*3.1. Analysis in Summer Conditions*

Figure 5 shows the system temperatures and the irradiance curve of a sample summer week from 10 July 2019 to 16 July 2019. *Ti2* and *To2* illustrate the inlet and outlet temperatures of the WFG. *T\_int* is the indoor temperature, and *T\_ext* is the exterior temperature. *T\_ext\_C* corresponds to the temperature in the corridor between the office and the exterior. The first day, 10 July 2019, was clear, with some evolution clouds between 16:30 and 18:00. On clear days, direct beam radiation prevailed over diffuse radiation. The typical irradiance curve (*Sun\_rad*) reached maximum levels above 700 W/m2. From 9:00 a.m. to 1:00 p.m., the south-west facade was shaded due to geometrical obstructions, and the irradiance was mainly diffuse, reaching values around 200 W/m2. However, in the afternoon, the facade was exposed to direct solar radiation, and the corridor temperature rose to 35 ◦C. On 11 July 2019, the indoor and outdoor temperatures showed a similar performance, although the oscillations of the inlet and outlet temperatures were different from those of the previous day. On 12 July 2019, the solar irradiance showed irregular values because of clouds, and it affected the temperature of the corridor, which was slightly above 30 ◦C. Over the weekend, on 13 July 2019 and 14 July 2019, the mass flow rate was 0 and the heat pump did not operate. Inlet and outlet temperatures of the WFG (*Ti2* and *To2*) did not show any difference and reached peak values of 32 ◦C. The indoor air temperature reached a maximum of 34 ◦C, whereas the temperature in the corridor (*T\_ext\_C*) was 39 ◦C. A WFG circuit is a closed loop and there are two cases, mass flow rate *m˙* = 0 or *m˙* = design flow rate. Over the weekend, the mass flow rate was 0 and the heat pump was not in operation. After two weekend days, the indoor temperature rose to 32 ◦C, making it necessary to cool down the office temperature. Figure 5 shows that the inlet and outlet temperatures dropped on Sunday 14/07/2019 before 7:00 a.m., although the

heating pump did not operate that day. The same behavior was shown on Monday, 15/07/2019, before 7:00 a.m. The reason was that the air heat exchanger operated both days for two hours when the difference between the top tank water temperature (*T\_tank\_top*) and the outdoor air temperature (*T\_ext*) was above 10 ◦C.

**Figure 5.** Solar irradiance and indoor and outdoor temperatures—sample summer week of 10 July 2019 to 16 July 2019.

Figure 6 shows the detailed evolution of temperatures on two consecutive days. Figure 6a shows that the irradiance curve on 10 July 2019 had some oscillations in the afternoon, and the outdoor temperature declined, which indicated the existence of clouds. The inlet and outlet temperatures (*T\_i2, T\_o2*) showed that the heat pump worked at three cycles per hour. The heat pump parameters were fixed to meet the manufacturer's requirement for minimum cycle times. Figure 6b showed that the minimum time between starts was, at least, forty minutes. On 10 July 2019 at 7:00 p.m., there was a peak in the corridor temperature (*T\_ext\_C*), and this peak did not occur on 11 July 2019. The corridor had a cooling system that was not monitored or controlled by the studied energy management system, and its temperature was a boundary condition of the studied space. The indoor air temperature rose to 27 ◦C on 10 July 2019 and to 29.5 ◦C on 11 July 2019. Although the temperatures might seem too high, due to the effect of radiating panels and a low mean radiant temperature, there is thermal comfort in the space, as shown in the discussion section.
