What are the principal advantages of using a single building information model of the existing conditions as the foundation for modeling proposed additions or renovations?

• Why not create a separate model for the new proposed design?

Using a single building information model, as opposed to creating numerous models representative of each progressive phase, is much more efficient and clean in terms of understanding the order in which changes are being made to a building. This method allows for the entire history of construction to remain visible and collectively organized in one space. Also, it provides the client with a visually clear idea as to how their building will be impacted. Lastly, due to all the readily accessible tools found in Revit, such as the demo view which overlays past and present construction, using a single model is most logical when displaying the flow of work a building undergoes.

What sort of complexities are introduced when you construct a building complex in phases?

• What happens at the interfaces between the buildings as the phases advance?
• How can you plan and prepare for these complexities as your create your initial building model?

When a building is constructed in phases, additional elements will only be seen in certain phases, depending on when it was added (existing or new phase). Similarly, if building elements are demolished in certain phases, it will affect the continuity of the construction when looking between multiple phases. Thus, the variable change between phases requires the designer to stay fully alert as to when they are adding or removing elements with a careful consideration toward the phase these actions are occurring in. To best prepare for this, one must always maintain a strict distinction between past and present--existing and new--to ensure all changes occur in the proper phase.

What are the principal advantages of using a single building information model of the existing conditions as the foundation for modeling several proposed design alternatives for a portion of the building?

• Why not create a separate model for each of the design alternatives?

In your project, which features of the proposed design did you choose to model as design alternatives?

• Why did you choose these building features? And what were the biggest challenges in modeling them as the design alternatives?