## 4 Conclusions  
Studies concerning libraries in historical buildings underline the priority of microclimate monitoring for evaluating critical issues in the conservation of artworks and the planning of future retrofitting or management strategies. This paper, in fact, illustrates the results of a methodological approach in which measured thermo-hygrometric parameters were analysed not only to investigate the environment in terms of human comfort and conservation requirements, but also to study biological and entomological issues and to provide a basis for restoration activities. Given the complexity of the case study, the aim of the research was to define a guideline for library staff based on an innovative monitoring system, in terms of effective strategies for risk reduction. The method was based on a multidisciplinary approach, which involved different professional figures and various areas of investigation: indoor microclimate monitoring, biological and entomological studies, and building simulations aimed at evaluating the impact of the strategies. The study showed that the intermittent operation of the heating system in winter caused temperature oscillations between day and night. The problem was the opposite in summer: without an air conditioning system, temperature values were too high, especially on the mezzanine level, due to the solar radiation through the windows which had no system of shading control. The worst season was during the warmer months when temperatures were outside the ranges recommended by conservators. This aspect was also confirmed by restorers, with high temperatures being identified as the main cause of damage to the books (darkening and discoloration of the ribs of many volumes and paper dissolution), while relative humidity resulted in values inside the acceptable range for all seasons. Analysis of the building highlighted the limits of the HVAC system, but being a listed building, any retrofitting strategies would have to be suitably designed and approved. For this reason, thanks to a calibrated thermal model of the building, some passive strategies with a low impact in terms of implementation and economic commitment were simulated at a preliminary stage. The first of these concerned the total closure of the internal shutters when the hall was not occupied. The second concerned the installation of solar control  
Figure 14: Protocol for the curators for the management of the windows’ shutters and natural ventilation during events. films on the windows. Each strategy was simulated individually and then combined. The effects in terms of temperature variations were very low, especially when a single strategy was adopted. When they were combined, in the warm seasons, the temperature decreased by about 1 \({}^{\circ}\)C. These strategies are, however, recommended for mitigating illuminance levels, even if this was not part of the study. Thanks to the new Wi-Fi sensor system, which also measured the CO\({}_{2}\) concentration (with recordings available online and in real time), it was also possible to propose window opening strategies for natural ventilation and obtaining air exchange during crowded events. In fact, this was the only way of guaranteeing human comfort in terms of air quality and in relation to external conditions, without a mechanical ventilation system. Thanks to the analysis of CO\({}_{2}\) concentration data registered during some relevant events, it was possible to estimate the benefits obtained from opening the windows before the CO\({}_{2}\) reached high values. Obviously, this empirical method was based only on CO\({}_{2}\) concentration, without considering anything in terms of energy saving or thermal comfort. Future developments concern the study of an MVHR system (Mechanical ventilation Heat Recovery System), capable of providing good indoor air quality and mitigating unsuitable conditions in warmer seasons while contemporaneously protecting the artistic, structural and historical characteristics of the hall. Conceptualization, E.M., F.S. and M.F.