Abstract: An environmental control system for a space including at least one window adapted for admitting light into the space. The system comprises an environmental controller (such as a fan, a light, an HVAC system, a window, a window covering, or any combination of the foregoing) for regulating an environmental condition, and at least one first sensor, such as a radiant heat flux sensor, for sensing an amount of radiant energy associated with the space and generating an output. A controller is provided for controlling the operation of the environmental controller based on the sensor output. Related methods are also disclosed.