Abstract

Highly glazed facades in office buildings are often affected by excessive solar heat gains and daylighting. The use of exterior shading devices is one of the most effective strategies for controlling daylighting and solar heat gains through glazed facades and for maintaining the thermal and visual comfort. Exterior shading systems can either be fixed or movable (tilting and/or retracting). The latter are frequently used with control systems. The objective of this study was to evaluate the impact of four control strategies applied to a shading device made of movable curved and perforated louvers on the visual comfort and total energy consumption (for heating, cooling and artificial lighting) of an office space using integrated thermal and lighting simulations. The investigated control strategies were: an incident irradiance control, a vertical eye illuminance based control, a cut-off angle control and a blocking control. The obtained results were compared to those of three systems with fixed (unmovable) louvers. Simulations were performed for four cities with different climatic conditions: Montreal (Canada), Santiago (Chile), Boulder (USA) and Miami (USA). The assessment of the visual comfort was based on the spatial daylight autonomy (sDA) and simplified daylight glare probability (DGPs). The results indicate that, for the cities of Montreal, Santiago and Boulder, the optimal strategy is the 'vertical eye illuminance control', together with the 'incident irradiance control' in the case of Santiago. These strategies minimize the total energy consumption of the office space while ensuring visual comfort. In Miami, the best strategy corresponds to the 'blocking control' for the south facade orientation while blinds with fixed louvers (tilt angle of 60 degrees) perform better than the active control strategies studied for the west facade orientation. The real world implementation complexity of each control strategy is also discussed.