Vent Operation

Openings tab in model data under Vents


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


The way this data is used depends on the Natural ventilation model option set:


A schedule can be applied to control timing of the vents. Note that the schedule should have values of 0 and 1 only and intermediate fractional values do not indicate partial opening.


The ventilation rate through the vent is calculated based on the wind and stack pressure effects.


External vent 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 vents.


Internal vents are modelled using the EnergyPlus 'Mixing' object which mixes air between the two adjacent zones.  DesignBuilder uses a very approximate empirical relationship to calculate the mixing flow:


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


where Farea-flow is a factor used to obtain the mixing flow from the opening area = 0.1.


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