Multiple Air Loops in the Same Thermal Zone

Hi Mingbo, first of all thanks so much for all your help Ironbug is amazing! I am trying to add two air loops to the same thermal zone but it’s not quite working. It creates both air loops, but it only assigns the thermal zone to the second one, and leaves the first one without any components on the demand side. I’ve tried a bunch of different configurations (duplicating the thermal zone, merging the air loops, etc.) but haven’t had any luck. Is there any way around this? This was the closest I got.


Hi @avril14
No, it is not possible, one zone can not be connected to more than one airloop. You will need to divide your zone to smaller zones, and assign different zone to different airloop.

Hi @MingboPeng, apologies to open this thread again, but I am also trying to insert multiple air loops into a single thermal zone. Checking Unmet Hours, they state at “as of EnergyPlus v8.8, you can indeed have multiple air loops serving a single thermal zone”. For more information about the EP version fix that allows this function, see the Github page here.

Are you aware how I can implement this with Ironbug? I have attached a simplified Grasshopper script of my file, where I am attempting to model an air-source split systems per zone for heating, cooling, and dehumidification, as well as a single centralised MVHR system for ventilation.
Multiple Primary Airloops in (57.1 KB)

The script correctly generates the air loop with the centralised MVHR in OS, shown below:

The script also correctly generates an air loop per zone for the split system in OS. However, the thermal zones are missing from the loops, as highlighted in red below:
4xSplit Airloops

Hi @Stranga, I don’t think the OpenStudio supports multiple air loops for a single zone even the EnergyPlus now supports it, which means Ironbug won’t be able to model it as it is built on top of the OpenStudio.

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Hi @MingboPeng, I was told by a NREL research engineer that apparently it can be done through the OS API. Where it needs use of the ‘multiAddBranchForZone’ method instead of the ‘addBranchForZone’ method. Though I have no idea how to implement this.

Thanks @Stranga for letting me know this ‘multiAddBranchForZone’ method. Let me think about it how to implement it and I will let you know once I have something for you.

Hi @Stranga,

It is easier than I thought. I just added this feature to the “ThermalZone” component. You can right-click the component to enable this feature.

There will be a new release of Ironbug later tonight, and here is a sample file. (28.7 KB)

Thanks again for looking into OS API and letting me know.


Hi @MingboPeng, thanks for looking into this so quickly and great to hear that it can be implemented in Ironbug so easily.

I’ve re-installed the Pollination single installer, and then ran the GH model from your last message. But I’m not seeing any settings to “allow multi-airloops” in the ‘thermal zone’ component (please see image below). When I run the script, the zone appears in the ‘DOAS’ loop, but not in the ‘air loop HVAC 1’ loop. Can you please let me know what am I doing wrong?

Hi @Stranga, sorry for the late reply.

The new Pollination installer that includes this new Ironbug version has not been released. After installing the Pollination installer, you can download the latest version of Ironbug from Releases · MingboPeng/Ironbug ( and Ironbug installer will override the old version that comes with the Pollination.