• 10 Jun 2020

BIM and curtain walling

As designers, our priority is to create spaces that are protected from the elements. The building envelope is the primary element which allows this. With BIM object modelling, the model envelope is a clear boundary which can be projected horizontally, vertically, or in perspective.

A gap, however, remains between facade design specialisms and the field of building information modelling. The same level of detail can be difficult to follow across all elements; often connectors, brackets, and shaped metal are too complex to create at the building scale. With file sizes limited to under 250Mb per file, element optimisation is necessary. Websites such as bimobject.com, revitcity.com, and bimstore.co can help a model progress in a short time, as well as being good sources for Revit families, CAD blocks, and project templates.


Design envelope

I would like to explain some steps necessary for creating a facade envelope. It is important to understand that the envelope is one assembly of a block in one file. The file has to be part of the coordination level. Creating a facade model is similar to real site procedures and time sequences; modelling should be considered a practical simulation of how efficiently site installation can proceed. We can then apply similar principles of transferring information from the model.

For this purpose, the envelope should be modelled as a series of manageable blocks, one by one. I would recommend a logical way of putting in sequence categories like a block of families in Revit. The principle is to develop all components, create a full sample, and subsequently test and retest the sample until correct. After completing all curtain wall testing, continue with external cladding and so on. This way allows for the continual improvement of each category.

Facade and cladding model are linked on grid lines which can then be manipulated as necessary.

Call out details allow open three-window viewports on one screen at the same time. Changes will appear simultaneously in each view.. Keynotes are used to add information to schedules. Call-out details are the best tool for bringing a fabrication-level of information to BIM.

For coordination purposes, three building models are key: architectural, structural, and MEP (mechanical and electrical). Developing a proper and functional facade model is extremely important to ensure a working federated model can perform to a high level of detail. I would recommend creating a separate envelope model.


Design analysis

The great advantage of BIM in facade design is its potential to undertake design analysis without having to design the whole building in detail. Geographic data may be imported to all for the automatic generation of shade diagrams and sun paths. Clash detection and energy analyses are other important aspects to consider; synchronisation with the federated model is key to their successful application.

BIM technology can offer an array of tools to architects and designers. Knowledge, preparation, consistent application of standards is crucial to ensure such methods act as productive additions to the design process. Working and learning in this way, we may find that the secret of good design is hidden in a good model.


Vladimír Kabát is the director of REVELIA, a company offering complete architectural services. As an RIAI overseas member operating in Central Europe (Slovakia), he has been working in BIM since 2010 and has gained extensive experience as a facade designer since 1998. info@revelia.sk / www.revelia.sk