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Journal of Building Engineering 52 (2022) 104482
Available online 10 April 2022
2352-7102/© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).
Cross-laminated timber for building construction: A
life-cycle-assessment overview
Adel Younis
*
, Ambrose Dodoo
Department of Building Technology, Linnaeus University, 35195, V¨
axj¨
o, Sweden
ARTICLE INFO
Keywords:
Cross-laminated timber
Carbon footprint
Life cycle assessment
Climate change
Sustainable multi-story construction
ABSTRACT
The building industry is a large contributor to greenhouse gas (GHG) emissions and a vast con-
sumer of natural resources. It is estimated that, in the next 40 years, around 415 Gt of CO
2
will be
released as a result of global construction activities. Therefore, improvements in construction
technologies are essential to reduce GHG emissions and thereby attain national and international
goals to mitigate climate change. Cross-laminated timber (CLT) has emerged as an innovative
alternative material to steel/concrete in building construction, given its relatively low carbon
footprint, not to mention its high strength-to-weight ratio, simple installation, and aesthetic
features. CLT is a structural composite panel product developed in the early 1990s, and the
contemporary generation of CLT buildings are yet to reach the end of their service life. Accord-
ingly, there has been growing interest to understand and optimize the performance of CLT in
building construction. In view of that, this paper presents an overview on the feasibility of using
CLT in buildings from a life-cycle assessment (LCA) standpoint. The authors performed a brief
review on LCA studies conducted in the past decade pertaining to the carbon footprint of CLT
buildings. On average, the ndings of these studies revealed about 40% reduction in carbon
footprint when using CLT in lieu of conventional construction materials (steel/concrete) for
multi-story buildings. Furthermore, the paper explores the challenges associated with conducting
LCA on CLT buildings, identies the gaps in knowledge, and outlines directions for future
research.
1. Introduction
The global construction industry is a signicant contributor to atmospheric greenhouse gas (GHG) emissions and a vast consumer of
natural resources in the built environment [1]. Recently, it has been estimated that, worldwide, the building sector makes up
approximately 40% of carbon dioxide (CO
2
) emissions and 35% of the total energy consumption [2]. In accordance with the Paris
Agreement, global carbon emissions need to be reduced by 50% by 2050 (with respect to 1990) to keep the global average temperature
rise well below 2 ◦C [3]. For this, a plausible remaining carbon budget of approximately 880 Gt CO
2
emissions is suggested by the
International Energy Agency (IEA) between the years 2015 and 2100 [4]. Given current annual CO
2
emissions of about 33 Gt
worldwide [5], one important step towards achieving such a vision is to mitigate, to the extent possible, the climate impacts induced by
the construction industry. Currently, around 415 Gt of CO
2
is estimated to be released in the next 40 years because of global building
activities [6]. This corresponds to about 50% of the aforementioned remaining carbon budget recommended by the IEA [4].
Accordingly, the World Green Building Council [7] has set a goal to reduce the GHG emissions due to the building sector by 84 Gt of
* Corresponding author.
E-mail addresses: adel.younis@lnu.se (A. Younis), ambrose.dodoo@lnu.se (A. Dodoo).
Contents lists available at ScienceDirect
Journal of Building Engineering
journal homepage: www.elsevier.com/locate/jobe
https://doi.org/10.1016/j.jobe.2022.104482
Received 25 February 2022; Received in revised form 1 April 2022; Accepted 7 April 2022
Journal of Building Engineering 52 (2022) 104482
2
CO
2eq
to achieve the net-zero vision for buildings by 2050.
Improvements in construction technologies are essential to accomplish sustainability goals in this sector. At the material level, this
can be realized by developing solutions that help to either use less of the same material or use alternative ‘greener’ materials in
construction. In this context, recent LCA studies highlighted the signicance of the structural material choice for the overall carbon
footprint of a building [8,9]: such effects are most pronounced at the production stage and represent a large share of the total envi-
ronmental impacts of modern energy-efcient buildings [10]. Nowadays, steel and concrete are the most commonly used construction
materials worldwide, and are deemed as carbon-emission-intensive materials [11–13]. According to the IEA, the production of one ton
of steel yields approximately 1.4 tons of direct CO
2
emissions into the atmosphere [14]. Another study concluded that around 1.85 tons
of CO
2
is released for each ton of steel produced (including indirect emissions), which ultimately makes around 8% of the global CO
2
emissions [15]. Every year, over 4 billion tons of cement are produced, each ton of which accounts for CO
2
emissions that range
between 250 kg (in case of high-blend cement) and 930 kg (in case of ordinary Portland cement) [5]. Likewise, according to another
study [16], every ton of cement produced emits approximately 600 kg of CO
2
and therefore, at least 8% of the global anthropogenic
CO
2
emissions is caused by the cement industry. On the other hand, several researchers reported the climate benets associated with
the use of timber-based construction materials as compared to conventional non-renewable alternatives (e.g. steel or concrete)
[17–19].
2. Cross-laminated timber (CLT)
Cross-laminated timber (CLT), aka massive timber, is a recent innovation in engineered wood products, which has revolutionized
the use of timber in structural applications. In concept, the CLT building system consists of large, solid timber panels that can be used as
walls or slabs: this in turn facilitates the construction of large-scale or multi-story buildings (as opposed to the limitations of traditional
light-timber frame construction). Typically, a CLT panel is composed of timber laminations that are glued together at 90◦conguration
(Fig. 1). CLT was rst developed in Europe in the early 1990s, after which it has been gaining popularity and general acceptance [20].
Nowadays, the CLT industry is booming around the world [21], especially in Europe where, as of 2017, around 70% of the global CLT is
produced [22]. Consequently, CLT has been globally attracting the interest of the researchers and practitioners of the construction
engineering industry and, eventually, design guidelines have been developed for monitoring CLT construction [23,24]. In effect, a
Fig. 1. Schematic view of CLT’s layered conguration [26].
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
3
recent nation-wide survey conducted in the US [25], which targeted the architectural community, revealed that over 50% of the
participants (numbered 286) believed that CLT is ‘very appropriate’ as a base construction material for multi-family residential
buildings, while only less than 5% of the responses were answered as ‘not at all appropriate’.
In all likelihood, the growing interest in CLT as a construction material is attributed to a number of advantages associated with it,
including but not limited to its low environmental impacts (particularly carbon footprint), high strength-to-weight ratio, ease of
installation, and aesthetic features. With a focus on its sustainability attributes, CLT stores carbon during its service life, which in turn
offers opportunities to make buildings into so-termed ‘carbon sinks’ [27,28]. This results in a reduced global warming potential (GWP)
impact in the production stage of mass timber structures, compared to steel or concrete structures [29]. Studies have shown that CLT
buildings have less than half of the embodied CO
2
of conventional reinforced concrete buildings [30], and their operation is not highly
energy-intensive [31,32]. Furthermore, CLT panels can be reused/recycled which further reduces the carbon footprint of buildings
[33,34]. As far as cost effectiveness is concerned, Silva et al. [35] indicated that CLT enables a reduction of up to 30% in construction
time, which considerably lowers labor costs. This can be explained by the fact that CLT allows for more simplied construction
compared to conventional wood-frame solutions, because fewer larger elements are involved (Fig. 2) [36]. Accordingly, the con-
struction pace per oor could be as low as 4–7 days in the case of CLT buildings, compared to 21–30 days in the case of conventional
concrete [25]. On top of its sustainability attributes and cost benets, CLT is competitive as a construction material in terms of
structural capacity [23,37], design exibility [35], as well as re [38], seismic [39], and thermal [40] performances.
3. Scope and signicance
Given that CLT is a relatively new construction material, contemporary CLT buildings are the rsts of their kind and yet to reach the
end of their service life. Several aspects of such new ‘greener’ materials need to be understood for widespread implementation.
Therefore, there has been growing research interest in the subject of CLT in the past few years to address knowledge gaps related to
material efciency, construction methods, structural performance, durability, and environmental impacts. In the latter context, this
paper focuses on the life cycle carbon footprint of CLT buildings. The effort presented here aims to provide the reader with a back-
ground on the life cycle assessment (LCA) of CLT buildings. For this, a number of LCA studies conducted in the past decade pertaining
to the carbon footprint of CLT buildings were briey reviewed. Furthermore, the paper explores the possibilities of improving the
methodology of LCAs carried out on CLT buildings. Improved LCA methodology would facilitate accurate analysis and understanding
of strategies to optimize the carbon footprint of CLT buildings, and thus maximize the potential use of CLT in the global construction
industry.
The specic objectives of this paper are three-fold: (i) to explore the subject of LCA of CLT buildings focusing on carbon footprint;
(ii) to shed light on the current trends of LCA studies pertaining to CLT buildings concerning methods and ndings; and (iii) to identify
potential gaps that need further research so as to achieve a fuller understanding of the life cycle environmental impacts associated with
CLT buildings. The latter aim is deemed signicant to optimize and improve the competitiveness and sustainability of CLT as a
construction material.
4. Life Cycle Assessment (LCA)
4.1. Concept
In principle, the sustainability of a building is evaluated by quantifying the economic, social, and environmental impacts associated
with it through its entire life cycle. LCA is an established tool that is used for measuring the environmental impacts associated with all
stages of a building’s life cycle. Fig. 3 presents the framework that is usually followed to conduct a LCA study, as provided by the
International Organization for Standardization (ISO 14040) [41]. The life cycle of a building starts with the extraction, production, and
transportation of raw materials and extends to construction, operation, maintenance, up until demolition and waste management at
the end of its service life [42]. In accordance with the European Standard EN 15978 [43], Fig. 4 outlines the four distinct stages that
make a building’s life cycle, from which environmental impacts occur. The stages encompass materials production and construction
(modules A1-5), service life (modules B1-7), end-of-life (modules C1-4), and potential benets/loads beyond the system boundary
Fig. 2. CLT Panel under construction [36].
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
4
(module D).
4.2. Selected LCA studies on CLT buildings
A signicant amount of research was devoted in the past decade to grasp, as far as is possible, the life cycle climate impacts of CLT
buildings [44–70]. In these studies, CLT was compared with different construction solutions in terms of their carbon footprint via a LCA
approach. The solutions encompass reinforced concrete (RC) [44], structural steel [47], glued laminated timber (GLT) [66], and light
timber frame [48] among others. Some researchers have compared new building construction with CLT to renovating existing
structures [53], and others have investigated the use of hybrid CLT/RC systems from an environmental-performance standpoint. For
instance, Pierobon et al. [54] conducted a cradle-to-gate LCA to compare the climate impacts between hybrid CLT/RC and conven-
tional RC structures for a mid-rise building, and reported ~27% GWP reductions associated with the former. In their survey, Cadorel
and Crawford [60] identied and compared nine LCA studies concerning CLT buildings, most of which utilized a cradle-to-gate
analysis approach. Yet, despite the growing number of LCA studies on mass-timber construction, some critical aspects of the CLT
building technology are not yet fully understood (e.g. end-of-life impacts, maintenance/repair activities, accounting for biogenic
carbon), for which simplied assumptions are commonly considered in the literature. A full characterization and optimization of the
climate impacts of CLT buildings requires consideration of all life cycle activities and GHG uxes. Accordingly, further research is
needed to achieve a comprehensive LCA study for CLT buildings that accurately accounts for all activities within a building’s life cycle.
As a step towards this aim, we conducted a brief review that involves 27 studies from the past decade pertaining to the LCA of CLT
buildings, in an attempt to evaluate the current state-of-the-practice methods and identify potential rooms for eventual improvement.
A systematic procedure, outlined in Fig. 5, was followed to perform the literature survey in accordance with the recommendations
Fig. 3. LCA framework based on ISO 14040 [41].
Fig. 4. Life cycle stages and modules of a building as per EN 15978 [43].
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
5
given by Jesson et al. [71]. At the outset, a preliminary search for references was made online in well-known databases: Google
Scholar, ScienceDirect, and Scopus. Relevant keywords such as “LCA for CLT buildings”, “comparative life cycle assessment for cross
laminated timber”, “carbon footprint for CLT buildings”, and “environmental impacts of CLT” were used in this initial search. Indeed,
an enormous number of references were noted: the search in Google scholar using the keyword “LCA for CLT buildings”, for instance,
yielded over 3700 publications. The search results were sorted by relevance and so, only the rst 50–100 outcomes were skimmed and
considered for a secondary ‘ltering’ process. Exploratory readings were carried out to build an initial perception about the topic and
to extract general data from the relevant references. Only LCA studies with focus on CLT buildings were then shortlisted for
further/in-depth analysis.
Table 1 lists the studies included in this review, along with signicant characteristics such as location, year, LCA aspects, etc. These
studies were basically peer-reviewed, and have been carefully chosen according to the following rationale:
•Time: Only studies conducted during the past decade were included. A range between Year 2012 and Year 2021 was considered.
•Location: studies were selected to cover widespread locations across the globe to achieve an international scope. The list contains
eleven countries from within continents/regimes where CLT is normally used in construction practice, namely, North and South
America, East of Asia, Australia, as well as Northern, Central, and Western Europe.
•The study goal: studies were selected to include different purposes, namely, (a) individual/industry-oriented case studies, (b)
comparative studies, and (c) survey/analytical studies.
•Contrasting material: studies were selected to allow for a comparison between CLT and different conventional alternatives such as
GLT, steel, RC, and light timber framed construction. It was observed that, among the alternatives to CLT, concrete was most
commonly considered as a reference construction material.
•Building prole: studies were selected so that a wide range of building sizes and heights were included. The buildings involved in
this survey were either single-story (i.e. family housing), low-rise (i.e. 4-7 stories), mid-rise (i.e. 8-12 stories), or high-rise (i.e. up to
21 stories), with a net oor area ranging between 72 to over 20,000 m
2
. The presence of RC basement was also noted, where
applicable.
Fig. 5. Outline of the literature survey.
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
6
Table 1
Selected LCA studies on CLT buildings.
Ref. Author(s) Year Location Study Characteristics Contrasting
Material
Service
life
Building prole for CLT
building
GWP for CLT building Remarks
[44] Andersen
et al.
2021 Norway Comparative, process-
based LCA, cradle-to-grave
RC 100
years
8 stories +RC basement;
3973 m
2
net oor area
340 kgCO
2
eq/m
2
(material
production only)
454.2 kgCO
2
eq/m
2
(excl. biogenic
carbon)
288.5 kgCO
2
eq/m
2
(incl. biogenic
carbon)
CLT showed 50% lower GWP
compared to RC in the baseline
scenario, and 65% when biogenic
carbon was considered.
[45] Dodoo et al. 2021 Sweden Individual/case study,
process-based LCA, cradle-
to-grave (excl. modules B1,
B5–7, and C4)
– 50 years 8 stories, no basement;
3374 m
2
net oor area
203.4 kgCO
2
eq/m
2
(material
production only)
268.0–280.5 kgCO
2
eq/m
2
(excl.
module D)
52.4–92.4 kgCO
2
eq/m
2
(incl. module
D)
A reduction of up to 43% in GWP is
possible with integrating
innovative engineering solutions.
[56] Durlinger
et al.
2013 Australia Comparative, process-
based LCA, cradle-to-grave
RC 50 years 10 stories, no basement;
1558 m
2
net oor area
54 kgCO
2
eq/m
2
per year (excl.
biogenic carbon)
49 kgCO
2
eq/m
2
per year (incl.
biogenic carbon)
CLT had 22% and 13% lower GWP
than RC with in/excluding biogenic
carbon, respectively.
[64] Kwok et al. 2019 US Individual/case study,
process-based LCA, cradle-
to-grave (excl. module A5,
modules B1-7, and module
C1)
– 75 years 8 stories +RC basement;
3019 m
2
net oor area
322 kgCO
2
eq/m
2
(excl. biogenic
carbon)
227 kgCO
2
eq/m
2
(incl. biogenic
carbon)
Considering biogenic carbon in the
analysis led to approx. 30%
reduction in GWP.
[65] Robertson
et al.
2012 Canada Comparative, process-
based LCA, cradle-to-gate
(excl. module A5)
RC – 5 stories +RC basement;
14233 m
2
net oor area
346.5 kgCO
2
eq/m
2
(excl. biogenic
carbon)
220 kgCO
2
eq/m
2
(incl. biogenic
carbon)
Up to 70% reduction in GWP was
realized with using CLT instead of
RC solution.
[66] Balasbaneh &
Sher
2021 Malaysia Comparative, process-
based LCA, cradle-to-grave
(excl. modules B1, B3–7,
C3–4, D1)
GLT 50 years Single-story family
house; 72 m
2
net oor
area
695–833 kgCO
2
eq/m
2
CLT building had ~20% lower
GWP than that built with GLT.
[67] Darby et al. 2013 UK Comparative, process-
based LCA, cradle-to-grave
(excl. module B)
RC 50 years 8 stories, no basement;
4154 m
2
net oor area
157.7 kgCO
2
eq/m
2
(assuming end-
of-life bioenergy and 100% carbon
sequestration)
A 60% reduction in GWP was
achieved with using CLT, based on
the aforementioned assumptions.
[68] Dolezal et al. 2021 Austria Comparative, process-
based LCA, cradle-to-grave
(excl. modules B1–3, B5,
and B7)
RC 100
years
8 stories, no basement;
3528 m
2
net oor area
~220 kgCO
2
eq/m
2
(cradle-to-gate,
modules A1-A5)
~ −250 kgCO
2
eq/m
2
(cradle-to-gate,
incl. C stock)
~2000 kgCO
2
eq/m
2
(cradle-to-
grave, w/module D)
A CLT building showed 18% lower
cradle-to-gate GWP compared to its
RC counterpart. This difference
decreased when considering the
full life-cycle stages.
[69] Jayalath et al. 2020 Australia Comparative, process-
based LCA, cradle-to-grave
RC 50 years 7 stories +RC basement;
750 m
2
net oor area
~700–800 kgCO
2
eq/m
2
A 30% reduction in the GWP was
realized with CLT construction.
[70] Chen et al. 2021 China Comparative, process-
based LCA, cradle-to-gate
RC – 8 stories, no basement;
3524 m
2
net oor area
221.3 kgCO
2
eq/m
2
A CLT building had 25% less GWP
compared to its RC counterpart.
(continued on next page)
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
7
Table 1 (continued )
Ref. Author(s) Year Location Study Characteristics Contrasting
Material
Service
life
Building prole for CLT
building
GWP for CLT building Remarks
[61] Grann 2013 Canada Comparative, process-
based LCA, cradle-to-grave
(excl. module B)
RC 60 years 4 stories +RC basement;
4060 m
2
net oor area
~132.8 kgCO
2
eq/m
2
(assuming end-
of-life landll, including carbonation
& biogenic carbon)
~7.2 kgCO
2
eq/m
2
(same
abovementioned assumptions but
incl. forest albedo)
CLT showed 40% lower GWP
compared to RC in the baseline
scenario.
[46] Felmer et al. 2021 Chile Comparative, process-
based LCA, cradle-to-usage
(i.e. modules A1–5 & B6)
RC 50 years 5 stories +RC basement;
1405 m
2
net oor area
90 kgCO
2
eq/m
2
(material production
only, modules A1–3)
101 kgCO
2
eq/m
2
(cradle-to-gate,
modules A1–5)
131 kgCO
2
eq/m
2
(cradle-to-usage,
excl. biogenic carbon)
−186 kgCO
2
eq/m
2
(cradle-to-usage,
incl. biogenic carbon)
Compared to RC, CLT offered
~60% reduction in the cradle-to-
usage GWP (incl. biogenic carbon).
[47] Allan &
Philips
2021 US Comparative, process-
based LCA, cradle-to-grave
(excl. module B)
Steel 60 years Varied height (5 or 12
stories), no basement;
7014 & 21161 m
2
net
oor area
161–165 kgCO
2
eq/m
2
CLT showed 30–40% reductions in
the GWP compared to steel.
[48] Dodoo et al. 2014 Sweden Comparative, process-
based LCA, cradle-to-grave
(excl. modules B3–5)
Light timber
frame
50 years 4 stories, no basement;
1058 m
2
net oor area
~120 kgCO
2
eq/m
2
(cradle-to-gate,
excl. C stock)
~ −510 kgCO
2
eq/m
2
(cradle-to-gate,
incl. C stock)
~220 kgCO
2
eq/m
2
(cradle-to-grave,
excl. C stock)
CLT showed 16% savings in GHG
emissions compared to light timber
frame.
[49] Liang et al. 2020 US Comparative, process-
based LCA, cradle-to-gate
RC – 12 stories, no basement;
8360 m
2
net oor area
193 kgCO
2
eq/m
2
A CLT building had 18% lower
GWP compared to its RC
counterpart.
[50] Skullestad
et al.
2016 Norway Comparative, process-
based LCA, cradle-to-gate
(excluding modules A4 &
A5)
RC – Varied height (3, 7, 12,
or 21 stories) +RC
basement; 2613–11823
m
2
net oor area
26.3–67.3 kgCO
2
eq/m
2
(depending
on building height)
CLT buildings showed 34–84% less
GWP compared to their RC
counterparts.
[51] Guo et al. 2017 China Comparative, process-
based LCA, cradle-to-grave
(excl. modules B3–5)
RC 50 years Varied height (4, 7, 11,
or 17 stories), no
basement;
~4900–26500 m
2
net
oor area
5930–6270 kgCO
2
eq/m
2
(mostly
from module B, incl. biogenic carbon,
assuming 50% recycle +50% energy
recovery from end-of-life CLT)
On average, CLT buildings showed
13% lower GWP compared to their
RC counterparts.
[52] Liu et al. 2016 China Comparative, process-
based LCA, cradle-to-grave
(excl. modules B3–5)
RC 50 years 7 stories, no basement;
2800 m
2
net oor area
730–1070 kgCO
2
eq/m
2
(depending
on CLT recycling % and the city
where the building is)
CLT showed 40% savings in GHG
emissions compared to RC solution.
[53] Ryberg et al. 2021 Greenland Comparative, process-
based LCA, cradle-to-grave
(excl. modules B3–5)
RC, Light timber
frame,
Renovation of
existing RC
30 years 4 stories, no basement;
~1000 m
2
net oor area
299.2 kgCO
2
eq/m
2
Renovation of existing RC was the
most sustainable solution.
(continued on next page)
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
8
Table 1 (continued )
Ref. Author(s) Year Location Study Characteristics Contrasting
Material
Service
life
Building prole for CLT
building
GWP for CLT building Remarks
[54] Pierobon
et al.
2019 US Comparative, process-
based LCA, cradle-to-gate
RC – 8 stories +3 RC
basements; 10702 m
2
net oor area
327–333 kgCO
2
eq/m
2
(cradle-to-
gate result for hybrid CLT/RC
structure)
A reduction of 26% in the GWP was
achieved in hybrid CLT/RC
building compared to sole RC
building.
[55] Puettmann
et al.
2021 US (3
regions)
Comparative, process-
based LCA, cradle-to-gate
RC – Varied height (8, 12, or
18 stories), no basement;
9776–21321 m
2
net
oor area
129–157 kgCO
2
eq/m
2
(Pacic
Northwest region)
106–149 kgCO
2
eq/m
2
(Northeast
region)
122–172 kgCO
2
eq/m
2
(Southeast
region)
CLT buildings showed 22–50% less
GWP compared to their RC
counterparts.
[62] Lolli et al. 2019 Norway Comparative, process-
based LCA, cradle-to-usage
(incl. modules A1–3 & B6)
GLT 50 years 9 stories +RC
basements; 3801 m
2
net
oor area
114.3 kgCO
2
eq/m
2
(materials
production only)
240 kgCO
2
eq/m
2
(operational
energy)
Using CLT to substitute RC in
stairwells and elevator shafts
yielded 6% potential reduction in
GHG emissions.
[63] Liang et al. 2021 US Comparative, process-
based LCA, cradle-to-grave
RC 60 years 12 stories, no basement;
8360 m
2
net oor area
3153 kgCO
2
eq/m
2
(90% of which
occurs at the service-life stage)
CLT option showed 17% lower
GWP due to material production,
but only 2% due to the full life-
cycle stages.
[57] Pe˜
naloza et al. 2016 Sweden Comparative, process-
based LCA, dynamic LCA,
cradle-to-grave (excl.
modules B1–5 & B7)
RC 50 years 4 stories, no basement;
approx. 1200 m
2
net
oor area
281 kgCO
2
eq/m
2
(static LCA)
260 kgCO
2
eq/m
2
(dynamic LCA,
100-year-based GWP)
218 kgCO
2
eq/m
2
(dynamic LCA,
300-year-based GWP)
CLT showed 42% lower GWP
compared to RC in the baseline
scenario.
[58] Teh et al. 2017 Australia Comparative, input-output
analysis approach, cradle-
to-gate
RC – 10 stories, no basement;
1558 m
2
net oor area
~40 M tCO
2
eq for the Australian
residential sector by 2050 with CLT
construction (excl. carbon
sequestration, modeling was based
on a CLT building in Ref. [56]).
Compared to traditional RC
solutions, a reduction of 40% in
GHG emissions was realized with
CLT construction.
[59] Rajagopalan
& Kelley
2017 US Survey/Qualitative RC, Steel – 9 stories, no basement N/A CLT showed an advantage over
other alternatives based on a
qualitative sustainability
assessment.
[60] Cadorel &
Crawford
2019 – Survey – – – 160–5980 kgCO
2
eq/m
2
Research needs were suggested
based on reviewing nine
publications.
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
9
•LCA characteristics: studies were selected to discuss the implications of using different LCA methodologies (e.g. process-based Vs.
input-output approach, cradle-to-gate Vs. cradle-to-grave analysis, static Vs. dynamic analysis, etc.). For cradle-to-grave analysis
studies, the service life periods assumed were also highlighted.
5. Discussions
In general, the outcomes of the LCA studies show a reduced carbon footprint associated with CLT construction compared to
conventional construction solutions. However, it was difcult to compare the greenhouse gas (GHG) emissions of the CLT buildings.
There was a broad variation among these studies for the GHG emissions associated with CLT construction, ranging between 0.05 and
6.3 tCO
2eq
/m
2
oor area. Such variations are attributed to the inevitable differences in the studies’ parameters and variables such as
regional climate, building regulations, building occupation, building height/shape, electricity mix, as well as those pertaining to LCA
methodology including system boundary, carbon estimation and data quality among others, as discussed in the following Sections
5.1–5.10. Improved understanding of the implications of these parameters and variables will help narrow the gap in the literature to
achieve a comprehensive LCA methodology for CLT buildings.
5.1. Effect of study location
An important characteristic that inuenced the LCA outcomes is the location/region in which the study was conducted. To
illustrate this, the operational energy required to reach the occupants’ comfort in severe cold regions (e.g. China [51] or Sweden [48])
is higher than that in more temperate locations (e.g. UK [67] or Australia [56]). As an example, over a 50-year life cycle for the same
CLT building, Liu et al. [52] reported signicantly different values of energy consumption per unit area between two different regions
in China, namely, 6.84 GJ/m
2
in Xi’an and 11.56 GJ/m
2
in Harbin. This is perhaps unsurprising as Harbin is a relatively cold region in
which temperature reaches −20 ◦F during winter, thus requiring additional energy for heating. The differences in the building design
codes or regulations among regions may also escalate variations in the carbon footprint of CLT buildings. For instance, a minimum of
245 mm of rock wool (estimated at R5.4) is required for an external CLT wall in Sweden (e.g. Ref. [48]) as per the local design
guidelines. On the other hand, the design code in China (e.g. Ref. [51]) requires just 50 mm of EPS (estimated at R1.78). Another
illustration is given by Puettmann et al. [55] who compared the GWP of a CLT building among three different regions in the US,
namely, Pacic Northwest, Northeast, and Southeast regions. The CLT building in the Pacic Northwest region exhibited the highest
GHG emissions per unit oor area: this was attributed to the additional components needed to meet the building code requirements for
seismic protection. Furthermore, the differences in the electricity mix among the buildings’ locations play an important role in the
variation of GHG emissions. For instance, the CLT building in Australia [56] is supposed to have an advantage over that analyzed in the
UK [67] due to the less severe climate experienced in the former country. However, the carbon footprint of the Australian electricity
mix [56] (mainly generated from brown coal) is relatively high when compared to that in the UK, where coal represents less than 40%
of the total electricity mix [72].
To demonstrate the signicance of geographic scope, Table 2 lists the GWP associated with CLT production (i.e. modules A1–3)
among different manufacturers worldwide, extracted from their corresponding environmental product declarations (EPDs). The
functional unit declared in all EPDs was 1 m
3
of CLT panels, with different unit weights (averaged as 475.7±54.0 kg/m
3
CLT) and
moisture contents (ranging from 10 to 15%). The initial GHG emissions due to CLT production (excluding the effects of carbon storage
in wood) were estimated as 152.0 kg CO
2eq
/m
3
CLT on average, but with a relatively high standard deviation of 118.4 kg CO
2eq
/m
3
CLT. These ndings conform with a recent comprehensive survey conducted by Rasmussen et al. [73] that involved a total of 81 EPDs
for structural wood products worldwide. In all likelihood, such differences in the declared GWP impacts can be attributed to the
variability in the energy resources among different manufacturers worldwide, notwithstanding the technological variances that lead to
different CLT unit weights. To conclude, it is important to take into consideration such regional variations when comparing results
from international studies, not to mention the fact that these variations will not stop evolving as construction practices continue to
change, the electricity becomes cleaner, and the climate changes.
Table 2
GWP per 1 m
3
CLT production (modules A1–3), as provided by different manufacturers.
Manufacturer Geographic
scope
CLT unit weight (kg/
m
3
)
GWP, excluding biogenic (kg CO
2eq
/
m
3
)
GWP, including biogenic
a
(kg CO
2eq
/
m
3
)
S¨
odra Building Systems [74] Sweden 430 34 −670
Stora Enso [75] Austria 470 60 −671
KLH Massivholz GmbH [76] Austria 480 192.9 −601.3
Binderholz Bausysteme GmbH
[77]
Germany 471 200 −761
Egoin [78] France 500–550 174.1
b
−685.5
Xlam [79] Australia 480 447 −293
Schilliger Holz AG [80] Switzerland 424 70 −623
SmartLam North America [81] Alabama, US 561 126 −779
SmartLam North America [82] Montana, US 561 178 −727
Nordic X-Lam [83] Quebec, Canada 411 121.9 −591
Structurlam [84] BC, Canada 420 89.8 −678.3
a
Refer to Section 5.6 for discussions related to the consideration of biogenic carbon.
b
Calculated based on data in EPD.
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
10
5.2. CLT Vs. other alternative materials
In this review, CLT construction was compared against other solutions that adopt different materials such as reinforced concrete
(RC), steel, and other timber products like glued laminated timber (GLT) or light-timber frames. Table 1 organizes the differences in
the GWP between CLT and contrasting materials for the listed LCA studies. Compared to RC, CLT generally showed an advantage in
terms of carbon footprint. For instance, Jayalath et al. [69] performed a comparative LCA study between CLT- and RC-based mid-rise
buildings in Australia. They reported approximately 30% savings in the GHG emissions associated with CLT compared to conventional
RC. While CLT did not exhibit actual global warming potential (GWP) benets particularly during the service-life stage (i.e. modules
B1-7), the authors [69] suggested that adopting energy-efcient methods as well as reuse/recycling timber at the building’s end of life
can further improve the life cycle performance of CLT buildings. These ndings were corroborated by another LCA study conducted on
a 7-story CLT building in China [52] that revealed 30% and 40% savings in energy consumption and GHG emissions, respectively,
compared to an equivalent RC structure. However, this 40% saving in the GHG emissions for CLT construction [52] was realized with a
full consideration of biogenic carbon in the analysis, in addition to the assumption of 55% recycling and 45% energy-recovery rates for
the end-of-life CLT. In the context of CLT-versus-steel carbon footprint, Allan and Phillips [47] reported that CLT buildings showed a
30–40% reduction in the GWP compared to those utilizing structural steel, based on their LCA study on mid- and low-rise buildings in
North America. As far as a comparison between CLT and other timber products is concerned, an LCA study by Balasbaneh and Sher
[66] for a single-story building in Malaysia compared CLT against GLT as a base construction material in terms of environmental
performance. They showed that CLT signicantly reduced the embodied energy of the building (by 40%), and exhibited lower impacts
with respect to GWP, terrestrial ecotoxicity, land use, and ozone layer depletion. On the other hand, CLT showed a 7% higher life cycle
cost and greater impacts concerning human-toxicity and fossil-depletion potential compared to GLT. Indeed, such comparisons be-
tween timber-based materials are not usually straightforward and may be inconclusive for decision-making processes. However, this
particular study [66] was carried out on a single-story residential building, for which CLT is not commonly used as a base construction
material. Finally, a comprehensive LCA study was conducted in Greenland by Ryberg et al. [53], in which four building solutions were
compared, namely, CLT, light timber frame, reinforced concrete, and renovation of an existing concrete structure. The study showed
that, among new construction alternatives, the timber-based solutions (i.e. CLT and light timber frame) had the best environmental
Table 3
GWP of a CLT building (measured in tons of CO
2-eq
) with different end-of-life scenarios [67].
Phase Reuse Recycling Incineration Incineration (with energy recovery) Landll
Up to construction −1100 −1100 −1100 −1100 −1100
Demolition 22 22 22 22 22
Transport 12 12 12 12 12
Re-manufacture – 10 – – –
Re-transport – 12 – – –
Re-construction 45 45 – – –
Combustion – – 1192 1192 –
Energy recovered – – – −628 –
Emissions from landll – – – – 1013
Total −1021 −999 126 −502 −53
Fig. 6. The concept of biogenic carbon [64].
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
11
performance. Nonetheless, the renovation of existing buildings, despite being relatively rare in construction practice nowadays, proved
to be the most feasible solution from a sustainability perspective. Therefore, the study [53] highlights the need to pay further attention
to renovation solutions for existing buildings, especially in regions where residential/housing problems are pronounced.
5.3. Effect of a building’s prole
An important characteristic that caused a wide variation in the carbon footprints of the reviewed studies is the building’s prole.
For instance, the presence of reinforced-concrete basements ultimately results in higher GWP associated with CLT buildings. As an
example, comparing the LCA studies by Andersen et al. [44] (8-story, with RC basement, Norway) and Dodoo et al. [45] (8-story, no
basement, Sweden), it is apparent that the GWP due to the production of materials of the former (340 kgCO
2eq
/m
2
) was approximately
70% higher than that of the latter (203.4 kgCO
2eq
/m
2
): this difference is partly related to the presence of RC basement. Furthermore,
the carbon footprint per m
2
oor area of the CLT building increases with the number of stories [47,50,51,55]. For instance, Skullestad
et al. [50] reported an increase in the cradle-to-gate GHG emissions associated with a CLT building from 26.3 kgCO
2
eq/m
2
(in case of 3
stories) up to 67.3 kgCO
2
eq/m
2
(in case of 21 stories). Likewise, Puettmann et al. [55] reported an up to 40% increase in GHG
emissions per unit oor area when a case study CLT building’s height is increased from 8 to 18 stories (Table 1). Given that the
foundations of CLT superstructures are usually concrete, this explains the fact that an increase in the number of stories leads to an
increase in the concrete’s share of the total mass of CLT buildings, since footings are sized according to a building’s height and column
loads. Besides, the taller the CLT building is, the greater the requirement for hybrid structural systems such as core walls, which are
usually concrete.
5.4. Effect of the system boundary
The system boundary considered in LCA methodology plays an important role in variations of the carbon footprint of the CLT
buildings reviewed. In principle, LCA embraces a holistic approach that involves the whole life cycle of a product; however, a
streamlined approach is often used in LCA studies of CLT buildings, in which a number of life cycle stages are excluded [85]. Table 1
shows that some studies consider the full life cycle of the building (i.e. ‘cradle-to-grave’), while others adopt ‘cradle-to-gate’ or
‘cradle-to-usage’ analysis approaches. In effect, the cradle-to-gate system boundary is deemed admissible as it helps identify the
environmental impacts during modules A1-5 (i.e. materials extraction, procurement, and construction stages). However, a major
drawback exists with such analysis, as it may lead to premature conclusions about GWP benets that may be counterbalanced in the
later stages of the building’s life cycle. For instance, Lolli et al. [62] reported a GWP of 114.3 kgCO
2
eq/m
2
for a 9-story CLT building in
Norway due to materials production (i.e. modules A1–3), but more than double this value (240 kgCO
2
eq/m
2
) was estimated solely for
the operational energy over its 50-year service life (i.e. module B6). Another example of the signicance of the system boundary is
given by Durlinger et al. [56] who revealed 30% reductions in GWP for modules A1–3 (i.e. material production) with the use of CLT
compared to conventional concrete. However, when including the construction, transportation and end-of-life stages, and considering
an end-of-life scenario without carbon sequestration, the GWP of the CLT building was 15% higher than that of the conventional RC
counterpart. Therefore, it is important to consider the full life cycle of buildings when evaluating the implications associated with the
use of CLT to draw reliable conclusions on the net reductions of GWP.
5.5. Service life and maintenance activities
Given that CLT is a relatively new construction material, the current literature lacks an accurate representation of the service life,
particularly the maintenance/repair schedule for typical CLT buildings. By observing the studies reviewed here (Table 1), one can
realize that the majority of LCA studies on CLT buildings have considered a service life of 50–60 years, which is reasonable being
consistent with what is commonly assumed for such studies on building construction (i.e. 40–75 years) [86]. Only a few studies have
assumed a service life below (as low as 30 years [53]) or above (up to 100 years [44,68]) this range. As far as maintenance/repair
schedule is concerned, most LCA studies on CLT buildings have adopted simplied assumptions in which (a) the repair/maintenance
activities (i.e. modules B2-4) are excluded from the cradle-to-grave analysis (e.g. Refs. [47,48,67]) or (b) CLT is not to be replaced (in
part or in total) during the building’s service life (e.g. Ref. [44]). However, it has been indicated, based on real-life anecdotal evidence
[87], that CLT may need to be replaced due to moisture-related issues during the building’s life time. Accordingly, Balasbaneh and Sher
[66] assumed the same maintenance schedule for CLT and GLT buildings, which is reasonable as both materials are
engineered-wood-based products. Dodoo et al. [45] assumed partial replacement for CLT material at certain locations (e.g. balconies),
in addition to regular inspection and painting activities taking place throughout the building’s life span (every 10 years). Nonetheless,
it can be observed that adequate service-life prediction models for CLT are critically needed to achieve accurate estimates of the carbon
footprint of CLT buildings due to maintenance/repair activities. Accordingly, the carbon footprint attributed to the service life of a CLT
building can be minimized by means of protective inspection and maintenance measures that mitigate repair/replacement of building
components.
5.6. Consideration of biogenic carbon
Carbon sequestration is dened as the process in which trees absorb and store atmospheric CO
2
as carbon in wood bers – which is
also known as “biogenic carbon” (Fig. 6) [88]. As long as wood products are being used, this biogenic carbon is assumed to be
‘withdrawn’ from the atmosphere, and that often leads to negative net estimations for GWP, at least during the production stages of
CLT. As shown in Table 2, the net GHG emissions calculated due to CLT production varies among different manufacturers worldwide,
with an average value of −643.6 kg CO
2eq
/m
3
CLT and a standard deviation of 130.9 kg CO
2eq
/m
3
CLT. As far as the biogenic carbon is
concerned in LCA studies, the 0/0 and −1/+1 approaches are usually considered for carbon accounting [89]. When biogenic carbon is
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
12
included, the carbon stored in the wood is initially counted as a credit that reduces GWP. In this context, two extreme end-of-life
scenarios are commonly considered, namely, (a) no storage of carbon in wood (0% sequestration) – this is the worst-case scenario
in which all biogenic carbon is returned to the atmosphere (e.g. bioenergy); and (b) 100% carbon sequestration – in which all biogenic
carbon is reused/recycled in another wood product or at least kept locked in landll. The life cycle carbon footprint of a CLT building is
highly dependent on the percentage assumed for carbon sequestration, and this may have led to inconclusive/conicting results among
different LCA studies on CLT buildings.
Several researchers have demonstrated the effects of whether or not to assume carbon sequestration on LCA outcomes for CLT
buildings. Overall, changes ranging from 10% to 300% in the GHG emissions were reported with respect to this variable (Table 1)
depending on the system boundary and end-of-life assumptions. In this context, Kwok et al. [64] carried out a LCA study on a
mass-timber multi-family residential structure and compared the two scenarios of 0% and 100% carbon sequestration. Based on the
study results, the cradle-to-gate GWP reported for the CLT building per m
2
oor area was 271 and 125 kg CO₂eq for the cases of 0% and
100% carbon sequestration, respectively. Moreover, the cradle-to-grave GWP measured for the 0% and 100% carbon sequestration
scenarios was 322 and 227 kg CO₂eq/m
2
oor area, respectively. Likewise, Durlinger et al. [56] performed an LCA study for a resi-
dential building in Australia to compare the CLT with concrete as a base construction material in terms of environmental performance.
The results showed that the CLT building has 22% lower GWP compared to that of a RC building if carbon sequestration is included in
the analysis, but 13% lower GWP if carbon sequestration is not considered. These results were corroborated by another LCA study
reported by Andersen et al. [44] concerning mid-rise CLT residential building in Norway. In this study [44], the GWP of a CLT building
was estimated for a functional unit of 1 m
2
oor area as 454.2 CO
2eq
and 288.5 CO
2eq
in the cases of excluding and including biogenic
carbon in the analysis, respectively (i.e. a reduction of ~37% in GWP associated with the latter). In addition, the same authors [44]
evaluated the potential forest transformations required to fulll new building construction in 2060, and predicted that 3% of the
existing global forest area would be needed. Grann [61] performed an in-depth analysis that involved not only the changes in the forest
albedo at the harvest site due to CLT production but also the concrete carbonation in the contrasting RC building. In his effort, Grann
[61] has also compared various end-of-life scenarios, including bioenergy, landll, and recycling, which in turn led to a more detailed
assessment of the biogenic carbon life cycle. Such a thorough approach in assessing the biogenic carbon life cycle helps identify
signicant outcomes regarding the potential GHG savings of CLT construction.
5.7. End-of-life scenarios
Accurate characterization of the end-of-life stage for CLT buildings has a great impact on their life cycle carbon footprint [90]. One
aspect of the end-of-life stage is the consideration of biogenic carbon, which has already been discussed in Section 5.6. Another
important aspect is the way the CLT material is treated following demolition. As mentioned before, most of the current CLT buildings
are the rst of their kind and are yet to reach the end of their service life. This has led to a lack of actual/representative data and
therefore, reliable assumptions can only be postulated as part of holistic LCA. In principle, different scenarios for end-of-life CLT can be
assumed, namely [91]: (a) reuse (in part or in total), (b) incineration (with or without energy recovery), and (c) landll. A combination
of different scenarios (with different percentages allocated for each) can also be assumed for CLT at the end of a building’s service life
[33,61]. In this context, Darby et al. [67] compared the carbon footprint among different end-of-life scenarios for a CLT building
(taking biogenic carbon into account), and a summary of the results is presented in Table 3. These demonstrate the clear advantage of
reusing/recycling CLT, or it being considered as a bioenergy source, from a sustainability perspective. Research conducted afterwards
[69,87] has corroborated these ndings and demonstrated the signicance of end-of-life assumptions on the ultimate climate impacts
of CLT buildings. For instance, Liang et al. [63] indicated that the end-of-life recycling of mass timber provides a carbon offset of 364 kg
CO
2
eq/m
2
, which further lowers the GHG emissions of the CLT building by 12% compared to its RC counterpart. Indeed, reusing CLT
was shown to be the most environmentally friendly alternative as it not only limits GWP the most [67] but also promotes a circular
model that supports a cradle-to-cradle analysis approach, thus optimizing sustainability in the construction sector [92]. Nonetheless, it
is to be noted that improvements in CLT technologies regarding material use, connection mechanisms, structural health monitoring,
and cascading of reused/recycled timber are essential to validate such assumptions for end-of-life CLT.
5.8. LCA approach and data quality
The majority of the studies reviewed here (Table 1) adopted a LCA approach to measure the life cycle carbon footprint of CLT
buildings, except for Refs. [59,60] which were survey studies. The survey conducted by Rajagopalan and Kelley [59] identied po-
tential ‘hot spots’ associated with CLT construction based on qualitative measures, while the literature review (based on nine pub-
lications) of Cadorel and Crawford [60] identied knowledge gaps that require further research. In summary, most of the LCA studies
on CLT buildings utilized a process-based approach to assess their climate impacts, with comparisons to conventional construction
materials. The process-based approach is deemed acceptable for such comparative studies, but according to Anand and Amor [93] as
well as S¨
ayn¨
ajoki et al. [94], this approach is insufcient to comprehensively estimate the carbon footprint associated with building
construction. Alternatively, other researchers [94,95] suggested the use of a more comprehensive input-output approach to estimate
GHG emissions over the entire life cycle of buildings. In this input-output approach, the true embodied energy as well as all subsequent
environmental burdens may be accurately estimated, and the results of such analyses can be utilized for extensive generalizations (e.g.
industry-wide studies, in which buildings are ‘averaged’ with a wide societal scope) [94]. To improve this input-output analysis
method, Teh et al. [58] proposed a hybrid method that integrates the precision of process-based analysis with the comprehensiveness
of the input-output approach to determine GHG emissions based on the model of a 10-story CLT building. The study concluded that, by
2050, a total saving of 26 Mt CO
2
eq in GHG emissions can be achieved by the Australian residential sector with the use of CLT as a base
structural material in lieu of conventional RC [58]. This predicted GHG saving becomes even greater with the consideration of biogenic
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
13
carbon, with an approximate potential reduction of 119 Mt CO
2
eq [58]. Nevertheless, this model is preliminary and involves only a
cradle-to-gate system boundary, thus requiring further development.
The quality of data used in the LCA studies conducted on CLT buildings has been an ongoing challenge. This is perhaps unsurprising
as CLT is a relatively new construction material serviced by a limited number of manufacturers. Furthermore, the current CLT
buildings have not yet reached the end of their service life. Accordingly, the data concerning the environmental performance of CLT
are not widely available [60], which in turn leads to approximations or signicant limitations while assessing the life cycle carbon
footprint of these buildings.
5.9. Dynamic Vs. static LCA
One common limitation observed in the existing LCA studies on CLT buildings is the lack of consideration of the temporal dynamics
related to GHG ows for wood products. The majority of these studies have utilized static analyses that do not consider the complex
interactions between CLT manufacturing and forest systems. However, such interactions are naturally dynamic and strongly affected
by variations in the CLT manufacturing and end-of-life scenarios, as well as forest management [96]. Therefore, a dynamic LCA
approach is suggested to address such inconsistencies of temporal assessment and improve the overall accuracy of LCA [97]. In such
analyses, a dynamic life cycle inventory (LCI) is rst obtained accounting for the temporal prole of emissions. Next, this dynamic LCI
is assessed for a given time horizon by real-time impact scores using time-dependent characterization factors [97]. Despite it applying
to any impact category, the dynamic LCA approach is commonly used for GWP [98,99]. In effect, considering dynamic variables may
lead to changes of up to 45% in the LCA outcomes compared to those of the commonly-used static LCA approach [100], and such
differences can be signicant enough to change the LCA outcomes and conclusions. Lan et al. [96] conducted a dynamic LCA study to
examine the carbon ows of the CLT life cycle in the Southeastern United States assuming a 100-year study period. They concluded
that, based on a 1-ha forest land, the net GHG emissions ranged from −954 to −1445 tCO
2eq
and from −609 to −919 tCO
2eq
for high
and low forest productivity scenarios, respectively. Considering 1 m
3
of CLT produced with a cradle-to-gate system boundary, the same
authors [96] reported fossil-based GHG emissions in the range of 113–375 kgCO
2eq
/m
3
, which is consistent with existing EPDs from
different manufacturers (Table 2). In the context of CLT buildings, Pe˜
naloza et al. [57] evaluated the climate impacts of a 4-story CLT
building with a 50-year service life using static and dynamic LCAs. Compared to static LCA, the authors [57] reported approximately
10% and 22% reductions in GHG emissions when applying dynamic LCA considering 100 and 300 years as the time horizon for climate
impact assessment, respectively (Table 1). To conclude, using dynamic LCA and forest growth data to evaluate the climate impacts of
CLT buildings can produce results with better resolution compared to traditional practices. Since the climate impacts of wood products
take place over long periods of time, a 100-year time horizon is barely enough to account for the effects of biogenic carbon in CLT using
dynamic LCA, and one should adopt a realistic time horizon for each specic case. Yet, as stated by Pe˜
naloza et al. [57], ‘the timing of
the carbon sequestration at the forest in the dynamic inventory seems to be a challenge for further dynamic LCA application,
considering the inuence it could have on the results and the lack of a robust method to deal with this assumption’.
5.10. Integration with the state-of-the-practice in structural engineering
The majority of published LCA studies compare CLT with other construction materials in terms of environmental performance.
However, given that CLT is a relatively new construction material whose technology is under ongoing development, it is essential to
understand the synergy between the state-of-the-practice structural engineering solutions and the climate impact of CLT (e.g. Fig. 7).
Such an understanding helps evaluate the carbon footprint due to implementing new technologies in the manufacturing or con-
struction of CLT, and thus improves the competitiveness of CLT buildings with optimized engineering design and reduced climate
impact. In general, the LCA studies of CLT buildings that integrate innovative engineering technologies with life cycle carbon footprint
are relatively scarce. In this context, Dodoo et al. [45] explored strategies to optimize the life cycle carbon footprint of a CLT building
based on a synergistic approach that combines knowledge from CLT utilization, connections among CLT elements, structural health
Fig. 7. Integration between structural engineering design solutions and life cycle carbon footprint of CLT buildings [45].
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
14
monitoring, and life cycle analysis. The authors [45] reported that a reduction of up to 43% can be reached in the life cycle carbon
footprint when implementing such a synergistic approach. These interdisciplinary studies demonstrate the importance of integrating
emergent engineering solutions with the carbon footprint analysis of CLT buildings. Therefore, future research is encouraged to
investigate the ongoing developments in CLT technology based on a life-cycle-assessment standpoint.
6. Summary and conclusions
This paper reviewed a number of relevant LCA studies dealing with carbon footprint of CLT buildings, based on which an overview
was presented on the feasibility of using CLT to achieve sustainable construction. In summary, the ndings of these studies revealed
notable savings in the GHG emissions (40% on average) associated with the use of CLT in lieu of conventional construction materials
(mainly RC) for multi-story buildings. These savings in the GHG emissions associated with CLT construction were most pronounced
when considering carbon sequestration in the analyses, along with adequate/greener assumptions for end-of-life wood products. Most
of the studies reporting the environmental impact of CLT were carried out on multi-family residential buildings, which is unsurprising
as CLT is most commonly used in such building types. However, in the past few years, CLT has also shown potential (and thus far has
been successfully applied) as a structural material in large-scale governmental projects (e.g. Ref. [101]), especially when accompanied
with RC elements to form hybrid CLT/concrete structures or even composite CLT/concrete slabs. Therefore, there is a perceptible need
to further investigate the use of CLT in such projects from a sustainability perspective.
In addition, it was observed that there is a wide range of variability in the LCA outcomes of CLT buildings, which can be attributed
to the diversity of the buildings assessed, regional variations, the way of treating biogenic carbon, the differences in LCA methodology,
and the utilized data source. Accordingly, the authors perceive that having a large number of different LCA outcomes with different
methods of assessment contained therein has not served the international construction engineering community particularly well. This
issue would become more noticeable when environmental engineers are working across international boundaries. What is required as a
rationalization of these LCA methodologies is an internationally recognized “best practice” to provide reliable predictions or assess-
ments of the climate impacts of CLT buildings.
Signicant uncertainties and challenges do still exist in the assessment of the life cycle carbon footprint of CLT buildings. These
include treatments of biogenic carbon, service-life predictions, maintenance/repair assumptions, accounting for temporal dynamics of
GHG ows, and end-of-life treatment of wooden materials. Further research is necessary in these topics to explore how the carbon
footprint of CLT building systems could be further optimized in a complete life cycle perspective. This will enable the wider promotion
of climate-efcient multi-story timber buildings and help increase the competitiveness of CLT as a construction material. Currently,
most LCA studies concerning the carbon footprint of CLT buildings are mainly based on cradle-to-gate data provided by manufacturers
and utilize simplied assumptions for the impacts of service-life and end-of-life stages. Accurate characterization of the service-life and
end-of-life stages is crucial to develop reliable carbon footprint assessments for CLT buildings that account for the entire life cycle. This
in turn provides a better understanding of the climate implications of CLT buildings, which is needed to further reduce the GHG
emissions associated with them.
Future research is encouraged for further in-depth LCA analyses that not only involve CLT production process data but also a
comprehensive consideration of concrete carbonation and biogenic carbon. The new knowledge, generated from such in-depth ana-
lyses can make a signicant contribution to the decision-making process to select structural building materials, especially when in-
tegrated within a framework to assess the environmental performance of mass timber construction. Finally, this paper highlights the
signicance of the interaction between the state-of-the-practice structural engineering solutions and life cycle assessment. Such
synergy, especially when implemented in the design stage, can help improve the sustainability performance and reduce the carbon
footprint of CLT buildings.
Funding
This research work was funded by the Knowledge Foundation through the project ‘Improving the competitive advantage of CLT-
based building systems through engineering design and reduced carbon footprint’ [20190026].
Declaration of competing interest
The authors declare that they have no known competing nancial interests or personal relationships that could have appeared to
inuence the work reported in this paper.
References
[1] Intergovernmental Panel on Climate Change (IPCC), Climate Change 2014: Mitigation of Climate Change, 2014, https://doi.org/10.1017/
cbo9781107415416.
[2] UNEP, Global Status Report for Buildings and Construction: towards a Zero-Emission, Efcient and Resilient Buildings and Construction, Global Status Report,
2020, pp. 20–24, 2020, www.iea.org.
[3] C.A. Horowitz, Paris agreement, Int. Leg. Mater. 55 (2016) 740–755, https://doi.org/10.1017/S0020782900004253.
[4] IEA, Global, Energy Review 2021, 2021. Paris, https://www.iea.org/reports/global-energy-review-2021.
[5] F. Preston, J. Lehne, Making Concrete Change Innovation in Low-Carbon Cement and Concrete, 2018. www.chathamhouse.org.
[6] N. Ahmed, M. Abdel-Hamid, M.M. Abd El-Razik, K.M. El-Dash, Impact of sustainable design in the construction sector on climate change, Ain Shams Eng. J. 12
(2021) 1375–1383, https://doi.org/10.1016/j.asej.2020.11.002.
[7] World Green Building Council. https://www.worldgbc.org/, 2021.
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
15
[8] U.Y.A. Tettey, A. Dodoo, L. Gustavsson, Carbon balances for a low energy apartment building with different structural frame materials, Energy Proc. 158
(2019) 4254–4261, https://doi.org/10.1016/j.egypro.2019.01.801.
[9] A. Zeitz, C.T. Grifn, P. Dusicka, Comparing the embodied carbon and energy of a mass timber structure system to typical steel and concrete alternatives for
parking garages, Energy Build. 199 (2019) 126–133, https://doi.org/10.1016/j.enbuild.2019.06.047.
[10] D. Satola, M. R¨
ock, A. Houlihan-Wiberg, A. Gustavsen, Life cycle GHG emissions of residential buildings in humid subtropical and tropical climates: systematic
review and analysis, Buildings 11 (2021) 1–36, https://doi.org/10.3390/buildings11010006.
[11] A. Kylili, P.A. Fokaides, Policy trends for the sustainability assessment of construction materials: a review, Sustain. Cities Soc. 35 (2017) 280–288, https://doi.
org/10.1016/j.scs.2017.08.013.
[12] F. Pacheco-Torgal, J.A. Labrincha, The future of construction materials research and the seventh un Millennium Development Goal: a few insights, Construct.
Build. Mater. 40 (2013) 729–737, https://doi.org/10.1016/j.conbuildmat.2012.11.007.
[13] G. Habert, S.A. Miller, V.M. John, J.L. Provis, A. Favier, A. Horvath, K.L. Scrivener, Environmental impacts and decarbonization strategies in the cement and
concrete industries, Nat. Rev. Earth Environ. 1 (2020) 559–573, https://doi.org/10.1038/s43017-020-0093-3.
[14] IEA, Iron and Steel, 2021. Paris, https://www.iea.org/reports/iron-and-steel.
[15] C. Hoffmann, M. Van Hoey, B. Zeumer, Decarbonization Challenge for Steel, McKinsey & Company, 2020, p. 12. https://www.mckinsey.com/~/media/
McKinsey/Industries/Metals and Mining/Our Insights/Decarbonization challenge for steel/Decarbonization-challenge-for-steel.pdf.
[16] Concrete needs to lose its colossal carbon footprint, Nature 597 (2021) 593–594, https://doi.org/10.1038/d41586-021-02612-5.
[17] A. Dodoo, L. Gustavsson, R. Sathre, Carbon implications of end-of-life management of building materials, Resour. Conserv. Recycl. 53 (2009) 276–286,
https://doi.org/10.1016/j.resconrec.2008.12.007.
[18] C.A.S. Hill, The environmental consequences concerning the use of timber in the built environment, Front. Built Environ. 5 (2019), https://doi.org/10.3389/
fbuil.2019.00129.
[19] D. Pe˜
naloza, M. Erlandsson, J. Berlin, M. Wålinder, A. Falk, Future scenarios for climate mitigation of new construction in Sweden: effects of different
technological pathways, J. Clean. Prod. 187 (2018) 1025–1035, https://doi.org/10.1016/j.jclepro.2018.03.285.
[20] O. Espinoza, V.R. Trujillo, M.F.L. Mallo, U. Buehlmann, Cross-laminated timber: status and research needs in Europe, Bioresources 11 (2016) 281–295.
[21] L. Muszynski, E. Hansen, S. Fernando, G. Schwarzmann, J. Rainer, Insights into the global cross-laminated timber industry, Bioprod. Bus. 2 (2017) 77–92,
https://doi.org/10.22382/bpb-2017-008.
[22] United Nations Publications, Forest Products Annual Market Review 2017–2018, 2019.
[23] T. Luthi, Mass Timber Design Manual, 2021. www.thinkwood.com.
[24] Research Institutes of Sweden (RISE), The CLT Handbook, 2019.
[25] M.F. Laguarda Mallo, O. Espinoza, Awareness, perceptions and willingness to adopt Cross-Laminated Timber by the architecture community in the United
States, J. Clean. Prod. 94 (2015) 198–210, https://doi.org/10.1016/j.jclepro.2015.01.090.
[26] Tallwood Design Institute, Cross-Laminated Timber: Introduction and Background (Info Sheet), 2019. www.tallwoodinstitute.org.
[27] G. Churkina, C.P.O.R. Alan Organschi, A. Ruff, K. Vinke, Z. Liu, B.K. Reck, T.E. Graedel, H.J. Schellnhuber, Buildings as a global carbon sink, Nat. Sustain.
(2020), https://doi.org/10.1038/s41893-019-0462-4. https://www.nature.com/articles/s41893-019-0462-4.
[28] S. Lehmann, Sustainable construction for urban inll development using engineered massive wood panel systems, Sustainability 4 (2012) 2707–2742, https://
doi.org/10.3390/su4102707.
[29] S. John, B. Nebel, N. Perez, A. Buchanan, Environmental Impacts of Multi-Storey Buildings Using Different Construction Materials, 2009. https://ir.canterbury.
ac.nz/handle/10092/8359.
[30] G.P. Hammond, C.I. Jones, Embodied energy and carbon in construction materials, Proc. Inst. Civ. Eng.: Energy 161 (2008) 87–98, https://doi.org/10.1680/
ener.2008.161.2.87.
[31] Y.J. Chen, Comparison of Environmental Performance of a Five-Storey Building Built with Cross-Laminated Timber and Concrete - Reported to: Sustainable
Building Science Program, Department of Wood Science, University of British Columbia, Vancouver, BC, Canada, 2012. https://sbsp.sites.olt.ubc.ca/les/
2012/07/SBSP-report-Jessie-Chen.pdf.
[32] Y. Dong, X. Cui, X. Yin, Y. Chen, H. Guo, Assessment of energy saving potential by replacing conventional materials by cross laminated timber (CLT)-A case
study of ofce buildings in China, Appl. Sci. (2019) 9, https://doi.org/10.3390/app9050858.
[33] R.N. Passarelli, The environmental impact of reused CLT panels: study of a single-storey commercial building in Japan, in: WCTE 2018 - World Conference on
Timber Engineering, 2018.
[34] H. Gu, S. Liang, F. Pierobon, M. Puettmann, I. Ganguly, C. Chen, R. Pasternack, M. Wishnie, S. Jones, I. Maples, Mass timber building life cycle assessment
methodology for the U.S. regional case studies, Sustainability 13 (2021), 14034, https://doi.org/10.3390/su132414034.
[35] C.V. Silva, J.M. Branco, P.B. Lourenço, A Project Contribution to the Development of Sustainable Multi-Storey Timber Buildings, Portugal SB13 - Contribution
of Sustainable Building to Meet EU 20-20-20 Targets, 2013, pp. 379–386. https://repositorium.sdum.uminho.pt/handle/1822/26947.
[36] K. Jones, J. Stegemann, J. Sykes, P. Winslow, Adoption of unconventional approaches in construction: the case of cross-laminated timber, Construct. Build.
Mater. 125 (2016) 690–702, https://doi.org/10.1016/j.conbuildmat.2016.08.088.
[37] J.W.G. Van De Kuilen, A. Ceccotti, Z. Xia, M. He, Very tall wooden buildings with cross laminated timber, Procedia Eng. 14 (2011) 1621–1628, https://doi.
org/10.1016/j.proeng.2011.07.204.
[38] A. Frangi, M. Fontana, E. Hugi, R. Jübstl, Experimental analysis of cross-laminated timber panels in re, Fire Saf. J. 44 (2009) 1078–1087, https://doi.org/
10.1016/j.resaf.2009.07.007.
[39] V. Hristovski, B. Dujic, M. Stojmanovska, V. Mircevska, Full-scale shaking-table tests of XLam panel systems and numerical verication: specimen 1, J. Struct.
Eng. 139 (2013), https://doi.org/10.1061/(asce)st.1943-541x.0000754, 2010–2018.
[40] H.B. Skogstad, L. Gullbrekken, K. Nore, Air Leakages through Cross Laminated Timber (CLT) Constructions, NSB 2011 9th Nordic Symposium on Building
Physics, 2011, pp. 89–96.
[41] ISO, ISO 14040, 2006 Environmental Management - Life Cycle Assessment - Principles and Framework, second ed., International Organization for
Standardization, Geneva, Switzerland, 2006. https://www.iso.org/standard/37456.html.
[42] R. Anex, R. Lifset, Life cycle assessment, J. Ind. Ecol. 18 (2014) 321–323, https://doi.org/10.1111/jiec.12157.
[43] European Committee for Standardization, EN 15978, Sustainability of Construction Works - Assessment of Environmental Performance of Buildings -
Calculation Method, 2011, 2011.
[44] J.H. Andersen, N.L. Rasmussen, M.W. Ryberg, Comparative life cycle assessment of cross laminated timber building and concrete building with special focus on
biogenic carbon, Energy Build. 254 (2022), 111604, https://doi.org/10.1016/j.enbuild.2021.111604.
[45] A. Dodoo, T. Nguyen, M. Dorn, A. Olsson, T.K. Bader, Exploring the synergy between structural engineering design solutions and life cycle carbon footprint of
cross-laminated timber in multi-storey buildings, Wood Mater. Sci. Eng. (2021), https://doi.org/10.1080/17480272.2021.1974937.
[46] G. Felmer, R. Morales-Vera, R. Astroza, I. Gonz´
alez, M. Puettmann, M. Wishnie, A lifecycle assessment of a low-energy mass-timber building and mainstream
concrete alternative in Central Chile, Sustainability 14 (2022) 1249, https://doi.org/10.3390/su14031249.
[47] K. Allan, A.R. Phillips, Comparative cradle-to-grave life cycle assessment of low and mid-rise mass timber buildings with equivalent structural steel
alternatives, Sustainability 13 (2021) 3401, https://doi.org/10.3390/su13063401.
[48] A. Dodoo, L. Gustavsson, R. Sathre, Lifecycle carbon implications of conventional and low-energy multi-storey timber building systems, Energy Build. 82
(2014) 194–210, https://doi.org/10.1016/j.enbuild.2014.06.034.
[49] S. Liang, H. Gu, R. Bergman, S.S. Kelley, Comparative life-cycle assessment of a mass timber building and concrete alternative, Wood Fiber Sci. 52 (2020)
217–229, https://doi.org/10.22382/wfs-2020-019.
[50] J.L. Skullestad, R.A. Bohne, J. Lohne, High-rise timber buildings as a climate change mitigation measure – a comparative LCA of structural system Alternatives,
Energy Proc. 96 (2016) 112–123, https://doi.org/10.1016/j.egypro.2016.09.112.
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
16
[51] H. Guo, Y. Liu, Y. Meng, H. Huang, C. Sun, Y. Shao, A Comparison of the energy saving and carbon reduction performance between reinforced concrete and
cross-laminated timber structures in residential buildings in the severe cold region of China, Sustainability 9 (2017) 1426, https://doi.org/10.3390/
su9081426.
[52] Y. Liu, H. Guo, C. Sun, W.S. Chang, Assessing cross laminated timber (CLT) as an alternative material for mid-rise residential buildings in cold regions in China-
A life-cycle assessment approach, Sustainability 8 (2016) 1047, https://doi.org/10.3390/su8101047.
[53] M.W. Ryberg, P.K. Ohms, E. Møller, T. Lading, Comparative life cycle assessment of four buildings in Greenland, Build. Environ. 204 (2021), 108130, https://
doi.org/10.1016/j.buildenv.2021.108130.
[54] F. Pierobon, M. Huang, K. Simonen, I. Ganguly, Environmental benets of using hybrid CLT structure in midrise non-residential construction: an LCA based
comparative case study in the U.S. Pacic Northwest, J. Build. Eng. 26 (2019), 100862, https://doi.org/10.1016/j.jobe.2019.100862.
[55] M. Puettmann, F. Pierobon, I. Ganguly, H. Gu, C. Chen, S. Liang, S. Jones, I. Maples, M. Wishnie, Comparative LCAs of conventional and mass timber buildings
in regions with potential for mass timber penetration, Sustainability 13 (2021), 13987, https://doi.org/10.3390/su132413987.
[56] B. Durlinger, E. Crossin, J. Wong, Life Cycle Assessment of a Cross Laminated Timber Building, 2013. http://www.fwpa.com.au/resources/market-access/230-
life-cycle-assessment-of-a-cross-laminated-timber-building.html.
[57] D. Pe˜
naloza, M. Erlandsson, A. Falk, Exploring the climate impact effects of increased use of bio-based materials in buildings, Construct. Build. Mater. 125
(2016) 219–226, https://doi.org/10.1016/j.conbuildmat.2016.08.041.
[58] S.H. Teh, T. Wiedmann, J. Schinabeck, S. Moore, Replacement scenarios for construction materials based on economy-wide hybrid LCA, Procedia Eng. 180
(2017) 179–189, https://doi.org/10.1016/j.proeng.2017.04.177.
[59] N. Rajagopalan, S.S. Kelley, Evaluating sustainability of buildings using multi-Attribute decision tools, For. Prod. J. 67 (2017) 179–189, https://doi.org/
10.13073/FPJ-D-16-00028.
[60] X. Cadorel, R. Crawford, Life cycle analysis of cross laminated timber in buildings: a review, engaging architectural science: meeting the challenges of higher
density: 52nd International Conference of the Architectural Science Association, 2018, pp. 107–114, 15978 (2019).
[61] B. Grann, A Comparative Life Cycle Assessment of Two Multistory Residential Buildings: Cross-Laminated Timber vs. Concrete Slab and Column with Light
Gauge Steel Walls, 2013. Vancouver, BC, Canada.
[62] N. Lolli, S.M. Fufa, M. Kjendseth Wiik, An assessment of greenhouse gas emissions from CLT and glulam in two residential nearly zero energy buildings, Wood
Mater. Sci. Eng. 14 (2019) 342–354, https://doi.org/10.1080/17480272.2019.1655792.
[63] S. Liang, H. Gu, R. Bergman, Environmental life-cycle assessment and life-cycle cost analysis of a high-rise mass timber building: a case study in pacic
Northwestern United States, Sustainability 13 (2021) 7831, https://doi.org/10.3390/su13147831.
[64] A. Kwok, H. Zalusky, M.I. Rivera, L. Rasmussen, H. McKay, Whole Building Life Cycle Assessment of a Mass Timber Multifamily Residential Structure -
Including & Excluding Biogenic Carbon, 2019. https://tallwoodinstitute.org/sites/twi/les/Carbon 12_RV5.pdf.
[65] A.B. Robertson, F.C.F. Lam, R.J. Cole, A comparative cradle-to-gate life cycle assessment of mid-rise ofce building construction alternatives: laminated timber
or reinforced concrete, Buildings 2 (2012) 245–270, https://doi.org/10.3390/buildings2030245.
[66] A.T. Balasbaneh, W. Sher, Comparative sustainability evaluation of two engineered wood-based construction materials: life cycle analysis of CLT versus GLT,
Build. Environ. 204 (2021), 108112, https://doi.org/10.1016/j.buildenv.2021.108112.
[67] H.J. Darby, A.a. Elmualim, F. Kelly, A case study to investigate the life cycle carbon emissions and carbon storage capacity of a cross laminated timber, multi-
storey residential building, in: Proceedings of the World Sustainable Building Conference, 2013, pp. 1–8.
[68] F. Dolezal, I. Dornigg, M. Wurm, H. Figl, Overview and main ndings for the Austrian case study, Sustainability 13 (2021) 7584, https://doi.org/10.3390/
su13147584.
[69] A. Jayalath, S. Navaratnam, T. Ngo, P. Mendis, N. Hewson, L. Aye, Life cycle performance of Cross Laminated Timber mid-rise residential buildings in
Australia, Energy Build. 223 (2020), 110091, https://doi.org/10.1016/j.enbuild.2020.110091.
[70] C.X. Chen, F. Pierobon, S. Jones, I. Maples, Y. Gong, I. Ganguly, Comparative life cycle assessment of mass timber and concrete residential buildings: a case
study in China, Sustainability 14 (2022) 144, https://doi.org/10.3390/su14010144.
[71] J. Jesson, L. Matheson, F. Lacey, Doing Your Literature Review: Traditional and Systematic Techniques, First Edit, SAGE Publications Ltd, London, UK, 2011.
https://uk.sagepub.com/en-gb/eur/doing-your-literature-review/book233413#description.
[72] Department of Energy and Climate Change, UK energy statistics: statistical press release - March 2013. https://www.gov.uk/government/news/uk-energy-
statistics-statistical-press-release, 2013.
[73] F.N. Rasmussen, C.E. Andersen, A. Wittchen, R.N. Hansen, H. Birgisd´
ottir, Environmental product declarations of structural wood: a review of impacts and
potential pitfalls for practice, Buildings 11 (2021) 362, https://doi.org/10.3390/buildings11080362.
[74] S¨
odra Skogs¨
agarna ekonomisk f¨
orening, Environmental Product Declaration for CLT (Cross Laminated Timber), 2020. https://www.epd-norge.no/getle.php/
1316508-1607949248/EPDer/Byggevarer/Heltreprodukter/NEPD-2587-1314_CLT–Cross-Laminated-Timber-.pdf.
[75] Stora Enso Wood Products, Environmental Product Declaration for CLT by Stora Enso, 2017. https://www.lilleheden.dk/Files/Files/Produkter/CLT/EPD - CLT
by Stora Enso 2017.pdf.
[76] KLH Massivholz GmbH, Environmental Product Declaration for KLH Cross-Laminated Timber Panels, 2019. https://www.klh.at/wp-content/uploads/2019/
12/environmental-product-declaration.pdf.
[77] Binderholz Bausysteme GmbH, Environmental Product Declaration for CLT (Cross Laminated Timber), 2019. https://www.binderholz.com/leadmin/user_
upload/pdf/approvals-certications/EPD_binderholz_CLT_BBS.pdf.
[78] Egoin, Environmental Product Declaration for EGO-CLT (Cross Laminated Timber) Wood Panel, 2018. https://portal.environdec.com/api/api/v1/
EPDLibrary/Files/7959eb60-06e1-4907-8b7d-a8dc7490d811/Data.
[79] XLam Australia, Environmental Product Declaration for XLam CLT Panel, 2021. https://portal.environdec.com/api/api/v1/EPDLibrary/Files/ac090c77-e5f8-
427b-0316-08d8f01e26c9/Data.
[80] A.G. Schilliger Holz, Environmental Product Declaration for Schilliger Cross Laminated Timber, 2020. https://www.schilliger.ch/wp-content/uploads/2020/
09/2020.06.23-_-EPD-cross-laminated-timber-GFP-English-_-02.09.2020.pdf.
[81] N.A. SmartLam, Environmental Product Declaration for SmartLam Cross Laminated Timber in Alabama, US, 2020. https://www.smartlam.com/wp-content/
uploads/2021/01/SCS-EPD-06682_SmartLam_Dothan_012221.pdf%0A.
[82] N.A. SmartLam, Environmental Product Declaration for SmartLam Cross Laminated Timber in Columbia Falls, Montana, US, 2021. https://www.smartlam.
com/wp-content/uploads/2021/01/SCS-EPD-06681_SmartLam_C-Falls_012221.pdf%0A.
[83] Nordic X-Lam, Environmental Product Declaration for Nordic X-Lam Cross Laminated Timber, 2018. https://www.nordic.ca/data/les/datasheet/le/EPD_
Nordic_X-Lam.pdf.
[84] L.P. Structurlam Products, Environmental Product Declaration for Cross-Laminated Timber Manufactured at Structurlam, 2018. https://www.structurlam.
com/wp-content/uploads/2016/10/Structurlam-R-EPD.CrossLamCLT-APA-SLP-2013.pdf.
[85] R.H. Crawford, X. Cadorel, A framework for assessing the environmental benets of mass timber construction, Procedia Eng. 196 (2017) 838–846, https://doi.
org/10.1016/j.proeng.2017.08.015.
[86] I. Zabalza Bribi´
an, A. Aranda Us´
on, S. Scarpellini, Life cycle assessment in buildings: state-of-the-art and simplied LCA methodology as a complement for
building certication, Build. Environ. 44 (2009) 2510–2520, https://doi.org/10.1016/j.buildenv.2009.05.001.
[87] A. Dodoo, L. Muszy´
nski, End-of-Life management of cross laminated timber multi- storey buildings : a case for designing for post-use material recovery and
environmental benets, in: Proceedings of the World Conference on Timber Engineering (WCTE) 2021, August 09 - 12, World Conference on Timber
Engineering (WCTE), Santiago, Chile, 2021.
[88] A. Kwok, H. Zalusky, M.I. Rivera, L. Rasmussen, H. McKay, Seeing the forest and the trees: environmental impacts of cross-laminated timber, Technology
Architecture and Design, 4, 2020, pp. 144–150, https://doi.org/10.1080/24751448.2020.1804754.
A. Younis and A. Dodoo
Journal of Building Engineering 52 (2022) 104482
17
[89] C.E. Andersen, F.N. Rasmussen, G. Habert, H. Birgisd´
ottir, Embodied GHG emissions of wooden buildings—challenges of biogenic carbon accounting in
current LCA methods, Front. Built Environ. 7 (2021), 729096, https://doi.org/10.3389/fbuil.2021.729096.
[90] D. Panojevic, E. Svensson, A Life Cycle Assessment of the Environmental Impacts of Cross-Laminated Timber, Lund University, 2019. www.bekon.lth.se.
[91] A. Hafner, S. Ott, S. Winter, Recycling and End-Of-Life Scenarios for Timber Structures, RILEM Bookseries, 2014, pp. 89–98, https://doi.org/10.1007/978-94-
007-7811-5_8.
[92] M. Norouzi, M. Ch`
afer, L.F. Cabeza, L. Jim´
enez, D. Boer, Circular economy in the building and construction sector: a scientic evolution analysis, J. Build. Eng.
44 (2021), 102704, https://doi.org/10.1016/j.jobe.2021.102704.
[93] C.K. Anand, B. Amor, Recent developments, future challenges and new research directions in LCA of buildings: a critical review, Renew. Sustain. Energy Rev.
67 (2017) 408–416, https://doi.org/10.1016/j.rser.2016.09.058.
[94] A. S¨
ayn¨
ajoki, J. Heinonen, J.M. Junnonen, S. Junnila, Input–output and process LCAs in the building sector: are the results compatible with each other? Carbon
Manag. 8 (2017) 155–166, https://doi.org/10.1080/17583004.2017.1309200.
[95] G. Finnveden, Å. Moberg, Environmental systems analysis tools – an overview, J. Clean. Prod. 13 (2005) 1165–1173, https://doi.org/10.1016/j.
jclepro.2004.06.004.
[96] K. Lan, S.S. Kelley, P. Nepal, Y. Yao, Dynamic life cycle carbon and energy analysis for cross-laminated timber in the Southeastern United States, Environ. Res.
Lett. 15 (2019), 124036, https://doi.org/10.1088/1748-9326/abc5e6.
[97] A. Levasseur, P. Lesage, M. Margni, L. Deschˇ
enes, R. Samson, Considering time in LCA: dynamic LCA and its application to global warming impact assessments,
Environ. Sci. Technol. 44 (2010) 3169–3174, https://doi.org/10.1021/es9030003.
[98] M. Head, A. Levasseur, R. Beauregard, M. Margni, Dynamic greenhouse gas life cycle inventory and impact proles of wood used in Canadian buildings, Build.
Environ. 173 (2020), 106751, https://doi.org/10.1016/j.buildenv.2020.106751.
[99] M. Head, M. Magnan, W.A. Kurz, A. Levasseur, R. Beauregard, M. Margni, Temporally-differentiated biogenic carbon accounting of wood building product life
cycles, SN Appl. Sci. 3 (2021) 62, https://doi.org/10.1007/s42452-020-03979-2.
[100] S. Su, C. Zhu, X. Li, Q. Wang, Dynamic global warming impact assessment integrating temporal variables: application to a residential building in China,
Environ. Impact Assess. Rev. 88 (2021), 106568, https://doi.org/10.1016/j.eiar.2021.106568.
[101] V¨
axj¨
o Kommun, V¨
axj¨
o Station and Town Hall Project, 2021. https://www.skanska.se/en-us/our-offer/our-projects/255699/Vaxjo-station-and-town-hall%2C-
Vaxjo/.
A. Younis and A. Dodoo
