Improving summer energy performance of highly insulated buildings through the application of a thermal analysis by numerical simulation

The work presented in this paper is aimed at deepening the optimisation of the energy performance of highly insulated buildings in summer conditions through the application of an original methodology of thermal analysis. The methodology, already presented in a previous work (Ballarini et al., 2011), allows us to investigate the building energy balance and identify the most important parameters affecting the energy performance under certain conditions. The analysis is developed through the application of a dynamic simulation tool (EnergyPlus). The methodology consists of analysing the different contributions to the convective energy balance on internal air and their interrelations with different boundary conditions. Each contribution is split according to the dynamic driving forces of outdoor and indoor environment, i.e. external air temperature, solar radiation, internal air temperature and internal heat sources, and it is referred separately to the specific groups of components that exchange heat with internal air. This work focuses on the application of the above thermal analysis to a highly insulated single-family house in summer conditions, in two different Italian climatic zones. The methodology provides the mean values and the standard deviations of the contributions to the convective energy balance on internal air, and allows both to identify the main causes of low energy performance and to quantify the effects of possible retrofit or operational measures. As an exemplification, the effect of increasing the air change rate by natural ventilation during the night is investigated. The results show how the energy performance could be improved also in highly insulated buildings located in warm climates.