Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings

Abstract

The building sector has revealed a need for process optimization, mirrored by the ongoing discussion around industry 4.0 and increasing automation in building design and construction. Within this context, the prefabrication and standardization of building elements provide interesting opportunities for optimizing the construction process. Off-site fabrication of building envelope and systems can provide significant advantages in terms of process, quality and safety management. This paper presents an outline of state-of-the-art building opaque envelope prefabrication, with particular focus on timber building skins, through a collection of best practices both in the field of building retrofit and new construction. This research is the result of shared research interests and synergies among the Institute for Renewable Energy at Eurac Research and the Innovation in Applied Design (IAD) Lab at the University of Sydney. Results highlight current limitations of envelope prefabrication and outline development opportunities both at technical and production process level. These findings and the conclusions we draw from them will set the foundations for expanding the adoption of an industrialized fabrication approach in the construction environment.

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123 JANUARY 17TH 2019 – MUNICH POWERSKIN CONFERENCE | PROCEEDINGS
Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
Market Survey of Timber
Prefabricated Envelopes for
New and Existing Buildings
Annalisa Andaloro1, Eugenia Gasparri2, Stefano Avesani3, Mathew Aitchison2
1 European Research Academy, Bozen, Italy, email: annalisa.andaloro@eurac.edu
2 University of Sydney, Sydney, Australia
3 European Research Academy, Bozen, Italy
Abstract
The building sector has revealed a need for process optimization, mirrored by the ongoing discussion around industry 4.0 and increas-
ing automation in building design and construction. Within this context, the prefabrication and standardization of building elements
provide interesting opportunities for optimizing the construction process. O-site fabrication of building envelope and systems can
provide significant advantages in terms of process, quality and safety management. This paper presents an outline of state-of-the-art
building opaque envelope prefabrication, with particular focus on timber building skins, through a collection of best practices both in
the field of building retrofit and new construction. This research is the result of shared research interests and synergies among the
Institute for Renewable Energy at Eurac Research and the Innovation in Applied Design (IAD) Lab at the University of Sydney. Results
highlight current limitations of envelope prefabrication and outline development opportunities both at technical and production
process level. These findings and the conclusions we draw from them will set the foundations for expanding the adoption of an indus-
trialized fabrication approach in the construction environment.
Keywords
Envelope prefabrication, o-site manufacturing, envelope retrofit, timber construction, construction process

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
1 INTRODUCTION
In recent decades, the construction sector has been evolving with the aim of achieving increased
sustainability objectives. This has been pursued through the adoption of life cycle design methods, as
well as application of industrial production principles and advanced manufacturing concepts (Aitchison
2018). In practice, research and technology development activities are translating these objectives
into a so called “lean” production approach, which is generally acknowledged as the combination of
sustainability in resource management (human and physical) and productivity optimization.
The sustainable use of resources in the building sector can be implemented through: use of
certified environmentally friendly materials, design of energy ecient construction solutions,
or even the adoption of a circular economy design approach. The latter is based on the re-use of
building elements at the end of service life to minimize environmental impact and optimize the
building economic cycle (Tebbatt Adams, et al. 2017). Productivity in the building sector is low if
compared to other manufacturing branches and the average global economy (McKinsey Global
Institute 2017). The authors propose prefabrication as a means to pursue both sustainability and
productivity in a synergic manner, which is able to boost construction productivity through the
following: (i) coordinated work of several players along the value chain; (ii) enhanced execution
speed and quality; (iii) advanced technological design eort and (iv) investment optimization, with a
focus on process innovation. O-site fabrication of building elements (or prefabrication) allows for a
deliberate shift of works towards the manufacturing site rather than the traditional construction site,
according to the degree of industrialization that is foreseen for a specific real estate development
or renewal operation (Smith 2010). The adoption of this approach can increase productivity up to
50-60% (McKinsey Global Institute 2017). However, it is important to point out that it is not enough
to move building production from the building site to the factory, rather, it is also important that the
manufacturing mindset be adopted to harness the full value proposition of prefabrication.
The market survey presented in the following section is focussed on the prefabrication of timber
building envelopes. This scope is viewed as a crucial research priority given the high tempo at which
structures and systems are already able to be built and produced.
1.1 AIM AND SCOPE
This work is the result of research synergies among the Institute for Renewable Energy at Eurac
Research and the Innovation in Applied Design (IAD) Lab at the University of Sydney, whose
activities focus respectively on designing energy ecient envelopes for building retrofit on the
side of Eurac, and advanced prefabrication methods for high rise timber buildings on the side of
the IAD Lab. In particular, this paper focusses on prefabricated envelopes conceived on a timber-
based structure (the core expertise of both institutions). The use of timber responds well to both
the sustainability and productivity challenge in the construction sector. Indeed, wood is a carbon
neutral and renewable resource, in line with the current de-carbonization objectives set by the
European Commission (European Parliament 2010), as well as highly compatible for prefabrication
and industrialized production. In addition, it is lightweight and characterized by high thermal
performance, features that make it even more suitable for use in the building envelope.
The aim of this research is to advance knowledge in the field of envelope prefabrication and
construction process optimization both for existing and new buildings. This is done through a
technical solution market survey to outline main achievements, limitations and perspective research
and technology development in the field.

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
2 TAXONOMY OF BUILDING ENVELOPE PREFABRICATION
Envelope elements prefabrication dates back to the 1950s and is generally associated with the post-
World War II need for rapid housing supply to the population. In the latest years, the concept has
been refined to describe the production and manufacturing of construction elements o-site to the
highest possible degree, so to minimize works to be performed on-site, apart from mere assembly
operations (Smith 2010). The 1990s saw a rather systematic push of industrial production concepts
into the building sector, such as mass customization or lean manufacturing. However, these concepts
are having a hard life within the construction market, struggling to be truly integrated in the value
chain of building production that persists in being rooted on an analogue based approach (McKinsey
Global Institute 2017).
It is commonly agreed that the attempt to drive the development of the construction sector towards
an industrialized approach to building production is based on the huge perceived advantages
of o-site working, such as: increased productivity in terms of time and cost, increased workers
safety, enhanced quality of the output, together with a more sustainable use of resources in terms
of construction site logistics, components manufacturing and waste minimization. Prefabrication
is based on three core promises: quality, cost and timeliness. These challenges have been a
recurring idea in housing and construction since the last two centuries, still without being totally
fulfilled in terms of objectives. More recently, the concept of prefabrication has been enriched with
environmental sustainability and possibility to integrate personalized features (Aitchison 2018).
Among those, multifunctional envelopes include a set of possibilities to integrate system elements,
allowing for enhanced energy performance of the building (Babich, et al. 2018).
As demonstrated by the successful example of unitized glazed curtain walls in tall construction,
the use of standardized components within the envelope of a building allows for a quick, reliable
and safe installation phase, shifting product’s detailed engineering work to the manufacturing
site (protected environment) and significantly reducing the need to work at height. Despite the
widespread use of unitised façade elements in high-rises, the mid to low-rise building sector is
characterised instead by the use of traditionally-conceived multi-layer opaque envelopes, which
allow for excellent energy performance but still rely on the traditional ad-hoc and site-assembled
approach to fit the case-specific features. This lack of uptake implies a consistent rise in production
costs, due to the impossibility to access an economy of scale.
3 METHODOLOGY
The authors analysed a set of case studies acknowledged as best practices examples by the
technical and scientific community, both in the field of new construction and retrofit operations.
Cases are presented in brief to allow the reader a general understanding of system technical
features, then compared along the reveal construction management dimensions, such as (i) use
of fixed scaoldings; (ii) level of prefabrication, according to the need to perform additional work
on the prefabricated wall unit after its installation in place; (iii) technical/economic convenience
with respect to traditional, single components based, construction techniques. In the case of new
buildings, the technical/economic convenience parameter has been discarded from the analysis, in
light of the significant market dierences connected with the geographic locations of the presented
buildings (Europe vs. Canada, as seen in 3.2).

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
FIG. 1 TES EnergyFaçade project – process digitization
(source: Gumpp & Maier)
FIG. 2 TES EnergyFaçade project – panel installation (source:
Gumpp & Maier)
3.1 RETROFIT CASE STUDIES
Europe’s existing building stock is much older, on average, than that of Australia and even the
USA. Despite construction traditions that date back many centuries, most of the existing buildings
are aected by severe underperformance from an energy and comfort point of view. A number of
collaborative research projects in the last decade have concentrated their design eort in the field
of existing buildings retrofit with advanced technological systems that can integrate renewable
energy sources (RES) and actively contribute to European decarbonization objectives. In this section,
the authors present a collection of projects in the field of envelope retrofitting using prefabricated
elements, characterized by high technology readiness level and real demo-case sites, followed by a
comparison of the most significant prefabrication related criteria (see Tab. 1).
TES Energy façade project (http://www.holz.ar.tum.de/forschung/tesenergyfaçade/) developed an
o-site fabricated modular façade to be applied in residential building retrofit (Larsen, et al. 2011)
(Fig. 1 and 2). The approach has been successfully developed and released in two versions, TES
(2009) and smartTES (2013), the latter also integrating system components in façade modules.
The project is based on a systemized digital workflow that embraces the whole value chain
from measurement, to planning, fabrication and mounting. The main technical features can be
summarized as follows: (i) large panel size, to cover one storey of the building; (ii) timber framed
insulated cassettes; (iii) external cladding, sills and reveals as well as steel weather profiles;
(iv) integrated windows.
FIG. 3 iNSPIRe façade installation sample, external side view
(source: Gumpp & Maier)
FIG. 4 iNSPIRe façade installation sample, internal side view
(source: Gumpp & Maier)
iNSPiRe – Systemic Energy Renovation of Buildings (http://inspirefp7.eu/) developed an o-site
fabricated modular system for ecient energy renovation of residential buildings, with the aim of

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
minimizing construction works on site for the deep renovation of façade, roof and energy systems
(Fig. 3 and 4). This project has further developed the results achieved in the TES Energy façade
project, focusing on system integration. The designed façade has been successfully deployed in two
dierent case studies. The main technical features can be summarized as follows: (i) large panel
size, to cover one storey of the building; (ii) timber framed insulated cassettes; (iii) external cladding,
sills and reveals as well as steel weather profiles; (iv) integrated windows. The iNSPIRe façade also
integrated multifunctional system components, such as micro heat pumps, heat recovery units and
related ducts (Dermentzis, et al. 2014) (Ochs, et al. 2015). Some hydraulic and aeraulic components
have been integrated in a dedicated system shaft, prefabricated as well and integrated within the
façade allowing to bridge the building apartments at dierent floors.
FIG. 5 4RinEU façade design process (source: Boligbygg Oslo
FK)
FIG. 6 4RinEu façade installation sample, external side view
(source: Municipality of Oslo)
4RinEu – Reliable models for deep renovation (http://4rineu.eu//) makes a step further with the
aim of supporting the use of o-site fabricated renovation packages with design methodologies and
reliable business models (Babich, et al. 2018) (Fig. 5 and 6). As for the case of TES EnergyFaçade
and iNSPire, this façade is equipped with the same layers and components before leaving the
construction site. However, the construction site shown in the pictures below has benefitted from
process optimization not only during the manufacturing phase, but also for construction site
management. In fact, the production facility is located in a short distance (3-4 hours) from the site
and modules were delivered just-in-time for installation.
FIG. 7 SINFONIA project – panel installation (source:
Benedikter Architekten)
FIG. 8 SINFONIA project – panel production (source:
Benedikter Architekten)
FP7 SINFONIA project - Low Carbon Cities for Better Living (www.sinfonia-smartcities.eu), has worked
on the development of an extensive set of energy saving measures spanning from smart transportation
systems to envelope retrofit solutions (Fig. 7 and 8). In this frame, prefabricated module types have

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
been chosen by the design team as façade concept, designed and applied in several construction
sites in Bolzano (Italy). Authors believe that there is potential for replicating this approach in future
works – even if some conceptual design work still needs to be performed to eliminate the need for
onsite work completion. Main technical features that characterize this solution can be summarized
as follows: (i) TJI timber frame structure, with massive studs applied as external frame and double T
shaped composite timber elements applied as intermediate reinforcement, to confine soft insulation
material; (ii) regulating layer, made of compressible insulation material applied at the back of the
prefabricated module and covered with waterproofing layer - this work is performed osite and allows
to speed up the installation process; (iii) connection system to the existing slabs based exclusively on
T shaped metal plates; air and water tightness fixing applied manually between the panels after their
installation; (iv) external cladding installed on-site, as in traditional construction.
3.2 NEW CONSTRUCTION CASE STUDIES
Prefabrication of the envelope for timber construction has seen an increased interest in the last two
decades, as it allows for quickly covering of the indoor volume and so protecting timber elements
from weather agents since the very first days on the construction site (Gasparri, et al. 2015).
In addition, the rise in average building height has created market need for envelope solutions that
can be installed in a short time and guarantee high workers´ safety level. This paragraph presents
a short collection of best practice examples in the field, proposing a simple comparative analysis of
the most significant prefabrication related parameters (see Tab.2). Dierently from the retrofit case
study collection, economic parameters are not included, as the geographic marketplaces in which the
buildings are standing are not directly comparable.
Holz8 building in Germany (2011) is a residential building composed of massive timber components,
with preassembled external walls. The prefabricated components are made of the following: (i)
CLT load bearing structure; (ii) insulation; (iii) windows and shutters. The façade system is highly
prefabricated, but joints between wall units require manual completion from the outside with
the use of scaolds.
CASE STUDY ID FIXED SCAFFOLDING PREFABRICATION LEVEL TECHNICAL/ECONOMIC CONVENIENCE
TES EnergyFaçade Yes – lifting crane + scaf-
folding
High – all layers included Average cost, the cost is above average when active
system components are integrated
iNSPiRe Yes – lifting crane + scaf-
folding
High – all layers included Cost above average, due to integration of active system
components1
4RinEU No – lifting crane + mobile
construction platform2
High – all layers included Average cost, the cost is above average when active
system components are integrated
SINFONIA Yes – lifting crane + scaf-
folding
Medium – external cladding
is installed onsite
Average cost, room for improvement in the production
process
1 In this case, higher costs are partly justified by the fact that this project brought to market a façade technology that was still a prototype until it was
developed within the project frame
2 The construction site is a two storey building, so the lack of scaold is also facilitated by the specific site features
TABLE 1 Retrofit case studies comparison according to relevant prefabrication criteria. The technical/economic convenience is evaluated through a
benchmark to an average price for advanced façade systems, fixed at approximately 2x the price of a traditional external insulation with ETICS.

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
FIG. 9 Façade installation process for the Holz8 building in
Bad Aibling (source: www.huber-sohn.de)
FIG. 10 Installation of LCT ONE façade system through
scaolds (source: ww.creebyrhomberg.com ©Darko-
Todorovic|Photography|adrok.net)
LifeCycle Tower One in Austria (2012) has been designed with the aim of reaching Passivhaus
standards despite guaranteeing reduced construction time through prefabrication. The prefabricated
wall components are made of the following: (i) timber frame support, free from any load bearing
function; (ii) insulation and watertight layers; (iii) external cladding; (iv) windows. The façade system
has a medium degree of prefabrication, as the watertight layer and the cladding were applied on site
through the use of scaolds.
Ywood «L’Ensoleillée II» building in France (2013) has been developed with the aim of providing
clients with flexible solutions characterized by reduced construction time and cost. The prefabricated
wall components are made of the following: (i) CLT load bearing structure; (ii) insulation; (iii) external
cladding and (iv) windows. This façade system is highly prefabricated, even if vertical joints are
completed on the construction site, acting from mobile platforms. A limited use of scaolds was
needed to complete building corners.
Brock Commons building in Canada (2017) has been designed with the aim of constructing the whole
envelope without the use of scaolds. This case study is not a timber-based technology, even if the
design phase has seen the use of timber as a possible option. However, it is interesting to include the
FIG. 11 Façade installation process for the Nexity Ywood
«L’Ensoleillée II» building in Aix-en-Provence (source: ©
Nexity, Yann Bouvier)
FIG. 12 Brock Commons fully prefabricated envelope
installation phase (source: www.naturallywood.com)

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
case in the review as it presents interesting elements in perspective for timber-based application
as well. This façade is made of steel stud wall elements, which are hanged onto concrete floors
through adjustable connectors as in curtain wall façade. This façade system has a high degree of
prefabrication, as the panels were delivered with all layers to the construction site. However, if on
the one hand, works on the envelope have actually been completed without any need to act from the
outside of the building, the lack of scaolding led to a bitumen based manual sealing operated from
the inside, which seems to be “unaligned” with such a high degree of prefabrication.
4 RESULTS DISCUSSION AND CONCLUSIONS
For the presented case study buildings in section 3.1, the average cost for square meter of renovated
façade is in the range of 400-900€. Of course, local construction market dierences need to be
taken into account, as we estimated that they may aect the total cost of works up to 20%. However,
a simple comparison with the result of the IEA ECBCS Annex 50: Prefab Systems for Low Energy/
High Comfort Building Renewal research back in 2010 concluded a renovation cost equal to approx.
1000 €/m2 of façade (International Energy Agency 2012), and highlights that the increasing interest
and design eort in the direction of prefabricated systems for façade renovation are working in
favour of cost reduction.
Current limitations to the adoption of prefabricated façade systems for building retrofitting
at a larger scale are mainly ascribed to the higher cost with respect to non-prefabricated
renovation systems, due to:
– Longer lead-time, with the necessity for more coordinated R&D before projects even begin to
establish the capacity to deliver new products on time and at a guaranteed cost.
– More intense design eort with respect to traditional construction sites, due to the diculty in
adapting a high degree of prefabrication to the variability of geometry in existing buildings (i.e.
construction tolerances).
– Lack of appropriate production infrastructures for the assembly of prefabricated panels. This reduces
production speed, increasing costs, and capital expenditure required to procure such a capacity.
– Use of more advanced technological solutions with respect to traditional energy performance
renovations, such as: integration of renewable energy sources (e.g. photovoltaic modules, solar
thermal collectors); integration of HVAC systems. These components are costly with respect to a
passive envelope solution, but the added value to the building in terms of comfort and performance
deserves consideration (Jakob 2006).
In the case of envelope prefabrication for the timber high-rises, as seen in section 3.2, the state-
of-the-art analysis shows how the design eorts carried out so far have not managed to solve the
“prefabricated joint dilemma” yet. In fact, despite varying levels of façade panel prefabrication
spanning from medium to high, which means including all functional layers and required
components to ensure envelope correct function, junctions still require manual work to be performed

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Market Survey of Timber Prefabricated Envelopes for New and Existing Buildings
CASE STUDY ID HEIGHT FIXED SCAFFOLDING PREFABRICATION LEVEL
HOLZ 8 8 storeys Yes – lifting crane + scaf-
folding
***
cladding and windows installed osite,
interfaces completed onsite
LCT ONE 8 storeys Yes – lifting crane + scaf-
folding
**
windows installed o-site, cladding and
interfaces completed on site
YWOOD BUSINESS 3 storeys Yes – lifting crane + platform
+ corner scaolding
***
cladding and windows installed osite,
interfaces completed onsite
BROCK COMMONS 18 storeys No – lifting crane only ***
fully osite finished panels installed
onsite
TABLE 2 New construction case studies comparison. Prefabrication level is rated 1, 2 or 3 stars (*), for lower to higher
prefabrication degree.
on-site in order to guarantee air and water tightness. The root cause of these unsolved issues can
be ascribed to the variety and complexity of multi-layer envelope systems, particularly in terms of
number of parts and their reciprocal interrelation. In particular, main criticalities are:
– The gap along the production value chain in terms of design methods, such as Design for
Manufacturing and Assembly (DfMA). To date, the manufacturing of opaque multi-layer
envelope systems requires a much higher number of assembly operations when compared to
unitized glass façades.
– The lack of coordination among suppliers to integrate dierent construction methods, optimise the
use of materials and connection systems (e.g. screws, nails, rivets, glue) and develop new organic
solutions in accordance with specific product requirements.
Further research eort in the future will focus on highlighting the extra-costs related to
prefabrication, both in terms of design and construction, to determine which steps of the value
chain are more likely to produce savings in the overall process. In addition, a point should be made
on quantifying the productivity increases that can be targeted through the adoption of automated
production lines.With respect to new construction, further research steps will also include the
design of construction site-ready solutions, which allow for complete installation without the need of
manual intervention after panel mounting.
Authors kindly acknowledge technical professionals and companies who have contributed in the
realization of presented works, sharing technical details and data: Manuel Benedikter (Benedikter
Arkitekten), Alberto Sasso (Ocina di Architettura), Maximilian Schlehlein (Gumpp & Maier GmbH),
Armin Knotzer (AEE Intec), Boligbygg Oslo FK, Nexity, Naturally Wood, Huber & Sohn, Cree by
Rhomberg. Authors also thank Eurac Research colleagues – namely Roberto Fedrizzi as coordinator
of the European project FP7 Inspire, and Roberto Lollini as coordinator of the European project H2020
4RinEU, for providing fruitful guidance in the technical review process for the outlined solutions.
This work is part of the research activities of the project 4RinEU, funded by the European Union’s
Horizon 2020 research and innovation programme under grant agreement No 723829.

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