How microclimate mitigation affects building thermal-energy performance in residential zero energy Italian settlements

A key research effort has been dedicated toward zero energy buildings in the last decades. Recent interest is currently switching its focus from single-building scale to the inter-building scale, by enlarging the thermal-energy balance up to the settlement level, with the purpose to optimize the whole district energy efficiency and its environmental sustainability. This scale enlargement up to the district size leads to further optimization opportunities that must be considered when performing building thermalenergy dynamic simulations. In this view, buildings within net Zero-Energy Settlements (nZES) can improve their performance thanks to outdoor microclimate improvement techniques that could succeed in mitigating both winter thermal losses and summer overheating risks. In this work, microclimate modeling and building dynamic simulation tools are integrated to assess the impact of varying microclimate conditions on the building energy performance at a settlement level. The case study is performed on a residential district in Italy. In particular, microclimate simulations are carried out to predict the mitigation potential of specific strategies applied at settlement scale, i.e. cool materials, greenery, and their combination. Therefore, starting from the results of the microclimate optimization, new microclimate boundary conditions are generated to be used within the dynamic simulation environment. The final aim is to quantify the impact of such optimized microclimate boundary conditions on the buildings energy performance. The results from the microclimate simulations, supported by the European funded Horizon 2020 project ZEROPLUS, highlighted how microclimate can play a key role in affecting outdoor thermal comfort conditions. Moreover, the dynamic simulations carried out by using the results from a microclimate optimization as input weather files, always show a decrease on the final energy needs of the building in the nZES. The highest and non-negligible reduction is reached in the final cooling need of the optimized scenario by coupling both cool and green optimization strategies, i.e. about 12 % of the initial value.