This thesis proposes the development of a new technology for improved energy efficiency in buildings by incorporation of more than one type of phase change material (hybrid PCM) in plastering mortars for façade walls. Such approach provides added benefits in regard to recent proposals of single PCM usage. Their application as lining of walls contributes to keep the indoor air temperature within acceptable comfort levels, and consequently reduce energy consumption associated to acclimatization. The focus was the strategy for minimizing heating/cooling energy consumption by applying mortars containing adequate proportions of PCMs with distinct melting temperatures and phase change enthalpies. The overall work methodology involved experimental (laboratory level, small scale testing) and numerical research with hybrid PCM, and aimed to develop a guideline for energy efficiency.
This thesis initially started with experimental part aimed characterization of the used materials (material level investigations). Then, the feasibility of hybrid PCM (i.e. incorporating more than one types of PCM with distinct melting temperature and enthalpies in the same mortar) to enhance the efficiency of PCM system was assessed through laboratory scale prototypes and real scale simulation. The experimental part of the
work aimed to demonstrate the effectiveness of PCM incorporated into the plastering mortars used as internal coatings of building spaces. Two small scale prototypes were prepared with distinct interior coatings: (1) one with common plastering mortars; (2) another mortar incorporated with hybrid PCM. Both test cells have been subjected to realistic daily temperature profile, and the effect of the coatings has been assessed with recourse to internal temperature monitoring. The collected results for daily cycles showed
that hybrid PCM acts reducing inside temperature amplitudes during the day and turning them closer to comfort temperature levels. Numerical thermal model was conducted to verify the experimental results. The numerical predictions for the temperature profiles were almost similar to those obtained from experimental observations. The obtained results and their comparison with monitored temperatures have shown that the numerical simulation methodology can provide feasible estimates of temperature in elements containing mortar with incorporated hybrid PCM. This confidence in the numerical framework for this purpose allows the possibility of evaluating alternative scenarios, both in terms of climate condition and melting temperature solutions of the PCM. Development and experimental evaluation were conducted for this two laboratory scale prototypes, as to enhance the  thermal energy storage potential of buildings. The prototypes were internally equipped with a heater that was programmed to keep the comfort temperature in the enclosure. A reference mortar without PCM was also applied in a prototype for comparative purposes. The hybrid PCM mortar development work has experimentally shown that the concept is feasible on the small scale and that the thermal storage of the hybrid PCM can be successfully reduces the energy consumption about 20%. It was further observed that the HPCMM plays a role in reducing the temperature variation of indoor environment, which assists to significantly decrease the energy consumption for buildings. Then, it is considered advisable to test the hybrid PCM concept in a real scale application, in order to assess thermal behaviour as well as energy saving potential of hybrid PCM mortar. The results further confirmed the energy saving potential of the hybrid PCM and consequently, provided the ground for better understanding the phase change phenomena and modelling approaches.