Natural Ventilation Questions

This is a discussion continuing from comments to the GH group page:

Hi Chris.

Thanks for your response, i used the attached gh file that you sent me and im trying to run the simulation but im getting the same “no ventilation will be assigned” result

am i using the component the wrong way ?


César (582 KB)


You are right about the readMe. There was a bug in the code for writing the readMe. The ventilation objects were still assigned correctly and were being run through E+.

I just fixed the bug and you can see a correct readMe in the attached file.

-Chris (582 KB)


im having very small changes in the zone temperature using all the glazeArea operable and the operable height (value set to 1) ill send you an attached GH file with the configuration im using.

im some cases im just getting a difference of .30 degrees in the zone

thanks for your time !!


A climatico gcom.3dm (1.47 MB)
clim_CWM (609 KB)


My guess is that you have chosen a day in your weather file that does not have good wind. Maybe you should look at the differences over a longer period.

Also, your window area is still relatively small in comparison to the size of your whole building and this might be another reason why the flow is not so good. You may want to try fan-forced natural ventilation (change the ventilation type to 3). This will help you understand what flow rates you will need to get the temperatures that you want. With fan driven ventilation, I image that you will get much better air flow.

Lastly, you should keep in mind that you are using a radiative temperature map to compare between cases when natural ventilation will probably change the air temperature much more than it changes the radiant temperature. Even though it’s one zone, I would use the color zone based on EP result for visual comparison (coloring the zone with the air temperature).



A new way to generate air temperature maps alongside radiant temperature maps is now available. My guess is that you will see the air change temperature a lot more than the radiant environment.

See an example file here:…


Hi Chris, Cesar,

I was wondering how I could model a zone with ideal air load parameters for heating during winter and natural ventilation during summer. Should I set my coolingcapacity to 0 and the connect my zones to the natural ventilation component?

Have you tried something similar? Also do the nat ventilation component allow to apply to interconnected zones? or is for a simple zone only?




To get rid of cooling form the ideal air system, you can either set cooling capacity to zero or the cooling setpoint to a very high number. You can also use the latter to model mixed-mode building by setting the cooling setpoint to the same value as the maxIndoorTempForNatVent.

For an explanation of how air walls and natural ventilation work together in the current version, see the latest release notes:…

Specifically, here:

Air Walls - Honeybee EnergyPlus models now officially support air walls (or virtual partitions) in a basic implementation. Now, any time that you use the air wall construction or set a surface type to “air wall,” the air between adjacent zones will be automatically mixed. At present, this mixing is just a constant flow based on the surface area between zones connected by air walls multiplied by an adjustable “flow factor.” It is important to stress that this basic air mixing is not with the EnergyPlus Airflow Network, although the groundwork laid in this release will eventually allow for the implementation of the Airflow Network in future releases. As such, this present air mixing is only suitable for multi-zone conditions where there is not significant buoyancy-driven flow between zones.

Natural Ventilation - To go along with the new potential introduced by air walls, there has been a basic implementation of EnergyPlus’s natural ventilation objects in a new component called “Set EP Airflow”. The current setup allows for three possible types of natural ventilation: 1) natural ventilation through windows (with auto-calculated flow based on window area, outdoor wind speed/direction, and stack effects), 2) custom wind and stack objects that can be used to model things such as chimneys off of single zones, and 3) constant, fan-driven natural ventilation.

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Hi Chris,

Thank you for your answer! Indeed setting up the cooling capacity to zero did work. I was also wondering if the wind direction could somehow take into account surrounding obstructions that influence the intensity and distribution of the wind - as happens in an urban environment with adjacent buildings etc! I guess this is also more on the CFD side right?