## 5 Discussion  
Monitoring results suggest that for the heating season, the radiant floor system allows better performance in term of thermal comfort and temperature distribution. All available data indicate another interesting consideration regarding air temperature value, taking into account that set point temperature, during the experiment, was fixed to 20 \({}^{\circ}\)C, as the normative for public buildings imposed in many countries. More in detail, assuming that for moderate environments the air temperature is a good approximation of the operative temperature, the percentage of time (tTa%) in which the air temperature falls within intervals derived from the comfort zone for the operative temperature was evaluated. Figure 16 shows the proposed index considering the value of air temperature recorded in the center of room, in each period, and for all systems. The baseboards are the more critical system, since for around 50% of monitored values, the set point is not met, and for the other hours, the air temperature is near 20 \({}^{\circ}\)C. Two reasons can be argued: the set-point is not adequate, or the surface covered by the baseboards is not enough and they should be installed on all four walls. During the period with fan-coils, air temperature was for much more time in the range of 22-23.5 \({}^{\circ}\)C (\(\approx\)63%) than in the range of 19-21 \({}^{\circ}\)C (\(\approx\)17%). In the case of the radiant floor, for the previous monitoring period, the Ta\({}_{\_}\)c tended to be higher than 21 \({}^{\circ}\)C for 75% of time but it never exceeded 23.5 \({}^{\circ}\)C. With both systems, a lower set point could reduce the energy consumption by avoiding air temperature higher than the assumed set-point. This is due to the inertial properties of the radiant floor system that continues to heat the room until the water inside the pipes cools down. For the fan-coil, the effect of ventilation increases the air temperature but, as shown in the previous section, also the non-uniformity of vertical and horizontal distribution. The statement that temperature exceeds the set point values for most of the monitored time seems to suggest that in a well-insulated structure and with good inertial properties, a management with lower set-point temperature could determine free-cost energy saving by guaranteeing at same time the respect of comfort limits. The analysis of the proposed result must be contextualized to the quality of the building envelope that influences the uniform condition and the comfort indices. Indeed, the test-room is a particular volume with a very insulated roof and basement as well as a technical wall that can be considered quasi-adiabatic. Assuming a real application, this can be considered an office room in the middle floor of a building (upper and lower heated rooms) with three exposed walls and a room at the same temperature on the north side (technical wall). Thus, the heat losses of the opaque envelope are quite limited, and this can be considered a typical condition of the new designed highly efficient building. More in detail, the insulation level of the basement helps to favor the direction of the heat exchange when the radiative floor system is activated. Indeed, the heat losses on the ground can  
Figure 16: Percentage of time in comfort range for all systems—air temperature. be considered null, and this is the main causes of the comparable values of T\({}_{\text{s\_floor}}\) and T\({}_{\text{a\_0,1}}\) and T\({}_{\text{a\_1,1.}}\). Instead, the extreme insulation of the roof negatively affects the thermal stratification with the fan-coils. Indeed, the heat exchange through the roof is also nullified, and the hot air stratifies. As regard the baseboards, these are installed on two exposed walls and also if these are well insulated (the thermal transmittance is comparable with the threshold value for Mediterranean cities), part of the radiated flow heats the walls and is exchanged with the outside. This could be one of the reasons why this system showed the least effectiveness.