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?
By using existing drawings, preferably as-builts, the designer can ensure that they have accurate information for what was built on the field. This allows for ease of planning demo, and prevents future headaches from following plans that are not the latest. Certain aspects of the preliminary design may have been changed during construction, this is why it is important for contractors to submit as-builts once constructions is complete, it benefits the client down the road immensely.
In your project, which features of the proposed design did you choose to model as design alternatives?
The features I used to model as design alternatives are furniture layouts. This is the best to provide to the client as a designer because it has a big visual impact on the the building but does not provide significant risk should the client change their mind during construction. FFE is usually the last thing a building has done and it is much simpler to replace than and exterior wall once it goes up.