Improvement of building envelope performance through phase change materials (PCMs): Results of experimental activities

The energy demand for indoor thermal comfort represents more than one-third of the total energy demand, thus forcing to introduce new strategies to improve the buildings’ performance. Further, the demand for space cooling applications is continuously increasing and is leading to serious environmental issues that force the development of passive cooling techniques to reduce the demand and therefore the consumptions. This, combined with the current scenario in which existing buildings are the greatest share and the rate of new constructions is only 1%, is forcing to find solutions that can be adopted especially in case of refurbishments. Among the possible passive cooling strategies that can be adopted on the building envelope there are heat modulation techniques, which can be achieved using phase change materials (PCMs). Focus of the research was the experimental investigation of the effect of the incorporation of a granular paraffin PCM in a lime-based plaster for the application on the outermost layer of a wall. The plaster chosen was a lime-based one, instead of the more common cement-based, as it is the most appropriate in case of application on historical buildings, while the PCM was in granular form so that the incorporation inside the plaster would avoid any leakage problem during the melting phase. A sample of a reference lime-based plaster was realized and used as benchmark that was compared to the other two samples realized, in both of which 10% by mass of PCM was added and whose melting temperatures were 27°C and 28°C, respectively. These were tested both in laboratory, under controlled conditions, as well as on a mock up building, under real conditions, and their behaviour was monitored in terms of temperatures and heat fluxes. The addition of the PCM allows an increase of the thermal inertia of the building envelope and aim of the research was to verify whether this brought to a reduction of the incoming heat flux, with a consequent reduction of the energy demand for cooling, and a reduction of the temperature fluctuations on the innermost layer of the wall, with the aim of improving the indoor comfort for occupants.