Great discussion @Grasshope @AbrahamYezioro . I would add two points.
First, there is a sliding scale of building conditions that will require more or less zone splitting to accurately reflect energy conditions. So the comparison of total EUI can vary widely based on where our building lies within those conditions. Secondly, when we do need to split zones, we can still be very computationally efficient if we are precise about identifying which conditions we need to model, and which we can interpolate from the performance of other zones in order to reduce the need to brute force simulate all zones in a building.
Essentially, I think it’s more important to model precisely the energy dynamics in detail of representative or sample spaces, and then multiply or interpolate that out across similiar spaces, rather then do the reverse by generically (and inaccurately) modeling the energy dynamics of all spaces in the building then brute-force simulating them all.
So for the first point, there are a couple of different factors that I believe will impact the total building EUI when comparing split vs non-split floors. I’ll list the conditions in which it’s important to split the zones here, and try and explain why they should result in a different EUI from a single zone.
- Higher surface area to volume ratios (i.e If you have a high SA:V building then the building energy use will be driven by external loads rather then internal loads. This means capturing the shifting external loads,by orientation should impact the EUI difference.
- Higher WWR. For a similiar reason as above, the building will be driven by external loads, and will be very sensitive to orientation of facade, contextual shading etc.
- More use of passive energy strategies. Natural ventilation, passive solar strategies are primarily targeting perimeter zones.
- Having highly varied, and significant wind and solar exposure around the building. Again, this will differentiate perimeter vs core zone EUI.
- Less internal loads in program. I.e offices tend to have high internal loads from occupants and equipment that will dominate the total EUI.
- Less (or more regulated) mass and energy transfer through your interior zone walls. If you have an open office space you’re modeling with airwalls, then there’s little difference between a single zone and multizone. If the interior walls are adiabatic, then there’s a huge difference, and you will need to split your zones. Or, if you have a more “regulated” transfer between zones (i.e. you have a system of fans circulating air through multiple interior zones) then again, you’ll need to split zones to capture this effect.
That’s all I can think of for now, but I’ll edit this list if I come up with more.
To the second point: you don’t have to model all the floors, or even all the rooms in your building. A floor level that is 3.5m higher or lower then its neighboring floors is not going to have significantly different energy loads from them (assuming they all have the same program). You can just model the floors that will have significantly differences, due to program, external conditions, or boundary conditions, and then multiply the results to estimate total energy. E+ has a good documentation on how to do this with Zone Multipliers and changing the boundary conditions of internal zone surfaces. For example this is how they model a multi-story residence:
Note that, I’m not sure if Zone Multipliers can be used in Honeybee (@chris?) so you may have to go outside of grasshopper if you want to implement it in a more rigorous fashion the way E+ does it.
In summary, I think we can still efficiently simulate larger buildings without taking up too much computational resources if we increase the resolution of simulation in certain area (via zone splitting) and reduce the resolution of simulation in other areas (via linear interpolation or multiplying loads).
- S