Heating, cooling and mechanical ventilation graph

Hi everyone,

I have a problem with the attached graph as a result of simulation of a simple box (10x10x10m). The issue I have is that when I run the system with cooling only and look at the results of cooling energy, it seems that when the inside of the box is hotter than the outside air, some “free” energy appears into the system because the outside air is used to cool the building instead of passing it through a cooling coil. I can’t seem to see where the mechanical ventilation is controlled in Honeybee so I can’t limit it or turn it off. There also seems to be some mysterious energy from “district” heating / cooling as well.

I would be extremely pleased if you can go through my GH components. I would be grateful if you can let me know how I can solve my problem and if there is any missing component.


HVAC ON-22.04.gh (959.2 KB)


I’m not sure what you mean by “free” energy. Do you mean you want to turn off the Economizer mode? Economizer mode is a default setting that increases the outdoor air rate if there’s a cooling load in the building and the outdoor air is cooler then the indoor air. So it’s “free” cooling. If you don’t want this you need to change your airsideEconomizer value to zero here:

However, even if you do this, there’s still going to be some fraction of the outdoor air that needs to be mechanically conditioned (heated, cooled, dehumidifed) to setpoint temperatures before entering the zone. So if you want to eliminate mechanical ventilation loads completely you need to set the ventilation requirements to zero. At minimum you’ll need to do set these three parameters to zero which determine the outdoor air flow amount. I believe the air system also has an “outdoor air per zone” quantity, which I don’t see as an input here, so there may be one more parameter you need to zero out… I’m not sure, but try these three first.
EDIT: Circling recirculatedAirPerArea_ in the image below was a mistake, it’s the two ventilationPer... inputs that you need to set to zero.

The “district” heating/cooling is just how the ideal loads air system (default system used by HB) reports it’s heating/cooling loads. So that value is just your cooling and heating loads, it’s not a mistake.