What the Owner should know about NBIMS during Building Design and Construction
Sunday, November 18, 2007 at 09:44PM | Print Article
In a previous post, (Building Information Modeling),I described Building Modeling, the Building Information Model, and the difference between them. Here I will to describe how I see the use of BIM changing the process of acquiring a new facility.
The National BIM Standard (NBIMS) is based on the internationally accepted IFC data standards. The IFC standards include early capture of site information, of design and program goals, of regulatory requirements, and of contract information. The NBIMS process, by capturing this information at each stage of the process, is able to verify whether these needs are met as the project progresses through design and construction.
Where CAD automated the Drafting process, Building Modeling fundamentally changes the design process. Drawings become mere views of the model. Designers can try out the models before the building is built, allowing iterations of design in which function is tested, in the same way that boat and aircraft designs have been tested in advance of construction.
There is an odd market dynamic going on right now. The best designers use a BIM that they do not share. The best Contractors develop their own BIM to produce their bid and to guide their construction process; they do not share this lest it increase their liability. The owner receives no BIM at all. Somehow, we can afford to throw out two BIMs but we cannot afford to share one. The forward thinking owner will reduce costs and receive higher quality by contracting for the maintenance and sharing of a single BIM through design and construction.
Emerging best practices, with names like Green Design, or Sustainable Design, or LEEDS, develop an energy model as part of the design process. The energy model looks at the design decisions and computes how much energy the building will use when operating. The energy model can then be compared to the design intents, and changes made to improve the design.
Energy Modeling should be an intrinsic part of design that extends throughout the life of a building. Too many of today’s energy models are merely grafted onto the design process without intrinsic link to the design. New modeling tools are now able to read the BIM directly to produce energy models. This turns Energy Modeling into a means to “commission” the design prior to construction. It also means that the effects of value engineering on cost of operations can be re-computed easily.
Even the best of traditional CAD-based design leaves many problems undiscovered. Building systems are designed by different teams and rendered on different flat pieces of paper. If, say, the ductwork and the electrical conduit run through the same space, it may only be discovered during construction, when it is more expensive. Delays and expensive change orders are the natural result.
Experienced contractors understand these deficiencies in traditional design. They add some margin into their bids to cover errors and oversights, and to allow for the inevitable inaccuracies and missing components. Early experience suggests that if a building is defined using BIM, and if the BIM is shared with the contractors during the bid process, that the bids will come in lower than if traditional blueprints only are shared. The ensuing reduction in change orders, and the resulting on-time delivery, are additional financial benefits.