This paper presents the results of 20 years of monitoring indoor microclimate conditions inside the Scrovegni Chapel in Padova (Italy). Since the late 1970s, the chapel has been the subject of a series of monitoring to assess the degree of conservation of the frescos and of the building structures. The early studies allowed to operate in the best for what concerns the choice of the proper instrumentation and their positioning. It was thus possible to operate before the beginning of any restoration work measuring values of surface temperature, vertical and horizontal gradients of air temperature and relative humidity. The approach has highlighted the importance of heat transfer as well as exchanges of mass between the indoor air and wall surfaces. A subsequent monitoring period allows to measure the air temperature, humidity and surface temperatures after the restoration works. During the same period, it was commissioned to assess the requirements for the air treatment plant. Monitoring is continuous in time and a reasoned comparison of the different indoor microclimatic conditions, which over the years have been met, is here proposed. These indications suggest possible improvements of the monitoring system and of the management of indoor microclimate. (C) 2014 Elsevier B.V. All rights reserved.