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Building Research & Information
ISSN: 0961-3218 (Print) 1466-4321 (Online) Journal homepage: http://www.tandfonline.com/loi/rbri20
Life cycle assessment of a Danish office building
designed for disassembly
Leonora Charlotte Malabi Eberhardt, Harpa Birgisdóttir & Morten Birkved
To cite this article: Leonora Charlotte Malabi Eberhardt, Harpa Birgisdóttir & Morten Birkved
(2018): Life cycle assessment of a Danish office building designed for disassembly, Building
Research & Information, DOI: 10.1080/09613218.2018.1517458
To link to this article: https://doi.org/10.1080/09613218.2018.1517458
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Published online: 20 Sep 2018.
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RESEARCH PAPER
Life cycle assessment of a Danish office building designed for disassembly
Leonora Charlotte Malabi Eberhardt
a
, Harpa Birgisdóttir
a
and Morten Birkved
b,c
a
Department of Energy Efficiency, Indoor Climate and Sustainability, Danish Building Research Institute, Aalborg University, Copenhagen,
Denmark;
b
Division for Quantitative Sustainability Assessment (QSA), Department of Management Engineering, Technical University of
Denmark (DTU), Kgs. Lyngby, Denmark;
c
SDU Life Cycle Engineering, Department of Chemical Engineering, Biotechnology and Environmental
Technology University of Southern Denmark, Odense, Denmark
ABSTRACT
The building industry is responsible for a large proportion of anthropogenic environmental impacts.
Circular economy (CE) is a restorative and regenerative industrial economic approach that promotes
resource efficiency to reduce waste and environmental burdens. Transitioning from a linear
approach to a CE within the building industry will be a significant challenge. However, an
insufficient number of quantitative studies exist to confirm the potential (positive) environmental
effects of CE within the built environment as well as a consistent method for characterizing
these effects. This paper considers key methodological issues for quantifying the environmental
implications of CE principles and proposes a life cycle assessment (LCA) allocation method to
address these issues. The proposed method is applied to a case study of a Danish office building
where the concrete structure is designed for disassembly (DfD) for subsequent reuse.
The potential environmental impact savings vary between the different impact categories. The
savings are significantly influenced by the building’s material composition, particularly the
number of component-use cycles as well as the service life of the building and its components.
The substitution of other material choices (e.g. glass and wood) for the concrete structure
exhibited a potential increase in impact savings.
KEYWORDS
building design; building
materials; buildings; circular
economy; design for
disassembly (DfD); end of life;
life cycle assessment; waste
reduction
Introduction
The demands from a growing world population will have
exceeded most limits on global resource reservoirs by
2050 if the present levels of human consumption con-
tinue (United Nations, 2012). Therefore, it is vital to
improve the management of resource consumption
and the associated environmental impacts.
Buildings are responsible for up to 40% of the
materials produced and consumed globally (by volume),
approximately 40% of the world’s waste generation (by
volume) (Becqué et al., 2016) and they account for 20–
35% of the contribution to most environmental-impact
categories such as global warming and smog formation
(European Commission, 2006). By 2030, it is expected
that the global middle class will have doubled from 2 bil-
lion to over 4 billion people (Kharas, 2017). It is esti-
mated that over the next 40 years, the world needs to
build more urban capacity than has been constructed
in the past four millennia (Biello, 2012). Thus, the con-
struction sector represents a major set of opportunities
for achieving local and global environmental objectives,
such as the UN Sustainable Development Goals (United
Nations, 2015).
Some new low-energy buildings have radically
reduced operational energy consumption. Energy gener-
ation for these new buildings is no longer considered to
be the most important contributor to building-related
environmental impacts (Anand & Amor, 2016;
Anderson, Wulfhorst, & Lang, 2015; Birgisdottir et al.,
2017; Blengini & Di Carlo, 2010; Dixit, Fernández-
Solís, Lavy, & Culp, 2012). A recent Danish study
found that the building materials of an office building
assessed over an 80-year reference study period were
responsible for 72% of the total greenhouse gas emissions
and 50% of the total primary energy consumption (Bir-
gisdóttir & Madsen, 2017). Recent building life cycle
assessment (LCA) method development emphasizes
that a narrow focus on just impacts associated with the
energy consumption of building will not identify all
© 2018 Informa UK Limited, trading as Taylor & Francis Group
CONTACT Leonora Charlotte Malabi Eberhardt lcl@sbi.aau.dk
Supplemental data for this article can be accessed https://doi.org/10.1080/09613218.2018.1517458.
BUILDING RESEARCH & INFORMATION
2018
https://doi.org/10.1080/09613218.2018.1517458
demands on global resources, and other initiatives are
needed to reach absolute sustainability in the building
sector (Brejnrod, Kalbar, Petersen, & Birkved, 2017).
Hence, there is an obvious need to regulate and optimize
the environmental performance of new buildings by
focusing on buildings’embodied energy and environ-
mental impacts over their life cycle (Birgisdottir et al.,
2017; Dixit et al., 2012; Rasmussen, Malmqvist, Moncas-
ter, Wiberg, & Birgisdottir, 2017). A growing political
and industrial interest exists to change from linear
(take, make, use and dispose) to circular (reduce, reuse
and recycle) business models. This will help to reduce
environmental impacts and secure future needs, while
at the same time exploiting remaining material value
and ensuring the sought economic growth (Advisory
Board for Cirkulær Økonomi, 2017; Ellen MacArthur
Foundation, 2015b; European Commission, 2016,
2017a; United Nations, 2015). In recent years, various
circular economy (CE) initiatives and policy agendas
have emerged in the construction sector, e.g. the adop-
tion of a CE action plan in the industrial sector by the
European Commission in 2015, establishing a tangible
and ambitious programme of actions along with a series
of legislative proposals on waste (European Commission,
2017b) and the ongoing development of 14 new CE stan-
dards that may affect future legislation from the Euro-
pean Commission (Dansk Standard, 2017). Legislative
proposals for waste in other industries (e.g. packaging,
transportation and electronics) have been successfully
adopted, but progress for the construction sector has
been slow due to a lack of specific environmental indi-
cators and targets/goals for the construction sector
(European Commission, 2017b).
A case study of Denmark identifies CE opportunities
for policy-makers, and it points to the construction
industry as the sector with the highest potential for the
implementation of CE models (Ellen MacArthur Foun-
dation, 2015a). The CE models put a focus on design
for disassembly (DfD) to extend the service life of build-
ing materials and elements through reuse and recycling,
potentially reducing future resource consumption, waste
generation and environmental impacts of future con-
structions (Bocken, de Pauw, Bakker, & van der Grinten,
2016; European Commission, 2016). DfD is not a new
idea in construction, but it has not yet gained a foothold
in the construction industry due to several obstacles
(Rios, Chong, & Grau, 2015). According to Aye, Ngo,
Crawford, Gammampila, and Mendis (2012), life cycle
aggregated environmental impacts can be significantly
reduced if the structural elements of a building are
designed to be durable and reusable, and if these attri-
butes are exploited. Although the majority of buildings
are constructed using durable concrete structures, and
although technical know-how exists on how to build
durable buildings with long service lives, the service life
of buildings in general has severely declined. There are
numerous cases of 30–40-year-old buildings being
demolished (for various reasons), indicating poor exploi-
tation of the concrete’s durability potential (Pomponi &
Moncaster, 2017). As the primary ingredient in concrete,
cement alone is responsible for 7–8% of anthropogenic
global CO
2
emissions, and therefore there is a need to
rethink the design of concrete structures from a life
cycle perspective, e.g. through DfD (United Nations
Environment Programme (UNEP), 2010).
The environmental and economic viability of CE sol-
utions will need careful assessment to provide a success-
ful and sustainable transition towards a circular built
environment (Pomponi & Moncaster, 2017). Recently,
a report by the Danish government’s Advisory Board
on CE recommended the development of new, consistent
life-cycle and total-cost calculation tools and method-
ologies to assess the environmental sustainability of CE
business models and products capable of handling
repeating life cycles due to reuse and recycling (Advisory
Board for Cirkulær Økonomi, 2017). This is also sup-
ported by researchers (Bocken et al., 2016; European
Commission, 2017b; Ghisellini, Cialani, & Ulgiati,
2016). Furthermore, the European Commission is com-
mitted to working towards a common European
approach to assess the environmental performance of
buildings, based in part on existing work, e.g. technical
standard EN 15978, as well as relevant research, and
focusing on priority materials, e.g. concrete (European
Commission, 2017b).
LCA is a scientifically based and International Organ-
ization for Standardization (ISO)-standardized method
for assessing resource consumption and environmental
impacts of a given product, system or service over its
entire life cycle (EN, 15978, 2012; ISO, 14040, 2008;
ISO, 14044, 2006; ISO, 21931-1,2010) and can facilitate
CE decision-making by identifying the largest environ-
mental impact-reduction potentials within building life
cycles (Pomponi & Moncaster, 2017). Use of LCA is
increasing within the construction industry, and LCA
has been used in some recently published CE studies
(Genovese, Acquaye, Figueroa, & Koh, 2016; Ghisellini
et al., 2016). Despite the political attention CE is gaining,
current political initiatives do not seem to build on exist-
ing LCA research covering construction and demolition
processes (Pomponi & Moncaster, 2017). Although there
are studies showing clear evidence of the environmental
benefits of CE principles at building material and com-
ponent level (Nasir, Genovese, Acquaye, Koh, &
Yamoah, 2017), few studies consider the overall building
level and the LCA methodological issues related to CE
2L.C.M.EBERHARDTETAL.
design methods such as DfD (Aye et al., 2012). Hence,
LCA faces considerable challenges in becoming a main-
stream environmental assessment approach for decision-
making/support in the building industry (Anand &
Amor, 2016).
The present paper offers a contribution to the devel-
opment of a future environmental performance evalu-
ation method for CE within the built environment. It is
structured as follows. First, the existing literature is
reviewed to present the state of the art of CE in the Euro-
pean built environment, particularly issues pertaining to
development of environmental performance assessment
methods. Next, an LCA allocation method is proposed
to address the identified key methodological issues of
quantifying environmental performance of CE within
the built environment. The proposed method is then
applied in a case study to assess the potential embedded
environmental impact savings of a Danish office building
when it is designed for disassembly (DfD). A sensitivity
analysis evaluates the influence of possible sensitive par-
ameters. The paper concludes with a discussion of the
methodological issues and how to further improve and
advance environmental performance assessment of CE
to promote the implementation of CE in the built
environment.
Background
Haupt and Zschokke (2017) stress the importance of
applying LCA to quantify the environmental impacts
of implementing CE principles. Such quantification will
clarify if the environmental performance of the new sys-
tem based on CE principles contradicts the fundamental
objective of the CE to improve environmental perform-
ance. However, multifunctional processes, such as the
CE principles, reuse and recycling, constitute a methodo-
logical challenge in LCA, as the LCA method is based on
the idea of analyzing environmental impacts of the pri-
mary function of individual product systems (Hauschild,
Rosenbaum, & Olsen, 2018). Hence, in order for LCA to
support CE, it needs to move from a ‘one-life-cycle’
approach towards a multiple life-cycle approach to sup-
port continuous loops of products and materials (Ghisel-
lini et al., 2016; Niero, Negrelli, Hoffmeyer, Olsen, &
Birkved, 2016). Furthermore, multifunctional processes
are shared between more than one product system, and
it is not always obvious to which product system the
environmental impacts and benefits should be attributed.
Nor is it always clear how substituted materials and pro-
ducts should be accounted for, which product system can
claim the benefit and how resource quality is to be taken
into consideration (Haupt & Zschokke, 2017; van der
Harst, Potting, & Kroeze, 2016). In addition, the long
lifespan of buildings increases assessment uncertainty.
There may well be unknown aspects that need to be
addressed in order to describe the future scenarios in
which the environmental impacts and future reuse or
recycling will occur in terms of LCA for long-term
decisions, e.g. CE in the built environment (Niero,
Ingvordsen, Jørgensen, & Hauschild, 2015). Moreover,
differences in the LCA approaches applied make it
difficult to compare the environmental performance of
buildings (Genovese et al., 2016).
Although some general LCA recommendations on
how to handle multifunctional issues have been provided
by different recognized standards such as ISO 14049, ISO
14044 and EN 15978, several competing approaches
exist, leaving room for interpretation (van der Harst
et al., 2016). The ISO 14044 standard distinguishes
between closed-loop product systems, where materials
are reused/recycled in the same product to replace virgin
materials, and open-loop product systems, where the
materials are reused/recycled from one product system
into a different product system. Consequently, there
is a potential need to allocate the environmental
benefits and burdens of reuse or recycling between mul-
tiple product systems (ISO, 14044, 2006). Furthermore,
the ISO 14044 standard states that changes in the
inherent properties of materials resulting from reuse
or recycling should be taken into account, but the stan-
dard does not state which changes and how to account
for them. ISO 14044 presents a hierarchical procedure
to deal with multifunctional reuse and recycling from
secondary material production and end-of-life (EoL)
processes:
.Allocation between multiple product systems should
be avoided by:
(a) dividing the processes into sub-processes
(b) system expansion, i.e. the secondary function
should be integrated into the system boundary.
.If allocation cannot be avoided, allocation should be
performed in the following order using:
(a) underlying physical relationship (e.g. mass)
(b) other relationships (e.g. economic value)
(c) number of subsequent uses of the recycled
material.
In contrast, the International Reference Life Cycle
Data System (ILCD) handbook recommends that the
ISO hierarchy should be applied when determining the
goals and scope of the LCA study (European Commis-
sion, 2010). However, there are limitations and weak-
nesses in each of the above approaches, e.g. subdivision
is not always possible, suitable substitutes to perform sys-
tem expansion cannot always be found and allocation
BUILDING RESEARCH & INFORMATION 3
can be based on an array of different parameters as there
is currently no single, widely accepted modelling
approach (Allacker et al., 2014; van der Harst et al.,
2016). Allacker et al. (2014), however, state that when
subsequent product systems are involved, allocation is
necessary to model EoL processes and secondary
material production (recycling, reuse, energy recovery
and disposal). Allacker et al. studied 11 different second-
ary material production and EoL allocation approaches
from recent modelling approaches and standards and
found that the methods can be broadly grouped into
three common approaches: 0:100, 100:0 and 50:50. The
0:100 approach attributes all impacts of the recycled
material to the product producing the recycled material
(Baumann & Tillman, 2004). The 100:0 approach attri-
butes impacts of the virgin material production to the
first product and impacts of the recycling process and
final waste treatment to the second product using the
recycled material (Baumann & Tillman, 2004). The
50:50 approach assumes that recycled material replaces
virgin material and attributes impacts of virgin material
production, waste treatment and recycling to the first
and the second product (Baumann & Tillman, 2004).
After comparing these three methods, Aye et al.
(2012) conclude that, since the potential future reuse of
a material can never be guaranteed, it makes no sense
to allocate any environmental credit to its initial use.
Aye et al. consider that if the material is, after all, reused
after its initial use, the building in which the material is
reused should be rewarded with the environmental sav-
ings resulting from the avoided processing and manufac-
turing of virgin materials. As it is not always clear from
previous case studies how environmental crediting of
reuse/recycling is actually conducted (Allacker et al.,
2014; Aye et al., 2012), EN 15978 (2012) states that
benefits from reuse, recovery and recycling (module D
in Table 1) should always be reported separately for
reliable decision support. According to Allacker et al.
(2014), an improvement in the product system model-
ling could potentially be to accommodate the average
number of times a material or element is recycled or
reused, e.g. using the principles in the ILCD handbook.
Among other things, the handbook proposes a formula
that takes into account the primary amount of material,
the recycling rate and the number of recycling loops
(European Commission, 2010). Some of the allocation
methods analyzed by Allacker et al. (2014)incorporate
a great number of other parameters, making them more
comprehensive, but also more complex. The main-
stream application of LCA for decision-making
requires simplification and standardization to enable
consistent and easy use in practice (Hellweg & Mila
i Canals, 2014).
Case study method
Based on the knowledge gained from the literature
review, LCA was applied to assess and, hence, quantify
the potential environmental impact savings of a Danish
office building DfD compared with traditional building
methods. The LCA complies with the requirements sta-
ted in EN 15978 (2012), ISO 14040 (2008), ISO 14044
(2006) and the Danish building sector’s implementation
of the Deutsche Gesellschaft für Nachhaltiges Bauen
(DGNB) certification system for assessing and bench-
marking sustainable buildings (Birgisdottir, Mortensen,
Hansen, & Aggerholm, 2013). The present study does
not use consequential LCA, i.e. LCA that applies broader
system modelling to quantify potential environmental
consequences of system changes. Instead, it applies attri-
butional LCA, i.e. LCA that quantifies the environmental
impacts that can be attributed to the product system
(Hauschild et al., 2018) in accordance with the DGNB
certification system (Green Building Council Denmark,
2014). Table 1 shows the life cycle stages as defined in
EN 15978. It also shows which modules are included
in the DGNB certification system.
The system boundary of the present study includes raw
material extraction, transportation and production of
building materials and components, replacement of build-
ing materials and components during the use stage, waste
recovery and disposal at EoL, and credits for potential
reuse, energy recovery and recycling of materials and
components in subsequent product systems. The focus
of this paper is on the material-related impacts, thus
energy consumption for operation is not included.
Table 1. Life cycle stages.
Life cycle stages Process Module DGNB
Production Extraction of raw materials A1
a
×
Transport A2
a
×
Production A3
a
×
Construction Transport A4
Construction/assembly A5
Use Commissioning B1
Maintenance B2
Renovation/repair B3
Replacement B4
a
×
Refurbishment B5
Energy consumption for operation B6 ×
Water consumption for operation B7
End of life Deconstruction/demolition C1
Transport C2
Waste recovery C3
a
×
Disposal C4
a
×
Next product
system
Potential for reuse, recovery and
recycling
D
a
×
Notes: Life cycle stages are according to EN, 15978 (2012) and modules
included in the Deutsche Gesellschaft für Nachhaltiges Bauen (DGNB) cer-
tification scheme.
a
Modules included in the study.
4L.C.M.EBERHARDTETAL.
The building lifespan can have significant effects on
the overall environmental performance of a building
(Marsh, 2017; Østergaard et al., 2018; Rasmussen & Bir-
gisdóttir, 2016; Silvestre, Silva, & de Brito, 2015). Thus, it
was set to 50 and 80 years respectively, according to the
DGNB certification system for office buildings, in order
to compare the effects of a longer and shorter building
lifespan (Green Building Council Denmark, 2014). The
functional unit was set to 1 m
2
of the building’s gross
floor area per year to provide comparability with other
studies. As most current published sustainability
research within the built environment tends to focus
on a limited number of impact categories, thereby
risking burden-shifting (Pomponi & Moncaster, 2017;
The European Commission, 2017b), the LCA was
performed using baseline characterization factors from
the Centre for Environmental Studies baseline 2001
method according to the DGNB certification system.
This is a commonly used and agreed-upon approach in
the construction sector, using open LCA v1.4 software,
but focusing on more impact indicator categories than
commonly used in practice, i.e. a set of environmental,
resource-use and toxicology midpoint impact cat-
egories (global warming potential [GWP], ozone
depletion potential [ODP], photochemical ozone cre-
ation potential [POCP], acidification potential [AP],
eutrophication potential [EP], abiotic depletion poten-
tialforelements[ADPe],abioticdepletionpotential
for fossil resources [ADPf], freshwater aquatic ecotroxi-
city potential [FAETP], marine aquatic ecotoxicity
potential [MAETP], human toxicity potential [HTP]
and terrestrial ecotoxicity potential [TETP]). The life
cycle inventory (LCI) of the background system was
based on the Ecoinvent 3.2 database using system pro-
cesses to obtain aggregated results. The LCI of the fore-
ground system was compiled using project-specific
building information models provided by the construc-
tion company to extract building material and com-
ponent volumes. Where data were lacking, estimation
procedures and assumptions based on technical data-
sheets, environmental product declarations (EPDs) for
different components and materials, as well as
Table 2. Construction materials by building element (including technical building services).
Building component Elements Element share (%) Component share (%) Mass (kg)
Columns Reinforced concrete 1 1 1.E+05
Beams Construction steel and reinforced concrete 3 3 4.E+05
Roof Reinforced concrete 7 8 8.E+05
Asphalt and plastic 1 8.E+04
Rockwool insulation 0.3 3.E+04
Foundation Reinforced concrete 6 6 7.E+05
Ground slab Reinforced concrete 9 10 1.E+06
Polystyrene insulation 0.03 4.E+03
Screed, epoxy and leca stones 2 2.E+05
Concrete sandwich facade Reinforced concrete 14 15 2.E+06
Rockwool insulation 1 6.E+04
Polystyrene insulation 0.03 4.E+03
Brick shells, mortar and bitumen membrane 1 6.E+04
Floor Varnish and oak tree flooring 0.1 38 1.E+04
Glass wool insulation 0.2 2.E+04
Gypsum 0.2 3.E+04
Galvanized steel 0.4 5.E+04
Reinforced concrete 37 4.E+06
Tiles, mortar and adhesive 0.01 7.E+02
Internal walls Gypsum 0.4 15 5.E+04
Rockwool insulation 0.3 3.E+04
Steel, stainless steel, aluminium 0.1 8.E+03
Glass 0.4 4.E+04
Acrylic paint 0.04 4.E+03
Reinforced concrete 14 2.E+06
Bitumen membrane 0.002 2.E+02
Staircase Reinforced concrete 2 2 2.E+05
Technical building services Stainless steel, galvanized steel and cast iron 1 1 7.E+04
PVC 0.001 7.E+01
Sanitary ceramics 0.03 4.E+03
Others Aluminium windows, doors and solar shading 1 1 8.E+04
Wooden doors 0.04 5.E+03
Total 100 100 1.E+07
Notes: All building related constructions and technical building services have been considered in the study.
BUILDING RESEARCH & INFORMATION 5
information from manufacturers/suppliers and other
professionals from the industry were used.
Office building
The case study office building assessed has a gross floor
area of 37,839 m
2
with eight wings of different heights
and a total of nine storeys. Owing to the large size of
the building, the basis of the study was a representative
section of the building. Table 2 lists the construction
materials by building elements and respective quantities.
The building’s structure was predominantly made up
of prefabricated concrete elements consisting of floor
slabs, facades, core walls, columns and beams.
DfD assumptions
The present study focuses on the internal building struc-
ture in terms of DfD and relies on the following
assumptions:
.assembly/disassembly are based on existing joint sol-
utions (Sommer & Guldager, 2016)
.the building is to be built today and decommissioned
in 50 or 80 years after the start of the assessment
(Green Building Council Denmark, 2014)
.the building materials are free of hazardous sub-
stances due to decontamination before disassembly,
i.e. contaminants have been designed out in the design
phase (Sommer & Guldager, 2016)
.owing to the long lifespan of concrete, no mainten-
ance of the prefabricated concrete elements will be
required during their service life to maintain their
quality and the elements are suitable for at least
three reuse cycles in three different buildings (Som-
mer & Guldager, 2016)
The percentage of elements suitable for reuse at the
building’s EoL was estimated by a demolition company
to be:
.90% of the concrete columns
.90% of the composite steel/concrete beams
.80% of the concrete beams
.60% of the concrete roof hollow core slabs
.90% of the concrete floor hollow core slabs
.80% of the concrete core walls
Modelled scenarios
A traditional case study building was used as reference
scenario T (all materials are disposed of after use either
by recycling, incineration or landfill) for comparison
with all other modelled scenarios. Two types of scenarios
were modelled:
.DfD: two scenarios where the structural elements are
assumed to be DfD for reuse at EoL in one or two
future subsequent product systems.
.O: four scenarios where the structural elements are
tested in terms of material choices, e.g. steel, wood
and glass, enabling easier disassembly, not necessarily
benefitting reuse solely but also for recycling to poten-
tially further decrease the building’s overall environ-
mental impacts. The four scenarios focus on the
structural concrete elements that make up the largest
percentage of the building’s total mass, i.e. potentially
the largest environmental impacts.
Table 3 provides an overview of the material compo-
sitions of the different scenarios modelled.
As the concrete facade was not considered for reuse in
the DfD scenario, despite making up 15% of the build-
ing’s total mass (Table 2), in all O scenarios the concrete
facade of the traditional building design was substituted
with a lighter glass double-skin facade with load-bearing
columns for reuse and recycling. Besides the glass
double-skin facade, the effect of using different materials
for the load-bearing columns at the facade was tested. As
the concrete hollow core slabs comprise 37% of the
building’s total mass (Table 2), the effect of substituting
them with bubble-deck slabs containing less concrete
due to plastic bubbles mixed with aggregate but with
Table 3. Percentage of material shares by weight (kg).
Material shares (%)
Scenarios
T DfD O1 O2 O3 O4
Concrete 81.8 81.4 80.6 76.6 78.0 73.8
Mortar 0.2 0.2 0.01 0.01 0.01 0.01
Glass 1.3 1.3 3.0
a
3.1
a
3.1
a
3.6
a
Gypsum 1.2 1.2 1.3 1.3 1.4 1.6
Insulation 1.7 1.7 1.2 1.2 1.3 1.5
Metals 6.6 7.6
a
7.2 10.4
a
7.2 10.5
a
Paints and varnishes 0.5 0.5 0.5 0.6 0.6 0.7
a
Plastic 0.2 0.2 0.2 0.2 0.2 0.6
Ceramics and clay 1.5 1.5 0.8 0.8 0.8 1.0
Stone and gravel 0.8 0.8 0.8 0.9 0.9 1.0
Wood 0.4 0.4 0.6 0.6 2.2
a
0.7
Asphalt 3.8 3.8 4.1 4.2 4.3 4.9
Notes: Material shares (kg) over a building lifespan of 80 years taking material
replacements into account.
a
Obvious material share shifting between the scenarios as a result of substi-
tuting concrete for other materials.
DfD = design for disassembly; O1 = optimization scenario 1 (concrete col-
umns); O2 = optimization scenario 2 (steel columns); O3 = optimization
scenario 3 (wooden columns); O4 =optimization scenario 4 (bubble
decks); T = traditional building design.
6L.C.M.EBERHARDTETAL.
increased reinforcement steel was also tested. Hence, the
O scenarios consisted of:
.O1: load-bearing concrete columns at the facade
assumed for reuse
.O2: load-bearing steel columns at the facade assumed
for reuse
.O3: load-bearing timber columns at the facade
assumed for recycling
.O4: load-bearing concrete columns at the facade
assumed for reuse and concrete bubble deck slabs
assumed for recycling
The reuse percentages assumed for the DfD scenarios
were applied to all additional concrete elements in the O
scenarios.
Allocation method
Reuse, recycling and energy recovery of materials were
modelled as avoided impacts according to the rec-
ommendations described in EN 15978 (2012). Thus,
the impacts of the primary material production that is
substituted by the reused, recycled or energy-recovered
material substitutes were subtracted from the net
impacts in module D. The amount of material recycled
and the amount disposed of at the EoL of the
buildings were estimated according to Danish waste
statistics and existing markets (Clean Innovation Green
Solutions, 2014).
For all scenarios, the LCA only focused on the first
product system from which the reusable building
elements originate. In this case, the study takes into
account a simple combination of the allocation
approaches 0:100 and 50:50 depending on the reusability
and recyclability of the different building materials and
elements using their physical relationship, i.e. mass.
Hence, the impacts of the building materials and
elements in reference scenario T, with no reuse but
material rates for disposal through recycling, incinera-
tion or landfill at EoL, can be represented mathematically
by equation (1) by applying the 0:100 approach and allo-
cating all the environmental impacts and benefits of
these materials and elements to the first product system:
IT=Iproduction +Iuse +IEoL +INext product system, (1)
where ∑Irepresents the total life cycle-aggregated
environmental impacts; and I
j
represents the environ-
mental impacts of the jth life cycle stage. For the DfD
and O scenarios, equation (1) applies for all building
materials and elements that cannot be reused. However,
reusable elements were modelled using the allocation
approach 50:50, where all burdens and credits from the
reusable elements are split between the buildings that
will potentially share them. Thus, one system will not
benefit over another based on the assumed number of
future reuse cycles. This also enables the LCA to take
into account and credit multiple future reuse loops,
thereby promoting CE. The impacts from the reusable
elements can thus be represented mathematically by:
IDfD,O=(Iproduction +Iuse +IEoL
+INextproductsystem)/U, (2)
where Urepresents the assumed number of use cycles;
and I
EoL
refers to the terminal EoL.
Results
Figure 1 shows how the individual life cycle stages con-
tribute to the environmental impacts over an 80-year
building lifespan in scenario T and DfD, with two and
three reuse cycles respectively. Note that for T and
DfD the life cycle stages’relative impact contributions
are very similar. The slight difference in the life cycle
stages between T and DfD is a result of the life cycle
impacts of the reusable components being allocated
equally between the use cycles relying on equation (2),
thereby crediting reuse in the Next product system.
The largest impact contribution is found for the pro-
duction and replacements stage in all impact categories
due to high impacts from production of the building
materials. Owing to recycling and energy recovery, the
life cycle stage and the Next product system exhibit
impact savings across all impact categories. The large
savings obtained in the Next product system within
FAETP, HTP and TETP are a result of the high recycling
rate applied for steel (99%) and for concrete and glass
(both 90%).
Figure 2 presents the environmental impact contri-
butions from the individual building components over
an 80-year building lifespan for scenario T and DfD
with two and three reuse cycles respectively. The
majority of the building’s embodied environmental
impacts originate from many of the structurally impor-
tant concrete components with long lifespans, e.g. floor
slabs and inner walls are responsible for large contri-
butions to the majority of the impact categories. The
technical building services also provide noticeable con-
tributions to most categories due to high replacement
of metals occurring during the lifespan of the building.
Windows, doors, roof, foundation, solar shading, stair-
cases, columns and beams account for a minor share of
the impacts, since these components account for a
minor share of the building’s total mass (Table 2). For
BUILDING RESEARCH & INFORMATION 7
DfD, the impact shares decrease for those building com-
ponents groups containing reusable elements, e.g. floors,
beams and columns, and increase for those building
component groups containing no reusable components
as a result of allocating the life cycle environmental
impact of the reusable components between the respect-
ive use cycles using equation (2).
The environmental impact contributions over an 80-
year building lifespan from building materials are pre-
sented in Figure 3 for scenario T and DfD, with two
and three reuse cycles respectively. As seen in Table 3,
although metal only makes up 6.6% of the reference
building’s total mass, it accounts for a large share of
most impact categories; however, it is most pronounced
among the toxicological impact categories FAETP, HTP,
MAETP and TETP with 54%, 50%, 36% and 75%
respectively, and 75% of ADPe caused by the technical
building services. The steel ventilation system is solely
responsible for a large share of these impacts due to a
high replacement rate of every 25 years. Compared
with the metals, concrete accounts for 81.8% of the
building’s total mass, with dominating contribution to
GWP ODP, POCP, AP, EP and ADPf amounting to
48%, 32%, 22%, 24% and 26% respectively of the total
impact within each category. Despite their minor share
the building’s total mass, the insulation, paint and
varnishes also account for a noticeable contribution to
many impacts due to the energy demands associated
with manufacturing glass and stone wool and a frequent
replacement rate of the paint and varnishes of every 10
and 5 years respectively. Wood-based materials yield a
negative GWP because CO
2
from the atmosphere is
bound to/stored in the wood (i.e. wood serves as a carbon
sink), hence there is a negative GWP value. For those
Figure 1. Contribution of life cycle stages’of environmental impacts over an 80-year building lifespan.
Figure 2. Contribution of building components’environmental impacts, T, over an 80-year building lifespan.
8L.C.M.EBERHARDTETAL.
material groups related to the reusable components, e.g.
concrete, it is seen that the impact share is reduced for
DfD due to allocation of the life cycle environmental
impacts of the reusable components between the respect-
ive use cycles using equation (2).
The accumulated embodied CO
2
emissions of T, DfD
and O with two and three reuse cycles over an 80-year
building lifespan are presented in Figure 4. For all scen-
arios, a drop in the graphs occurs after 80 years due to
the potential embodied CO
2
emissions savings obtained
in module D from crediting reuse, recycling and energy
recovery. T and DfD mimic each other well, since the
only difference between them is that the impacts of the
reusable components are allocated using equation (2),
i.e. these impacts are split between the assumed number
of reuse cycles. The embodied CO
2
emissions of T is
large due to material replacements accounting for 21%
of the building’s total embodied CO
2
emissions over
the 80 years. Reuse of the concrete structure two and
three times results in potential CO
2
emissions savings
of 15% and 21% respectively compared with
T. Substitution of concrete with different material
choices such as steel, wood and glass in O reveals higher
CO
2
emissions saving potentials compared with DfD.
Table 4 presents the potential embodied environmental
impact emissions savings of the reusable components
compared with no reuse.
Considerable savings are observed for all components
across all impact categories, as is also evident from the
weighted impact savings calculated as the average saving
of each component group using equal weighting factors
for each impact category assessed. The floor slabs rep-
resent the largest savings in all impact categories com-
pared with the other components, as they account for
37% of the building’s total mass (Table 2). The lowest
savings are found for the core walls compared with the
Figure 3. Contribution of building materials’environmental impacts, T, over an 80-year building lifespan.
Figure 4. Accumulated embodied CO
2
emissions over an 80-year building lifespan.
BUILDING RESEARCH & INFORMATION 9
beams and columns, which make up a smaller percen-
tage share of the building total mass (Table 2). This is
due to the much more environmentally burdensome
construction steel within the beams and the high reuse
percentage of the columns compared with the core
walls. Table 5 shows the potential embodied environ-
mental impact savings for the different building scen-
arios for 50 and 80 years compared with no reuse.
Although potential savings are obtained across most
impact categories covered, compared with the large rela-
tive savings exhibited for the reusable components in
Table 4, it is evident from Table 5 that these considerable
savings cannot be matched at building level. This is
because the material composition has a big influence
on the savings and magnitude of the savings obtained
for the individual building scenarios within the different
impact categories. Impact categories such as ADPe,
FAETP and TETP that are mainly influenced by the
buildings metals will benefit less from reusing the con-
crete components. Consequently, the largest weighted
impact savings are 14.5% and 22.9% for O1, as well as
15.3% and 22.6% for O3 for 50 and 80 years of building
lifespan respectively. The only savings obtained that
match those of Table 4 are found for the O3 GWP for
two component-use cycles: 54% and 49%, and for three
component-use cycles: 59% and 55%, for a building life-
span of 50 and 80 years respectively using wooden col-
umns compared with concrete or steel columns.
However, similar savings are not found for O3 across
the remaining impact categories. This is also reflected
by the much lower weighted impact saving for two com-
ponent-use cycles: 12.1% and 18.7%, and for three com-
ponent-use cycles: 15.3% and 22.6% for the 50 and 80
years building lifespans respectively. Although the
bubble decks in O4 use 41% less concrete compared
with hollow core slabs, the average impact savings
obtainable from the bubble decks are very low compared
with the other cases using hollow core slabs. This is
because of the increased amounts of reinforcement
steel needed for the bubble decks. O2 performs worse
Table 4. Potential embodied impact savings of the reusable component compared with no reuse.
Note: Weighted impact savings are calculated as the average impact savings of each reusable component compared with no reuse using equal weighting factors
for each environmental impact category assessed. This includes GWP, ODP, POCP, AP, EP, ADPe, ADPf, FAETP, MAETP, HTP and TETP. For abbreviations, see the
text.
Table 5. Potential embodied impact savings of the building scenarios compared with T.
Notes: Energy consumption during operation is not included. Weighted impact savings are calculated as the average impact savings of each building scenario
compared with no reuse of the reusable components using equal weighting factors for each environmental impact category assessed. This includes: GWP, ODP,
POCP, AP, EP, ADPe, ADPf, FAETP, MAETP, HTP and TETP. For abbreviations, see the text.
DfD = design for disassembly; O1 = optimization scenario (concrete columns); O2 = optimization scenario 2 (steel columns); O3 = optimization scenario 3 (woo-
den columns); O4 = optimization scenario 4 (bubble decks).
10 L.C.M.EBERHARDTETAL.
compared with O1 due to the use of burdensome steel
columns, resulting in higher impacts across many of
the covered impact categories compared with concrete
columns. Both O2 and O4 show worse performance
within the impact categories ADPe, FAETP and TETP
compared with T due to increased amounts of steel for
columns and bubble decks respectively (Table 3).
Table 5 shows that the highest weighted impact sav-
ings are obtained for a building lifespan of 50 years as
a result of the reduced number of material replacements
over the shorter building lifespan. Thus, the reusable
concrete structures thereby represent an increased
share of the total environmental impacts resulting in lar-
ger saving potentials. Furthermore, the impacts are
spread out over a shorter time period, making the
impacts as well as the savings appear larger. However,
the DGNB in Denmark is about to phase out the use
of a building lifespan of 50 years in favour of 80 years
for office buildings instead, thereby deviating from the
other DGNB countries in Europe.
Both Tables 4 and 5show that, with the proposed allo-
cation method, the more reuse cycles, the higher the
potential impact savings.
Discussion
This section discusses the results of the case study
obtained by applying the life cycle impact assessment
method as well as the proposed allocation method
described in the methodology . Recommendations are
provided on how to apply LCA within CE based on
the experiences gathered from the present study.
Focusing on more impact indicator categories than
usual revealed that the magnitude of the savings varies
from impact category to impact category as well as
from scenario to scenario, as the material composition
has a significant influence on the building’s embodied
environmental impacts and greatly depends on the num-
ber of component reuse cycles, the material’s life span
and the building’s lifespan. Thus, optimization of a single
component group leading to potentially high environ-
mental impact savings (Table 4) may not necessarily
benefit the overall building level to the same extent
(Table 5). Hence, it is not obvious which scenario per-
forms best and which material choices to aim at. Since
studies identifying material interdependencies and influ-
ences on the environmental performance of different
building types are lacking, the material choices applied
in this study are based on intuition. Other material
choices than those used here might improve the build-
ing’s overall environmental burden even further.
It is considered realistic to expect that the potential
impact savings of DfD with three reuse cycles should
be even larger compared with two reuse cycles (Table 5).
However, a fraction of the prefabricated concrete
elements will not be suitable for reuse. Thus, the impacts
from these elements are allocated to the initial building,
making the potential impact savings of three reuse cycles
smaller than expected. Furthermore, for the DfD scen-
arios, only a moderate share of the building’s concrete
and metals (approximately 50% and 20% respectively)
can be reused, because only the internal concrete struc-
tures are considered for reuse. Since concrete and metals
are responsible for the largest shares of most impacts
(Figure 3), this also results in smaller savings within
the different building scenarios (Table 5). This is also
reflected in the small difference in impacts between T
and DfD seen on Figure 1. Hence, it is likely that consid-
ering additional building components for reuse will
potentially further increase future impact savings.
Virgin material states were assumed for all materials
used for the initial building, as it is still unclear how to
account for multiple material uses with changing material
qualities in LCA (Haupt & Zschokke, 2017). As a result,
high recycling and energy recovery rates were assumed
at the EoL, providing high avoided impacts in the Next
product system (Figure 1). Diverting material from recy-
cling to reuse at the building’s EoL will most likely increase
the potential future environmental impact savings.
As the material composition of the building scenarios
significantly affected the results, the sensitivity coefficient
resulting from a 10% input value increase was calculated
for input parameters that control the material amounts,
i.e. the material’s mass, material’s service life and the build-
ing’sservice life in scenario T, since all scenarios derive
from T (see the sensitivity analysis in the supplemental
data online) (Hauschild et al., 2018). The input parameters
that exhibited highest sensitivity coefficients were found to
be the service life of the ventilation ducts (25 years) in AP,
EP, ADPe, HTP and TETP with –30%, –20%, –516%,
–26% and –11% respectively. Furthermore, the material
mass of the ventilation ducts has a high contribution of
–66% in ADPe. The high negative sensitivity coefficient
in ADPe is caused by the technical building services’
high contribution to ADPe (Figure 2). However, the build-
ing’s service life was found to have the highest sensitivity
coefficient in all impact categories assessed (between
21% and 93%). All other input parameters tested only
had minor sensitivity coefficients in comparison.
As existing studies in the field are limited, validation
of the results found from this study is challenging. How-
ever, comparing the result with an LCA study of an office
building (Rasmussen & Birgisdottir, 2015), the material
composition is similar to that of the office building
assessed in this study except for metals which are more
pronounced in the present study. Comparing the life
BUILDING RESEARCH & INFORMATION 11
cycle stages impact share shows that trends in GWP,
ODP, POCP and AP assessed in the LCA study are simi-
lar to those found in the present study, except for the
impacts at EoL and the Next product system, which
yield much higher negative impacts in the present
study, indicating differences in EoL modelling and cred-
iting. Comparing the building components impact share
show for both studies that the floors have large contri-
butions; however, the trends for the other building com-
ponents differ. Comparing the material impacts shares
shows that the cement-based materials have by far the
highest contribution in both studies, followed by the
metals. Comparing the elements share of the CO
2
emis-
sions in the present study with that of a related study of
prefabricated reusable building modules (Aye et al.,
2012) shows similar trends, i.e. the external walls and
floors have the highest contribution. However, due to
differences in assessment method and building elements
included in the study, it is difficult to make a direct
comparison.
Module D (Next product system) in Table 1 acknowl-
edges the design for reuse and recycling concept, and
quantifies the net environmental benefit or loads result-
ing from reuse, recycling and energy recovery beyond the
conventional system boundaries (EN, 15978, 2012).
However, using equation (2) means that credits for reus-
ing the building elements are not directly reported separ-
ately in the Next product system as stated by EN 15978,
since the life cycle impacts as well as credits of each reu-
sable element are split between the respective use cycles
that will share them. Hence, some form of crediting
occurs within each life cycle stage of the elements.
The results obtained from applying the proposed allo-
cation method shows benefits of prolonging the service
life of the structural components, i.e. the more reuse
cycles the better, thereby both avoiding the generation
of new products consuming virgin raw materials and
waste production as well as reducing environmental
impacts in accordance with the CE idea. However, as
made evident in previous studies (Allacker et al., 2014;
Aye et al., 2012), several different allocation approaches
exist. Hence, using another allocation methodology is
likely to influence the results significantly, e.g. if the
impacts and benefits of reuse are allocated entirely to
the first or second use and the result does not display
the benefits of product service life extension. Further-
more, allocating the impacts and benefits to the first
use will ascribe no environmental benefits for a sub-
sequent system, and allocating to a subsequent
system potentially means that no product takes respon-
sibility for these parts if no reuse occurs in the future.
There is also a risk of double-counting impacts and
benefits between the systems when allocating to one
system over another. Although the proposed allocation
method is based on an uncertain number of assumed
future reuse cycles, a fairer share of the environmental
impacts and benefits of the reusable components is cred-
ited to the first use and potential subsequent uses, thus
promoting CE.
As noted above in the literature review, the long life-
span of buildings and change in use during their building
lifespan lead to increased uncertainty about future scen-
arios and future environmental impacts (Haupt &
Zschokke, 2017; Niero et al., 2015). The present study
relies on the traditional LCA methodology, i.e. a
restricted system boundary limited to the initial building
from where the reusable elements originate (EN, 15978,
2012;ISO, 14040, 2008; ISO, 14044, 2006). In this study,
subsequent uses of the reusable elements are taken into
account indirectly through allocation of the potential
environmental impacts based on the assumption of two
or three future reuse cycles. Hence, any potential
additional future reuse cycles beyond the assumed two
or three cycles before the terminal EoL are not taken
into account. Furthermore, the lifespan of the reusable
elements will be 2 × 80 years and 3 × 80 years with two
and three reuse cycles respectively, with a building life-
span of 80 years. However, the potential future reuse of
a material can never be guaranteed (Aye et al., 2012),
neither can the actual lifespan of the building. Addition-
ally, a static LCA approach was used, i.e. dynamic
changes during the building’s long life span were not
included in the study. Such dynamic changes include
future resource scarcity, future waste systems, nearing
tipping points (global warming), and future economy
and energy systems. Thus, the potential of reuse in the
future found in this study is not guaranteed, as these
future circumstances are not known nor easily predict-
able. A solution could be to perform LCA scenario analy-
sis allowing for inclusion of estimated future projections
and of the uncertainty relating to prospective assess-
ments (Niero et al., 2015). Consequently, instead of a
single output analysis, a range of possible scenarios will
give an output in the form of a span within which the
future impacts can be expected to be present.
The temporal representativeness of the data used in
the study is challenging, as the building is assumed to
be built today and decommissioned in 50 or 80 years.
Hence, calculation of the potential environmental impact
savings in future is based on environmental impacts
from production today; however, the potential future
reuse will not occur until 240 years (after three use
cycles), when module D is expected to occur.
Although potentially qualified joint solutions exist in
the market allowing assembly and disassembly of con-
crete structures with the purpose of subsequent reuse
12 L.C.M.EBERHARDTETAL.
(Sommer & Guldager, 2016), a concept such as DfD also
requires changing traditional building methods and con-
struction waste management to store and relocate reusa-
ble components (Sommer & Guldager, 2016).
Conclusions
In order to reduce the negative impacts on the natural
environment, successful implementation of CE prin-
ciples, such as DfD, is both necessary and attractive.
The potential for the reuse of materials and components
by the construction sector can be aided and accelerated
by identifying the most effective long-term improvement
opportunities and efforts. This will require clear decision
support for environmental performance assessment, e.g.
LCA. The literature review identified the lack of a unified
method for how to credit reuse and the many uncertain
future circumstances in which the environmental
impacts and benefits will potentially occur.
To address these concerns, a simplified allocation
method was presented. This method divides a fairer
share of the impacts between the potential use cycles
and was applied to an LCA of a case study of a Danish
office building with a concrete structure DfD. The case
study found that the material’s composition has a signifi-
cant influence on the building’s embodied environmental
impacts and greatly depends on the number of com-
ponent reuse cycles, the material’s service life and build-
ing’s service life. However, the longer the lifespan and
the more reuse cycles the better, as the service life of
materials is prolonged. This, in turn, postpones the pro-
duction of new products consuming virgin raw materials.
Before a consistent prospective LCA concept promot-
ing CE in the building industry can be formulated,
further research is needed:
.to identify improvement opportunities by under-
standing the interdependencies and influence that
material compositions have on the environmental
performance of different building types
.to account for substituted materials and products as a
result of reuse and recycling
.to generate consensus on how to handle future cir-
cumstances in which the potential environmental
impacts and benefits of CE concepts will occur
.to determine how to best implement these factors into
environmental performance assessments
This will provide key stakeholders (designers, clients,
users, authorities etc.) with a valid and consistent basis
for life cycle-based decision-making and policy initiat-
ives to better link CE concepts to the environmental
performance of buildings. It will help to establish clear
objectives and targets regarding CE concepts.
Acknowledgement
The authors thank MT Højgaard A/S for providing infor-
mation and data on the case study building used in the study.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Leonora Charlotte Malabi Eberhardt http://orcid.org/0000-
0002-8974-4537
Harpa Birgisdóttir http://orcid.org/0000-0001-7642-4107
Morten Birkved http://orcid.org/0000-0001-6989-1647
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