Light and energy performance of an active transparent façade: an experimental study in a full scale office room mock-up

This paper deals with energy and light performance assessment of two configurations of an Active Transparent Facade (ATF), which are investigated by means of an experimental campaign that makes use of a full-scale mock-up room of an office building. The two configurations of the ATF (a Climate Facade integrated with the HVAC system) differ in the technology of the inner glazing (extra-clear single glass or double pane glazing with low-e coating), while share all the other features - i.e. external glazing, shading system, airflow path and ventilation rate, control strategies. The aim of the research activity is both to define a methodology to assess energy and light performance of each configuration, through elaboration of experimental data, and an attempt to apply the methodology to the specific case, in order to test it. Experimental investigations in test cells and/or real scale mock-up provide high quality data, but their representativeness and direct application is not always straightforward. Dedicated data analysis procedures and methods need thus to be developed in order to translate experimental data in useful information. Moreover, investigations are usually carried out on either the thermal or the light aspects, while combined analyses are not common, since this increases the degree of complexity of the analysis and measurement requirements are often quite different. The ATF module equipped with extra-clear single glass pane (Module A) shows, compared to that with a low-e coated double pane glazing (Module B), an increase in the average luminance, over the analyzed surfaces, in the range 20%-52% and 16%-81%, in absence and in presence of the shading systems respectively. A higher amount of daylight is then guaranteed within the indoor space by Module A, but this might result in a higher probability of visual discomfort for the occupants. On the other hand, the Module B determines lower daily energy transmitted toward the indoor environment than Module A: on average, the daily energy gain/loss from/toward the outdoor environment are reduced of about 30%, in summer (with or without the reflective roller screen), and in the range 30-40% in winter (with or without the reflective roller screen)