A ZONE is a specified region of your model that the simulation is focused on. This current version of Desktop Radiance supports only one Zone per drawing. Defining a Zone helps increase simulation accuracy and provides a set of pre-defined views, like "plan," "elevations," etc., that are easy to access from the interactive rendering program. These will be supported in future versions of Desktop Radiance. A Zone is not required to begin a simulation, but is recommended when the area of interest inside the drawing is less than half of the overall drawing size.
Figure 6. The Zone Properties dialog box.