## 4 Conclusions  
The present paper is aimed at assessing the thermal properties of macro encapsulated PCMs under conditions that are representative of the actual behaviour of the material when it is used in building components. Most of the information available in data sheets, such as the nominal melting temperatures and latent heat, are in fact typically measured on bulk materials and under laboratory conditions that are quite different from those to which the material is exposed in real buildings. Firstly, the measurements are conducted on small samples of the bulk materials. Such a configuration is far from being representative of macro encapsulated PCMs, since the bulk material is enclosed within containers which, apart from influencing the thermal properties of the ensemble, create air pockets and shape variations. The consequence is that the overall thermal properties are affected to a great extent. Secondly, the temperature variations during the tests are faster than the temperature time gradients that occur in a real environment. In the present paper, two measurement methods have been proposed and investigated in order to overcome these glitches. One makes use of laboratory measurement apparatus, while the other resorts to a purposely-designed test cell. More specifically, the equivalent thermal properties of macro encapsulated PCMs (Infinite R(tm)), with different nominal phase change temperatures (21, 23, and 25 \({}^{\circ}\)C), were investigated under laboratory conditions and then applied to roof components. An experimental piece of apparatus, available at the Politecnico di Torino, called TRIS--Testing Roof Innovative System, was adopted for the latter test. Finally, the results of these tests were compared with the typical nominal values of the various materials available in data sheets. A graphical representation of the measurement results, related to the change phase phenomena, has been proposed (see, e.g., Figures 12 and 16), that could help designers  
Figure 16: Monitored PCM temperatures: (**a**) PCM temperature of room B (the reference day 17/10); (**b**) PCM temperature of room C (the reference day 17/10). make an appropriate choice of the most suitable PCM (that is, determining the optimal range of phase change temperatures in relation to the envelope component temperatures). The results of the laboratory characterization show similar equivalent thermal conductivity values for the three analyzed PCM samples, which range between 0.15 and 0.22 W/mK. These results clearly demonstrate that the equivalent thermal conductivity of a macro-encapsulated PCM might be quite different from the thermal conductivity of the bulk PCM typically reported in data sheets and literature (the literature values for salt hydrate PCMs are reported to be between 0.540 and 1.088 W/mK [9; 32; 33]). As far as the results of enthalpy, as a function of temperature, are concerned, it is worth mentioning that a significant hysteresis phenomenon (from 2 \({}^{\circ}\)C to 4 \({}^{\circ}\)C) was observed for all the PCMs. Moreover, the measured peak enthalpy of melting and solidification (average values) were slightly higher than the nominal melting/solidification values. It has emerged, from the laboratory results, that it is important to use equivalent properties of the macro-encapsulated PCMs for building energy modelling purposes. Indeed, simplified simulation models require equivalent data, when a homogeneous PCM layer is assumed. Therefore, the use of data relative to the bulk PCM might not fully consider the complexity of the macro-encapsulation, which might lead to a significant alteration of the PCM behavior and of its melting/solidification processes. The application and monitoring of two macro-encapsulated PCMs (Infinite RTM 21 and Infinite RTM 23) with different transition temperatures in a real roof component have allowed the benefits achievable, in terms of heat fluxes and temperature variation reduction, to be detected.