Ancient Romans and daylighting: the case of Villa of the mysteries in Pompeii

The goal of the paper is to analyse the daylighting design criteria in ancient Roman domus, by using as case study a famous ancient Roman building: the villa of the Mysteries in Pompeii. At this purpose the work is divided in two sections: a typological analysis of the roman houses, aiming at understanding the link between the ancient building criteria and the daylight harvesting ones; a dynamic simulation of the daylight conditions inside the Villa of the Mysteries. In this regard, to assess the indoor daylight availability an ad-hoc methodology, based on the proposal of a new set of performance metrics (the Characteristic Daylight Illuminance -CDI-; the minimum CDI - CDImin-; the spatial CDI -sCDI-) is introduced in order to process simulation results. Results demonstrate that in the past there was a strong correlation between building criteria and daylighting ones: the choices about the dimensions of the windows and the use of static shading systems (porches and peristyles) were wise and reasoned. Moreover, there was a correspondence between daylighting criteria and the functions of the spaces: the more prestigious a room was, the more daylight entrance was permitted. Daylight levels were generally higher in representative spaces like atria, triclinia and tablina, with CDImin values generally comprised between 200 lx and 500 lx, and lower in cubicula and service/working spaces, with CDImin values generally comprised between 0 lx and 100 lx. The obtained results can be useful to design the modern electric lighting system in the villa. Moreover, the proposed analysis methodology can be easily exported to other applications (both ancient and modern buildings). Further studies should apply the same methodology to other case studies to verify if the outcomes of the research are generalizable.