How to simulate the Basement?

Hi everyone! I’m a kind of freshman with Honeybee. Would like to ask how you guys model a building with a basement.

It seems all the tutorials on google and Youtube only introduced rooms above ground. Could somebody suggest me how to manage to build a model with basement? Or where can I find the tutorial for that?

I really appreciate any help you can provide!

You can use you can use the HB Properties by Guide Surface to define a surface as a boundary condition for a basement (use “Ground” as a key).
Also Custom Ground component is an option.

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Thank you for your prompt reply! Does it seem I don’t need to consider the soil condition surrounding the basement?

@AdamQi

There is already a default assumption for soil conditions if you set the surface boundary condition to Ground (as @mkdg suggested). Specifically, EnergyPlus will either use ground temperatures specified by the user, or by default assume a constant of 18C[1].

However, this is a big simplification. If you search these forums, you’ll see a couple of discussions on the additional complexity needed in thermal simulations to capture the coupling between the ground and the building, for example here and here.

The base EnergyPlus (EP) surface heat transfer method is actually too simple to capture this, which is why it relies on auxillary programs to capture more representative ground heat transfer. I reccomend checking EP’s Engineering Reference for a good overview of the options and respective trade-offs.

[1] 18C is reasonable for commerical buildings in heating-dominated climates. I think there may be some additional logic in HB that sets a higher constant ground temperature for cooling-dominated climates… but I’m not completely certain. You can always check your OSM input or the ERR output files to confirm what ground temperatures is being used.

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Thank you so much! Will check these references.