Chapter 4 Discussion Questions
5.3 BIM USE IN DESIGN PROCESSES
5.3.1 Concept Design and Preliminary Analyses
As the previous sections indicated, major decisions regarding the value, per- formance and costs of a building are made during concept design. Thus the potential benefi ts that design fi rms can offer to clients will increasingly focus on the differentiating services they can offer within the concept design phase. Concept design based on early analysis feedback is especially impor- tant for projects involving medium or high levels of information development.
We expect this to become an increasingly important area of design fi rm differentiation.
Today, a growing number of easy - to - use tools are available that were con- ceived not for heavy - duty production design but as light - weight, intuitive tools that are relatively easy to use, so much so, that they become invisible aspects of the designer ’ s thinking process. Each provides functionality that is important for preliminary design. Some tools focus on quick 3D sketching and form gen- eration, such as Google SketchUp® (Google 2007), or for larger and more geometrically complex projects, form · Z. Other software programs support lay- out according to a building program, such as Facility Composer and Trelligence (Trelligence 2007) or simple layouts and interfaces for energy, lighting, and other forms of analysis relevant to conceptual designs, such as EcoTect (Square One Research 2007), IES and Green Building Studio. Another important area for conceptual design is cost assessment, which is offered by Dprofi ler (Beck Technology 2007) plus others. Unfortunately, no one of these programs pro- vides the broad spectrum of functionality needed for general concept design, and smooth interoperability between these tools is not yet a reality. In practice, most users rely on one of the aforementioned software tools. Of these, few are able to interface easily and effi ciently with existing BIM authoring tools. A quick review of these various secondary tools follows.
3D Sketching Tools
The earliest available conceptual design tools were those for 3D sketching.
form·Z can be considered the grandparent of this category, having served as a 3D design tool since 1989. It supports powerful 3D solid and surface modeling capabilities that can represent any form imaginable, for architects and product designers. In its early days, it was considered the most intuitive solid modeler
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FIGURE 5-2 Competition models using form·Z.
Courtesy of View by View, San Francisco.
available, but with growth in functionality and new competitors, form·Z is a trade - off between powerful freeform surface modeling and intuitiveness. An example project developed using form·Z, for a high speed train station in Pusan, Korea, is shown in Figure 5 - 2 . Other products with similar functionality include Rhino and Maxon, which also emphasize freeform capabilities.
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FIGURE 5-3
A massing design study done in SketchUp.
Other applications focus on the quick sketch 3D layout of building spaces and envelopes. Products of this type include SketchUp® and the now defunct Architectural Studio® from Autodesk. These tools support quick generation of schematic designs and rendering in a manner conveying the character of the proposed space and building shell. An example project and multiple views generated in SketchUp are shown in Figure 5 - 3 .
These applications support easy sketch defi nitions of the geometric forms used in architecture but typically do not carry object types or properties other than material color and/or transparency, which are only useful for rendering.
As a result, they do not interoperate well with other concept design tools, such as those described below.
Space Planning
A building ’ s requirements often center on a set of spatial needs defi ned by the program, describing the number and types of spaces that the client expects, their respective square footages, the environmental services they require, and in some cases the materials and surfaces desired. Critical relations between these spaces are further detailed according to organizational practices; for example, access required between different wards and treatment facilities within a hospital.
Space planning involves organizing the spatial needs defi ned by the client and expanding them to include storage, support, mechanical, and other ancil- lary spaces. Typically, these applications depict the space program in two forms, as a series of line items on a spreadsheet and as a block diagram layout of the proposed fl oor plan. Software products that incorporate this functionality
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include Visio Space Planner®, Vectorworks® Space Planning Tool, Trelligence®, and the Army Corps of Engineers ’ Facility Composer. Autodesk Revit ® and ArchiCAD ® ’ s links with Trelligence provide similar spreadsheet capabilities within these BIM design tools. A composite of three screen shots from Facility Composer is shown in Figure 5 - 4 . The fi gure shows the program spreadsheet of space types, indicating what has been laid out (actual) and what remains to be allocated (available) by building and by story. A plan of one story and the schematic massing of the entire building are also shown in Figure 5 - 4 .
These applications explicitly represent the spaces within a building, with or without development of space enclosures. A spreadsheet shows the current layout allocation in relation to the space program requirements. All current space planning programs support massing based on a blank sheet of paper, without envelope constraints; thus none appear to support generation of layouts within the confi nes of a given building shell, or within a form that captures a target image. These tools provide another set of important but incomplete schematic design capabilities.
FIGURE 5-4 Like most space planning systems, Facility Composer supports development of massing diagrams based on a program spreadsheet and compares the current layout in relation to the given program.
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Environmental Analysis
The third type of application and interface focuses on energy and environmental aspects of a candidate design. IES Virtual Building®, Ecotect® and Green Build- ing Studio are three products in this area. Some images from Ecotect, providing performance feedback to the building model, are shown in Figure 5 - 5 . These products operate through a mixture of a simplifi ed building model and also with direct translators to existing analysis/simulation applications. Ecotect and IES have their own building model with form generation and editing capabilities and have some of the functionality of sketching applications.
With drawing systems, the preparation of datasets to run an application was so cumbersome, that if applied at all, they were relegated to the later stages of design. With BIM, the interfaces to applications can be automated, allowing almost real - time feedback on design actions. These environmental analysis applications incorporate interfaces to a set of energy, artifi cial and natural lighting analyses, fi re egress and other assessment applications, allow- ing quick analysis of schematic - level designs. gbXML provides an interface from existing BIM design tools to its set of analysis applications. The different interfaces supported by Ecotect, IES and gbXML are shown in Table 5 - 1 .
These environmental analysis tools offer insight into the behaviors associ- ated with a given design, and provide an early assessment of gross energy, light- ing use, as well as estimated operating costs. Until now, such performances relied mainly on designer experience and rules of thumb. These application suites offer
FIGURE 5-5 Images from Ecotect, showing A) solar heat gain between buildings, B) computational fl uid dynamics of thermal fl ows within a building, C) sunlight inside a building and D) acoustics analysis.
(See color insert for full color picture).
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Table 5-1 Analyses supported from application suite’s building model.
Ecotect - own building model plus IFC input
DAYSIM lighting simulator
Radiance lighting simulator
CIBSE energy analysis
Energy+ energy analysis
solar radiation analysis
reverberation time acoustic analysis NIST-FDS, Fluent
and WinAir4
general interface for multiple computational fl uid dynamic analyses
IES – own building model plus direct link with Autodesk Revit® ApacheCalc heat loss and gain
ApacheLoads heating and cooling loads ApacheSim dynamic thermal simulation ApacheHVAC HVAC plant simulation
SunCast sun shading
MacroFlo simulates natural ventilation and mixed mode systems MicroFlo interior computational fl uid dynamics application
Deft value engineering
CostPlan capital cost estimates
LifeCycle estimates lifetime operating costs IndusPro ductwork layout and sizing
PiscesPro pipework systems
Simulex building evacuation
Lisi elevator simulation
gbXML – XML link from Autodesk Revit®, Bentley Architecture and ArchiCAD®
DOE-2 energy simulation
Energy+ energy simulation
Trane2000 equipment simulation
building product information
only limited compatibility with existing BIM design tools (as reviewed in Chap- ter 2 ). In this regard, gbXML export interfaces are available within ArchiCAD ® , Bentley Architect and Revit ® . Ecotect has IFC interfaces with ArchiCAD ® and Digital Project. IES has a direct interface with Revit ® .
Environmental analysis tools also require signifi cant amounts of non - project specifi c information, including details that may affect incident sunlight
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Table 5-2 Concept design applications and the exchange formats they support.
Import formats Export formats
L S
Others
L S
Others
S G F M E T S G F M E T
D W X R G A D W X R G A
Application 3 D D V I S 3 D D V I S
Massing and Sketching
SketchUp • • • • • • • obj, Epix
form.Z • • • • • act, obj,
rib, w3d, stp, stl, 3dmf
• • • • • • act, Epix,
ArtL, obj, rib, w3d, stp, stl, 3dm
Rhino • • • • obj, stp, stl,
3dm
• • • • • • 3dm, stp,
obj, x_t, stl, xgl
Maxon • • • direct3d,
stl, cct
• • • direct 3d,
stl, cct Space Planning
MS Visio • • wmf, xls xls
Vectorworks • • • • • • • • stl, epix
Facility Composer • IFC, stp • IFC, stp
Trelligence • • gml, csv
Environmental Analysis
IES • • dgn,
gbXML, Revit®
Revit®
Ecotect • IFC • •
GreenBuilding Studio
• rvt, dgn,
XML
•
and any objects or effects that may restrict sunlight or views of existing structures, such as geographic location, climatic conditions, structures, or topography. This information is not typically carried within BIM design tools but by secondary analysis tools. These distributed datasets often introduce management - level problems, such as determining which analysis run gave which results and based on which version of the design. In this respect, repositories can play an impor- tant role (see Chapter 3 ).
More broadly, the exchange formats supported by all existing conceptual design tools are shown in Table 5 - 2 . At the moment, most of the information gen- erated by these tools must be regenerated in the transfer to a BIM authoring tool.
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Other Issues of Conceptual Design
For completing what has traditionally been schematic design, two other aspects of a design must also be defi ned: site development (including existing conditions) and typological identifi cation of all building systems. Site develop- ment involves building placement, elevation, defi nition of all major site and ground contour changes and enhancements, and the general scope of site development. Use of the site is often an important aspect of an overall conceptual design. Some BIM design tools support site planning, as listed in Table 2 - 1 , and some environmental analysis tools support site as well as exte- rior solar and wind studies. To our knowledge, outside space functions can currently be dealt with in space planning tools using block spaces to make site layout allocations.
Conceptual design usually involves identifying the ‘type’ for each of the building systems, including structural, exterior envelope, energy and HVAC, lighting, and vertical circulation. This information is needed for generating ini- tial cost estimates at an early stage; verifying that the project is within eco- nomic scope and satisfying the program. Most existing environmental analysis applications identify HVAC system types but not structural or other systems.
Traditionally, cost estimation for small projects at the conceptual stage involved ‘ back - of - envelope ’ calculations based on a single gross unit measure, such as square footage or the number of rooms. Validation of the proposed design concept for larger projects usually involves a detailed cost estimate prepared by a consultant. With the proper setup, BIM supports rapid generation of cost estimates, so it is now practical to undertake cost esti- mates throughout the concept exploration and development process. While at this level of design development only rough estimates of construction cost can be generated, the information provided can inform the designer of potential issues early, or alternatively provide confi dence that the proposed design can be developed within range of the project ’ s budget. The issues associated with generating almost real - time cost estimates are reviewed in Sections 5.3.2 and 6.6 .
The only software currently available for representing all building systems and supporting concept-level cost estimation is DProfi ler, which enables rapid composition of a concept model and generation of a cost estimate. It can only be used for certain predefi ned building types. Like the energy - related concept tools, the DProfi ler building model is distinct and supports only DXF/DWG export to other applications, such as the concept design tools listed above or the BIM design tools. DProfi ler is described more fully in the Hillwood Com- mercial Project case study in Chapter 9 .
Another aspect of understanding the building context is in capturing as - built conditions. This is a critical issue for retrofi t work and remodeling.
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New surveying techniques, based on laser scanning with point clouds, offer a valuable new technique to capture as - built conditions. These are discussed in Chapter 8 .
Concept Design Summary
Concept design tools must balance the need to support the intuitive and creative thinking process when a basic design scheme is fi rst being defi ned and explored with the ability to provide fast assessment and feedback based on a variety of simulation and analysis tools, allowing more informed design. Unfortunately, each of these tools only does part of the overall task, requiring translation between them and later with the major BIM tools discussed in Chapter 2 .
None of the tools available today support the full scope of conceptual design services. They require users to either gain and maintain competency in a number of different software programs, each with different user interfaces, or fi ll the gaps by relying on manual paper - based modes of assessment (or more likely, intuition). Data exchange and workfl ows between these applica- tions are also limited, as shown in Table 5 - 2 . In large fi rms, the various tasks associated with schematic design (and their supporting applications) may be split among multiple people using custom API - based interfaces. Small fi rms are likely to select one of these tools and forgo the benefi ts of using multiple, due to the costs of developing custom workfl ows between them.
Toward the end of the schematic design phase, output from these applica- tions must be transferred to a general BIM design tool. Ideally, such an exchange would be easy and two - way, allowing for simple analyses or complex form - generations to be revised and re - evaluated. But as noted earlier, even in the primary direction this transfer is not yet well - supported by existing BIM tools.
How could these diverse conceptual design applications be integrated?
There are at least four ways to integrate the different functionality needed for schematic design, as reviewed here: (1) a single application is developed that covers all the functionality; this has not yet happened; (2) a suite of integrated applications could be developed based on a business plan that is mutually ben- efi cial to various companies, using a set of direct translators or plug-ins; this also has not happened, but some such arrangements exist; (3) the applications support a neutral public standard exchange interface (such as IFC) and rely on it to support integration; this has begun, as in the case of Ecotect; (4) the easier - to - use BIM authoring tools expand their capabilities , such as Revit ® or ArchiCAD ® , to include the functionality reviewed here. All but the fi rst of these integration efforts are being applied in varying degrees.
To summarize, while the front - end services associated with conceptual design are likely to become increasingly important as BIM is adopted, the current
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technology base is not yet in place to support such a change. Existing conceptual design tools provide only very limited solutions. On the other hand, BIM model creation tools are generally too complex to be used for sketching and form - generation. Paper and pencil remain the dominant tools for such work. In the near future, the authors anticipate evolutionary progress in this area, with effec- tive concept design systems solutions emerging soon.