# Improving School Transition Spaces Microclimate to Make Them Liveable in Warm Climates
## 1 Introduction  
Global average temperatures have increased over the last decades and their effects are worrying for today's population. This rise in average temperatures is speeding up even more in large cities with the so-called urban heat island (UHI) effect influencing the daily life of these cities [1]. This thermal phenomenon implies that, while in rural areas the temperature decreases during the night, in the cities this cooling does not occur, producing an overheating of the urban downtown. UHI is more noticeable in hot periods when materials with high thermal capacity act as urban heat sinks during the night. Furthermore, in addition to the thermal accumulation produced by the materials, the massive construction of the ground in the big cities prevents adequate ventilation that helps to reduce this effect. This singularity, related to urban density, has been confirmed by numerous studies at different latitudes, with a value reaching up to 12 \({}^{\circ}\)C between rural and urban areas [2, 3]. The main difference between the two areas is the presence of hard materials, which are thermally absorbent compared to the nature that invades the rest of the spaces. Therefore, the increase in the presence of vegetation can help to balance this aspect. Increasingly prevalent summer heatwaves are detrimental to people's comfort and impair their abilities and health [4]. These heat waves are causing even higher overheating in large cities dueto the UHI effect. In the city centers, the UHI in the summer is caused by the absorption of the high solar radiation by the urban surfaces [5]. Therefore, the comfort of the inhabitants of large cities is compromised and, hence, mechanical cooling of homes and workplaces is generally used, modifying the air quality and contributing to the city overheating [6]. Overheating is directly related to health. Heat absorption by the human body can lead to serious health problems in populations at risk. Reducing warming, especially in large cities, is a real and current problem. Therefore, making cities cooler seems to be of vital importance for public health [7]. Passive strategies such as courtyards have been incorporated by traditional architecture helping to temper the buildings overheating [8]. Not only their geometry but also the building envelope, especially cladding materials used in facades and outdoor pavements, are elements involving a great impact on the microclimatic conditions of the building's environment. This influence is especially relevant in semi-outdoor or transition spaces such as inner courtyards since their specific microclimates are less dependent on climatic phenomena such as wind speed and direction and other associated thermal convection flows. Courtyards are essential for the proper balance of city porosity, understanding porosity as building voids, so their treatment and study will be fundamental in reducing the UHI effect of cities. The percentage of urban areas assigned to these spaces is significant in Mediterranean cities, so variations in their cladding materials can widely modify the overheating of these spaces [9]. Courtyards not only generate a specific microclimate but also are in direct contact with the building's internal rooms, contributing to the comfort of these indoor spaces and reducing the use of mechanical cooling systems, a fundamental aspect in the increase of temperature and air quality in cities [10]. The albedo is defined as the measure of the diffuse reflection of solar radiation out of the total solar radiation that is reflected by the surface of a particular material. The albedo value ranges from 0 to 1, being 0 the value for a material surface that absorbs all the radiation it receives, and 1 for a material surface that does not absorb any radiation but reflects 100% of it [7]. The materials used as the coating surfaces have an important role in the reduction of the thermal gains and the overheating of the cities.