A model is clean only when someone else can open it and trust it. buildingSMART International wrote that idea into a spec. Its Information Delivery Specification (IDS) turns “what the model must contain” into a machine-checkable file instead of a paragraph in the BEP. On Wednesday, 14 October 2026, our next Archicad Powersession takes that same discipline down to the desk: Modellhygiene, the unglamorous habits that decide whether your model survives a handover.

We are not running this because hygiene is fashionable. We are running it because of a pattern. Offices that come to us with a slow file, a broken IFC export or a coordination round that never ends rarely have a software problem. They have accumulated drift: storeys nobody uses, layers named three ways, zones without numbers, library parts loaded twice, objects floating outside any storey. Each item is small. Together they make the model the place where good intentions go to wait.

Why now, and why in Archicad

The timing is not arbitrary. As AEC Magazine reported, Graphisoft has unveiled Archicad 30 and laid out an AI roadmap for the platform. Whatever that roadmap brings to a given office, it will read the model you already have. An assistant that queries your zones, or a script that rebuilds your schedules, is only as good as the structure underneath it. Messy data does not become clean when a model reads it. It becomes confidently wrong at speed.

←TODAY: A Swiss BIM handover is still checked by eye, file by file, in most offices. →3012: Every model arrives with its own audit trail, and an unreadable file is as unthinkable as an unsigned plan. Fulcrum: The hygiene you set this autumn is the data every future assistant will inherit.

The session is for Archicad users who own a template or live inside one. That means BIM coordinators who receive models from three consultants, project architects who wonder why the file takes four minutes to open, and office leads deciding what “done” means before a model leaves the Büro. If you have taken our Archicad Bootcamp, where we framed PARAM-O, Grasshopper, GDL and Python as the places automation happens, this is the ground floor that work stands on. Automation only scales on a model that is already in order.

Hygiene is also where our own tools came from. Several of the routines bundled in PAZ-BOX began as cleanup tasks we repeated two hundred times, such as room stamps, naming and checks. If you want to see how those routines live inside Archicad today, the PAZ Archicad add-ons page shows the current set. The session itself teaches the habit, not the product.

Atelier: An office starting to put AI next to its Archicad models faces a quiet risk. The assistant will treat every stale layer and unnumbered zone as truth. Before anyone pilots a model-reading tool, agree on what a clean file means for you. On Monday, write a ten-line “model is ready” checklist and pin it inside your template’s project info.

Hack: Find every element in an exported IFC that belongs to no storey, which is the drift that coordination software silently drops. IfcOpenShell is maintained by Dion Moult, Thomas Krijnen and the open IfcOpenShell community, and it reads the export Archicad already writes. Five lines give you a punch list:

import ifcopenshell, ifcopenshell.util.element as ue
m = ifcopenshell.open("handover.ifc")
loose = [e for e in m.by_type("IfcElement") if ue.get_container(e) is None]
print(len(loose), "elements without a storey")
for e in loose[:10]: print(e.is_a(), e.GlobalId, e.Name)

Parts nested inside assemblies or curtain walls can show up here legitimately, so read the list rather than deleting from it. The trade-off is plain: a check run on the export finds problems after the fact, so the real fix always goes back into the Archicad file.

How to join

Date, format and registration are on our session page: Archicad Powersession – Modellhygiene. Bring a real file, ideally the one you are slightly embarrassed to share. Those teach the most. Run the five lines above on your latest export before Wednesday, and come with the number it prints.