Optimisation criteria of an active transparent façade based on IEQ and energy efficiency issues: results from an experimental campaign in a full-scale mockup

Active transparent façades are building envelope systems largely used in new office and public buildings, whose optimization (e.g. types and number of glass panes, of shading device, integration with HVAC) is a complex problem with a multidisciplinary perspective. As far as the energy and indoor environmental performance are concerned, thermophysical, optical and acoustic properties need to be taken into account through a synergic approach so that an optimal overall behaviour is achieved. The research activity presented herewith was aimed at supporting the contractor’s decision process about the layout of an Active Transparent Façade (Climate Façade typology) for a high-rise office building. An extensive monitoring on a full scale office room mock-up was thus designed to compare two ATF solutions, assessing the most viable trade-off between high performance and costs, taking not only energy efficiency but also thermal, visual and acoustic comfort into account. Two ATF modules with slightly different configurations (type of inner skin) were tested in the mock-up. The energy efficiency analyses showed that, as predictable, the ATF module equipped with the best inner skin was able to significantly increase the thermal resistance, reducing the winter heat loss and the summer heat gain, though this impact was not so relevant when the overall energy balance at building level was considered.The inner skin played, instead, a relevant role when considering thermal comfort, especially during summer peak conditions. From a visual comfort perspective, the two technologies did not perform in a significantly different way in the presence of the screen, but differences were observed in winter (with retracted screen), since the higher luminance values measured for the single skin could cause glare. Considering sound insulation, the façades presented comparable values and no significant differences were measured.