The role of wall layers properties on the thermal performance of ventilated facades: Experimental investigation on narrow-cavity design

In this paper we have investigated how different materials and thermal masses impact on the perfor- mance of ventilated facades with narrow cavities, by measuring the variation in terms of heat flows and ventilation efficiency. While geometry has been widely explored, the role of wall composition has re- ceived much less attention. To bridge the gap, three real-scale prototypes of ventilated facades were built and tested all over the year on a mock-up in Central Italy: (i) L, with a lightweight external enclosure, as a baseline reference, (ii) IM, with a massive layer enclosed in the gap and (iii) EM, with an external massive cladding. The results demonstrated that the EM solution more effectively mitigated the average surface temperatures (both external and internal), with values of –2 °C and –1 °C in summer and of –3 °C and –0.5 °C in winter, when compared to the L solution. Moreover, in the EM case, the ventilated cavity reduced both the incoming and outgoing heat fluxes, since the outer mass operated as a thermal buffer between the outdoor and the ventilation chamber. Conversely, the presence of an internal mass determined an increase of the heat transfer towards the indoor environment. The position of the thermal mass in the outer layer also increased the air velocity in the gap thus enhancing the stack effect.