Present and future potential of natural night ventilation in nZEBs

The increase in the energy need for cooling is one of the major challenges in nearly Zero Energy Buildings. Recent constructions are characterized by high thermal insulation levels, which can be effective in preventing summer discomfort in combination with accurate control of solar gains through glazed surfaces and discharge of overall gains via ventilation. In addition, urbanization, densification and the global warming trends registered in the last decades can increase the risk and magnitude of overheating effect if an accurate design and use of correct technologies and good practices are not considered. The paper investigates the effects and the potential of natural night ventilation, as a strategy to reduce the energy need for cooling even taking into account the evolution of surrounding urban area with the exacerbation of urban heat island under future weather projections. Among the different tools available for the assessment of the cooling potential in buildings, the research focuses on two methodologies, which are adaptable to the conceptual design phase, where a first approximation of the natural ventilation potential is required. The study is developed on the weather datasets referred to the area of Milan and shows the future evolution of the night cooling potential, highlighting the importance of orienting building design towards greater integration between different passive cooling strategies for the summer period.