## 4 Results
### Air Temperature Distribution
#### 4.2.1 Air Temperature Field
The temperature profiles relating to the same height but on different sectors were quite comparable; there was not evident horizontal asymmetry, especially at a height of 1.1 m and 2.1 m. Instead, considering the position at 3.1 m, the difference between air temperatures recorded at the same time in S1 and S2 varied between \(-\)4.0 \({}^{\circ}\)C and \(+\)2.0 \({}^{\circ}\)C, and it varied from -2.6 \({}^{\circ}\)C and 3.7 \({}^{\circ}\)C considering sectors S2 and S4. At the height of  
Figure 10: Air temperature at different heights with fan coil units: (**a**) 3 rd sector, (**b**) 4 th sector. 0.1 m, the greatest variation happened between S1 and S3 (\(-\)3.6 \({}^{\circ}\)C \(\div\) 0.3 \({}^{\circ}\)C) while the temperature difference varied between 0.2 \({}^{\circ}\)C and 2.9 \({}^{\circ}\)C considering sectors S2 and S4. The same analysis was proposed for the radiant floor system for which also the surface temperature was shown. The monitored data for the first and second sectors are proposed, respectively, in Figure 11a,b; the profiles for the other sectors are reported in Figure 12.  
In all cases, it is evident that the long start-up period of the system allowed 20 \({}^{\circ}\)C to be reached in more than three hours, starting from air temperature of around 17 \({}^{\circ}\)C. After this transient period, the air temperature trend at 0.1 m was close enough to values at other heights; this phenomenon did not happen with the fan coil system, due to the different heat exchange mechanism. For each other height, air temperature values were comparable, and these were very close to data recorded by the sensor in the room center; for instance, considering the whole monitoring period in S1, T\({}_{\text{a,mean}}\) was 21.0 \({}^{\circ}\)C at 1.1 m, 21.4 \({}^{\circ}\)C at 2.1 m, and at room center it was 21.7 \({}^{\circ}\)C at 3.1 m. In the second and third sectors, the mean values were around 21.2 \({}^{\circ}\)C at each height, and T\({}_{\text{a,mean}}\) was 21.5 \({}^{\circ}\)C in the last considered sector. Figure 11: Air temperature at different heights with radiant floor system: (**a**) 1 st sector, (**b**) 2 nd sector. The higher values were 23.8 \({}^{\circ}\)C in S2 and 26.4 \({}^{\circ}\)C in S3, and in both cases they were recorded by sensors at 0.1 m; this was due to the combined effect of increased surface temperature and solar gains. This situation was strongly different from the operation period of the fan coil units. Moreover, the peak values recorded by the other sensors were comparable, and these did not have a large deviation for a device at 3.1 m, unlike the fan coils. For instance, T\({}_{\text{a\_max}}\) was around 23 \({}^{\circ}\)C in the first and fourth sectors, and it was around 23.5 \({}^{\circ}\)C for 2S, while it was also 24.3 \({}^{\circ}\)C in the third sector (1.1 m). It could also be observed that the surface temperature should not exceed the value of 29 \({}^{\circ}\)C suggested by the standard [5]. For each sector, the recorded values were very close to the records of the sensor at 0.1 m, and this is another aspect that underlines the uniformity of the temperature field inside the room. The switch-off was clear when there were rapid drops in temperature; the lower recorded value ranged between 17 \({}^{\circ}\)C and 19 \({}^{\circ}\)C. However, some deviations can be noted. First of all, S3 and S2 were usually characterized by the higher value of T\({}_{\text{s\_floor}}\). These sectors were the ones with the coils closest to the  
Figure 12: Air temperature at different heights with radiant floor system: (**a**) 3 rd sector, (**b**) 4 th sector. flow manifold, and therefore the hottest water circulates; for this reason, the temperature at ignition increased faster and to a higher value (24.5 \({}^{\circ}\)C) in S3. Moreover, during the sunniest hours, the temperature increased; for instance, in the last day of monitoring at 13:30, with an outdoor temperature of 15 \({}^{\circ}\)C, T\({}_{\text{s,floor}}\) was 27.4 \({}^{\circ}\)C for S2 and 27.6 \({}^{\circ}\)C for S3.