Monday, August 19, 2013

Finding the Efficiency of BIM

Revit Model
With two weeks until first building department submittal, our "GA" apartment project has steadily evolved since the decision to continue using BIM was made. We now have three Reviteers involved.

The GA project is a large stacked flat apartment building. We have evolved a method that incorporates groups, links, design options and phasing to achieve the maximum efficiency in creating and managing the BIM for construction documents.

SketchUp Model
In multi-family housing CADthe design development process relies on surface modeler SketchUp. While most agree it is a "great design tool", the model is not connected to the plan development, and frequently loses its fidelity.

Projects often receive client or agency approval in spite of inconsistencies. When a project moves from DD to CD, the 2D plan files developed by the designers are handed over to production staff who refine the building plans and develop construction documents. It is they who must decipher or verify the "design intent" while applying their knowledge of building codes and constructability. The redundancy and inefficiency in this process is apparent. The obvious solution is to use the same program for both modeling and plan development. That is the reason that BIM and Revit exist.

Are designers really challenged by the process change required to switch from SketchUp to Revit? It is a move which offers many benefits. For those not familiar with the MacLeamy Curve, one effect of BIM is that effort is shifted forward where the  ability to impact cost and functional change is greater, and the cost of making changes is less.

Repeat: The cost of making changes is less.

In the technologically held back housing industry, the perceived additional effort to start up a Revit project at the CD stage is a difficult sell, especially when the client has not requested it. 

Vasari is an alternative
for concept design.
The efficiency of BIM is found in moving the effort forward where the cost is less. Designers should be eager to to accept the challenge of learning new methods, when there are benefits for all involved.

Once the basic building form has been conceived, designers must evolve the aesthetic concept, optimize dwelling unit mix and design, and provide accommodation for the infrastructure, services and common facilities.

The arrangement of the various unit types has significant impact on the building's form. Using mass families these unit types may be modeled as multi-story elements that can be driven parametrically to analyze and optimize the building design. Over time a library of plan types and plan forms will be developed that may be combined to rapidly complete the plan development. 

The mass family is also the basis for development of building modules that will be linked into a host model. At this stage design options may be used to explore and evaluate different material and finish options. With this method, "skinning" the building is achieved by manipulating the unit type model and propagating geometry and material changes throughout the model.

Groups are used for the interior of each unit type model to assure floor-to-floor consistency and modeling efficiency.

Revit is very entrepreneurial, and even within the same company, there are often as many modeling strategies as there are modelers. Methods also vary depending on the type of project. My goal is always to improve both the process and the product. The knowledge gained will be applied to subsequent projects, regardless of type.