The microclimate inside the Pollaiolo and Botticelli rooms in the Uffizi Gallery, Florence

To characterise the evolution of the internal climate in some of the rooms of the Uffizi Gallery (Florence), the main thermo-hygrometric parameters (air temperature, relative humidity, specific humidity, dew point, atmospheric stability) were measured automatically for some years, and also manually, with seasonal measuring surveys. Measurements were started in 1997 and are still continuing. The use of heating, air conditioning, ventilation and lighting and the daily flux of a huge number of visitors produce rapid changes and marked thermo-hygrometric gradients in the rooms. Sharp variations are found when the system is switched on in the morning, and switched off in the evening, instead of operating day and night, which is desirable for the preservation of the paintings. The humidifying system in the Pollaiola room was found to be much too powerful, so that, instead of mitigating the relative humidity drop that is expected after a daily rise in air temperature, it increases it, forming an undesired excess of moisture. In the long run, all these cycles risk becoming harmful to the exhibits if air-temperature and air-humidity control is not regulated in accordance with the results of this study. These problems and the possible approaches to the installation of a new plant and the mitigation of these negative effects are discussed.