

Proper room climate is essential for the health and maintenance of living spaces. Adequate climate can effectively prevent the formation of mold in colder places of exterior walls or in humid rooms. To avoid mold on the walls, it is necessary to maintain the humidity at a level comfortable for tenants and buildings through ventilation, adopting ventilation procedures that meet certain conditions. For more information on proper ventilation, you can find it on our info page Windows and ventilation of living space.

The ratio of temperature, humidity and mold growth

The amount of moisture contained in one cubic meter of air varies as a function of air temperature. Warm air can absorb more moisture than cold air. At a room temperature of 20 ° C and a relative humidity of 60%, one cubic meter of room air contains 10 g of water. If the room temperature drops to 8 ° C, the room air can only absorb half the moisture. This means that 50% of the moisture evaporates and appears as condensed water, mostly on the colder outer walls, and at these points the risk of mold growth also increases.

Dew point and critical temperature for the appearance of mold

When the relative humidity reaches the limit value of 100%, excess moisture begins to condense and forms condensed water. The temperature at which condensation occurs is called the dew point. Since relative humidity is a function of air temperature, the dew point varies depending on the situation. For example, the dew point at room temperature of 20 ° C, with a relative humidity of 50%, is 9.3 ° C.

It is known that mold can begin to form as early as 80% humidity. As in the example just given, this means that mold can form on surfaces with a temperature of 12.6 ° C or lower, on walls, and especially in corners and niches.

Humidity it can be regulated and maintained at a comfortable level, primarily by proper ventilation. Due to modern construction standards and growing demands for energy efficiency in new buildings, more and more importance is attached to the topic of residential ventilation. Since 2009. The ventilation standard DIN 1946-6 prescribes the preparation of a ventilation concept that ensures minimal air exchange in new buildings or during major renovations.

For more information on this topic you can find on our info page aboutDIN 1946-6 or at a web address

For advice on new buildings or renovations, Deceuninck partners are at your disposal!