Risk indexes evaluation in view of a new showcase designing of “L’Annunciata” by Antonello da Messina

Museums are often hosted by heritage buildings, where the indoor thermal conditions are usually subjected to a free-floating regime, due to the difficulty of equipping them with HVAC systems that, generally, are highly impacting tools from a visual point of view. These technological tools, in fact, could conflict with the established arrangement of the works of art. This would represent a problem, since the indoor physical conditions of these premises must fall within the ranges of values suitable to ensure the safety of the works of art there exhibited. In addition, the increasing time spent by visitors inside museums (now offering various possibilities of leisure, ranging from the book shops to the restaurants) calls for a new attention of their indoor microclimatic conditions to comply also with the thermal comfort requirements of visitors. In the paper, a stepwise procedure is proposed, that can be easily replicated to other situations characterized by the same order of problems. Starting from the thermo-hygrometric monitoring of the site and with reference to the thermal-hygrometer requirements for the exhibited works of art (as suggested by the in force standards and rules), pertinent indicators of risk are computed. These parameters allow checking the current indoor situation and the possible needs for modifications. A discussion of these outcomes will lead to the proposal of a technical solution, suitable for the exhibition requirements of the considered site. The method is here applied to the “Palazzo Abatellis” museum building, where important artefacts are exhibited, like the famous painting of Antonello da Messina, “L’Annunciata”. It is currently displayed in a showcase specifically designed by the architect Carlo Scarpa, who established the original arrangement of the Gallery. The field application of the method revealed that the indoor conditions of the room mainly fall outside the safety ranges for this oil on wood painting. Since the layout of the museum is almost unchangeable for artistic reasons, the proposed technological solution is a new showcase, inserted into the old one, able to ensure the needed thermo-hygrometric range of values for the analysed oil on wood.