*3.1. Analysis of the Prototype. Free-Floating Temperature Regime*

In 2019, the "Peltier" device was switched off, in a free-floating temperature regime. Figure 8 presents the interior temperature of both cabins and the exterior temperature over the last week of April, May, June, July, September, and October of 2019. In all the cases, the interior temperature of the WFG cabin (*Tw\_air*) was 5 ◦C below the internal temperature of the Reference cabin (*Tr\_air*) and reached similar or slightly lower values compared to the outside temperature (*T\_ext1*). When analyzing 27/04/2019, *Tw\_air* almost reached 20 ◦C, while *Tr\_air* was 25 ◦C. Likewise, during the night on that day, the minimum *Tw\_air* remained at 7 ◦C, while *Tr\_air* dropped to 3 ◦C when the outdoor temperature reached 0 ◦C. Furthermore, in July, the maximum values for *Tw\_air* were below *Tr\_air* and *T\_ext1*. The minimum temperature inside the WFG cabin did not drop as much as that inside the Reference cabin. On 24/07/2019 the graph shows that the maximum *Tw\_air* was 34 ◦C, while the *Tr\_air* reached 40 ◦C, and *T\_ext1* remained at 38 ◦C. During the night, *Tw\_air* reached 25 ◦C, while *Tr\_air* was 21 ◦C, when *T\_ext1* dropped to 18 ◦C.

Besides, Figure 8 shows the curve of the indoor temperature of the WFG cabin as a damped wave shape compared to the interior temperature curve of the Reference cabin or the outside temperature. The temperature difference between day and night inside the WFG cabin did not exceed 10 ◦C in most cases. However, the temperature difference between day and night inside the Reference cabin was around 20 ◦C. Analyzing the same parameters on 24 July 2019, it can be observed that the difference between the maximum (34 ◦C) and the minimum (25 ◦C) temperature inside the WFG cabin was 9 ◦C, while the difference between the maximum (40 ◦C) and the minimum (21 ◦C) temperature inside the Reference cabin was 19 ◦C. However, the difference between the maximum (38 ◦C) and the minimum (18 ◦C) outside temperature was 20 ◦C. The interior temperature curve of the WFG cabin is flatter than the reference glazing one.

**Figure 8.** Comparison between indoor temperature of WFG cabin (*Tw\_air*), indoor temperature of Reference cabin (*Tr\_air*), and outdoor temperature (*T\_ext1*). Free floating temperature regime.

Figure 9 presents the indoor temperature of both cabins (*Tr\_air, Tw\_air*), the outdoor temperature (*T\_ext1*), and solar radiation from 24 July 2019 to 30 July 2019. The maximum value of solar radiation was above 720 W/m2, almost every day. Despite these high values of solar radiation, the interior temperature of the WFG cabin remained under 35 ◦C on 24 July 2019, while the Reference cabin temperature was above 40 ◦C.

**Figure 9.** Indoor temperature of both cabins (*Tr\_air*, *Tw\_air*), the outdoor temperature (*T\_ext1*), and solar radiation from 24 July 2019 to 30 July 2019.

The next step was to analyze a typical summer day in both cabins. Figures 10 and 11 show the glazing temperatures, measured in different points. There is a little difference between the surface temperatures of the outer glass pane in the WFG cabin (*Tw\_extU* and *Tw\_extD*) with the Reference cabin (*Tr\_extD*). The effect of the water flowing through the glazing affected the indoor surface temperatures in both cabins. Figure 10 illustrates that the measured indoor glass surface temperatures in the Reference cabin (*Tr\_up*, *Tr\_down*) are remarkably variable during the daily hours, according to the relevant variations of the outdoor thermal conditions and the low thermal inertia of the glazing. However, there is no difference between *Tr\_up* and *Tr\_down*. The indoor surface temperatures in the WFG was measured at the bottom and the top of the indoor glass pane. The water heats up as it moves through the glazing, and the figure explains the influence of the water flow in the temperature distribution.

**Figure 10.** Temperatures of the Reference glazing, both on the outside (*Tr\_extD*) and the inside face of the glazing (*Tr\_up*, *Tr\_down*). Sample day 25 July 2019.

Figure 11 shows the surface temperatures of the WFG facade, both on the outside and the inside face of the glazing. The external pane reached temperatures above 41 ◦C, while the maximum surface temperature on the inner pane was 34 ◦C. There was no significant difference between *Tw\_ext\_U* and *Tw\_ext\_D*. When it comes to the interior pane, the water absorbed part of the solar radiation as it flowed. There were two sensors in the upper part (*Tw\_up\_L*, *Tw\_up\_R*), and two sensors in the lower part (*Tw\_down\_L*, *Tw\_down\_R*). A 2 ◦C difference was observed between the lower and upper probe of the inside surface of the glazing. The lower part of the inner glass reaches a maximum temperature of 32 ◦C, while the upper part reaches 34 ◦C.

**Figure 11.** Temperatures of the WFG facade, both on the outside (*Tw\_ext\_U*, *Tw\_ext\_D*) and the inside face of the glazing (*Tw\_up\_L*, *Tw\_up\_R* for the upper probes, *Tw\_down\_L*, *Tw\_down\_R* for the lower ones). Sample day 25 July 2019.
