The deterioration of the walls caused by humidity involves important aspects not only aesthetic but also of hygienic nature.
As far as hygiene and health aspects are concerned, it is appropriate to discriminate between practical evaluations (chemical compounds and microorganisms that often lead to human health problems: infections of various kinds, allergic reactions, release of harmful substances in the internal environments) and definitions relating to the “legal” aspects that may follow and for which it is necessary to refer to the “Municipal Regulations of Hygiene and habitability”.
In general, it is worth pointing out that bioclimatic defines the ideal range of humidity between 40 and 60% as the ideal humidity range of an indoor environment (intended as the hygrometric degree of the air).