A model for programming design interventions aimed at reducing thermal discomfort in urban open spaces

The environmental quality of urban spaces is strongly related to the thermal comfort perceived by people in open areas. At the micro-scale of neighbourhoods, the mitigation of the heat island effect can improve both the well-being of cityusers in the public realm and the energy performance of buildings. A model intended for urban designers is presented, and it sets out to evaluate critical areas in the city context and defi ne sustainable design solutions and concrete actions on the physical environment, in order to increase thermal comfort. In particular, variables used in the model are basically related to urban geometry, such as the accessibility of sunlight, sky view factors, aspect ratios of street canyons, and to the physical materials in the city, such as the albedo of horizontal and vertical surfaces and vegetation density. The technique is based on the use of algorithms defi ned in a Matlab environment and derived from image processing of Digital Elevation Models (DEMs) of the urban texture. The application was tested on the case study of the Politecnico di Milano’s main campus, located in the city of Milan. Especially in the case of limited resources, the results of the analysis suggest how public administrators and decision-makers could benefi t from programming specifi c site interventions, based on the identifi cation of critical weaknesses emerging at several points in the city. Moreover, the study focuses on the application of cool surfaces, the role of building layout (shape and size) and the effects of increasing the vegetation. Even in the absence of expensive thermal imagery from remote sensing, but simply referring to available cartography, this low-cost technique makes it possible to very quickly set up feasible environmental strategies over extensive urban areas.