I’m working on a Honeybee model that uses the Airflow Network (AFN) for natural ventilation. In my model, I have a skylight that I’ve specifically set to “Not Operable”. However, when I connect the output of the AFN component to check the properties of the apertures, the skylight still appears listed as operable.
I’m attaching a screenshot that shows this issue.
Is this a known bug or a limitation in Honeybee’s export to AFN? I understand that AFN doesn’t support operable skylights anyway, but I want to make sure my model is correctly configured and that I’m not missing something.
This isn’t a bug/limitation in the simulation, it’s just a misleading display in HB by using the is_operable attribute.
When the model is converted to IDF, HB creates an Energy Management System (EMS) that keeps non-operable windows closed at all times, and opens others according to the settings you previously set in the HB Ventilation Control.
You can however double-check this by looking at the ach in rooms without operable windows or you can verify the IDF by checking the EnergyManagementSystem:Program objects for the actual opening logic.
@MatteoMerli is correct that the horizontal window is not opening in the EnergyPlus simulation but the reason why it gets set to be operable has to do with EnergyPlus AFN conventions. VentilationOpening IDF objects are not only used for assigning airflow through open windows but also infiltration through closed windows.
So everything gets set to “Operable” when you pass it through the AFN component so that infiltration through the closed window can make it into the E+ AFN. But, if you check the “Fraction of Area Operable,” you will see that it is zero for the windows that were originally non-operable:
Long story short, if you are looking to understand which windows are opening in an AFN simulation, the “Fraction Area Operable” is the better property to check rather than the “Aperture is Operable” property.
Thanks @chris for your help and the clarity, it’s been really helpful.
I’m working on an energy model for a house that integrates some bioclimatic strategies. One key feature is a covered interior courtyard designed to help regulate temperature. The cover should be operable to allow for natural ventilation.
I understand that using the AFN (Airflow Network) model would be the most accurate approach for this type of simulation. However, since the AFN doesn’t support operable skylights, I’m considering replacing the skylights with windows by adjusting the default roof angle and redefining those roof surfaces as vertical walls.
Would this be a valid workaround to simulate operable roof elements in the courtyard? Or is there a better way to model this condition?
At the moment, I’ve modeled the courtyard (a box) and the skylight (a triangular prism) as separate Breps—i.e., independent rooms—with air boundaries between them using Solve Adjacencies. Is this a valid approach, or would it be better to model everything as a single Brep using a Boolean union of the box and the prism?
I’m attaching the Grasshopper file for reference.
Thanks in advance!
