Why do I need a controlled room ventilation system? Until now I did just fine without one.

Due to the intention to save energy, the requirements in terms of air tightness of the building envelope have been considerably tightened in recent years, for example, due to the Energy Savings Regulation (EnEV).

Against this background, new buildings and refurbished buildings became air tight in such a way that a sufficient air quality within the building can no longer be ensured by normal ventilation behaviour.

A well-known example: new tight windows. Opposite windows would have to be opened for about 10 minutes (depending on wind and outside temperature) every 2 hours each day and night. These requirements can hardly be fulfilled so that the serviceability of the flat or the building is no longer safeguarded.

The result is such a bad air quality due to mould growth, radon, evaporations of construction materials etc. that the number of respiratory diseases and allergies has quickly increased in recent years. Mould can also cause permanent damage to the building. Besides the possibility of selectively making small holes into the external wall (“external wall air outlets�), which is rather senseless with regard to energy and hygiene, there is nothing else for it but to ensure the minimum ventilation using fans.