Revit IFC Hosting

[Patrick Thompson]

Hi All, 

An issue that keeps brewing for us is IFC exchange with Revit companies. We are in a position where a large international engineering company is becoming increasingly frustrated with collaborating with us. I suspect it is coming to light as in the last year or so there are more and more users collaborating on B360 using the swimlanes with their native Revit models. Essentially there is additional friction to collaborating with an architect using Archicad. 

The latest issue is the electrical engineers 'expect' to be able to host all of their items in our geometry. Their commentary here:

Common issue we encounter at every IFC model exchange

• Wall-hosted devices move to a random location
• As shown in the images below at least 20 devices have moved unexpectedly for BAL Level 01 following inclusion of a new architectural model,
• This has become more obvious as we have finished and drawn the circuiting and the wires for both buildings,
• To rectify this it requires us to re-host the devices and completely re-draw all the wires every time we consume a new model.
• Usually, this effects fixtures & devices that are hosted on an architectural wall.
• At this stage we have not been able to determine an explainable pattern for which devices would move and which will stays, it seems to be consistently ad hoc.

Proposed solution

• We will need to update or swap all the wall-hosted devices family to become a “non-hosting” family (which is not standard practice for us).
• Please note, what this will mean is that it will lead to “objects floating in air” or “clashing inside wall” and will require a check of alignment with every model exchange. Hopefully walls/ architecture wouldn’t change making this process a bit more simple, however it is still an additional review that will be required.

We suspect its because everytime we send an update, they open the IFC in revit, and link that into their model. From what we understand that generates new GUID's for the created revit elements. Therefore an elements jump to other locations as the GUID is either missing or has been allocated to another ifc element. 

In what we are finding a very autodesk dominated market... which is increasing, has anyone found a way around this?

FYI I did find other threads on this but they were from circa 2015. 

[Miha_M]

How is your model used in revit? It should be used as a linked reference model (and agreed on in the BEP). If such a model element has referenced  other discipline elements (which is most likely a possible situation in revit) I don't think this should be a problem, if a linked reference model has to be updated on revits side.

Help | About Linking to IFC Files | Autodesk

At the BIM manager program I took part in two years ago we got some advice on how to handle data exchange on Revit side. GS suggests that such data exchange should be done based on the Revit plugin GS has made available, but you probably know about this already.

IFC Model Exchange with Archicad for Revit 2023 (graphisoft.com)

Interoperability – Graphisoft

I don't work with Revit so I don't have much experience with this, but I think this plugin works with the "link method", where the Archicad model is imported as a reference model. There is another "open method", where you import the IFC file and save it as a .rvt file, then this file is further linked to other revit files. This "open" method needs some additional workarounds: first option is exporting from archicad into three different models: ceilings only, floors only, everything else. Importing and linking the ceiling model IfcCovering to the Ceiling category, to the Floors category for the second model and Generic models category for the third model. Second option doesn't require multiple exports from archicad, but one IFC model only. On the Revit side this model needs to be imported with the open method with all elements, but the ceilings turned off. Then another import with the "link method" of the same file with all elements turned off, but ceilings turned on. There were several other suggestions made, but I don't think these would be applicable to your situation.

We are currently also exchanging data with another company on Revit. We also have some weird problems (correct geolocation in archicad using the survey point places the imported content in revit on a doubled Z position, two different file version exports with same export settings don't align perfectly (?!), but for general purpose of a reference model from our side to revit everything works well. Until now, most of the problems were identified, caused and solved on Revit side.