The building process has been refined over thousands of years. While every project’s process is slightly different, projects generally progress along these major phases. It’s important to know the right type and level of information that’s needed within each phase to add the most value.
Project Phases
In the construction industry, the design process is described by the phases of pre-design, conceptual design, design development, and final design. The building life cycle process is described by the phases of construction and building operation.
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Typical Design Process of Buildings
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Level of Detail (LOD)
In order to efficiently manage the process of working in a BIM workflow, the industry has adopted a formal language of describing the completeness of a digital model at a given point in time. This language is “Level of Development” (LOD). LOD, in the BIM world, ranges from 100 (basic/conceptual) to 500 (highly detailed/precise). It is not unusual for levels of expected development to be part of the contract documents as described by the American Institute of Architect’s Building Information Modeling Protocol.
LOD phases can be summarized as follows.
- LOD 100: Modeled elements are at a conceptual point of development. Information can be conveyed with massing forms, written narratives, and 2D symbols.
- LOD 200: Modeled elements have approximate relationships to quantities, size, location, and orientation. Some information may still be conveyed with written narratives.
- LOD 300: Modeled elements are explained in terms of specific systems, quantities, size, shape, location, and orientation.
- LOD 400: Continuation of LOD 300 with enough information added to facilitate fabrication, assembly, and installation.
- LOD 500: Modeled elements are representative of as installed conditions and can be utilized for ongoing facilities management.
It is worth mentioning that a relationship between LOD and design phases can be loosely established. However, it should be emphasized this relationship is not empirical. For instance a project as a whole may be in design development, but in the digital model, the building envelope system may be fully detailed with exact materials and thicknesses. More so, plumbing systems might be represented with single lines, not modeled geometries.
LOD and Building Performance Analysis
Building Performance Analysis (BPA) is related to LOD on two fronts. First, what prevents modeled elements from progressing to the next step of LOD is the absence of information. The answers to discrete questions have not been found. BPA can be a mechanism for finding answers to these questions and informing the design process.
Secondly, digital methods of BPA are dependent upon the amount of information that is digitally modeled. Therefore it becomes beneficial to comprehend what LOD a model is at, and what that means in terms of available data, so analysis methods can be associated with the digital information that is readily available. For example, a model at LOD 100 will not allow one to conduct energy modeling that is required for LEED certification, but energy modeling with a LOD 100 can identify how the building’s energy consumption can be influenced by solar radiation. For these reasons, the LOD of a model and BPA practices share a feedback loop that at times are not as linear as the steps to developing levels of detail in the BIM model. This may be best explained with the following graphic.
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Level of Development and Building Performance Analysis Interaction Diagram
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Drawing the BPA connection
If we understand BPA as a tool for answering design questions, while simultaneously relying on modeled information, we can then establish relationships to how certain BPA practices may be related to LOD and the time scale of how a design project evolves. The following are some examples of how these relationships work during the design process.
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