Properties are a huge source of confusion and inefficiency in BIM. I was reminded of that at the Eurovent meeting in Paris last week, talking with manufacturers of heating, ventilation and air conditioning equipment. The HVAC industry’s move to BIM is being slowed by the lack of standards for object properties. I think everyone in AEC feels similar pain. And I’m ready to work on a solution.
There are no agreed ways to name element parameters, choose units of measure, or decide how many and which ones to include. That means BIM models I create, or Revit families for products that I provide, may be incomprehensible or unusable for the people I share them with. That’s a problem.
IFC? Well, if you’re a programmer or a machine it might help. IFC is about file forms and data encodings for different software platforms. The terminology is extremely technical, and properties are spread across a large and complex tree that’s built for coders. IFC is not human readable.
Existing BIM standards don’t go into classes of element properties. They list a few examples of what could be added to the geometry, with no naming conventions or anything like that. In practice, as Graphisoft says on its web page, properties today are just “user-defined custom data” connected to an element. That means everyone chooses, names and specifies their BIM object parameters as they prefer, hoping that everyone else who needs to use the model will interpret them correctly. The result is a virtual infinity of different names for the same properties and different sets of properties for the same object type. That’s a source of confusion, mistakes and more generally – headaches.
We badly need a human-readable classification of BIM element properties. That would facilitate communication, help fill in gaps in the BIM process, and make it easier for every actor to obtain and understand the information that they need at any given moment.
If I’m a building owner, I don’t know what software will be used for design, architecture, and so on. I’m not knowledgeable about Revit and Tekla. I don’t know yet who my architect or contractors or facility managers will be. But I need to specify the information requirements, defining them once in such a way that they’ll be usable through the whole lifecycle of the building. I want all the different users to work with the same names for the same parameters and to interpret them in the same way!
If I’m a contractor, I want to be able to bid easily for any project, regardless of who prepared the specifications, confident that I fully understand what’s being asked for and what I’m proposing.
My vision is for a property classification system based on BIM uses and the needs of specific BIM actors, to ensure that deliverables are right for every drop point, to provide just the right set of information to each actor at every moment. The entry classes might look something like this:
And of course there would also be appropriate sub-classes, making it possible to be very specific regarding every parameter. Common three-letter codes would identify each specific property.
With such a system, it would be relatively easy over time, based on actual real-life behaviour, to define standard sets of properties for each specific BIM object type.
