How to model an exhaust ventilation system?

Hi everyone,

I am working on simulating energy use and thermal comfort of a few apartment buildings for my thesis and I got stuck at one point. As a common practice, buildings in the nordics using exhaust ventilation systems, meaning to extract air from the building using a fan and dumping it without any heat recovery. The air intake is usually through openings in the exterior facade or window frames. I already tried by setting 8760 different supply air temperatures in the ´HVAC Air Details` component and heavily failed with this.

So I was trying to model this for quite some time, using a simple shoebox and I sort of got a reasonable method, by modelling the ventilation as fan driven natural ventilation. The file where I am doing so is attached: (709.5 KB)

Now, I tried to apply this method to a multi storey building, but as soon as there are multiple zones, the input ´fanFlowRate` get´s tricky, in the way, that the prescribed constant ventilation rate per square meter of heated floor area is resulting in a different fan flow rate for each zone.
Since I couldn´t find a solution just yet, I have two questions concerning this matter:

  1. Does anybody have a different approach to model such a ventilation system?
  2. Does anybody have an idea on how to make the workflow simpler, than adding a single component to each and every of the zones I modelled?

Thanks in advance for any kind of help!


Did you try to add a Zone:Exhaust Fan to the zone?

Hi Mingbo,

good idea, I tried so now. For the single zone model, it works just as good as the natural ventilation. For the multi zone model, it get´s as difficult as with the natural ventilation method, as I would have to add a maximum flow rate for each zone itself, so it seems not like a very clean workflow…

@Jonas ,

There are probably a few different ways to do this depending on what behavior of the fans you need to capture.

I think the simplest is probably just to generate a list of the different fan flow rates for each zone depending on that zones’s ventilation requirements and the floor area. You can see that the Set EP Airflow component can accept lists of flow rates that align with the zones: (483.2 KB)

There are some other ways of tricking the DOAS of some of the templates into now having any heating or cooling. Also, you can always write an OpenStudio measure to assign the exhaust fan object that @MingboPeng has pointed out. However, I would only resort to this if the first method doesn’t work for you somehow.

Hello @Jonas, did you get you need?
I´m trying to include an exhaust fan in a single zone, using Ironbug from @MingboPeng. My problem es I´m getting the same result with or without exhaust fan or incrementing/decreasing exhaust fan flow rate.
Someone can bring light here? thank you (615.3 KB)

Hi All,
Using LBT 1.5 and Ironbug 1.1.1 is it possible to set up the Zone:Exhaust Fan object with a multi-zone Airflow Network model? For this to work, I believe Ironbug would need to add the following objects to the IDF along with the right node connections:

AirflowNetwork:MultiZone:Surface (referencing exhaust fan as leakage component associated with a particular surface)

I first tried to just add everything to the HB Model to OSM component as additional strings, but this has been an error-prone process so far.