## 1 Introduction
### Bioclimatic Techniques  
Climatic control of open spaces requires new strategies or techniques for improving their habitability. These techniques contemplate reducing solar radiation, the temperature of the surrounding surfaces, and the air temperature.  
The effective blocking of solar radiation is the most effective measure, to such an extent that there is practically no interest in implementing any technique without eliminating the radiant exchange by a significant percentage. The immediate solution to blocking radiation is the integration of vegetation. Vegetation effectively reduces thermal radiation in urban open spaces. Many studies have quantified the reduction in mean radiant temperature under trees. For example, [PERSON] et al. [15] showed that the mean radiant temperature in a grove was 7.4 K lower than in an open space, on average. Also, [PERSON] et al. [16] showed that a 10% increase in the coverage of urban vegetation could reduce the mean radiant temperature by up to 8.3 K in general.  
In addition to using vegetation, either trees or plant covers, another possible solution is artificial covertures, whose objective is to block solar radiation. [PERSON] et al. [17] evaluated different shading strategies that integrated, in addition to vegetation, the installation of artificial covers to improve the thermal sensation in the open spaces of the students of the Faculty of Engineering of the University of Egypt. The study results showed that their integration caused a reduction in the average radiant temperature of 7 K. The use of artificial covers also presents the need to study the materials used to reduce the high absorption of solar radiation. In this line, [PERSON] et al. [18] investigated different textile materials in terms of the sensation of external thermal comfort of pedestrians in summer for their integration in solar awnings. The results showed how the integration of low-emissivity infrared textiles in the lower layer of the ceilings achieved an average daily reduction of PET (physiological equivalent temperature) of up to 2.5 K. Finally, the studies of highly reflective materials and their integration in urban architecture to mitigate the heat island and improve the habitability of spaces have been studied [19; 20].  
In addition to shading strategies, it is necessary to reduce the temperatures of the surrounding surfaces, as previously commented. In this line, the vegetation also plays a fundamental role. It is essential to block short-wave radiation (solar control solutions). However, this type of solution absorbs part of this radiation and increases its surface temperature. So, it is a significant challenge to develop solar control solutions with low temperatures (under air temperature). This effect is not the same as talking about cold material at temperatures higher than the surrounding air. That is why researchers speak of vegetation as a proper surface treatment. Many authors have studied the influence of vegetation on the decrease in surface temperature. For example, [PERSON] et al. [21] measured a vertical plant surface and obtained that its maximum temperature was 24 K lower than a reference wall. In addition to vegetation, high reflectance surfaces also have lower surface temperatures than a conventional surface treatment. The decrease in surface temperature on high-albedo surfaces has been analysed in various studies. For example, [PERSON] et al. [22] investigated the application of cold materials on ceilings and pavements. The study results showed that the surface temperature was reduced by 10 K compared to the conventional situation.  
Finally, and in general, the temperature reduction was achieved by driving cold air into the space to be conditioned, where the air was cooled through environmental heat sinks [23] and therefore had a higher temperature than cold air used in conventional building conditioning. The use of a natural sink for air cooling is possible with known techniques such as evaporative cooling [24] and innovative systems such as the \"falling-film system\" [25].