EXPERIMENTAL CHARACTERIZATION OF ADAPTIVE TRANSPARENT FAÇADES: LESSONS LEARNED FROM THREE CASE STUDIES

The latest European energy policy, aimed at reducing the energy demand and CO2 emissions due to the building sector, has been pushing researchers, designers, manufacturers and contractors towards the development of novel concepts and technical solutions, with special emphasis on building envelopes. Relevant improvements can be achieved by adopting a new approach, conceiving envelope components as "living" membranes, interacting with indoor and outdoor boundary conditions and with users' needs thus performing an adaptive behaviour. Adaptiveness may be based on different driving factors, may be performed at different timescales (from few minutes/hours to diurnal/seasonal variations) and may take place at different components'/systems' levels (macro or micro scale). This implies that adaptive façades are particularly complex to be comprehensively characterized. Furthermore, a lack of metrics and standardized procedures to define these technologies’ thermo-physical behaviour is highlighted, this representing one of the major barrier to promote their widespread adoption. Conventional experimental activity reveals to be unsuitable in most cases and ad hoc experimental procedures have to be defined depending on the adaptive mechanism and the façade typology. In this paper some lessons learned from the experimental activities carried out on three types of adaptive transparent building envelope components are summed up: Active Transparent Façades, Switchable Glazing and Phase Change Materials integrated into glazing/shading devices. These three selected case studies are presented, focusing on metrics adopted, measurement methodologies and post processing procedures, highlighting potentials and criticism. Through long-term experimental campaigns in test cells and field monitoring, energy and lighting performances have been investigated, focusing the research mainly at the component level rather than measuring indoor environmental quality parameters. Most of the analysis were carried out obtaining data through direct measurements on the components and deriving indoor environmental related aspects via numerical modelling and simulations. Results show the importance to use a multi-objective approach in order to assess both energy and lighting performance of adaptive façades.