Zones are groups of Spaces used to establish some commonality between those Spaces - such as having the same orientation, the same function, or being served by the same HVAC system.
Zones do not actually contain any geometric data themselves, but are simply a container of one of more Spaces for the assignment of Zone level information, such as a HVAC system that serves those Spaces.
Zones are groups of Spaces
It’s important to differentiate here between Zones and ‘Zoning’ (or ‘Blocking’ or ‘Chunking’). As illustrated on the Spaces page, the act of combining multiple rooms or spaces into a single Space is often described as ‘Zoning.’ By contrast, Zones could be used to tie multiple Spaces together.
It is possible for all Spaces to be part of the same Zone. Or, on the other extreme, it is possible for each Space to have its own Zone. In practice this decision is largely driven by HVAC system design and is not considered until detailed design and analysis. Important variables for Zone designations and energy efficiency are: building level, orientation, or function/program.
Combining Spaces into Zones allows you to apply properties to several spaces at once.