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Building on the Paris Agreement: making the case for embodied carbon intensity targets in construction


Abstract and Figures

Progressive clients are targeting embodied carbon reduction through the introduction of carbon intensity targets (CITs). CITs challenge design teams to deliver buildings with supply chain carbon emissions below a set level per functional unit. Despite CITs acting as catalysts for innovation, there are few drivers for their use and substantial variations in their implementation. There is also no means for ensuring consistency between project CITs and national mitigation targets, nor a mechanism for ratcheting up ambitions as anticipated by the Paris Agreement on climate change. This paper discusses these concerns and suggests how CITs could in future be determined, implemented and enforced.
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Jannik Giesekam1, Danielle Densley-Tingley2, and John Barrett1
1 Sustainability Research Institute, School of Earth and Environment, University of Leeds,
Leeds, UK.
2 Department of Civil and Structural Engineering, University of Sheffield
Progressive clients are targeting embodied carbon
reduction through the introduction of carbon intensity
targets (CITs). CITs challenge design teams to deliver
buildings with supply chain carbon emissions below a
set level per functional unit. Despite CITs acting as
catalysts for innovation, there are few drivers for their
use and substantial variations in their implementation.
There is also no means for ensuring consistency
between project CITs and national mitigation targets,
nor a mechanism for ratcheting up ambitions as
anticipated by the Paris Agreement on climate change.
This paper discusses these concerns and suggests how
CITs could in future be determined, implemented and
The UK’s principal construction strategy,
Construction 2025, sets a target of halving greenhouse
gas (GHG) emissions from the built environment over
the coming decade (HM Government, 2013). This is
with a view to achieving longer term reductions
consistent with the national target of an 80% reduction
in GHG emissions by 2050 compared with 1990 levels
(Climate Change Act, 2008). The Green Construction
Board’s Low Carbon Routemap for the Built
Environment set out the steps required to achieve this
and called for an increased focus upon embodied
carbon mitigation (GCB, 2013). A recent update on
Routemap progress found a widening gap to sector
targets and restated the need to achieve reductions in
embodied carbon in addition to operational emissions
(Steele et al., 2015). The update recommended the
introduction of embodied carbon intensity targets
(CITs). CITs challenge design teams to deliver
buildings with supply chain carbon emissions below a
set level per functional unit and can act as a significant
driver of innovation. However, the approach by which
CITs should be determined, implemented and
enforced remains unclear. This paper addresses a
number of outstanding questions on this topic.
The first two sections briefly outline the embodied
GHG emissions associated with UK construction
activity and current carbon assessment practice. The
third section highlights a number of inconsistencies in
the current determination of CITs. The fourth section
proposes measures to improve the future
determination of CITs, and the fifth section considers
the corresponding drivers for their use. The final
section draws together some outstanding questions
that should be the subject of future research.
Over recent years, embodied carbon emissions in the
construction supply chain have typically accounted for
a quarter of total GHG emissions from the built
environment and are comparable in magnitude to
annual tailpipe emissions from all cars on UK roads
(see Figure 1). Analysis of their distribution reveals
that the bulk of emissions are associated with material
production and a significant proportion occur overseas
(see Figure 2). This restricts the scope of policies
addressed at UK and European material producers
(such as the EU Emissions Trading Scheme) to
achieve substantial emission reductions. With the
Government’s central estimates suggesting that the
UK population will increase by 14 million by 2050
(ONS, 2011), demand for housing and infrastructure
is expected to markedly increase. DCLG projects an
additional 3.6 million households will require new
homes by 2030 (DCLG, 2015); meanwhile the
National Infrastructure Delivery Plan 2016-2021 sets
out projected infrastructure investments of £483
billion (IPA, 2016b). This increased construction
output is likely to incur signficant embodied carbon
emissions. Scenario analysis with the UK Buildings
and Infrastructure Embodied Carbon model (UK
BIEC), developed at the University of Leeds, reveals
that anticipated reductions in the carbon intensity of
the electricity supply are unlikely to offset the impacts
of this increased construction activity (Giesekam et al,
In Press) (see Figure 3). Consequently, sizeable
reductions in embodied carbon intensity will need to
be achieved through design changes across projects of
all types if the targets set out in the GCB Routemap
are to be achieved whilst meeting anticipated increases
in demand. The required reductions in carbon intensity
will be even greater if carbon capture and storage
technology continues to be uneconomic for material
Embodied carbon assessment has been commonplace
in certain sectors of the industry, such as water and
sewerage, for some time (Keil et al., 2013). Though,
in recent years there has been increasing interest
throughout the industry, reflected in a number of well
attended cross industry events (UKGBC, 2014;
UKGBC, 2015b). This proliferation of embodied
carbon assessment has been supported by improved
guidance for designers and clients (e.g. RICS, 2012;
Clark, 2013; UKGBC, 2015c), and development of
resources that facilitate project-level benchmarking
(RICS, 2012; WRAP & UKGBC, 2014). The recent
launch of PAS 2080: Carbon Management in
Infrastructure seeks to instate a common language and
carbon management process for the entire
infrastructure value chain. A growing number of
clients are also targeting carbon reduction in project
briefs through CITs. At the time of writing 53
organisations had signed up to the Infrastructure
Carbon Review and over 30 companies had introduced
commitments relating to embodied carbon assessment
or reduction in buildings.
One of the principal objectives of the UK Government
Construction Strategy 2016-2020 is to “enable and
drive whole-life approaches to cost and carbon
reduction (IPA, 2016a). This includes a specific
commitment (Objective 3.6) to “develop data
requirements and benchmarks for measurement of
whole-life cost and whole-life carbon (embodied and
operational)” with a view to ultimately forming
“recommendations for a future approach”. Though
regulators, such as Ofwat, have begun to include
reporting requirements on some infrastructure
projects, similar requirements have yet to be put in
place for buildings. However, precedents have been
set elsewhere. For instance, the Netherlands
introduced embodied carbon reporting requirements
for residential and office developments over 100m2 in
2013 and LCCAs have been compulsory on publicly
funded German buildings since 2008. The European
Commission has also proposed including embodied
carbon as part of a suite of common indicators for
assessing the environmental performance of buildings
(EC, 2014).
Assessment of embodied carbon can be conducted at
different stages of the project development. Best
practice is to track embodied carbon throughout the
project from an initial design phase estimate through
procurement and construction to a final assessment
upon project completion. For a practical example of
this see the publicly available embodied carbon
tracking report from British Land’s 5 Broadgate
development (Arup, 2014). Whilst this represents best
practice, in most cases where embodied carbon is fully
assessed by the UK industry it tends to be only after
the building has been constructed (Moncaster &
Symons, 2013). Despite the introduction of BS EN
15978 in 2011, approaches to assessment are still far
from standardised with many practitioners using
different system boundaries, assumed life times and so
on (Gavotsis & Moncaster, 2015). Consequently the
bulk of current research on embodied carbon focusses
on standardising assessment procedures or developing
integrated tools to support real time assessment.
Though some of this research has called for additional
drivers, such as regulation (Gavotsis & Moncaster,
2015; Giesekam et al., 2016), little work has been
done to develop robust policy proposals (Battle,
2014), or understand how CITs should best be
determined, implemented and enforced.
Though the use of CITs so far has been sporadic,
examples have demonstrated that CITs can be an
effective driver of innovation. For instance, the
introduction of CITs in Anglian Water has motivated
major changes in established design and construction
practice and the use of alternative materials. CITs
supported the achievement of a 54% reduction in
embodied carbon by 2014 against the company’s 2010
baseline (Anglian Water, 2015). Comparable
reductions have been achieved on some building
projects, such as the University of East Anglia
Enterprise Centre (Pearson, 2015). On this project the
client set the design team a whole life carbon target of
500 kgCO2/m2 emitted over the anticipated 100-year
life of the building. This motivated radical changes in
design, including extensive use of bio-based materials
(>70%), and resulted in an achieved footprint of 440
kgCO2/m2 around a quarter of the typical footprint
of an equivalent university building. The
Infrastructure Carbon Review has strongly advocated
that this innovation, reduced material and energy use
also yields cost savings (HM Treasury, 2013). Setting
assessment or reduction targets can also encourage
good on site practice and skills development amongst
contractors (Davies et al., 2014). Therefore, at a
project level, there are clear benefits associated with
the introduction of CITs.
The current process of determining boundaries and
values for building CITs varies widely between clients
and projects. Some CITs apply only to embodied
carbon, others target whole life carbon. The specific
target boundaries also vary, with some CITs
encompassing all embodied emissions, others only
targetting key materials or ‘carbon hot-spots’. For
example, the British Land 2014 sustainability brief
required that embodied carbon in “concrete, steel,
rebar, aluminium and glass” be reduced by 10%
compared to the concept design (British Land, 2014).
In comparison Marks and Spencer target the carbon
hotspots in walls, ceilings and floors (Marks and
Spencer, 2014). Whereas the Crown Estate adopt a
simple headline project target in kgCO2/m2/yr (The
Crown Estate, 2013). Where headline targets such as
this are adopted the baseline can also be determined in
different ways. Some baselines are determined against
an initial project design. Others are against a notional
reference building. Some are compared with past
projects the client has been involved in. Others are
determined from comparison with similar buildings or
benchmark data from the WRAP database and similar
sources (RICS, 2012; WRAP & UKGBC, 2014). The
desired reduction against this baseline is also often
determined in an arbitrary manner. Commonly a
simple percentage reduction is set based on the clients
intuition or past experience. In some cases a specific
round value is selected. In other cases, highly specific
targets have been instated through a desire to offset
operational emissions. For instance, on the Westgate
Oxford development a CIT for embodied emissions
reduction against the RIBA Stage C design was set
equal to the anticipated regulated operational carbon
over the building life.
Should these differences be considered as welcome
variety or as frustrating inconsistencies? It can
reasonably be argued that for different project types
with different distributions of carbon, adopting
different functional units and assessment boundaries
makes sense. However, this can increase complexity
for project participants and reduce the comparability
of results between projects. Even ignoring these
concerns, the typical relative comparison between one
building design and another allows for benchmarking
but does not indicate if the design’s emissions are
consistent with sectoral or national mitigation targets.
Furthermore, whilst an individual client or design
team is principally concerned with determining an
appropriate CIT for their current project, firms,
educators and product developers must prepare for the
implications of deep long-term reductions. This may
require significant changes in design and construction
practice and the workforce must be skilled
accordingly. This requires an appreciation of how
targets may change over time and the concomitant
changes in materials and design practices.
This discussion highlights a number of problems.
Firstly, how should the approach to setting CITs be
standardised (if at all)? Secondly, how can target
setters ensure consistency with sectoral or national
targets? Thirdly, how should these targets be adjusted
over time in response to changes in international
ambition or developments in other sectors of the
economy? The following section addresses these
questions in turn.
Standardising the approach
An ongoing Innovate UK funded project
‘Implementing Whole Life Carbon In Buildings’
seeks to address a number of outstanding issues in the
standardisation of embodied carbon assessment.
However, in the case of CITs, the priority must be
standardising project practices not assessment
boundaries and methodologies. On different projects,
particular building elements may contribute more or
less to the project total, requiring a more or less
detailed assessment. Accordingly, clients must set CIT
boundaries that encompass the principal sources of
carbon whilst avoiding excessive assessment time and
thus expense. For instance the Embodied Carbon Task
Force propose a common set of boundaries that
encompass product and construction stage emissions
for substructure and superstructure (Battle, 2014).
Irrespective of boundary differences, there are
potential benefits to adopting a more standardised
approach to establishing, introducing and reporting
against project CITs. This could be done by adopting
a common set of project embodied carbon
checkpoints, such as those suggested by the GLA
(2013) and Doran (2014). An example set is presented
in Figure 4 against the 2013 RIBA Plan of Work.
Under such an approach an initial project CIT would
be introduced at RIBA Stage 1. The early introduction
of a target will influence the initial concept design and
ensure low carbon solutions are embedded early in the
project. This high level target could subsequently be
translated into a carbon plan (analogous to a cost plan)
that breaks down the carbon budget by building
elements. Subsequent steps would ensure routine
reporting against the target throughout the project.
Ensuring consistency with sectoral and national
With targets currently set largely on an ad hoc basis
by a selection of clients relative only to a baseline
design or a comparable building, there is no means to
ensure consistency with sector or national mitigation
targets. Firstly, the sample of assessments is too small
to reasonably assess the status quo across the sector.
Secondly, the intermediate link between project level
assessments and aggregate sector emissions is not yet
in place. The form of such a link has been proposed
with the UK BIEC model (Giesekam et al., In Press),
but the available data remains insufficiently granular
to return detailed project targets. Even once such
targets are computed, the best means of
communicating these to the industry has yet to be
One potential form would be the preparation of a
series of common documents, or an online resource,
that compiled headline targets, example carbon plans
and benchmark data for a set of standard building
typologies. This resource would be updated
periodically and adminstered by a respected industry
body, such as the RICS. This would provide clients
with an advised target, consistent with national targets,
which they could choose to use or exceed.
Establishing such a common, central resource would
allow clients to set appropriate targets without
particular expertise in this area, enabling a swifter
propagation of best practice.
Developing a ratchet mechanism
If such a resource was established, periodic updates
could incorporate the impacts of progressive grid
decarbonisation, additional building assessment data,
and adjustments to sector targets based on national
mitigation progress. The introduction of future Carbon
Budgets and any changes in national targets motivated
by the Paris Agreement ratchet mechanism could be
translated into new project targets using the
intermediate model.
In addition to significantly reducing current emissions,
the construction industry must also be prepared to
deliver a large volume of carbon sinks in order to meet
the Paris Agreement goal of achieving a balance
between anthropogenic emissions by sources and
removals by sinks of greenhouse gases in the second
half of this century(United Nations, 2015). The
market for sinks is potentially lucrative given the
anticipated growth in the price of carbon. In the UK
these sinks will likely take the form of increased
forestry, and the resultant wood could in part be used
for construction. The emergence of other bio-based
building materials, such as hemp-lime and modular
straw bale, into mainstream construction may also
contribute to achieving the long-term net zero goal
(MacDougall, 2008). This should be supported by
further development of products incorporating UK
resources such as: CLT from domestic wood species
(Crawford et al., 2015), brettstapel (Smith, 2013) and
novel biocomposites (NetComposites Ltd, 2014). The
potential is sizeable, with one report estimating that
net carbon sequestration of up to 22 MtCO2e could be
achieved by 2050 through policies promoting wood
products alone (Sadler & Robson, 2013).
In addition to addressing concerns with current
practice, the research community must consider the
drivers needed to replicate best practice across the
industry. This will require proposals for long-term
policy and market drivers that ensure widespread
implementation and enforcement of CITs. Let us
consider the critical characteristics of such drivers.
Client led drivers
Clients must be seen to value this issue if CITs are to
be introduced and enforced. Clients can demonstrate
leadership by providing a strong inventive for other
members of the supply chain. For example, the scoring
of tenders based upon sustainability credentials
provides a competitive advantage for designers and
contractors that can deliver embodied carbon
assessment and mitigation. The introduction of shared
targets and rewards in contract documents also
motivates the requisite collaboration and exchange of
ideas across the supply chain. Motivated members of
the client team must also work internally to ensure
organisational buy in. This is critical to ensure CITs
exist beyond the project brief and are reported against
throughout the project.
However, clients cannot be expected to seek out and
develop expertise in this area in the absence of strong
financial or regulatory drivers. Progressive clients
need additional support from the research community
and proactive recommendations from designers and
contractors. Industry institutions must also provide a
better platform for clients to share experiences and
standardise approaches. The development of a
centralised information source containing guidance,
benchmark data and suggested targets (as proposed in
the previous section) could also support engagement
from smaller clients with less organisational capacity.
Were such a central resource to be introduced,
complementary drivers may also be required to
encourage clients to specify CITs beyond the
recommended levels. Potential incentives could be
perceived reputational benefits and positive marketing
opportunities, through facilitating claims such as
completing a ‘2050-ready’ building. Alternately,
competition could be encouraged between firms
through a public league table of carbon commitments.
In the longer term, measures such as extending listed
company emissions reporting to include principal
sources of Scope 3 emissions, could provide a strong
financial driver. Voluntary initiatives that promote
early action also offer clients the opportunity to be
ahead of the curve with regards to any future
In a recent industry survey respondents highlighted
that regulation is potentially the greatest driver of
embodied carbon reduction (Giesekam et al., 2016).
However, if regulations promoting embodied carbon
measurement or reduction are to emerge a number of
issues must first be resolved. These principally
concern ownership, advocacy, narrative development,
and evidence gathering.
Ownership and advocacy
No Government department has sole ownership of this
issue. Whilst DECC notionally formulates plans for
climate mitigation, BIS are tasked with determining
industrial strategy. Policies affecting new build are
principally set by DCLG and local authorities.
Meanwhile numerous other departments, such as the
Department for Transport and DEFRA, determine the
overall demand for new buildings and infrastructure
through their investment decisions. In addition to the
present lack of cross-departmental strategy and
collaboration, even within departments it is difficult to
identify individuals whose remit could sensibly
include embodied carbon. Consequently, for
advocates within the industry lobbying for action it is
difficult to distinguish appropriate points of influence.
Embodied carbon has yet to garner serious
consideration within mainstream policy circles and, in
many ways, remains an issue without a home.
Similarly, within the industry there are few suitable
organisations who can take effective ownership of this
issue. Many of the actions advocates propose to drive
forward this agenda, such as establishing and
maintaining a common UK LCI and EPD database,
require investment and long term commitments to
maintenance from an impartial and respected source.
This source must be willing to demonstrate leadership
and be seen to represent firms spanning the full supply
chain. Recent movements from professional
institutions such as the RICS, and membership
organisations such as the UKGBC, have been positive
but there remain few commercial advantages to
demonstrating leadership on this issue at the present
time. If progress is to be made, it will require not just
leadership from a handful of high profile firms but
sustained support and coordination from a cross
industry group. One potential solution could be the
establishment of a formal body, such as a UKGBC
Task Group. In the meantime, it remains difficult for
the current assortment of small and isolated advocates
to develop the requisite social and political capital.
Narrative development
It is essential for advocates to consider the narrative
and framing of potential policy options. In the absence
of a broader strategic narrative for climate change in
the UK, it is impossible to appeal to the benefits of
action addressing embodied carbon purely in terms of
climate mitigation (Bushell et al., 2015). In order to
secure engagement from a multitude of actors across
the complex industry supply chain, it may be
necessary to simultaneously appeal to numerous co-
benefits or to a broader narrative of improved
competitiveness. Whilst the most prominent narrative
to date ‘reducing carbon reduces cost’ has inspired
some action; the majority of embodied carbon
assessment has been undertaken by a small number of
exemplar firms: ‘the usual suspects’ (UKGBC, 2015a
p. 12). Many within the industry remain sceptical that
the demonstrated cost and carbon savings on these
projects can be replicated at scale outwith this group
of innovative firms. To overcome this, it is imperative
that advocates develop more effective means of
ennumerating and expressing the other co-benefits
associated with the more sustainable use of building
materials. The current political narrative of
deregulation to “keep Britain building” (Osborne,
2015) is also a substantial hurdle.
If the strategic political narrative does change, it is
imperative that an evidence base is already in place
that can support appeals to the new narrative.
Effectively capitalising on changes in narrative
requires a prolonged accrual of evidence, rather than a
frenetic response to opportunities presented by
consultations and the like. This requires a structured
process of data collection and input from a multitude
of stakeholders.
Evidence gathering
Despite growing industry interest and expertise, the
evidence base that could inform policy making
remains limited. The aggregate number of assessments
to date remains insufficient to form detailed
benchmarks, and there is no central depository for
information on costs incurred. Consequently, there is
insufficient evidence to undertake the sort of
economic analysis required under a typical policy
impact assessment. Encouraging sufficient
assessments to form a robust evidence base may
require additional stimuli. However, additional stimuli
are unlikely to be introduced without a robust
evidence base. Overcoming this catch 22, in an
environment where funding for exemplar projects is
limited, will likely require leadership from industry
institutions alongside support from the research
community. This will require extensive collaboration
and a willingness to share data and experiences.
In the long term, a multi-level response will likely be
required, with local authorities and a small cohort of
firms initially demonstrating best practice, introducing
progressively more stringent requirements,
assembling an evidence base for policy makers, and
disseminating their experiences to the mainstream
industry. Only once respected advocates are
identified, a robust evidence base is in place, and an
appropriate narrative determined, is national
regulation likely to proceed.
In addition to addressing the outlined concerns, the
research community must:
Articulate a vision for the construction industry
in a net zero emissions future.
Develop alternative low carbon building
materials and design approaches, particularly
for high-rise structures, which currently have a
very limited range of viable materials.
Improve the understanding of current barriers to
uptake of alternative and re-used materials
Develop a range of policy options for
addressing whole life carbon emissions
Substantial reductions in embodied carbon will be
required to meet sectoral and national climate
mitigation goals. These reductions must be motivated
by the introduction of project CITs. Examples to date
show CITs can encourage innovation; however, a
number of issues must be addressed if CITs are to
achieve widespread adoption consistent with targeted
emission reductions. Approaches to target setting and
reporting should be further standardised, steps must be
taken to link sector and project level targets, and
additional drivers for embodied carbon reduction must
be introduced. This paper has offered initial insights
on these topics, proposed some potential solutions and
highlighted a number of areas requiring further
The contribution of the first and third authors forms
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Figure 1 Carbon emissions attributable to the UK built environment 1990-2013
Figure 2 Distribution of UK built environment supply chain GHG emissions in 2007
(based upon data from Giesekam et al., 2014 and Giesekam et al., In Press)
Figure 3 Projections of future embodied GHG emissions from UK construction. All
demand projections taken from scenario analysis with UK BIEC model (Giesekam et
al, In Press) including decarbonisation of the electricity supply at the rate projected
by DECC (2014).
Figure 4 Suggested project embodied carbon checkpoints, adapted from GLA (2013) and Doran (2014).
... Policy interventions have supported reductions in operational emissions; however, there is no equivalent policy targeting embodied emissions. In the absence of strong commercial or policy drivers, a minority of construction firms are assessing or targeting reductions in embodied emissions (De Wolf, Pomponi, & Moncaster, 2017; Giesekam et al., 2016) but there is no clear plan to ensure that this practice becomes mainstream. As a result of the current lack of action on embodied emissions, and their important contribution to achieving emissions reductions targets, the case study will focus specifically on embodied emissions. ...
... The absence of carbon intensity data for materials, products and projects is a widely cited barrier to the uptake of alternative materials and construction methods (Giesekam et al., 2016b). It also makes it difficult to establish appropriate benchmarks for inclusion in procurement documentation (Giesekam et al., 2016). The drivers for development of such data are weak, and many construction product manufacturers are unlikely to invest in the development of Environmental Product Declarations (EPDs) 5 without additional controls. ...
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Climate change mitigation has two main characteristics that interact to make it an extremely demanding challenge of governance: the complexity of the socio-technical systems that must be transformed to avoid climate change and the presence of profound uncertainties. A number of tools and approaches exist, which aim to help manage these challenges and support long-term decision making. However, most tools and approaches assume that there is one decision maker with clearly defined objectives. The interaction between decision makers with differing perspectives and agency is an additional uncertainty that is rarely addressed, despite the wide recognition that action is required at multiple scales and by multiple actors. This article draws inspiration from dynamic adaptive policy pathways to build on current decision support methods, extending analysis to include the perspectives and agency of multiple actors through a case study of the UK construction sector. The findings demonstrate the importance of considering alignment between perspectives, agency and potential actions when developing plans; the need for mobilizing and advocacy actions to build momentum for radical change; and the crucial influence of interaction between actors. The decision support approach presented could improve decision making by reflecting the diversity and interaction of actors; identifying short-term actions that connect to long-term goals and keeping future options open. Key policy insights • Multiple actors, with differing motivations, agency and influence, must engage with climate change mitigation, but may not do so, if proposed actions do not align with their motivations or if they do not have agency to undertake specific actions. • Current roadmaps, which assume there is one decision maker with control over a whole system, might overstate how effective proposed actions could be. • Decision making under deep uncertainty needs to account for the motivations and agency of diverse decision makers and the interaction between these decision makers. • This could increase the implementation and effectiveness of mitigation activities.
... Yet in spite of the observed barriers and limited drivers, numerous construction firms have publicly adopted carbon reduction targets. These targets vary widely in scope [29] and are typically determined by esoteric means, with many simply decided by individual CEOs, through comparison with competing firms, or copied verbatim from headline national mitigation commitments [30] . Few firms have targets that are truly aligned with sectoral, national or international mitigation commitments, though demand for such alignment has been growing of late. ...
... Recent work by WRAP [68] , the Carbon Leadership Forum [69] , RICS [70] and De Wolf et al. [71] , has sought to address this, but it will likely be many years before benchmark data is available for a broad range of project types. In the meantime it will remain difficult to set project embodied carbon reduction targets, which are a key means of delivering any company's reduction commitments [29] . Even once this benchmark data is available, further work will be required to understand what the embodied carbon reduction potential is of different assets types. ...
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In the face of a changing climate, a growing number of construction firms are adopting carbon reduction targets on individual projects and across their portfolios. In the wake of the Paris Agreement, some firms are seeking a means of aligning their targets with sectoral, national and international mitigation commitments. There are numerous ways by which such an alignment can be achieved, each requiring different assumptions. Using data from the UK construction industry, this paper reviews current company commitments and progress in carbon mitigation; analyses the unique challenges in aligning construction targets, and presents a series of possible sectoral decarbonisation trajectories. The results highlight the disparity between current company targets and the range of possible trajectories. It is clear that a cross-industry dialogue is urgently required to establish an appropriate response that delivers both a widely-accepted target trajectory and a plan for its delivery. This paper is intended to stimulate and support this necessary debate by illustrating the impact of different methodological assumptions and highlighting the critical features of an appropriate response.
... Limiting any increase in global average temperature to 'well below 2°C', as outlined in the Paris Agreement (UNFCC, 2015), requires that all nations rapidly reduce greenhouse gas (GHG) emissions to achieve a balance between sources and sinks in the second half of this century. The construction industry has a critical role to play in climate change mitigation, being a significant emitter of GHGs both directly through its activities and supply chains and indirectly through operation of the assets it creates (Giesekam et al., 2016a;Müller et al. 2013). In addition to being one of the largest emitters, the built environment is also one of the largest potential stores of carbon dioxide, through sequestration within biogenic building materials (Giesekam et al., 2014;Lawrence, 2015;Sadler and Robson, 2013). ...
... Many of these firms are assessing and reporting scope 3 emissions associated with the development of new built assets, and an increasing number are also targeting reductions through the use of embodied carbon or whole-life carbon intensity targets. De Wolf et al. (2017) provided an overview of current carbon dioxide assessment ('carbon assessment') practices, and Giesekam et al. (2016a) summarised the various approaches to target setting. This increased interest in 334 Engineering Sustainability Cite this article embodied carbon has been paralleled by a growth in guidance for practitioners and cross-industry efforts to ensure consistency in assessment procedures. ...
The construction industry, through its activities and supply chains as well as the operation of the assets it creates, is a major contributor to global greenhouse gas emissions. Embodied carbon emissions associated with the construction of new assets constitute a growing share of whole-life cycle emissions across all project types and make up nearly a quarter of all annual emissions from the UK built environment. Yet, these embodied emissions are still rarely assessed in practice, owing to the perceived difficulty and lack of supporting guidance for practitioners conducting an assessment. This briefing paper retraces recent advances in the field of embodied carbon assessment and highlights existing and forthcoming practical guidance that could support more widespread assessment. The paper constitutes a where-to rather than a how-to, directing assessors towards appropriate resources, of which there are many. Though the paper does highlight some remaining gaps in the field and identifies corresponding research priorities, recent additions to the body of guidance are generally sufficient to support more widespread assessment. Now the industry must demonstrate its commitment to tackling climate change by using this guidance to drive deeper carbon reduction.
Network Rail is tackling the problem of the GHG (primarily CO2) emissions it produces and is committed to the Government’s pledge to achieve Net Zero carbon emissions by 2050. It recently published its Environmental Sustainability Strategy 2020-2050 [1], which includes setting Science Based Targets for its Scope 1, 2 and 3 emissions. In this context, Expedition Engineering has been supporting Network Rail’s Technical Authority and Decarbonisation Programme in efforts to reduce the CO2e associated with its construction projects, primarily on those using concrete. This has included developing a Routemap to Net Zero Carbon Concrete, partnering with existing supply chains to decarbonise precast platform components used in high volume, and a feasibility piece focused on enabling significant carbon reductions in the ready-mix supply chain. The work has revealed the current difficulties and potential solutions within the UK concrete industry, as well as the value of supply chain partnering and putting research into practice. This paper summarises a combination of works completed and ongoing, and preliminary proposals under review. The route to Net Zero by 2050 must involve reduction in material quantities through design and construction efficiencies and a shift to using and developing materials with reduced CO2e intensity. In the immediate term this will mean maximising Portland cement replacement and accelerating adoption of current state-of-the-art low carbon technology. In the medium- to long-term it is anticipated that use of calcined clay and limestone as cement replacement will form a key part in the progress to reduce CO2e as the availability of PFA and GGBS reduces. The development of a standalone CO2e Reduction Protocol document is proposed as being a useful mechanism to organise new guidance and requirements and tie in with existing standards and contracts.
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The majority of carbon emissions arise from the built environment, a fact which has led to a global policy focus on reducing carbon and energy from buildings in use. However, research demonstrates that embodied carbon is also an increasingly significant proportion of the whole life impacts from buildings. Embodied carbon is not yet the subject of regulation, and although the CEN TC350 standards provide a methodology, there remains a significant variation in its measurement. This paper investigates some of the issues and difficulties that need to be addressed before widescale regulation can be enforced. The investigation uses a detailed case study of a low-energy school building, studied during its construction phase. The cradle-to-grave embodied impacts were modeled to the TC350 Standards using an innovative tool, and the operational impacts were modeled to incorporate future climate predictions. In spite of the care taken over data collection and the collective support of the process from all stakeholders, the study demonstrates a high level of uncertainty in results, resulting from industry-wide barriers to embodied carbon measurement. Key recommendations are made for industry and policy, in order to overcome the current barriers and enable more accurate and comparable measurement of the embodied carbon of buildings.
Technical Report
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Progress update on the 2013 Low Carbon Routemap for the Built Environment
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There is a significant 'action gap' between what scientists argue is necessary to prevent potentially dangerous climate change and what the government and public are doing. A coherent strategic narrative is key to making meaningful progress.
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As is the case in a number of countries, the UK construction industry faces the challenge of expanding production whilst making ambitious greenhouse gas emission reductions. Embodied carbon constitutes a growing proportion of whole-life carbon emissions and accounts for a significant share of total UK emissions. A key mitigation strategy is increasing the use of alternative materials with lower embodied carbon. The economic, technical, practical and cultural barriers to the uptake of these alternatives are explored through a survey of construction professionals and interviews with industry leaders. Perceptions of high cost, ineffective allocation of responsibility, industry culture, and the poor availability of product and building-level carbon data and benchmarks constitute significant barriers. Opportunities to overcome these barriers include earlier engagement of professionals along the supply chain, effective use of whole-life costing, and changes to contract and tender documents. A mounting business case exists for addressing embodied carbon, but has yet to be effectively disseminated. In the meantime, the moral convictions of individual clients and practitioners have driven early progress. However, this research underscores the need for new regulatory drivers to complement changing attitudes if embodied carbon is to be established as a mainstream construction industry concern.
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This is the author accepted manuscript. The final version is available from the Athens Institute for Education and Research via
The article reflects on the value of the UK forests for timber production and the need to overcome the negative image of tree felling. Despite testing times for UK construction, the future predicts significant development. The latest UN population trends predict that the UK population will continue to grow, potentially increasing from 63m to 73m by 2050, overtaking Germany to become Western Europe's largest population. Primary UK softwood species are Sitka spruce and Scots pine, with significant other species including larch, Douglas fir, Lodgepole pine and Corsican pine. The balance between UK hardwood species is more even, with oak, birch and ash being the most abundant. A number of UK groups are researching the use of home grown timber for construction. Work at Edinburgh Napier University is providing useful data on Sitka spruce for various applications including cross laminated timber. BRE, Bath University and Cambridge University are all working with wood, looking at a diverse set of study areas from nonmetallic connectors to polymer modification.
The concepts of green building and sustainable construction have received tremendous interest in North America in the past decade, as shown by the growth in the numbers of L.E.E.D.™ certified projects (Kibert 2005). Parallel to this has been a growing interest in natural, vernacular, or traditional building materials and techniques. Examples of these include straw bale construction and rammed earth construction. From an environmental point of view, these materials offer a low embodied energy and low embodied carbon alternative to conventional building materials such as concrete and steel (Woolley 2006, Walker 2007). In the case of straw bale construction, use is made of a waste material with excellent insulation properties. Other benefits of many natural materials include their ability to passively regulate humidity in a building, reduced toxicity, high thermal mass, and biodegradability at the end of life (Walker 2007). There remain many barriers to the use of natural building materials in the mainstream construction industry, including a lack of scientific data to quantify their true performance (Woolley 2006) and lack of experience by the mainstream construction industry in using these materials. This leads to the perception that these materials are low-tech and have poor performance. This perception, however, is changing. There is a growing body of research that is quantifying the performance of natural building materials and showing that they can compete with conventional building materials. There are also some excellent recent examples of the integration of natural building materials in mainstream construction projects. This paper describes three natural building material products that have been successfully integrated into mainstream construction projects in the United Kingdom: straw bale panels by ModCell; a hemp-lime composite called hemcrete and marketed by Tradical; and, rammed earth and unfired clay bricks. The information in this paper is based on interviews and site inspections undertaken by the author during February 2008. Some of the research supporting the use of these products will be described. Finally, some lessons and cautions for the use of these products in North America will be discussed. A caveat regarding the limitations of this paper is in order. This paper does not claim to be an exhaustive review of natural building materials and their performance. Other references should be consulted for more details on thermal or fire performance, for example.
Embodied (or embedded) greenhouse gas emissions are commonly overlooked in corporate carbon accounting, although they can represent a large proportion of overall emissions. In this paper, we utilise embodied emission data submitted to Ofwat, the economic regulator of water and sewerage companies in England and Wales, as part of their review of price limits. This is the first time that water and sewerage companies have presented embodied emissions associated with their capital programmes. In total, embodied emissions add an extra 50% on top of companies' operational greenhouse gas emissions. We consider the drivers for embodied emissions and show that capital maintenance programmes are the largest source. We highlight the relationship between capital expenditure and embodied emissions, and discuss why there are significant differences in embodied emission intensities between companies. Many of the differences arise from the way the common methodology for estimating embodied emissions is applied.
Initial embodied energy includes energy use during material, transportation, and construction life cycle phases up to project practical completion. Contractors have an important role to play in reducing initial embodied energy levels due to their significant involvement in preconstruction and onsite construction activities. Following an extensive literature review a comprehensive framework was designed to highlight the significance of initial embodied energy levels relative to specific construction packages, activities and subcontractors. This framework was then applied to a new UK industrial warehouse project using a case study approach. Capturing information from a live project during the entire construction phase helped highlight the practical challenges inherent when capturing and assessing initial embodied energy levels. A series of contractor current practices was reviewed to determine their compliance with the framework requirements. The findings revealed that the ground and upper floor, external slab and frame were the most significant construction packages in terms of embodied impacts. Many challenges embedded within the contractor’s current practices in terms of data detail, legibility, and terminology were also revealed. The framework provides a practical approach for initial embodied energy assessment which can readily be adopted by contractors to help highlight opportunities to increase efficiency.