How to output zone air speed for free-running buildings?

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Hello,

I'm simulating a free-running building, with natural ventilation activated (air flow network) based on setpoints. I need to have Zone Air Speed (m/s) as an output for some calcualtions but haven't found a way to do it. The closest thing I found in the engineering refrence is AFN Zone Mixing Mass Flow Rate [kg/s]. I think the air speed is already calculated, as it is necessary to calculate the SET, which EnergyPlus already does, but I haven't found a way to get it as an output. If anybody could help me out, thanks!