Influence of shading control patterns on the energy assessment of office spaces

This work reviews existing models of control patterns for occupant-shading interactions in office buildings, and studies their influence in terms of energy demand when comparing transparent façade alternatives. It starts by establishing a review of visual comfort criteria in office buildings and of the conditions that prompt occupants to interact with shading devices and electric lighting. Given the large variety of parameters identified as primary variables in the existing literature–hence the variety of conditions considered comfortable depending on the chosen reference–a sensitivity study was carried out based on dynamic simulations. The aim of the study was to characterize the impact of choosing a given shading control model (pattern or strategy) on the calculated overall energy demand for heating, cooling and lighting, as well as the impact on choosing the best-performing transparent façade option for a single-occupant office. The results show that both the calculated energy performance and the ranking of transparent façade alternatives (glazing and shading) often vary very significantly with control patterns considered for the occupant-shading interaction. They further show that, amongst the eleven control strategies that were considered, the behavioral model based on a glare acceptability threshold (expressed as DGI > 20) is the one that, when considered individually, would most reliably express an average ranking from all considered strategies. The implications of these findings are discussed in view of their applicability to energy performance-based façade design choices evaluation as well as to façade design choices.