Investigation on the interaction between the outdoor environment and the indoor microclimate of a historical library

none3noIn recent years, the study of the indoor microclimate has assumed increasing importance, both in relation to the health of people living in confined environments for a considerable part of their time, both for the problems associated with the conservation of works of art and cultural heritage housed in museums, galleries and libraries. In this paper, we present the results of a measurement campaign carried out in two periods of the year, which can be considered "extreme" from the meteo-climatic point of view, in the Classense Library located in the city of Ravenna (Italy). This is a famous Italian historical library that houses many books of great value. The campaigns took place one in the summer period (from July 22nd to August 6th 2014) and another one in winter (from 15th December to 30th December 2014). During these measurements campaigns, we have characterized different and heterogeneous indoor environments. The internal pollutants concentrations and thermo-hygrometric data have been compared with the external ones, obtained from nearby measuring points. In this way, we have been able to determine the Indoor/Outdoor ratio (I/O ratio) of the pollutants concentrations. From these data and from the estimated air exchange rate, the pollutants deposition velocities have been calculated, too. The building has no air conditioning systems and our experimental data show that it is characterized by a relatively low rate of air exchange and a high thermal inertia. We have also compared the analysed microclimatic data with the specific values recommended by different norms and standards, in order to verify the conditions of preservation of the precious texts. Finally, we have applied a mathematical model to study the indoor pollutants concentrations, in order to confirm that the correlations between the outdoor and the indoor pollutants levels can be explained in terms of the building characteristics. The results of the model application fit well the experimental data and the consequent theoretical estimates made in this work; in fact, they are consistent with very low values of air exchange ratio of the building. These results can be used to define a specific "Performance Index" (PI) of the building, expressed as the percentage of time in which the microclimatic parameters of the library (i.e. the thermo-hygrometric values) do not match the recommended values. Furthermore, they can also provide a first step, based on experimental data, for the development, in close collaboration with the conservation scientists, of a methodology for risk assessment, specifically to be used for cultural heritage housed in museums, galleries and archives.noneAndretta, Massimo; Coppola, Floriana; Seccia, LeonardoAndretta, Massimo; Coppola, Floriana; Seccia, Leonard