Door Operation

Openings tab in model data under Doors

The operation of doors can be defined by entering data under Operation headers:

• % Area door opens - defines the area of the door which opens relative to the total area to give an approximation of the actual opening size and,
• % Time door is open - defines the average time the door is in the open position.  Accounts for the fact that during occupied periods the door may open and close repeatedly.
• Opening position - defines where in the door the airflow opening is located. Select from:
  • 1-Top,
  • 2-Bottom,
  • 3-Right and
  • 4-Left

The way this data is used depends on the Natural ventilation model option set but in both cases the concept of doors opening and closing is approximated by reducing the size of the door opening area to account for the fact that the door is closed for much of the time.

Note: the same Opening position and % Area door opens data is used for both EnergyPlus Calculated natural ventilation and CFD calculations. % Time door is open is not used in CFD.

Calculated natural ventilation

The average door opening size used in the simulation is calculated by multiplying the % Area door opens by the % Time the door is open by the gross door area. The position of the opening within the door is defined by the opening position. The ventilation rate through the door opening is calculated at each time step based on the wind + stack pressure difference across the opening at the time.

Operation schedule

The Operation schedule is used to control timing of the door opening. Note that the schedule should have values of 0 and 1 only and intermediate fractional values do not indicate partial opening.

Scheduled natural ventilation

External door opening is not modelled explicitly with the Scheduled natural ventilation model data setting. Instead, the total natural ventilation flow rate and operation is defined for each zone on the HVAC tab. No operation data is entered on the Openings tab for external doors.

Internal doors are modelled using the EnergyPlus ZoneMixing object which mixes air between the two adjacent zones.  DesignBuilder uses an approximate empirical relationship to calculate the mixing flow:

Flow (m3/s) = Door area (m2) * % area door opens * % time door is open * FAirflowRatePerOpeningArea

where FAirflowRatePerOpeningArea is a factor used to obtain the mixing flow from the opening area. The value of this factor can be defined on the Model options dialog on the Advanced tab under Natural ventilation. The default value is 0.1 m3/s-m2.

A schedule can be applied to control timing of the mixing flow.

Note: The Airflow through internal openings model option must be checked to obtain airflow through internal doors when using Scheduled natural ventilation.

Operation schedule

The Operation schedule is used to control timing of the mixing flow. Note that the schedule should have values of 0 and 1 only and intermediate fractional values do not indicate partial opening.

Note: For both Scheduled and Calculated natural ventilation options, door opening is controlled entirely by schedule and is not affected by natural ventilation controls.