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Tuesday, 18 May 2010
IFC Building Models for productivity

Paper for AXIS

IFC Building Models for Productivity

Paul A. Hay

30 March 2005


Early in 1970, software developers marketed computer-aided design [CAD] systems, which had three-dimensional [3D] draughting features, to large mechanical engineering firms.  UK-based developments such as RUCAPS, and software from Applied Research of Cambridge, introduced CAD to the practice of architecture, but the goal was to conceive a novel method of 3D design, not merely to replicate manual draughting.[1]  In the United States, architectural firm Skidmore, Owings and Merrill [SOM] used CAD software to draught building plans for Pacific Bell, in November 1983, hoping to "fast-track" the design process by facilitating design changes during the construction phase of works.[2]   Later, IBM partnered with SOM to develop the IBM/SOM AE Series [AES], and is reputed to have licensed 3D CAD technology from the Belgian firm, BricsWorks, about the same time AES was being developed.[3] 


Currently, SOM has been commissioned to design the first tower to rise on the World Trade Center site, and Autodesk - the world's leading design software company - has announced its collaboration with SOM on the project.  Construction commenced on 4 July 2004 and the fast-track schedule required close collaboration initially between over one hundred team members to expeditiously complete tasks and secure approvals from the project's diverse stakeholders; but is expected to facilitate collaboration between thousands more members before the completion of construction.  Autodesk's "AutoCAD" [ACAD] is the primary CAD software being used.     ACAD is a 2D CAD program with limited 3D capability.  So, Autodesk's "Revit" and "Architectural Desktop" [ADT] - which are both 3D architectural CAD programs - are also being used: the latter to enable energy analysis to be undertaken by a third-party application, directly from the drawing file.[4]


Notwithstanding, Dr. Paul Teichoiz - Professor Emeritus at the Department of Civil and Environmental Engineering, Stanford University, California - has bemoaned the decline of productivity in the U.S. construction industry over the last forty years and stated that adoption of information technology over the past thirty-five years has failed to improve productivity because it has not facilitated collaboration between project members.  He explained that stand-alone applications hinder quick implementation of changes by their reliance on paper output, which has to be manually checked, and data subsequently re-entering into other programs.  To correct this anomaly, he recommended that project teams use 3D CAD programs for design and the internet for communication.  He further explained that fast and error-free sharing of information between dissimilar computer applications would result from the use of 3D CAD models which implement data standards developed by the International Association for Interoperability [IAI].[5]


Dr. Teichoiz makes specific reference to the U.S. Construction Industry, but his observation and recommendation would no doubt be relevant to the Caribbean, particularly if we accept the premise that improving collaboration between members of a project team will effect the productivity gains which are still being sought by SOM after twenty years of effort.   Change is therefore inevitable and this change has to be concurrent between education and practice within the building Industry.


In education, CAD training needs to extend to discipline-specific, 3D programs compliant with IAI standards: ideally as an inter-faculty venture.  In practice, use of similar programs is required; sharing of CAD files needs to replace blueprints; and all members of the project team: client, consultants, contractor and sub-contractors, need to collaborate by the Internet or Intranet.  The technology already exists.  But, it needs professionals trained to realize the productivity gains expected with improved collaboration.



Students of the Caribbean School of Architecture [CSA] are trained to use ACAD over a local area network [LAN].  Although CSA does not use the stand-alone version, ACAD is used in stand-alone mode: as a group of students do not modify a single file simultaneously, but individually modify separate files .  Also, ACAD is not currently IAI certified and Autodesk CAD programs are not currently available for McIntosh [Mac] computers.


The typical Caribbean practice uses either manual draughting, or stand-alone 2D CAD programs which save in propriety formats that are not readily transferable between different versions of the same program, let alone dissimilar programs.  Internet usage is also limited to e-mailing, rather than linking computer systems used by the project team.  Both personal computers [PCs] and Macs are used.  In 2002, I conducted an informal survey in which members of the professional institutes in Barbados, Trinidad, and Jamaica were asked to identify the computer systems they used.  One-in-six responded that they use Macs: Jamaica having the highest proportion and Barbados the least.  This group of architects used either VectorWorks or ArchiCAD.  The former is the 2D offering of Nemetschek North America [NNA] and the latter Graphisoft's 3D program.  So, 3D CAD programs, such as Graphisoft's ArchiCAD [as well as, Autodesk's Architectural Desktop (ADT) and NNA's VectorWorks Architect] are already in use in the Caribbean, though small in number.  But, CSA graduates have to be re-trained in the use of them.



RUCAPS and AES represent an initial effort to move architectural and engineering design away from the "orthogonal drawing process" to a "model-based design process", in which paper-based drawings are simply reports generated from a data-base model.  Many of the RUCAPS developers later established another modeling program called "Sonata" by the end of the 1980s.


By the mid-1990s, Autodesk purchased Softdesk - the developer of an AutoCAD add-on - and developed ADT.  Some of Sonata's developers created a new modeling application called "Reflex".  Reflex was sold to Parametric Technology Corporation [PTC] in 1997, and PTC developers created Revit that same year.  This early version of Revit bore remarkable similarities with Reflex technology,:but its developers claim there is no connection between the two.  Nevertheless, Revit was later acquired by Autodesk.[6]



Ronald Filson - Professor of architecture and Dean Emeritus at Tulane University -- developed a course in 2002 using Revit.  Initially, some faculty members "..expressed concern that using Revit might limit creativity because the students select elements and objects from Revit's (and some manufacturers') libraries rather than drawing each component from scratch".  But, their concerns waned as they became familiar with the program.  In fact Professor Filson remarked that:

"In the past, my students would design in plan and section almost to the end of the semester.  Now, they can work with perspectives, renderings, and 3D models as well, at any time during the semester, because Revit calculates these automatically from the building model

            Student design projects are now more thoroughly developed and refined.  Revit also requires students to think more deeply about how to integrate mechanical and structural systems into the design."[7]                     



IAI is a non-profit organization responsible for the development of  new standards for describing  buildings.  These standards have been called Industry Foundation Classes [IFC].  No software developer holds rights to the IFC format and it is independent of operating systems.  Linear description by line, arc, etc., used in 2D CAD, is replaced with descriptions of building components (e.g. roof, walls, floor, doors, doors, etc.) according to their geometry, material, finish, and other required specifications.[8] 


The IFC model is designed to facilitate interoperability across individual and discipline-specific applications used in the design, construction and operation of buildings.  In 2002, it received ISO certification and efforts are being made to extend its usefulness.  Each IFC version describes more entities and relationships relevant to a building's life-cycle.. These include spaces, organization, schedules, costs, and other more abstract entities.  The seventh and latest version, released in 2003,  is IFC 2x2.  It defines 623 different components or concepts. 


The "IFC Model Server Project" in Finland, stores model data for use by IFC compliant applications over the Internet; and Singapore is investigating use of IFC models to automate their building-code checking and approval process.



Autodesk's Revit is currently not IFC-compliant[9], neither is NNA's VectorWorks Architect.  But, both developers claim their respective products are Building Information Model [BIM] Applications.   Phillip G. Bernstein -- Lecturer in Professional Practice at Yale University's School of Architecture, and Vice President  at Autodesk's Building Solutions Division -- states that Autodesk coined the concept in 2002 and defines it as:

"A design approach that uses the power of information technology to solve problems across the building cycle.  On-going access to reliable up-to-date, and fully coordinated building information (integrating the parameters of design scope, schedule, cost, quantity and performance) offers a potent capability for architects, engineers, builders and building owners to dramatically transform how buildings are designed, built and managed."[10]


Many "BIM concepts" were present in RUCAPS.  These include a building model stored in central database, which comprised data on 3D building components; multi-user access to the building model, and a clear distinction between model data and reports: drawings being interpreted as "graphical reports".  The benefit of this approach was that drawings were kept up-to-date.  Early adapters discovered that conceptual designs had to be given more thought before drawings could be produced.  But, it became easier for other team members to work out the details.  Nevertheless, implementation was short-lived and had no marked impact on the design process.  RUCAPS would however be considered crude in comparison to contemporary products from Autodesk, Graphisoft, and Nemetschek.[11]


Dr. Lachmi Khemlani - founder and editor of AECbytes Newsletter,  who specializes in intelligent building modeling - confirms that the concept of interoperability between programs was the subject of architectural research early in 1970, when an effort was made to develop an integrated design system capable of supporting a suite of applications operated individually or collectively.  She describes four categories of CAD software products.  "General-purpose CAD" programs, like ACAD, use geometric data models; as do "General-purpose 3D-modeling" software, like Autodesk VIZ.  But, "Architecture-specific 3D add-ons", like ADT use a building data model on top of a geometric model; and 3D parametric applications, like Revit and ArchiCAD, only use building data models.[12] 


To avoid the confusion, this paper makes no distinction between 3D programs and is strictly relevant to IFC-compliant 3D CAD products.  Consequently, the term IFC building model is used, rather than the more popular BIM.  Autodesk, Graphisoft, and Nemetschek are all IAI members, and each has an IFC-compliant offering: all being specific to the design discipline targeted.  In the following, we will therefore examine a single product from each vendor which is  specific to architecture; mechanical, electrical and plumbing [MEP]; or structural engineering. 



A-E-C Automation Newsletter states that ArchiCAD was the first 3D architectural CAD program developed for micro-computers.  It was introduced in 1984 exclusively for Macs, but a MS Windows version was introduced in 1993.  ArchiCAD is IFC compliant.  ArchiCAD uses a central data base to store building data.  ArchiCAD's TeamWork feature allows groups of architects to share information across a local-area network [LAN] or Intranet.  Each member signs in to a project over the network and saves a "satellite" version of the master project file to their workstation, thus eliminating dependence on the network's server.  Later, changes can be uploaded to the master file, and the latest revisions downloaded to the "satellite" file.  Thus, the building model remains up-to-date as the work proceeds.  Users are able to instantaneously generate complete plans, sections, elevations, quantity take-offs, schedules, and presentation materials such as renderings and walk-throughs.[13]


ArchiCAD TeamWork feature is used to assign rights to each member of the project team.  The Administrator can add users, define security access and sharing of resources.  The team leader has more rights than the typical user and can change basic project attributes: such as the number of storeys.  But, he cannot otherwise edit the building form.  Typical users can create and edit elements of the building model defined in their workspace. A "mark-up participant" can view the building model, add comments, and mark-up model elements; while a  "view-only participant is only allowed to view the model and add comments.


ArchiCAD was used by Fender Katsalidis Architects to design the Eureka Towers.  This building commissioned by the joint-venture company, Grocon Riverside Developments and Michelmersh, commenced in 1998 and is scheduled for completion in 2005.  It is located in Melbourne, Australia, comprises 92 storeys, and is reputedly  the world's tallest residential building at 300 metres high.   The complete model file was 330 Mb in size and took twenty minutes to load.  So, it was broken down into sub-projects: each sub-project being linked together using ArchiCAD's "hot-link" feature.  One member of the project team was designated "Model Manager" and was responsible for validating the accuracy of the 3D model, thus maintaining the careful arrangement of sub-projects.  Any changes made to a sub-model was automatically represented in the "parent-level models" to which the sub-model was hot-linked.  However, collaboration between the project team was limited to distribution of one thousand individual sheets of drawings, because consultants and other team members only possessed 2D CAD capabilities.[14]

Typical users define both a spatial and a conceptual workspace in which they can edit elements of the building model.  The spatial workspace can comprise a specific floor zone or a space of several floors.  The conceptual workspace can be specific building systems, such as exterior walls, core, partitions, etc.  It is possible to create objects outside of one's workspace and propose changes to the workspace owner.  When the main project file is updated, new elements can be made available to other users and, when the owner of the workspace sees recommended changes, he may choose to accept it or not.  Mark-up entries are represented as a 3D place holder and a 2D revision cloud, which must be revised before the document can be issued.  When saved to the main project file, the entry is automatically added to the respective teammate's To-Do list inclusive of comments.


Dr. Khemlani used ArchiCAD to evaluate the interoperability of multiple applications certified as IFC 2.0 compliant, and concluded that some issues needed to be resolved but interoperability was definitely possible.  A floor plan was first drawn using Microsoft's Visio: a template-based 2D CAD program, which uses a drag-and-drop drawing interface.  The plan was exported as an IFC model to ArchiCAD, where it was developed as a 3D model.  Again the file was exported as an IFC model to Solibri Model Checker 1.0, where it was checked for proper relationships to enable reliable analysis (e.g. energy analysis, quantities and cost estimation) by other applications.  Finally, Timberline Software's Precision Collection 6.2 used the IFC model to estimate the cost of the building.[15] 


Dr. Khemlani concluded her investigation of interoperability by adding structural elements to the previous floor plan, repeating the process with the same suite of applications, and came to the same conclusion.  But, she noted that structural analysis tools were not interoperable with CAD applications, nor able to evaluate the suitability of structural entities at that time.  She postulated that this would not be resolved until IFC 3.0 was released: which was expected to include information on structural connectivity in building models.[16]



Besides the VectorWorks line of products, marketed by NNA, AEC Magazine states that their German parent-company Nemetschek AG has been active in the United Kingdom since 2001 and  produces the AllPlan suite which comprises modules for urban planning, architecture, mechanical and structural engineering.  Their structural and civil engineering application -- AllPlot - is credited as making the process of detailing of reinforced concrete "a whole lot more efficient".


It automatically produces plans, elevations, sections and bar schedules from 3D models.  IFC models can be imported from other CAD programs, or created in "AllPlan".  The shape, size, number and steel-grade of the reinforcement bars are selected from a "bending catalog", along with concrete cover, and the program correctly puts them in place without prior calculation of their exact lengths.  Bar marks are inserted and linked to a central steel database from which schedules are generated.  AllPlot also provides tools for detailing area and mesh reinforcement for large areas.  Recesses are accounted for and changes made to the shape of the building results in corresponding changes to the reinforcement.[17]



ADT is Autodesk's IFC-compliant 3D architectural CAD program, and Autodesk Building Systems [ABS] is the equivalent MEP CAD program.[18]  In a review of ABS 2004, Cadalyst Magazine stated that ABS was developed according to the "object-based" technology of ADT.  It uses catalogs of standard parts and equipment as well as an extensive collection of pre-defined objects used in the architecture, engineering and construction [AEC] industry: all being compatible with ADT.  It also has interference-detection capability to determine conflicts between MEP objects and those of other disciplines: such as conflicts between piping or ducts with structural elements.  However, there may be traditional or cultural resistance to its implementation , as greater input is required from the engineer early in the design, and engineers are required to work closely with the CAD operators during the design process.


Most of the electrical content is of a single-line or schematic nature appropriate for the majority of electrical drawings.  Heating, ventilation and air-conditioning [HVAC], as well as piping is the most developed discipline and a duct flow calculator is provided to assist in duct sizing.  A flow calculator is also provided for sizing plumbing pipes, and all plumbing can be automatically rendered.[19]   Drawing tools automatically insert fittings where needed and suggests layouts to complex routing problems, including symbols that can slide or be anchored along the layout.


 ABS 2005 includes tools to convert ACAD floor plans into "intelligent engineering models" storing results of analysis, as well as dimensional information. HVAC analysis that once took over a week to complete is performed in hours.  In fact, it is described as " the only truly integrated object-oriented application created specifically for Mechanical, Electrical, and Plumbing Engineers".  ABS 2005 also facilitates use of "BIM data" by third-party applications for analysis of energy-use, load, fire protection and hydraulics.[20]



Change is therefore inevitable if productivity is to improve, and has to be concurrent between the education and practice of building professionals.  This can be illustrated by description of a scenario based on Dr. Khemlani's experiment.  A Caribbean architect works on his laptop awaiting a flight back home having received a major foreign commission.  He quickly completes a floor plan and uploads the IFC file to his company's project website and e-mails to his assistant as the plane descends for landing. 


Arriving at the office, the plan has been transformed to a three-dimensional model.  Elevations are completed periodically glancing at the 3D renderings and an occasional walk-through.  As works proceeds, the plan, sections and schedules are automatically updated.  Next, the master file is updated and e-mails sent to consultants to start working on it.  Later, the interior designer, mechanical, electrical, plumbing, and structural engineers all commence work on the same model.


His to-do list includes a request from the mechanical engineer to increase the floor-to-floor height because the air-condition ducts need more space.  He makes the change, which updates all elevations, sections and perspectives.  The structural engineer's plans, elevations, sections and bar schedules are also updated.  The plumbing engineer places some openings in the floor slabs to allow pipes to pass through, and the structural engineer's drawings are again updated.  As the interior designer works to conceal the pipes, the electrical engineer suggests a light fixture. 


The IFC drawing of the fixture, complete with lighting characteristics, is downloaded from the manufacturer's web-site and placed in the proposed building.  Photo-realistic interior renderings illustrate the illumination expected from the fixture and it is approved.  The quantity surveyor then generates the quantities from the model and the client is invited to view the model on the website, complete with an estimated building cost: but without a line being drawn, no prints made, and no courier needed to deliver the drawings.

[1] Day, Martin.  "Intelligent Architectural Modeling", AEC Magazine, September 2002. .

[2]  Donelan, Jenny. "Part 6: Architecture Retrospective". Computer Graphics World, June 2002 . PennWell Corp., U.S.A.

[3] Laiserin, Jerry.  "Some Other Brics in the Wall".  The Laiserin Letter, Issue 16, December 2003.

[4] Autodesk, Inc.  "World Trade Center Design Team Partners with Autodesk to Help Facilitate Freedom Tower Design and Construction Process".  PR Newswire, 16 June 2004,

[5] Teichoiz, Paul. "Labor Productivity Declines in Construction Industry: Causes and Remedies", AEC bytes Viewpoint No. 4, 14 April 2004.

[6] Laiserin, Jerry.  "Some Other Brics in the Wall".  Laiserin Letter, Issue 16, December 2003.

[7] Filson, Ronald & Ron Nyren. "Students Learn with Integrated Building Modeling". Architecture Week, 27 August 2003, pp. T1.1 - T1.2.

[8] Nannetti, Maurizio. "Inside the Virtual Building", Multi-CAD Magazine, Dec. 2001/Jan. 2002.

[9] Khemlani, Lachmi.  "The IFC Building Model: A Look under the Hood".  AECbytes Newsletter, 30 Mar. 2004. .

[10] Bernstein, Phillip G.  "Going Further Process Evolution in the Building Industry".  AECbytes Newsletter, 11 Feb. 2004. .

[11] Day, Martin.  "Intelligent Architectural Modeling". AEC Magazine, Sept. 2002, .

[12] Khemlani, Lachmi, "Building Information Modeling". CADALYST Magazine AEC Tech News No. 90, 29 Jan. 2003. .

[13] Newton, Randall S. and David S. Cohn.  "Graphisoft Leads in the Move to Virtual Building Technology".  A-E-C Automation, Feb. 2003, Vol. 26, Issue 1.

[14] Khemlani, Lachmi. "The Eureka Tower: A Case Study of Advanced BIM Implementation".  AECbytes Newletter, 2 June 2004, .

[15] Khemlani, Lachmi. "An Exercise in Interoperability - Part 1".  CADENCE Magazine AEC Tech News No. 69. 28 Feb. 2002. .

[16] Khemlani, Lachmi.  "An Exercise in Interoperability - Part 2".  CADENCE Magazine AEC Tech News No. 70. 13 Mar. 2002. .

[17] Corke, Greg.  "AllPlot", AEC Magazine, 18 Mar. 2003.  .

[18] Autodesk Inc. "Autodesk Architectural Desktop 2005 Ships, Offering Immediate Productivity Gains to Architects". PR Newswire. .

[19] Dakan, Michael, "Autodesk Building System 2004" Cadalyst Magazine, 1 Dec. 2003.  .

[20] Autodesk Inc.  "Autodesk Delivers Increased Productivity and Process Benefits to Mechanical, Electrical & Plumbing Engineers".  PR Newswire.  .

Posted by phcjam at 2:51 PM EDT

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