I am working on an energy model and i would like to isolate some results without the wind effect and compared with how much the wind impact is. This model has a series of operable rooflights that will open in the night for flushing the heat, so i do want to account for other effects such as buoyancy.
I have done this before in Design Builder by reducing to 0 the wind factor of the operable openings, so i guess than in theory this could also be done in Honeybee (they both use E+), but i just cant figure out how. As it is mentioned in the DB help it is a Cp multiplier basically.
Has anyone tried this before? if so, How did you do it? Any idea how can i integrate this multiplier in HB?
I am not familiar with how this is implemented in LBT, or if its available.
Some options are not available in LBT, and some of these can be written directly to the IDF file before running. This might be an option, but I haven’t tried it.
Otherwise, an alternative solution is to read the .epw in, and overwrite wind with 0, and then construct it again. Perhaps a dumb solution, but workable.
Thanks @LittleBuddha. Yes that was the workaround i thought about, however the convection losses of the envelope are not considered either, so it is not exactly accurate, but for now i will go with this.
I thought about editing the IDF file with the additional string feature in Open Studio, but i am not familiar either and everything i tried so far reported an error.
As far as I’m aware, the only way to exclude wind-driven ventilation is by modifying the IDF directly, by setting the Opening Effectiveness to zero in the ZoneVentilation:WindandStackOpenArea object. This removes the wind component from the total ventilation rate equation, leaving only the stack ventilation. Unfortunately, you can’t modify existing objects in the IDF using additional strings from HB (which only allow you to add new objects).
Regarding infiltration, if you’ve built your model through HB, the infiltration will be constant and not affected by temperature difference or wind speed/direction. That’s because the B, C, and D terms in the ZoneInfiltration:DesignFlowRateequation are set to zero by default. Again, if you want to change these coefficients, you’ll need to edit the IDF after it’s generated.
That said, if you’re using the Airflow Network model, it’s a completely different story.
Thank you for your response. About your question I am using the airflow network, i have seen in this other conversation to change the airflownetworkcontrol to input instead of surfaceaveragecalculation, but i am not sure if this can be set directly in the additional string input for open studio.
I have ended up doing it manually as @LittleBuddha sugessted
However not ideal, i belive it does the trick. If you can think on any other way i would love to heat about it. The idea is to remove the pressure coefficients from the simulation or being able to set how much influence i want the wind to have in my model.
Glad that you found the solution there. And, yes, the Honeybee SDK only supports setting wind pressure coefficients using E+'s native simple approximation of a bounding bounding box. You’ll see that most of the inputs on the HB Airflow Network component relate to this bounding box model. If you really wanted to set the wind pressure coefficients to be something different, you would have to post-process the OSM using the OpenStudio SDK using a custom Python component like you see here in these old release notes.
Just to add to @MatteoMerli 's answer for those people using simple ventilation objects instead of the AFN, there’s a very easy way to remove the effects of wind. All that you have to do is set _wind_cross_vent_ to False on the HB Window Opening Component. That will set the the Opening Effectiveness to zero in the ZoneVentilation:WindandStackOpenArea object as @MatteoMerli mentioned.
