AECbytes Feature (February 28, 2005)
Prefabrication of Timber Buildings based on Digital Models: A Perspective from Norway
A few months
ago, in November 2004, I had the opportunity to visit Norway to
participate in a seminar and workshop organized by the Norwegian University of Science and
Technology (NTNU), aimed at developing a new study and research
program on the prefabrication of timber buildings based on digital
models. The faculty at NTNU anticipates that in contrast to pure
geometric and 2D CAD models, the product intelligence in a building
information model (BIM) will enable a higher degree of industrialization
and prefabrication in the construction process in Norway, and is
a subject worthy of critical research. The objective of the seminar,
which was held in Oslo and open to all professionals, was also to
make the Norwegian building industry better aware of this technology
shift that was happening in the AEC industry at large.
snapshot of Oslo taken during the NTNU seminar in November 2004.
At the seminar,
I provided a broad overview of building information modeling (BIM)
and explored its potential application to the design and construction
of prefabricated timber buildings. Other presenters included developers,
architects, and academics from Norway, Germany, and Switzerland,
as well as a representative from the US-based firm of KieranTimberlake
Associates, best known for its principals' seminal book, Refabricating
Architecture. This AECbytes feature article captures the highlights
of the NTNU seminar from a technology perspective, and briefly explores
the possible correlation between the computational technology of
BIM and the constructional technology of prefabrication. But first,
here is an overview of the building and construction industry in
Norway for those not familiar with it.
and Construction in Norway
Wood has always
been the most widely used building material in Norway, a natural
choice considering that close to 37% of the surface area of the
country is covered by forest. An example of both a traditional Norwegian
structure as well as a modern-day building is shown in Figure 1.
Apart from its ready availability, wood is seen in Norway to have
other advantages when used as a building material: the construction
is simple and gives warm, tight houses when built according to good
craftsmanship; it is also a material well suited for artistic work.
There is a high level of competence in the use of wood in Norway.
Pine is a commonly used raw material; also popular is glued, laminated
timber ("glulam"), a specially developed, lightweight
and strong product that is used for homes, large public and commercial
buildings, and even bridges. The main terminal building of the Oslo
Gardermoen Airport (see Figure 2) is the largest laminated wood
structure in the world. Norwegian manufacturers export various timber
and wood products such as wood flooring and prefabricated elements,
as well as other building materials such as granite, larvikite ("blue
pearl"), marble, schist and several varieties of slate to the
global market for construction purposes.
more information about Norway's architectural heritage and its building
and construction industries, see www.olavsrosa.no and www.nortrade.com respectively. Another useful resource is the article "Architecture
in Norway" authored by the manager of the Norwegian Architecture
. Some snapshots of traditional and modern Norwegian architecture.
(Top) One of the 155 historic buildings from different national
regions that are featured in the open-air section of the Norwegian
Museum of Cultural History
in Oslo. (Below) One of the residential
buildings in Pilestredet Park, an urban renewal project in the heart
of Oslo that includes new construction as well as renovation of
Figure 2. The main terminal building of the Oslo Gardermoen Airport,
designed by AVIAPLAN, a group of architects including Niels Torp,
Narud Stokke Wiig, Skaarup & Jespersen, and Hjellnes Cowi. (Courtesy:
of the important characteristics of wood-based construction is its
suitability for prefabrication. Components can be built offsite,
and are not too heavy and unwieldy to be transported and lifted
into place. Prefabrication also controls construction costs by economizing
on time, wages, and materials. It is particularly useful in countries
like Norway because of the extreme climate. Barring a few months
of the year, it is simply too cold to be building on site. Thus,
there is growing interest in Prefabrication in Norway, which, along
with systematic building, has also helped to extend the dominance
of wood in its construction industry.
Prefabrication and Digital Models
Since the purpose
of the NTNU seminar was to investigate the still unexplored link
between digital models and Prefabrication, most of the individual
presentations were focused on either digital models or on Prefabrication.
Three different representatives from Norway's building industry
provided their individual perspectives on the state of the art of
its technology adoption, particularly with respect to digital models.
Gunnar Næss of Næss Architects, President of the Norwegian
Association of Consulting Architects, described how his firm used
ArchiCAD in advanced ways for projects ranging from interior design
to congress buildings and urban planning. A case in point was the
Congress Center Folkets Hus project, where a 3D model was built
with ArchiCAD and all the other deliverables including 2D drawings,
renderings, animations, and schedules were derived from it (see
Figure 3). The firm also uses ArchiCAD's GDL scripting language
to build its own libraries of parametric "intelligent"
objects, particularly furniture and lights for use in its interior
projects since these are not yet available from manufacturers. An
advanced example of the use of GDL is Cinema Designer, an application
created inhouse by Næss Architects for designing the interior
of a cinema hall, in which not only are all the objects fully parametric,
but the relationships between them are captured in parameters as
well and can be manipulated interactively. The firm has also used
ArchiCAD for a 4D project, the Hommelvik School, where the 3D model
was linked with time sequencing to explore construction scheduling
(see Figure 4).
Figure 3. The Congress Center Folkets Hus project, showing the 3D model
created in ArchiCAD and all the other deliverables that were derived
from it. (Courtesy: Næss Architects)
Figure 4. The 4D approach, linking the 3D model with a construction
schedule, was used by Næss Architects in the Hommelvik School
project. (Courtesy: Næss Architects)
developer's perspective was presented at the seminar by Lars Christensen
of the Selvaag
Group, a company engaged in several businesses and projects,
one of which is construction. Its subsidiary company, Selvaagbygg,
is a leading house builder in Norway that has built nearly 45,000
homes, ranging from traditional houses to apartment blocks, in and
around Oslo. It is currently building 1500 new homes at Løren
in Oslo, creating a totally new urban district. Selvaag Group sees
technology as a critical component of its business, and has a dedicated
subsidiary company, Selvaag BlueThink, which develops methods and
IT-based tools for knowledge based industrialized house building.
It also has Selvaag SpinOff, an incubator for the development of
pioneering processes and materials supporting the group's construction
activities. The company researches and uses technology in advanced
ways, going way beyond CAD (2D drawings) and even beyond BIM (object-based
3D model) to a model-based specialized application for housing design:
RDBH (Rule Based House Developer). This system captures housing
design rules and domain knowledge to automate different aspects
of design: generative rules are used to automatically create a detailed
design from a conceptual model, while evaluative rules are used
to check the designs for the satisfaction of specified criteria
and constraints. Selvaag is also developing a digital product catalog,
called Intelligent House Configurator (IHC), for use in their housing
designs. The IFC is a critical component of Selvaag's technological
vision to achieve quality, efficiency, and cost-effectiveness throughout
the design and construction chain, and the company is very involved
in the IAI interoperability effort. One of its projects, House 6
on Munkerud, is one of the four official test cases for the IFC
2x2 certification, and it brings together the use of several applications
from different vendors, as shown in Figure 5.
Figure 5. This housing project by the Selvaag Group is one of the four
official test cases of IFC2x2 certification. (Courtesy: Selvaag
A detailed example
of the use of BIM on a Norwegian building project was provided by
Kjell Ivar Bakkmoen of C. F. Møller Architects, which is
working on the Akershus
University Hospital project, a major hospital in the suburbs
of Oslo, Norway. The old hospital is being replaced by approximately
120,000 sq. m. of new buildings, with 5,500 rooms of which 1000
are unique. The project budget is NOK 7.64 billion (approximately
1 billion USD). Construction began in March 2004, with occupancy
planned for October 2008. Given the huge size and complexity of
the project (see Figure 6), the main focus of the use of BIM was
to keep track of all the objectsrooms, components, fixtures,
furniture, and equipmentnot just during design and construction
but throughout the project lifecycle. To date, over 3000 drawings
have been derived from the model created in ADT. IFC was again a
critical component of this project, enabling the model to be used
for consistency checks, quantity takeoffs, clash detection, energy
analysis, fire egress and environmental hazard studies, 4D visualization,
and checking the design for the satisfaction of programming requirements.
Needless to say, the Akershus University Hospital project is regarded
as a front runner in Norway in the use of IFC-based BIM.
. The Akershus University Hospital project in Oslo has made
extensive use of IFC-based BIM. (Courtesy: C.
F. Møller Architects
A variety of
perspectives on Prefabrication were also presented at the seminar.
Chris MacNeal of KieranTimberlake Associates described his firm's
extensive research and actual work in the areas of modularity, mass
customization, and offsite construction for building components
ranging from composite door panels and curtain walls to entire rooms,
as in the case of an addition to a residential college at Yale University
that was located on a restricted site with other construction constraints.
While the firm makes extensive use of rapid prototyping in its work,
it currently uses generic 3D modeling applications such as AutoCAD
and Rhino for building its 3D models. While these models are useful
to the designers and the clients for better visualization and also
serve as input to 3D printers, the firm sees the need to eventually
develop 3D models capturing real world material and property information
for a more efficient and effective modular design and offsite fabrication
of the University of Munich in Germany drew from his extensive experience
with construction in Japan to describe the role of robotics in the
mass production of building components and modular construction.
Paul Schär described the use of digital tools in his company,
Hector Egger Holzbau, which is based in Switzerland and specializes
in the production of timber structures and components. It has developed
its own inhouse web-based application, BauOffert, which links to
its catalog of components and can be used to quickly design the
structure of a timber building and produce a cost estimate. And
finally, Martin H. Kessel of Technical University of Braunschweig
in Germany provided a look at the state of the art of its prefabricated
housing technology. He also provided an overview of Cadwork, a popular
CAD/CAM system developed in Germany that was specially tailored
to the demands of timber/log construction and provides an integrated
solution for all stages of their design and fabrication (see Figure
. Examples of timber structures designed using Cadwork. (Courtesy: The
How BIM and Prefabrication Connect
to be a natural correlation between the computational technology
of BIM and the constructional technology of Prefabrication. Imagine
if all the individual components that go into making standardized
or modular building elements were available digitally as BIM modelssupplied
by their manufacturersthat represented as accurately as possible
their geometry as well as their properties. Systems could then be
developed that could assemble these components to create many different
compositions, both digitally during design as well as physically
during offsite construction. This would make it possible to have
Prefabrication without the uniformity and monotony that characterized
the mass customization architectural movement in the pre-computer
days, and which also prevented it from taking off at that time.
These specialized systems for prefabrication could be customized
for different materials, different building types, different methods
of construction, and so on, and could include all the associated
information needed for the analysis of cost, structure, energy performance,
and so on. If this technology was available and used even for partial
prefabrication today, it would help to dramatically reduce the construction
time of a project and make it far more efficient and cost-effective
than the linear, on-site, one-off construction methods that continue
to be the norm in the building industry.
How long it
will take for this technology to become available is hard to predict.
What is certain, however, is that we cannot even make a proper start
until building component manufacturers start developing and routinely
publishing digital models of all their components. Only then can
intelligent design systems for prefabrication, or any other specialized
construction system, be built.
My sincere thanks
to Prof. Knut Einar Larsen and NTNU for inviting me to participate
in the seminar, and to the companies credited here for making the
images of their work available for publication in this article.
About the Author
Lachmi Khemlani is founder and editor of AECbytes. She has a Ph.D. in Architecture from UC Berkeley, specializing in intelligent building modeling, and
consults and writes on AEC technology. She can be reached at email@example.com.
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