Exploring the impact of the urban modified albedo on the indoor temperature and the ventilative cooling potential in a typical Italian residential building

Urban heat island, with the associated urban overheating, is a well-documented phenomenon, which demonstrates the hazard related to local climate change and the related negative impacts at environment, economic, social and public health level, with heavier consequences on the low income and more fragile segment of the population. The phenomenon takes origin by the positive thermal balance in the urban built environment mainly, depending on the synergic effect of different causes. It is also associated with a typical atmospheric circulation, playing a significant role in local dispersion processes. The interaction of local and global climate change exacerbates the thermal quality of cities, with more frequent and more intense extreme events, being the heat waves the most relevant. Several solutions exist to counteract urban overheating, and three main categories are identified: blue (water), green (vegetation) and white (materials) technologies. The present study investigates the potential of ventilative night cooling improvement in residential buildings in the city of Rome, Italy, by dynamic analyses carried out at mesoscale and building level. Initially the land and atmospheric models of the city are implemented in the Weather Research and Forecasting model, in a next phase the whole model was validated against the near surface temperature and wind speed ground measurements., Then, a number of different albedo scenario is defined and simulations are run for the hottest months (July and August) of the year 2020. The so obtained weather data set are used as input to simulate the thermal performance of a typical residential Italian buildings using TRNSYS 17 software, with a dedicated routine based on a simplified model to take into account the contribution of the natural ventilation. The operative temperature is the key performance indicator for the analyses and the number of discomfort hours, calculated according to the relevant standard, are used to quantify the impact of the urban modified albedo on the thermal response of residential buildings.