A zone is typically defined as an area with similar heat gains, similar temperature and humidity control requirements, or an enclosed space within a building with the purpose to monitor and control the zone's temperature and humidity with a single sensor e.g.
[4] Cooling load calculation methodologies take into account heat transfer by conduction, convection, and radiation.
Methods calculate the cooling load in either steady state or dynamic conditions and some can be more involved than others.
[2] Another reason is that the inability of the cooling system to keep dry bulb temperature and humidity constant.
In air systems, convective heat gains are assumed to become a cooling load instantly.