Experimental analysis of grills configuration for an open joint ventilated facade in summertime

This paper focuses on the experimental analysis of a ventilated facade made of recycled materials, under typical summertime Mediterranean conditions. The test area is around 16 m(2) and it is equipped with several sensors for a complete seasonal characterization of the chimney phenomenon and the thermal performance. Indeed, despite several studies are available in the literature, these are usually based on short monitoring campaign and the experimental installations have limited size. The study introduces a new statistical approach for selecting the daily reference scenarios aimed at the comparison of the thermal field and the ventilation with two degrees of openness of the grids in the air-gap. A seasonal analysis is also developed by means of violin plots constructed in order to study both the real distribution and the statistical indexes of the analyzed parameters. The analysis indicated that the opened channel is always characterized by higher air flow speeds with 75% of monitored values under 0.4 m/s and peak values near 2.0 m/s compared to the semi-closed configuration. In the seasonal analysis, the surface temperature of the insulation has a median values 4.5 degrees C lower than the semi-closed configuration meanwhile the third quartile is respectively 36.5 degrees C and 41.1 degrees C. Considering the temperature differences across the back wall, with the opened configuration, around 25% values indicated an outgoing conductive heat flow meanwhile during the sunniest hours, the median value is 3.3 degrees C in case of opened channel and 7.4 degrees C in the semi-closed one. The proposed method and results could help designers for select the best performing solution for their climatic conditions and researchers to develop more accurate analysis with short and long time-step.