Experimental tests to assess the effects of Phase Change Materials in building envelopes

Enhancing the thermal inertia of lightweight buildings significantly limits thermal energy needs. Phase Change Materials (PCM) can be used for this purpose exploiting the absorption and the release of latent energy to improve the storage features of the building fabric. An experimental campaign carried out on different wall samples, in which PCM can face both the internal and the external surface, allowed for thermally characterizing opaque building elements. Through proper dynamic indices, the thermal performances of the opaque component were measured in a climatic chamber by the heat flux meter method, by varying the PCM position inside the wall. A sinusoidal solicitation was applied on the external surface, whereas the internal side was left at a constant temperature. When compared with the base case (sample without PCM) the allocation of a single layer of phase change material on the inner side produced a limitation of 81% in terms of decrement factor and an increase of slightly over 2 hours for the time lag. The periodic thermal transmittance reduced from 0.148 W/m
²
K to 0.091 W/m
²
K. If PCM layers are inserted facing both the sample sides, the time lag further increased by 1.6 hours and periodic thermal transmittance decreased to 0.086 W/m
²
K. Nevertheless, a paradoxical increase in the decrement factor was observed. The melting and solidification processes, in fact, affect negatively the sample surface temperatures subjected to the solicitation.