## 5 Conclusions and Discussion
Part of the thermal energy embedded in the structures is not lost when the water stops flowing in the pipes, but it is later released to the room. When considering the overall energy consumed by a water to water heat pump (including the auxiliaries) the increased amount of hours of pumping in the case of variable temperature is counterbalanced by the higher COP of the heat pump, which increases when the supply temperature decreases; overall the climatic control leads to 5-6% better performance in floor heating systems and 7-8% better performance with radiant ceilings. Overall the radiant ceiling consumes always morethan the two floor systems due to the higher supply temperature (about 11% in the case of variable temperature and 15% in case of fixed temperature). Of course, the higher the insulation the higher the performance, hence, the light structures perform better than the masonry structures due to the lower U-values. Looking at long-term comfort evaluations results, no particular problem has been found in the period from December to February according to EN 15251 category II. The analysis carried out was mainly related to check the overtemperature, i.e., when the temperature is above the set-point temperature plus the dead band fixed in 0.5 \({}^{\circ}\)C in the present work. The results show that overtemperature rises when the insulation increases. In masonry structures radiant ceiling has always the highest values of WF\({}^{+}\), especially in case of constant supply temperature. This is due to the higher water temperature supply, although the radiant structure is light. In well-insulated light structures the dry floor shows the highest overtemperature. Anyway, it has to also be underlined that in the ideal convective system simulations the overtemperature is comparable with the ones of the radiant systems simulations. In particular when dividing WF\({}^{+}\) by the number of hours when the overtemperature occurs h\({}^{+}\), the intensity of overtemperature (WF\({}^{+}\)/h\({}^{+}\)) shows that the results of radiant systems and ideal convective case are of the same magnitude. This means that, with radiant systems the amount of hours when the overtemperature occurs, h\({}^{+}\) is higher, but the intensity of the overtemperature is similar than in the ideal convective case. Resuming the results, the work carried out shows that in general the better the quality of the envelope the better the overall performance of the radiant system. Evaluating the efficiency in dynamic conditions leads to higher efficiencies compared to steady state conditions, former standard EN 15316-2-2007 and also the new standard EN15316-2-2017 and new suggested values are provided. Working at variable temperature leads to lower consumptions compared to fixed supply temperature over the season. No problems of comfort have been found in the period from December to February. Overtemperature effects are not especially due to radiant system, but they also happen in any case with ideal convective systems. As with all emission systems, the radiant systems may lead to higher overtemperature effects, but the effect is evident in terms of higher amount of hours when the overtemperature happens rather than too high temperatures because of the radiant system operation. In general, the radiant ceilings perform worse than radiant floor systems in heating conditions and there is no evidence that dry floor systems perform better than wet screed systems in all the types of buildings regardless of the level of insulation and thermal inertia. As a final remark, it has to be underlined that it would be interesting to analyse the same building in cooling conditions, where the radiant ceiling could work better than the radiant floor system. Moreover, the work which has been carried out here considers a unique room; a further interesting study would be to analyse different rooms, i.e., looking in detail at the distribution of the inner space and checking the different possible control strategies. Simulations and data analysis, G.A.