Observations of the urban heat island effect in outskirts of Venice

According to European Environment Agency. data, approximately 75 % of the European population currently live in urban areas, and by 2020 it is estimated that this figure will increase to 80 % . High rate of urbanization means that increasing numbers of people will suffer the consequences of the well-known phenomenon identified as the \u2018urban heat island\u2019 (UHI) effect in the future. It is necessary that existing city spaces and new developments deal with the impacts of urbanisation and climate change designing and implementing suitable strategies that are able to promote the thermal comfort in outdoor environments. This poses great challenges, but also great opportunities in terms of urban design in finding suitable ways to mitigate the heat stress of thermal environments in outdoor urban spaces. The purpose of this current research seeks to review the methods that may be used to increase the thermal comfort conditions in outdoor spaces. This work uses an area of Mestre, the outskirt of Venice, as a case study area integrating field observations and numerical simulations to study the urban heat island phenomenon. The study focused on an area simulation of 486,000 m2 north of Via Torino and was performed during the summer period of 2012. The reasons for the choice of this area as the subject of this empirical study are the extensive use of flat roofs that are suitable for applications of mitigation strategies including green roofs, the increasing of hard surfacing (sealing) to provide parking, and the high density of commercial property with their impact on the environment for ensuring occupant thermal comfort. In the area there are also buildings for three technical laboratories of the Universit\ue0 Iuav di Venezia and for part of Ca\u2019 Foscari University which is expanding the campus adding new buildings on the existing site. Simulations performed with ENVI-met permitted to model the area and their physics behaviour, observing the effect of introducing vegetation or cool materials at street and roof level. Different mitigation scenarios are evaluated. The focus of the analysis is, in particular, on the use of permeable surfaces vegetative soil or grassed parking instead of conventional asphalt or cement pavement as soil compensation mechanisms for soil loss and on the changing replacement of traditional roofs with cool or green ones. This study aims to quantify the factors that contribute to urban heat island development proposing practical, feasible and specific solutions for mitigating their effects