Weather-responsive shade control system

A method for automatic daylighting, the method comprising:

• detecting an interior light illuminance level primarily due to exterior light entering a window into a room;
• determining whether the room is in a heating mode;
• detecting whether the room is occupied by people;
• detecting whether occupants have manually operated an adjustable window covering for the window in the room;
• detecting an exterior sky condition;
• calculating an adjustment of the adjustable window covering, such that the adjustable window covering is modulated to
• i) block direct sunlight from entering the room through the window when the exterior sky condition is a sunny sky state and the room is in a cooling mode,
• ii) subject to satisfying (i), provides a desired daylighting interior light illuminance level through the window that is within a target daylighting range and provides a desired interior solar heat gain through the window that is within a variable target heat gain range;
• and
• automatically adjusting the adjustable window covering based on the calculated adjustment, wherein the adjusting is delayed when the estimated exterior sky condition changes from a sunny sky state to an overcast sky state.