Contributo alla conoscenza delle proprietà termofisiche delle murature storiche palermitane

This paper presents the preliminary findings of in situ measurements of thermal transmittance taken in a monumental complex in Palermo. The objective of energy efficiency, one of the main aspects of sustainable construction, is now relevant also for historic architecture. The research aims at analysing the energy performance of the stone walls of the complex, characterized by various thickness, age and construction features. Measurements are taken in accordance with the international standard ISO 9869:1994. The U-values so obtained are compared with tabular data from the Italian standard UNI/TS 11300-1:2008 and with values calculated following the UNI EN ISO 6946:2008. Nine preliminary measurements have been taken of the southern façade of the cloister; the walls, whose thicknesses are 96 cm, 56 cm and 59 cm, are plastered. The results of the comparison with calculated values depends on the standard used for the thermal properties of materials. The values calculated referring to “tufo” (ρ=1.500 kg/m3, UNI 10351) are similar to the results from measurements (the difference is no more than 17 %), while the transmittances based on “extra soft limestone” (UNI EN 1745:2012) overestimate the U-values from measurements between 10% and 39%. These preliminary findings highlight the need to study in depth the influence that local material and construction features have on the energy performance of historic architecture.