Ashrae Journal - December 2008 - 45

allows the energy model to directly determine space areas (for example) without having to sort out wall thicknesses or other elements. The key is in the way that a space must be defined and recognizing that the architect’s definition of a space is much different than an energy model’s definition. For an energy model, the space must be defined in three dimensions, it must have direct association to components such as windows, it must be oriented to a compass direction, and it must know occupancy expectations, etc. An energy model has difficulty when there is not enough information or it must sort through extra information. This is difficult for simple, single-story spaces, but it is significantly more difficult for complex or multistory (e.g., atria) spaces. The required energy model space definition can be created as a subset of the architect’s view using available tools or features in most architectural CAD packages but it is by no means automatic. An architect could create all of the space definitions prior to exporting to a transferable file, but to do so requires a level of expertise in the details of energy modeling. In the near future, it is likely that architects will become more accustomed to creating Figure 1 (top): Architect’s model view of a building ἀoor plan.1 Figure 2 (bottom): Energy a space model view that better facilities simulation model view of a building ἀoor plan.1 architectural space management. It may become a standard part of design. The U.S. General Services Middleware performs an interpretation of the exported data Administration (GSA) has created a space model view definition and manipulates the data into a form that can be read more easily (MVD)2 and will require this on future GSA projects. Architects by the energy modeling program. In some cases, even after the may be creating model views for factors such as energy code data is converted by a middleware tool, it will require conversion compliance of building envelopes, which is a BIM feature under again. In the case of Energy Plus, the steps would be to export development by the International Code Council. Either of these an IFC file, interpret the IFC file with middleware, and then would bring the architect’s “standard” model view that much redefine the data into Input Data File (IDF) format.3 closer to something that would completely meet the needs of The objective of this example was to show that implementaan energy model application. tion of BIM or interoperability has two key aspects that must be At some point, there may be enough cases done by the ar- considered. The first and perhaps more obvious aspect is that a chitect where data exchange would be seamless. In the ideal certain level of technology development must exist in the tools world, this data, if based on a fully defined view, could be ex- that are used. Everyone recognizes that a multidisciplinary 3D ported as an IFC or gbXML file and used directly by an energy object based CAD tool must be used but most don’t recognize the modeling program. In reality, use of data extracted from an important role that middleware tools play or in a broader sense, architectural file, even one that is fully defined, still requires a what tools beyond the CAD are required. The second aspect of level of conversion before it can be used directly by an energy BIM implementation that must be considered is the manner in modeling program. This conversion is done with tools called which team roles and responsibilities are defined or assigned. middleware.1 In the future, the energy modeling tools could The current roles of engineers and architects on a conventionbe redesigned to be configured to accept BIM data directly or ally produced project are well established. Integrated design architectural software could be designed to export data in the approaches (whether involving BIM or not) have forced the proper format. For now, it appears it is easier to develop the reexamination of these roles to some extent but here in North middleware tools than to reconfigure the entire energy model America, the architect assumes a well defined leadership role data format or architectural data. on most building projects. With roles defined in this way as the December 2008 ASHRAE Journal 45

Ashrae Journal - December 2008

Table of Contents for the Digital Edition of Ashrae Journal - December 2008