## 3 Results  
### CFD numerical simulation  
The results of the simulations show how the air moves towards the building, generating a small turbulence in the lower part of the enclosure (Figure 3a) due to the impossibility of going out in the angle created between the facade and the ground. In Figure 3b, the displacement of some air particles is observed, shown in red. The simulations make it possible to observe the air particles in movement on the basis of infographics or videos. Figure 4 shows snapshots of this sequence, in which the air is introduced into the chamber through the lower part, increases its temperature, and rises until it leaves the upper part. Figure 4: Displacement and temperature of the air particles inside the chamber. From (**a**–**e**) steps of the air flow. Figure 3: Speed and direction of the air in its encounter with the building: (**a**) Model elevation and (**b**) perspective. Figure 5 shows the temperatures and relative humidity, both with low (\(\times\)1) and moderate (\(\times\)3) air velocities, for all the air chamber thicknesses studied: 1, 3, 5, 10 and 25 cm. In particular, the cutting plane is located on the outside of the air chamber, that is, on the inside of the stone cladding. Determining temperature and humidity makes it possible to locate the areas that may be susceptible to condensation (low temperatures and high humidity). This condensation is liable to deteriorate the stone material. A better knowledge of the areas in which this condensation may be produced will greatly improve the durability of the material and, therefore, the facade. This figure makes it possible to establish a qualitative analysis of the hydrothermal behaviour of the air chamber in a stone cladding enclosure with different thicknesses of air chamber and different speeds of external air. When the thickness of the air chamber is 1 cm, the inside temperature of the building is affected a lot, and the air temperature of the chamber is very high. Infiltrations of cold air from outside are clearly visible. When the air velocity is moderate (\(\times\)3), a clear decrease of the temperature inside the chamber is also shown. The relative humidity is high when the air enters the chamber, but it is drastically reduced inside the chamber. If the thickness of the chamber varies from 3 to 10 cm, the temperature decreases with greater thickness of the chamber, and the relative humidity that penetrates the chamber increases with the thickness of the chamber. For chamber thicknesses of 25 cm, being a large dimension, it can be observed that strong convection movements occur, mixing the air at different temperatures before leaving the chamber. Temperatures are higher and relative humidity is lower on the ground floor than in the upper two (Figure 5). This effect can be explained because the air does not access the air chamber with such ease through the lower part of the enclosure. As can be seen in Figure 3, turbulence occurs in this area. The following figures make it possible to analyse the data obtained by the simulations. Figure 6 shows the temperature of a horizontal plane of the air chamber, depending on its thickness and for each of the three floors of the building. The higher temperatures are logically registered together with the thermal insulation (15 \({}^{\circ}\)C approx.). Inside the air chamber, the decrease in temperature is more pronounced close to the thermal insulation, and it is less pronounced away from it. Figure 7 shows the evolution of the temperature inside the air chamber according to its thickness for the ground floor of the building, and considering low air speed (\(\times\)1) and moderate speed (\(\times\)3). In this way, it is sought to see what the influence is of air velocity on the interior temperature of the air chamber. Figure 5: Temperature and humidity for each of the ten cases studied. In cases where the air chamber has a thickness of 1 cm, there is no appreciable difference, since the curves on the graph are superimposed.