Indoor microclimatic study for book heritage preservation in historic buildings by experimental and numerical analysis: the case study of the Mario Marte library, Perugia, Italy

In order to ensure the correct conservation of the book heritage, the hygrothermal conditions of the buildings where the books are stored must respect precise ranges of temperature and relative humidity. The library “Mario Marte” (Perugia, Italy) has a basement books depository that has shown problems related to the formation of mold on books, especially in one of its rooms. This is probably caused by a combination of several factors: a low ventilation of the room, the storage of the volumes, which are placed in compact shelving and high values of relative humidity. The paper presents the results of more than 15 months of microclimate monitoring in the rooms of the book depository, in the surrounding basement and in the floors above the book depository. One of the most critical periods is the summer season when the relative humidity values are higher (up to 20%) than the suggested values for most of the time. Also in winter, even if the hygrothermal parameters remain within the ranges recommended by the regulations, there are sudden variations in temperature, caused by the heating system, which could cause mechanical stress to the books. Monitoring was useful not only to understand what the critical issues were but also to create and calibrate a thermal model of the building by using EnergyPlus 8.7. Finally, with the help of the model, interventions were proposed to obtain the best conditions for the conservation of books, trying not to use systems too expensive in terms of energy and costs.