On the indoor thermal behavior of a building with cool envelope components

During the last decade, computational fluid dynamic simulation tools have been widely applied for accurately modelling outdoor airflows and local microclimate conditions. In fact, a complete understanding of heat transfer phenomena occurring within the built urban environment is needed to properly predict the energy balance, both on a single-building and on an inter-building scale. In this scenario, several research studies have been carried out to evaluate the impact of local passive solutions on buildings indoor environment, especially by means of dynamic simulation tools. However, only a few investigations were performed by considering the local distribution and spatial variability of the indoor building physics generated by the application of passive cooling strategies. The present research is aimed at bridging this gap by modelling the indoor thermal environment of a case study prototype building, i.e. square cavity, located in central Italy, by considering indoor heat transfer phenomena. A calibrated and experimentally validated CFD model of the building was elaborated to predict the indoor temperature distribution and profile generated by the application of an innovative highly-reflective cool façade painting and cool roofing membrane on the building envelope, compared to a more traditional "non-cool" envelope finishing. So far, the authors have produced only one work about cool roofs in buildings that concerned sloped roofs in a non-insulated building envelope. Here, we deal with insulated architectures, designed according to the recent energy efficiency regulation, and a combined cool roof and cool façade indoor effect. The experimental validation of the model is carried out by means of experimental data that are continuously monitored both inside and outside the case study building by means of dedicated microclimate and weather stations. Simulation results were therefore post-processed in terms of (i) indoor temperature and (ii) indoor airflows. Main findings confirmed the huge potentiality of the model in realistically reproducing the indoor behavior of the case study building and therefore the urgent need for a CFDbased approach in investigating thermal-comfort conditions. In fact, a non-negligible and positive impact of the cool building envelope on the local indoor thermal comfort conditions is detected with respect to the more traditional non-reflective component.