Basic descriptive statistical methods for monitoring and evaluation of microclimates in Cultural Heritage

Inappropriate temperatures and relative humidity (RH) conditions quite often affect the conservation state of heritage buildings and outdoor archaeological sites. In such cases, a long-term microclimate monitoring is the first step to assess the conservation risks and to propose corrective actions. When a set of temperature and RH sensors are installed for this purpose, the amount of recorded data is usually high, and a suitable statistical methodology is necessary for the data analysis. A case study dealing with this issue is presented here. A set of 26 RH data-loggers and 26 temperature data-loggers were installed in four rooms of Ariadne's House (Pompeii, Italy) at different heights and wall orientations during 372 days. A negative correlation was found between mean values of temperature and RH. Plots of mean daily trajectories show that ambient conditions are different in each room, which provides guidelines about corrective measures to be taken. Principal components analysis was also applied to better characterize the data variability.