The four facades are oriented
towards the four cardinal directions. Interior materials are
entirely diffuse. Illuminance is measured on a sensor
plane located at a workplane height of 3ft (0.9m) above the
floor. The sensor plane is divided into five zones, one for
each perimeter zone and a core zone which is 10ft by 10ft
(3.1m x 3.1x) in area (Figure 1).