Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
SwitchableGlazing can be modulated for daylighting control to meet an illuminance setpoint. But if your control variable is not illuminance, then you would need to use EMS with the Surface Construction State actuator.
From the Input Output Reference, WindowProperty:ShadingControl.
Somewhat hidden at the end of the introductory paragraphs
For Shading Type = SwitchableGlazing the state of the window is either clear (unswitched) or dark (fully switched) for all Shading Control Types except MeetDaylightIlluminanceSetpoint. In this case, the transmittance of the glazing is adjusted to just meet the daylight illuminance set point at the first daylighting reference point (see Daylighting). This type of control assures that there is just enough solar gain to meet the daylighting requirements in a zone, and no more, thus reducing the cooling load.
Under field Shading Control Type
MeetDaylightIlluminanceSetpoint: Used only with ShadingType = SwitchableGlazing in zones with daylighting controls. In this case the transmittance of the glazing is adjusted to just meet the daylight illuminance set point at the first daylighting reference point. Note that the daylight illuminance set point is specified in the Daylighting:Controls object for the Zone; it is not specified as a WindowProperty:ShadingControl SetPoint. When the glare control is active, if meeting the daylight illuminance set point at the first daylighting reference point results in higher discomfort glare index (DGI) than the specified zone’s maximum allowable DGI for either of the daylight reference points, the glazing will be further dimmed until the DGI equals the specified maximum allowable value.
