The effect of Phase Change Materials (PCMs) to optimize indoor thermal comfort conditions and reduce cooling energy requirement when included in envelope components and materials is demonstrated by an extensive scientific literature (Zhou et al., 2012. Orò et al., 2012). In this view, this research consists of the development and prototyping of an innovative passive cooling polyurethane based membrane with PCMs inclusion for roofing applications (Pisello et al., 2015). The nanoscale morphological characteristics of the composite membrane are assessed and compared to the classic one without PCM inclusions. Then, thermal-optical properties are determined through laboratory analyses. Additionally, calorimetry tests are performed to study the role of different concentration and phase change temperature of PCMs in terms of thermal storage/release potential. In particular, PCMs with transition temperatures at 25°C and 55°C are considered. Finally, the thermal-energy analysis of such composite membrane is performed by means of calibrated dynamic simulation of a prototype building located in central Italy (Figure 1). In particular, the effect of PCMs with varying phase change temperature is assessed in different climate conditions both in winter and summer conditions. To this aim, the roof configurations are simulated and compared with and without the integration of PCMs with different transition point i.e. 25°C, 35°C, 45°C, and 55°C, in Mediterranean climate, i.e. Rome, and in Hot desert climate, i.e. Abu Dhabi. Additionally, the inclusion of PCMs into non-cool bitumen based membrane is evaluated with the purpose to optimize the choice of the proper PCMs by taking into account the passive cooling capability of the inclusion medium.