Vents and Holes

Openings tab in model data

Vents

DesignBuilder vents are used for modelling airflow through openings and are 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.

• Vent Placement
• Vent Operation

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.
• Discharge coefficient of 0.65 is used whereas with 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 DETAILED OPENING' and other associated AIRFLOW components, providing a controllable flow path. You can define Vent operation.

Scheduled Natural Ventilation (and 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 have an EnergyPlus 'Mixing' object using parameters set in the Model options dialog. External vents .

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 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.

• EnergyPlus 'AIRFLOWNETWORK:MULTIZONE:COMPONENT DETAILED OPENING' and other associated AIRFLOW components, providing a controllable flow path. You can define Vent operation.

Scheduled Natural Ventilation (and Design Calcs)

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 vents have an EnergyPlus 'Mixing' object using parameters set in the Model options dialog. External vents.