## 1 Introduction
The use of cold roofs, together with the increase in the number of green spaces, is a passive cooling method that can be implemented in existing urban areas or that may be built [10]. Green spaces can minimize the impacts of urban growth, for example, by reducing the energy consumption of buildings [11]. In densely built urban areas, it is difficult to build large green areas and, therefore, replacing \"typical\" roofs with green roofs or cold roofs may be a good solution for UHI mitigation [12]. Roofs can provide an excellent space to apply these two mitigation techniques. Reflective (or cool) roofs have lighter colors and high albedo, increasing reflection and contributing to a decrease in surface temperatures. Also green roofs have several advantages, such as longer durability of materials (which are protected by vegetation), reduction of energy consumption for cooling (in summer period), improved air quality, and noise reduction, thereby contributing to the mitigation of the UHI [13]. In addition to the materials and the types of urban surfaces, urban geometric forms also play a key role in the formation of UHI. Urban morphology determines the variation of air and surface temperatures and the urban structure of a city can be considered the main cause for the formation of UHI [14]. Urban geometry is determinant in the development of heat islands since they regulate the absorption and the emission of heat, modifying the temperature of the air in the urban boundary layer, as well as the surface temperatures. Dense urban forms are usually responsible for multiple reflections of solar radiation, influencing air convection out of urban canyons and heat losses due to a low sky view factor (SVF). High buildings and narrow streets reduce SVF by increasing the amount of shaded area on the surface, keeping the bottom of the urban canyon cooler during the day but warmer at night [15]. In 2005, [PERSON] et al. proposed some mitigation measures for the UHI and urban heating of Lisbon [4]. The authors mentioned the need to maintain a high SVF, to create more green spaces within urban areas to select appropriate building materials. In addition to these wide-ranging guidelines, and with a view not only to mitigate this phenomenon but also to tackle progressive urban warming, they pointed to the need to maintain the main ventilation paths of the city and to implement \"cold\" or greens roofs in the city. In 2010, [PERSON] et al. carried out a study at the microscale, highlighting three factors that reduce urban heating, guarantee ventilation conditions, and increase summer thermal comfort [16]: urban geometry, green spaces, and building coating materials used within the city. Regarding the choice of what type of materials should be used in urban areas, three characteristics should be considered: albedo, thermal conductivity, and heat capacity [16]. This selection should be made carefully, ensuring the reduction of heat storage. However, the possible harmful effects that the choice of materials may have, such as chaining phenomena of passers-by or increasing radiative input on the human body, thereby increasing the thermal stress, also need to be considered. The present work intends to be a contribution to the decision-making and implementation of mitigation measures for the UHI adapted to the urban context of Lisbon, not only looking at the city as a flat surface but also considering the third dimension of urban areas. The main objectives of this work are (1) to calculate the radiative balance of a groups of facades in Telheiras, located in the northern part of Lisbon, (2) to obtain thermal images of the facades, using thermal infrared thermography, (3) to understand how the temperatures of the facades and other surfaces affect air temperatures of the urban canyon, and (4) to comprehend how radiative balance values recorded on facades and different surfaces influence air temperature.