Honeybee / DesignSpecification:OutdoorAir

Hi @Mostapha @chris

I have a question regarding how air changes get exported to openstudio and energyplus. I am working on a hospital project that has to meet certain ventilation requirements. I been using the HB ACH component to apply my required air changes

The question I have though is regarding the structure of how things get translated to energyplus / IDF. My model has 19 different space types (over 300 zones) with different air change requirements and 22 mechanical units. When I checked the idf file I was expecting to see either 19 objects (for each space type) or over 300 objects (representing each individual zone) in the IDF input called “DesignSpecification:OutdoorAir”, but instead I only see 9. These 9 DSOA objects get distributed to all zones through the IDF input called “Controller:MechanicalVentilation”. That controller input has 22 objects representing the 22 mechanical units which is what I would expect.

So I am trying to find a solution on to how to properly export my DSOA objects, so that I can have the 19 ACH values exported rather than just 9. I do not understand why the model chose those 9 nor what happened to the other 10.

Is each setzoneEPloads components that has an incoming value from the ACH component supposed to export as one object in the “DesignSpecifcation:OutdoorAir” input? or is there another way these objects gets exported?

and just to clarify I export my Honeybee models using the openstudio export component.

Thanks in advance.

@FabianPosadas ,

You are using the correct method to set the patient room ventilation. I model a lot of hospitals myself and the only change that you should make is that the recirculated air in Honeybee is done in addition to the outdoor ventilation air. So you should either be setting that recirculated value to 4 ACH (for a total of 6 ACH) or 2 ACH (for a total of 4 ACH if you are using the most recent ventilation requirements for hospitals in the US).

I should also mention that, if you are modeling a patient room with chilled beams, all re-circulation typically happens within the beam so you can set the recirculated air to 0 (since it’s not being recirculated all of the way back to the air handler).

To answer your specific question about DesignSpecification:OutdoorAir, the probable reason that you are ending up with 9 objects is that you have several space types with the same ventilation requirements. So, if two space types have the same ventilation requirement, they will reference the same single DesignSpecification:OutdoorAir object in order to save space within your IDF. It’s probably easier to check this within the OpenStudio GUI rather than the IDF editor since you can actually check the outdoor air object referenced by each space type.

The “zoneHVACParams” from the generate EP output component are also helpful for validating that the ventilation is working as you expect (it might be more manageable to check this with a single zone before you scale it up to 300 zones, though).


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