Comparison of Shading Control Modes On Offices Space Energy Performance

Interior roller shades are widely used in office buildings to control solar heat gain and glare. Automated operation can result in energy savings depending on the control strategy used. This paper investigates the impact of shading control modes on office space energy performance using year-round transient integrated thermal and lighting simulation. For office spaces, the most important function of interior roller shades is to block direct sunlight so that the occupants are not disturbed by glare. In this paper, four shading control modes, all of which are developed to settle glare problems, are analyzed and compared. In the first control mode, the roller shades automatically close completely when direct solar radiation is incident on the façade. The second shading control algorithm improved the first by closing shades when daylight illuminance transmitted through glazing exceeds a certain value, which can be determined by real-time full scale measurements or simulation. In the third control mode, the shades do not close completely but move to a position to just prevent direct sunlight from projecting on the work plane surface at pre-defined distances from the facade. When daylight illuminance is extremely low/high, the shades completely open/close respectively. These extreme values for daylight illuminance can also be obtained from experiments or simulation. In the fourth control mode, thermal considerations are included: on the premise of no glare, the shades close completely when the outdoor temperature is higher than a pre-defined value (in cooling season) and transmitted solar heat gains through the glazing are much higher than the respective value if the shades were closed. After developing the shading control modes, a transient lighting and thermal simulation model, validated by experimental measurements, was used to estimate the annual lighting, heating and cooling demand for a typical private office space with different window size and shading properties. The results show the effects of interior roller shade controls on office space daylight performance and energy consumption.