Hi order of rooms seems to be an ongoing issue in the Pollination ↔ Ladybug universe. 
First result I get when I plug my model right out of pollination into an energy simulation.
Second one looks way more reasonable after processing the same model through the HB Airflow Newtwork component.
Latest Pollination update, LB Sync Grasshopper File applied
Can I trust the results?
Any idea whats going on?
Edit: basic workflow…
Hi @martin6, I know that you are loading the model from Pollination Rhino but the rest of the work is in Ladybug Tools and doesn’t have to do with Pollination. I don’t see why loading the Model from Rhino should make any differences in the results.
Can you share the model with us? Either here or through a private message?
Hey @martin6 ,
I don’t follow what you mean by “room order.” The AFN component only changes the properties of the Rooms and their constituent Faces/Apertures in the model. It doesn’t change the order of anything.
Are you just saying that the results are very different depending whether you model airflow with the default constant airflow objects vs. the AFN? Well, yea. That’s expected. The two methods are wildly different ways to model air flow through a building.
Or are you asking which method is more accurate? Then the answer is always “it depends.” The AFN models airflow in a way that is truer to real building physics but, for that reason, there are many more properties that have to be set for the simulation to be an accurate representation of a real building. Most of these parameters aren’t things you would be able to easily measure on a real building (eg. the area of “cracks” in interior walls) let alone choose accurate estimates during design.
For this reason, a constant airflow that has been matched with a building-wide blower door test is pretty much always going to be more accurate for energy use estimation than an AFN model where you didn’t change any of the defaults.
Sorry @chriswmackey for not being precise enough in the first post.
This is the only thing I changed in the setup
I understood what you were asking about the first time, @martin6 . Is it clear that the HB Airflow Network component switches the model to run using a very different model-wide airflow strategy? Or is there something else about my explanation above that was not clear?
Or am I still missing something about what you mean by “room order”? Nothing about the order of the rooms in the model object is changed by the AFN component so I still don’t know what you meant by this.
Well @chriswmackey what was strange to me is, the simulation right out of pollination tells me there are 66 kWh/m² in the cellar of a well isolated building necessary. And 87 kWh/m² in a bathroom under the roof.
Then AFN is used and it’s 82 kWh/m² in the cellar and 65 kWh/m² in the bathroom at the top.
The distribution of loads in the AFN case makes total sense to me, but without I wonder why the loads are kinda “switched” from top to bottom.
What I’d expect is the same tendency of distribution like in the AFN case, sure not the same numbers.
Cellar highest demand, 1st floor bit less, 2nd more less and slightly more under the well isolated roof due to the large exposed surface.
To me it looked like the loads are assigned in the printout in a different order. Maybe I’m totally wrong with that assumption?
Thanks, @martin6.
I see now that your concern doesn’t have to do with any order changing and you just want to know why the results are different when you simulate with the AFN as opposed to constant airflow objects on a room-by-room basis. In that case, you should re-read my explanation here:
If it was not clear from my previous explanation, infiltration airflow is modeled on a room-by-room basis when not using the AFN. So air only flows between each room and the outdoors in isolation of the other rooms of the model (unless you use AirBoundaries between rooms, in which case, there is some constant air mixing that happens across the air boundary). But it’s all very simple and allows for a fast simulation that can still be accurate on a building-wide result if you coordinate the room-by-room infiltration flows to a blower door test.
Conversely, the AFN models things like pressure differentials over the height of the building. So, even if there are no air boundaries between rooms, air can flow from lower stories to upper stories with warm air rising. This is truer to physics but, even if it “feels” more accurate, it might not always be the case because there are a lot of coefficients to be set in the AFN that are tough to know like the air permeability of interior walls and floors.
So, of course the AFN is going to give you different distributions of energy usage than modeling with the default room-by-room infiltration. Can you clarify why you were expecting this?
