Solar radiation entering through openings: coupled assessment of luminous and thermal aspects

Abstract

Usually the effect of global solar radiation on buildings is evaluated by focusing on the visible part of its spectrum, namely daylight, or on the thermal equivalent of sunlight, solar heat gains through external windows. At present, due to the difficulty of integrating and comparing thermal and daylighting results, approaches considering the integrated effect of global solar radiation are scarce. As a consequence, both approaches separately provide strategies for sustainable buildings – strategies that can, in fact, be contradictory. In order to evaluate daylighting potential and its correlated solar heat gains, a common framework of calculation is established and a set of metrics are defined. These metrics are based on the Daylight Sufficiency criterion, the recommended illuminance ranges for visual tasks and the trigger irradiance value defined in the Blindswitch-A model. The results of applying this method to a simple model show the correlation between the luminous and the thermal performances that are simultaneously achieved on the workplane. This method, therefore, allows both aspects of solar radiation entering through windows to be visualised on one graph, thus enabling an integral assessment, so necessary if strategies that consider both aspects at the same time need to be proposed.