Underground basement level with open areas simulation


I’m trying to simulate a building with a basement level that contains open areas (sort of a lower ground/English court level), I tried creating HB zones for the supposed voids while assigning them an air wall construction material. My problem is that e+ keeps giving me the same errors:
((( "1. The simulation has not run correctly because of this severe error:
** Severe ** FenestrationSurface:Detailed=“0BF-CIGAR_SRF_3_GLZ_0_13C484814F72425DA386”, invalid blank Outside Boundary Condition Object )))

I feel like there’s a problem with HB understanding the idea of having underground windows?

I would be very grateful if anyone could provide any useful information or previous discussions regarding the subject.

Hi Omar,

My understanding is that energyplus, and most thermal simulation programs, will not simulate a zone which has a void in it. Essentially, a zone which has a permanent opening is like having an external zone that will be the same as the outside (though perhaps the microclimate itself will be a little colder etc).

If you really care about the thermal results of this zone under your building, you should consider instead of using air walls, assign them as windows which are permanently open with a set ACH coming through. This should effectively simulate it as an external area.

Though I would question why you want to model in this zone in the first place - consider your building’s thermal envelope and add in your context shading.

Hope this makes sense / helps.

Kind regards


Hello Elly,

Thanks for the prompt reply. I’m not trying to simulate the void, but the problem is that I tried not creating a void form, and e+ considered the “void” space as earth because I’m below ground level (hope I’m making sense).

It’s like having digged your backyard till it’s on the basement level, and now you want to simulate the basement in that condition, noting that if I move the whole building vertically till the basement is on 0 Z level, it works just fine

Hi @Omar.Mowafy,

Can you try something like following?

Using HBsurfaces to create the zone and assigning the surface type.

Hi Omar,

How are you creating the building itself? You could create the floor to the basement via a honeybee surface, and choose the option “outdoors” as the EPBC (energyplus boundary condition).

Otherwise, I would suggest you create the basement with a window for the ‘hole’ and asign an ACH to it to mimic the window being permanently open thus a hole.