INFLUENCE OF THE BUILDING ENVELOPE ON THE OUTDOOR CLIMATE: AN INVESTIGATION ON AN URBAN CANYON IN MEDITERRANEAN CLIMATE

The properties of the materials used in the building envelope play an essential role in defining building performance in terms of thermal comfort and energy savings. However, researchers have seldom considered that two separate effects must be investigated. Indeed, as a first effect, for a given outdoor climate the envelope features directly affect the heating and cooling load generated to ensure indoor comfort. On the other hand, the building envelope has also signifi-cant influence on the urban climate, due to radiant and convective heat exchange with the out-door environment. This modifies the local microclimate, both in terms of local outdoor air tem-perature at the street level, and in terms of Mean Radiant Temperature (MRT) perceived within urban canyons. It is thus attractive to explore the influence of envelope retrofit strategies in terms of mitigation for urban and indoor climate, in light of this twofold effect. This paper de-scribes a preliminary study of the outdoor comfort in an urban canyon located in Catania, based on a parametric model built through Grasshopper for Rhino. As a first step, the Urban Weather Generator Tool was used to morph the Typical Weather File available for the airport of Catania and adapt it to the local urban context. Then, thanks to the Honeybee/Ladybug plugin, it was possible to calculate the MRT perceived within the canyon in the summer, as well as the Universal Thermal Climate Index (UTCI). As a second step of the study, a series of enve-lope solutions were tested, and their effect was considered both on the cooling load of the building and on the MRT/UTCI values. Finally, the capability of different finishing materials to change solar reflectance and thermal emissivity and to mitigate local microclimate of urban can-yons was considered.