The ENBRUNI project is in line with the current challenges of French and European research by being at the interface of several fields structuring the action plan of the APP ANR 2023. The team is composed of three UMRs and one UAR in the humanities and materials sciences, and is associated with professionals in the field of conservation-restoration of built heritage, whose complementary skills are in line with the interdisciplinarity of the project. It also relies on the metal working group (GT Metal) of the CNRS/Ministry of Culture scientific project created after the fire at Notre-Dame Cathedral in Paris. The impact of climate change on heritage buildings is at the heart of the concern of heritage conservation actors. Lead metal, which covers or adorns many buildings, has taken on a dark-red staining colour in recent decades that differs significantly from its usual grey appearance. The formation of plattnerite, a lead dioxide, is responsible for this, without modifying the corrosion resistance properties of this metal. However, it remains poorly understood. The problematic of the ENBRUNI project is therefore built from a concrete field observation. This research aims to contribute to the understanding of the appearance of the phenomenon of the dark-red staining on lead used in historical monuments. It is articulated in three axes. The first axis is devoted to the establishment of a thorough report on the emergence of this phenomenon: from the collection of archival data (photographs and climatic data), the aims is to compare the evolution of the dark-red staining on the national buildings, according to the uses of lead (rooftop, sculpture, geographical orientation), with the environmental changes (evolution of pollutants such as ozone, the dioxide of sulphur, the dioxide of nitrogen, the pluviometry, the temperature...) during the last thirty years. The second axis aims at characterizing the mechanisms of dark-red staining formation by the implementation of ageing in climatic chambers (sulphur dioxide, nitrogen dioxide, ozone) and multi-scale studies of real samples taken from a selection of buildings under restoration works (Saint-Pierre de Beauvais cathedral, Notre-Dame de l'Assomption cathedral of Clermont-Ferrand, the Sainte-Chapelle, Notre-Dame de Paris cathedral...). Finally, the third axis will be dedicated to the communication of the conclusions of this research. Indeed, in a context where the lead issue is essentially based on public health injunctions, the results obtained will contribute to an update of the knowledge acquired so far on the ageing of this material used for the roofing and the decorations of prestigious buildings of our heritage.