Thermal-energy analysis of roof cool clay tiles for application in historic buildings and cities

More than 90% of historic buildings have traditional clay tiles as roof covering exposed to solar radiation, largely impacting buildings' thermal-energy performance and urban climate, since most of historic buildings are located in dense urban contexts. In this view, the optimization of these traditional elements could represent a key research issue, with the purpose of building energy retrofit and the constraint to preserve architectural heritage. This paper concerns the year-round analysis of the thermal-energy performance of a typical 16th century historic residential building located in central Italy where an innovative cool clay tile is installed in a continuously monitored two-floor residential unit. Main results show that the proposed tiles, having good visual similarity with respect to the classic tiles, represent an effective solution to improve building energy efficiency during the cooling season and, if applied at larger scale, they could represent an effective UHI mitigation technique. In particular, maximum primary energy saving for cooling is 51%, while heating energy penalty is lower than 2%. The combined multi-scale analysis finally showed how these tiles represent an effective non-invasive strategy to (i) optimize thermal-energy performance of historic buildings even in temperate climate, and to (ii) mitigate urban climate.