Mould growth is caused by poor construction standards or poor/insufficient ventilation, not by levels of insulation.
In fact, if you insulate your house properly, you will prevent mould growth. This can be seen in many passive houses and in buildings undergoing energy retrofitting. These buildings are well insulated, airtight and completely free of mould. If the external walls are not satisfactorily insulated or not insulated at all, air moisture condenses in the cold areas, thus giving rise to the development of mould. Thermal insulation of the façade tends to raise the surface temperature of the external wall and prevent moisture from accumulating.
In this context, it is important to identify and eliminate all thermal bridges in the building. These include, for example, window apertures, i.e. the wall surfaces facing into the window or door openings, against which the respective frames are placed. In addition, external walls should not be encumbered with furniture, as this prevents the indoor air from circulating, meaning that the surfaces behind any furniture cool down.
Therefore, in summary, proper insulation of the façade and adequate ventilation are key measures that prevent mould growth.
