How to model Night Purge

asked 2026-02-24 03:28:16 -0500

Keigo
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Has anyone modelled night purge (night ventilation) in EnergyPlus using AvailabilityManager:NightVentilation?

I ran two ExampleFiles: 5ZoneNightVent1.idf and 5ZoneNightVent3.idf (V25-1-0). Night purge is not modelled in 5ZoneNightVent1.idf and modelled in 5ZoneNightVent3.idf.

I got exactly the same annual cooling end use from the two files, which suggests that night purge in 5ZoneNightVent3.idf is not working.

The simulation results show that the fan operates at night when the condition allows, but the outdoor air is not reaching each zone. Only 4 nodes in OutdoorAir:Mixer have 0.5m3/s airflow during night purge. Other nodes have no airflow. This may be a bug.

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For what it's worth, I ran all 3 models:

5ZoneNightVent1.idf
5ZoneNightVent2.idf
5ZoneNightVent3.idf

... for an entire year (not a week), and in a colder climate zone (than Fresno, California):

fan energy use varied between all 3 models, from 2 to 3%
slight differences in cooling (< 1%) between 1 vs 2, and 2 vs 3
as you observed, no differences in cooling between 1 vs 3

Have not taken a deeper dive as to why?

Denis Bourgeois ( 2026-02-24 06:50:57 -0500 )edit

5ZoneNightVent2.idf models night purge with ZoneVentilation:DesignFlowRate. That's another option. I'm wondering if AvailabilityManager:NightVentilation will work. If not, ZoneVentilation:DesignFlowRate is only per zone, but I think it is possible to mimic the existing fan objects.