The dialog itself gives a hint - see attached. I believe that this is in part to grab the thermal properties of the fill as associated with a Building Material for the "Thermal bridge simulation on ArchiCAD [2D] details" of EcoDesigner STAR. See the video with that name at near the bottom of this page: http://www.graphisoft.com/archicad/archicad_17/energy_evaluation/
For construction elements (Wall/Slab/Beam/Column/Roof/Shell/Morph/Mesh): Cut fills are assigned via the Building Material attribute. When such an element is exploded (e.g. in a Detail Drawing), the resulting fill will be in the Cut Fill – Building Material category. A detail Fill in this category retains the Physical properties of the original construction element.
For example, if you draw a fill as a detail patch, to be used as a cut fill, change its category from “Drafting” to “Cut Fill – Building Material”. This way, this fill will behave like the Building Materials of construction elements in the project,
I'm glad you asked, as I hadn't noticed this feature.
One of the forum moderators • AC 25 USA and earlier • MacOS 11.6.6, iMac Pro
Does this also mean we can add cut fill materials to an existing thermal simulation. Meaning we can model up a quick simulation of a hypothetical wall assembly to test its performance, without creating an actual wall in the model.
Richard Wilden Design. Ltd
Dunedin, New Zealand.
Imac 27" i9 3.6GHz; 32GB Ram Mac OS 11.3