Vents and Holes

Vents

DesignBuilder vents are used for modelling airflow through openings and can be easily added to the model by navigating to the appropriate surface and checking the Vents fitted option. This adds a single vent under each of the windows (if the vent spacing is the same as the window spacing). Alternatively, for more control over the placement position of the vents, you can go to surface level and draw the vents using the Draw vent command. On surfaces where custom openings have been defined, any changes to vent layout model data on the Opening tab is ignored.

Note: if you have drawn custom vents at the surface level then these will be used even if the Vents fitted checkbox is not checked. The Vents fitted checkbox only controls the automatic generation of vents, not their use in the calculations.

The properties of the vent are defined by the selection of the vent type:

Holes

Holes are modelled in a similar way to vents with some exceptions:

Holes must be drawn at surface level
Airflow through holes is uncontrolled, i.e. the airflow path is active all the time.
Drawing holes can be used as a way to merge two zones when the Merge zones connected by holes Model option is set.
Holes are used internally with DesignBuilder to model the heat transfer and airflow through Virtual partitions.
The discharge coefficient to be used for all holes (and doors) in the model is defined on the Advanced tab of the Model options dialog under the Natural Ventilation header. The default discharge coefficient is 0.65 is used. For vents the vent component defines the discharge coefficient.

Vent modelling

Calculated Natural Ventilation (Simulations only)

Each vent is modelled using:

An EnergyPlus Door. The heat conduction through the vent Door component is displayed in results as Internal Natural vent and External Natural vent.
An EnergyPlus AirflowNetwork:MultiZone:Component:DetailedOpening and other associated AirflowNetwork components, providing a controllable flow path. You can define Vent operation.

Scheduled Natural Ventilation (and Heating and Cooling Design Calculations)

Each vent is modelled using:

An EnergyPlus Door. The heat conduction through the vent Door component is displayed in results as Internal Natural vent and External Natural vent.
Internal vents also have an EnergyPlus ZoneMixing object using parameters set in the Model options dialog. External vents do not exchange air explicitly with Scheduled natural ventilation.

Hole modelling

Calculated Natural Ventilation (Simulations only)

Each hole is modelled using a sub-surface and an airflow connection:

Sub-surface:

If using 1-Minimum shadowing or 2-Full exterior solar distribution the hole is represented using an EnergyPlus Door. In this case heat conduction through the vent Door component is displayed in results as Internal Natural vent and External Natural vent.
If the 3-Full interior and exterior solar distribution Model option is set then the hole is modelled using a 'perfectly clear' window which transmits solar radiation and visible light.

EnergyPlus AirflowNetwork:MultiZone:Component:DetailedOpening and other associated AirflowNetwork components, providing a controllable flow path. You can define Vent operation.

Scheduled Natural Ventilation (and Heating and Cooling Design Calculations)

Each hole is modelled using a sub-surface and a 'mixing' flow:

Sub-surface:

If using 1-Minimum shadowing or 2-Full exterior solar distribution the hole is represented using an EnergyPlus Door. In this case the heat conduction through the vent Door component is displayed in results as Internal Natural vent and External Natural vent.
If the 3-Full interior and exterior solar distribution Model option is set then the hole is modelled using a 'perfectly clear' window which transmits solar radiation and visible light.

Internal holes have an EnergyPlus ZoneMixing object using parameters set in the Model options dialog. External holes do not exchange air explicitly with Scheduled natural ventilation.