Thermal Performance of Innovative Building Envelope Systems in Mediterranean Climate

Energy efficient buildings, besides saving energy, should provide adequate indoor thermal comfort. Hence, to max- imize advantages, a balance between different energy effi- cient technologies and solutions must be found. In this sense, the European directives on the energy performance of buildings have defined a high standard of thermal insu- lation for buildings in order to comply with strict energy performance limits. However, several studies have high- lighted that such an approach can have negative effects in summer, especially in the Mediterranean area, thus induc- ing an increase in the energy needs for cooling and a remarkable overheating. In this context, the main objective of this study is to inves- tigate the thermal performance of Vacuum Insulation Pan- els (VIPs) and Phase Change Materials (PCMs) when applied to the building envelope, and their ability to im- prove the building thermal behavior in the Mediterranean area. To this aim, a numerical model of a test room with standard construction technologies was implemented on Design Builder. This model was validated against experi- mental measurements available in the literature. Once the model was calibrated, a further series of simulations was performed by applying to the same test room the above- mentioned innovative building envelope systems. The simulations were run both in free-running conditions, in order to assess thermal comfort and thermal inertia of walls, and by assuming the presence of an HVAC system, to calculate the energy needs for space heating and cooling on a yearly basis. The results highlight that, in summer, thermal discomfort and remarkable increases in the energy needs for cooling may occur when the building is retrofitted with VIPs, whereas better conditions are achieved with PCMs.