Unitary multizone

The Unitary multizone option allows you to model constant volume direct-expansion (DX) based HVAC configurations with several different heating options. Direct expansion (DX) includes single packaged rooftop systems commonly seen in commercial buildings and split systems commonly seen in residential buildings. In this system, central heating and cooling coils are used to condition air which is delivered to the each of the zones in the system through an air delivery system. Air delivery can be set up to ensure minimum fresh air supply and there are options for economisers to provide free cooling and heat recovery.


For a multizone system, only one zone is specified as the control zone. The thermostat is located in this control zone as set by the Thermostatic control zone for unitary system at the top of the HVAC tab at zone level. So when using this system you should be careful to locate the thermostat in a zone which will have a representative temperature for the whole building, otherwise some zones may become over/under heated/cooled.  


Only one Unitary multizone system can be defined per building and it can serve up to 400 zones.



The Compact HVAC type must be set to Unitary multizone at building level and in all zones which are part of the system. Other zones can have HVAC type Unitary single zone or Fan coil units but not VAV or CAV.

Technical EnergyPlus

EnergyPlus needs both the heating coil and cooling DX coil to be defined so even if heating or cooling is not selected in the input, DesignBuilder will include both coils in the IDF data supplied to EnergyPlus and schedule the appropriate coil to be off.