## 4 Conclusions  
In light of the current energy crisis and the need to improve building energy efficiency, this study analyzed the suitability of non-air-conditioned historical building museums to properly preserve different types of artworks. To this aim, two museums in Florence, Italy, namely, the Vasari Corridor and La Specola Museum were investigated as case studies. These museums host the exhibitions of artworks and objects that require specific microclimate for optimal preservation, according to the reference technical standards. The existing thermophysical survey and 1 year microclimate monitoring data provided the necessary information to understand the behavior of each building in terms of the trend of air temperature and relative humidity in the absence of an air-conditioning system. The analysis of data monitored during the year 2013 for La Specola and 2017 for the Vasari Corridor showed that the temperature and relative humidity trends inside the uncontrolled environments follow the outdoor climate, albeit markedly dampened in sudden hourly and daily changes. In particular, zones characterized by envelope with low inertia and/or higher exposure to external conditions, such as room X in La Specola and Ponte Vecchio in the Vasari Corridor, have indoor temperature trends similar to the external temperature trend. Moreover, the low thermal inertia of the Vasari Corridor, with large glazed surfaces and lightweight external walls and roof, is the cause of rapid variationsin temperature (over 2 \({}^{\circ}\)C) and relative humidity (up to 5%), even within the same day. However, significant differences were detected between Lungarno and Ponte Vecchio, which have different exposure to solar radiation and ratio of transparent surfaces. On the one hand, position B in Ponte Vecchio, characterized by large windows, is much more exposed to external conditions, which results in higher temperature (and lower relative humidity) in summer and vice versa in winter. On the other hand, room XXII in La Specola, which presents higher thermal inertia, and which is located inside the building and, thus, more protected from the outdoors, presents a flatter trend of indoor temperatures and significantly lower values of relative humidity throughout the year. Nevertheless, in all the analyzed non-air-conditioned zones of the two museums, the indoor temperature and relative humidity values are outside the recommended range for the preservation of the kind of objects exhibited according to the reference technical standard for most of the year. This result suggests the need to install an air-conditioning system for the proper conservation of the artwork. However, give the current energy crisis, which could even prevent the opening of smaller museums due to unattainable operation costs, to minimize the energy consumption, while preserving the artworks, this work suggests the use of a different, more variation-tolerant approach, according to the standard UNI EN 1575:2010. This approach is based on the analysis of the historical climate within the exhibition zones. The campaign of indoor microclimate monitoring conducted over a period of at least 1 year allows defining the historical climate in each exhibition zone. The analysis of the measured data using this approach allows wider objective temperature and relative humidity ranges than the individual target values that are commonly accepted as ideal conditions for the conservation of cultural heritage by the reference technical standard. Indeed, when the artworks are observed to have suffered no damage, the historical climate can be used as the actual reference range for the proper preservation of the artworks. The results of this work show that the switch to these wider ranges could limit the energy consumption for the required air conditioning without compromising the preservation of the exhibits.