Exceeding what percentage of relative humidity could lead to mildew in a building?

Mildew growth in buildings is strongly influenced by humidity levels, and maintaining appropriate humidity is crucial for preventing fungal growth. The threshold at which mildew begins to form is typically around 60% relative humidity. When humidity levels surpass this percentage, it creates an environment conducive to moisture accumulation, which can subsequently lead to the proliferation of mildew and other fungi.

In situations where the relative humidity consistently exceeds 60%, not only does it provide the necessary moisture for mildew to thrive, but it also inhibits the drying process of building materials, further exacerbating the problem. Keeping indoor humidity below this threshold is thus a vital aspect of building maintenance and indoor air quality management.