## 2 Materials and Methods
### Thermal Comfort Index  
The thermal comfort model COMFA was used to predict the impact of outdoor school conditions on the human body. For the present study, acceptable thermal comfort conditions are considered to be those defined in the research proposal by [PERSON] et al. [43] for outdoor environments. An exhaustive analysis of models of thermal comfort and the applicability of each according to the climate and the intended aim was recently conducted by [PERSON] et al. [44]. This research distinguishes between three categories of thermal comfort: thermal indices, empirical indices, and indices based on linear equations. The indicator used in this study is proposed in the COMFA model, proposed by [PERSON] et al. [23] and later reformulated as COMFA+ by [PERSON] et al. [45]. This update adds the impact of urban shapes on the thermal load using the factors BVF and GVF. The authors propose calculating these parameters using simulation tools. Likewise, [PERSON] et al. [13] reviewed 26 studies about methods and tools to calculate outdoor comfort. The authors conclude that verifying that the COMFA rating is acceptable in other conditions is necessary. For example, it should be verified in hot regions such as Seville using measured data and the evaluation of subjective thermal sensation. This is one of the aims of this study. The heat load indicator, \(Q\) [W/m\({}^{2}\)], is defined as the heat load that the body needs to gain (in winter) or lose (in summer) to maintain its comfort zone. This indicator belongs to the group of direct indicators as it can be calculated using a basic measurement of the environmental conditions [24]. The thermal load \(Q\) [W/m\({}^{2}\)] was calculated through Equation (1). \[Q=\left(M-W\right)-\left(R+C\right)_{req}-E_{req} \tag{1}\]  
where \(M\left[W/m^{2}\right]\) is the heat generated by metabolism, \(W\left[W/m^{2}\right]\) the mechanical work, \(\left(R+C\right)_{req}\) are the convective and radiant heat fluxes exchanged by the person but taking a required skin temperature \(T_{SKreq}\) To reach outdoor comfort conditions according to  
Figure 10: Example of a survey session. ISO 7933:2004 [46]. Likewise, \(E_{req}\) refers to the perspiration required by the body as defined by the same ISO 7933:2004 [46]. Both terms are defined in Equations (2) and (3). \[T_{SK_{req}}=35.7-0.0274-(M-W) \tag{2}\]  
\[E_{req}=0.42-(M-W-58.15) \tag{3}\]  
All of the above variables are defined in terms of a person's transfer area as defined by [PERSON]. & [PERSON] [47]. The definition and quantification of these variables have been defined in detail by ASHRAE [10]. For the present work, the acceptable thermal comfort conditions defined by the proposal of [PERSON] et al. ([PERSON] et al., 2014) for exteriors have been considered. The authors override the work value W and take a value of \(M\) of 2.5 met (116.3 W/m\({}^{2}\)), which is equivalent to an average activity between light (2 met) and moderate (3 met). Light activity refers to people at rest or walking slowly, and moderate activity refers to a walk at 1.3 m/s. The excitations of the outdoor are formulated in the term \((R+C)_{req}\) of Equation (1). This term refers to the flow of heat exchanged by the person. (Skin temperature required since Equation (2)) with the air (convective), surroundings (radiant flux--longwave), and with the sun (radiant flux--shortwave). Equation (4) shows the details of the formulation. \[(R+C)_{req}=h\cdot\left(T_{SK_{req}}-T_{oA}\right)+\varepsilon\cdot\sigma \cdot\left(T_{SK_{req}}^{\  
The methodology designed can be described with the following points:  
* Choose an area to study. It should be an open space representative of the city. This work has chosen the common areas of an educational area (see Section 2.1). This area has characteristics that justify its interest, as shown in Section 2.5.1. * Once the study area has been chosen, a fixed environmental monitoring system is installed (see Section 2.2 and Figures 5-7).