Comparative control strategies for roller shades with respect to daylighting and energy performance

Traditionally, automated shading operation includes open-closed strategies trying to maintain a comfortable environment while controlling glare and solar gains. Four different dynamic shading control strategies with constant and variable set points were developed and studied in this paper using year-round transient integrated thermal and lighting simulation, to investigate their impact on outdoor view, daylighting metrics, thermal loads and energy consumption as well as on excessive illuminance that can cause visual discomfort in private offices. The strategies and generic and can be applied to any location, orientation and climate if appropriate set points are selected. The results showed that: (i) shades remain open for a significant portion of working hours depending on orientation and weather conditions (ii) controlling shades based on solar radiation as suggested in previous studies might not be an effective method; instead, illuminance thresholds are probably more appropriate (iii) the third control strategy leads to reduced source energy consumption and maximized daylight utilization; however, careful consideration of interior illuminances is needed to avoid the risk of glare; (iv) differences in annual source energy consumption between control strategies range from 10.1% to 34.4% depending on glazing and shading properties and (v) different strategies should be used in different orientations. Validation of results with full-scale experiments is presented for representative cases. The interactions and integration between daylighting benefits and thermal requirements need to be studied through the interplay between lighting energy use, solar and internal heat gains, while considering comfort parameters that vary depending on the shading control strategy used.