The automation issues with shading may seem simple and straight forward, but, they are not. There are multiple effects we try to optimize with shading and they are interrelated. For example, daylight harvesting may allow us to dim lights but also affects heat gain, possibly occupant comfort, and productivity due to increased glare or brightness. Shading done properly reduces the demand for cooling and provides a modification of the lighting to a space that improves the amount and dispersal of the lighting.
Several manufacturers of motorized shades have addressed this through shading management software, which optimizes the position of the shade based on multiple criteria. These include sun position, solar intensity, BTU Load, readings from indoor and outdoor photo sensors, and radiometers. Some software is able to calculate the optimum shade position every 60 seconds and position the shade accordingly.
There are three systems that need to act in tandem: lighting control systems, the HVAC system, and the shading system. The lighting and HVAC control systems involve energy consumption, so optimal operation should take into account the cost of energy for both systems (i.e., saving money on dimming lights versus the additional cooling due to increased heat gain). Complexity increases when you start to consider systems schedules, sun sensors, occupancy sensors, room temperature, and time of day. Each deployment of automated shading will have different variables to consider, so one generic solution is unattainable. The questions to be raised are what will automatically trigger shading? Will shading be used with daylight harvesting? What level of integration do we need between the systems? And finally, if we are to integrate the systems, what is the sequence of operation among the three systems?