Openings tab in model data under External Glazing, Internal Glazing and Roof Glazing headers
Note this data is only shown if Natural ventilation is activated on the HVAC tab at the current level.
The operation of windows in the EnergyPlus simulation airflow network simulation can be defined by entering data under Operation headers. The data will depend on the Natural ventilation model option set:
The % Glazing area opens data allows you to define the openable window area as a percentage of the total window area. For example enter '20' if 20% of the window area can open.
The air flow opening is assumed to be a gap in the side of the window which takes on the full height of the window.
Note: % Glazing area opens data does not define the size of the opening for CFD. The size and position of the opening in CFD calculations is defined on the CFD tab.
Note: if modulation is switched on (it isn't by default) the glazing opening areas defined here are multiplied by a factor to account for external conditions.
Tip: In some cases it is best to switch off the Lump similar windows on surface model option when using Calculated natural ventilation. Particular cases where this is important are a) when there are windows of the same size and type but different % Glazing area opens values on the same surface and b) where the air flow rate through individual windows is required, e.g. when preparing boundary conditions for a linked EnergyPlus CFD study.
The schedule that specifies when window venting is available. A zero or negative schedule value means window venting is not allowed. A value greater than zero means venting can occur if other venting control conditions (specified by natural ventilation Control Mode) are satisfied.
This schedule allows you to turn off venting at certain times of the day (at night, for example), of the week (on weekends, for example), or of the year (during the winter, for example).
If used with natural ventilation Control Mode = 4-Constant, the ventilation rate is constant only when this schedule allows venting; otherwise the ventilation rate is set to zero. If Ventilation Control Mode = 1-NoVent, this schedule has no effect.
The windows are 'open' when:
Tzone_air > Tsetpoint AND Tzone_air > Toutside_air AND the schedule value = 1
The ventilation rate is calculated based on the pressure difference across the opening calculated from wind and stack pressure effects using equations described in Natural Ventilation Modelling.
Airflow through external windows, vents, doors and holes are not modelled explicitly with Scheduled natural ventilation because the natural ventilation airflow from outside is explicitly defined using the total natural ventilation flow rate and operation on the HVAC tab. No operation data is entered on the Openings tab for external windows in this case.
Note: Natural Ventilation can be overridden to be off on the HVAC tab for both Calculated and Scheduled model options.