Cool roof for passive cooling: simulations of an existing building in southern Italy

Roofs are the envelope component more severely hit by solar radiation in summer (1470 kWh/m2 on average in Italy), hence one may expect that using cool materials on the finishing layer of a roof should provide a significant reduction in the heat flow entering the building, with sensible relief in terms of building cooling load.  In this paper a case study is presented, based on the dynamic simulation of an existing office building in Catania (Southern Italy). In this building, a part of the roof has been recently treated with a commercial cool painting, with the aim of improving the thermal comfort in summer. Hence, the simulations represent a preliminary study, that will allow to assess the expected effectiveness of the intervention. More in detail, the results of the simulations will be discussed both in terms of thermal comfort and energy savings due to the use of the cool painting, through the evaluation of parameters such as the roof surface temperature, the operative temperature and the cooling load for both conditions, i.e with and without the cool painting on the roof.  
The paper also discusses the potential increase of the energy needs for winter heating, and looks at the overall balance in terms of primary energy. These aspects are usually not well highlighted in the current scientific literature.