SEPTEMBER 2020
Building the Case for Net Zero:
A feasibility study into the design,
delivery and cost of new net zero
carbon buildings
Advancing Net Zero Programme Partners
Lead Partner: Programme Partners:
F O U N D A T I O N
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UK Green Building Council | Building the Case for Net Zero
FOREWORD 4
EXECUTIVE SUMMARY 4
INTRODUCTION 8
Scope and methodology 9
Project overviews 13
Net zero targets 14
SECTION 1: DESIGN CHANGES 17
Net zero ofce 18
• Results 18
• Structure 20
• Façade 22
• Building systems 24
• Fitout design 26
Net zero residential 28
• Results 28
• Structure 30
• Façade 32
• Building systems 34
• Apartment design 36
SECTION 2: COST CHANGES 39
Net zero ofce 40
• Overview 40
• Key cost drivers 42
• Whole life costing 45
Net zero residential 47
• Overview 47
• Key cost drivers 49
Carbon offsetting 52
SECTION 3: CONCLUSION 55
Summary of fndings 56
Market transformation 57
Next steps 58
REFERENCES 59
ACKNOWLEDGMENTS 60
QUESTIONS & FEEDBACK 60
Contents
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UK Green Building Council | Building the Case for Net Zero
The original idea for this study was developed by Hoare
Lea and JLL, as Partners to UKGBC’s Advancing Net Zero
programme. The study would not have been possible
without their support and contribution of signifcant
team resources which UKGBC is grateful for.
Project supporters:
UKGBC would like to sincerely thank all design team
participants, alongside all stakeholders involved for
their feedback, assistance and contributions over the
course of the project. The design teams included
representatives from the following organisations:
• Alinea
• Bennetts Associates
• Cast
• Cundall
• EPR Architects
• Heyne Tillet Steel
• Hoare Lea
• JLL
• Robert Bird Group
This document is produced for general guidance only.
How you choose to use it is up to you. While the guidance
has been produced in good faith it does not constitute
advice and UKGBC and the authors of this guidance do not
represent or warrant that the content is suitable for your
purposes, accurate, complete or up-to-date. UKGBC and
the authors exclude all liability whether arising in contract,
tort (including negligence) or otherwise, and will not be
liable to you for any direct, indirect or consequential loss or
damage, arising in connection with your use of, or reliance
on, the guidance.
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UK Green Building Council | Building the Case for Net Zero
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UK Green Building Council | Building the Case for Net Zero
Executive Summary
In late 2018, the IPCC issued a stark warning. It clearly established that achieving the ambitions of the Paris Climate
Agreement and limiting warming to 1.5°C to avoid the most catastrophic impacts of climate change will require action
at an unprecedented pace and scale.1 The UK’s target to reach net zero emissions by 2050 reinforces the imperative
for businesses to assess their operating models in line with climate science. By better understanding the practical
implications of achieving net zero carbon, businesses can be made more resilient to future operating conditions and
pivot to embrace the upcoming change.
The World Green Building Council (WorldGBC) is catalysing
the construction and property industry to lead the transition to
a net zero carbon built environment through its Advancing Net
Zero campaign. The campaign is calling for all buildings to be
net zero carbon by 2050 and for all new buildings to be net zero
in operation and to reduce embodied carbon by 40% by 2030.2
In the UK, the operation of buildings accounts for around 30%
of emissions, mainly from heating, cooling and electricity use.3
For new buildings, the embodied emissions from construction
can account for up to half of the carbon impacts associated
with the building over its lifecycle4. UKGBC’s Advancing Net
Zero programme is helping to drive the transition to net zero
carbon buildings, including through its publication of the Net
Zero Carbon Buildings Framework5 in 2019.
In addition, a growing body of guidance is helping the
buildings sector better understand the key requirements for
new net zero buildings, such as performance targets developed
by UKGBC,6 LETI7 and RIBA.8 However, there is currently
a limited understanding of the practical implications for
designing and delivering these buildings including, critically, an
evaluation of the cost impacts.
PURPOSE
This report presents the fndings of a feasibility study that
shines a light on the real-world implications for achieving
new net zero buildings. It illustrates how new buildings can
be designed to reach net zero performance targets and the
effect this has on cost. The fndings are intended to improve
the collective understanding for the buildings sector and help
build the case for new net zero buildings.
Climate change is one of the greatest challenges
of our time. We are already seeing a range of
environmental changes around us: the increase in
severity and frequency of extreme weather events,
rising temperatures, flooding risks and impacts on
human health. Global warming will impact biodiversity,
agriculture, infrastructure, educational environments,
living conditions and business productivity. The
economic consequences of not controlling greenhouse
gas emissions will be significant and impact us all.
The built environment sector, responsible for nearly
half of global greenhouse gas emissions, remains
relatively inefficient and is ripe for radical change.
There is an opportunity for built environment
professionals to work together to reduce carbon in
new buildings and existing stock. This report shows
how designs for residential and workplace buildings
can be influenced to improve resource efficiency,
reduce running costs and get to net zero carbon. This
should be the target for all new buildings by 2030.
The findings of the study show that the increased
capital investment in net zero buildings needn’t cost
the earth. Failure to mitigate climate change will
however, impacting everyone including those not
living and working in the new buildings that are being
constructed.
1. Design changes
The study is based on two real-world projects that were
in concept design stage at time of publishing – an offce
tower and a residential block. UKGBC convened the project
teams for both schemes to iterate the existing designs –
considered the ‘baseline scenario’ representing business
as usual – to achieve two net zero design scenarios. In
comparing these different design scenarios, the fndings are
intended to provide insight into some of the key changes
required to the way buildings are currently designed and
delivered.
The two net zero design scenarios were based on future
net zero performance targets for embodied carbon and
operational energy published by UKGBC, LETI and RIBA.
An ‘intermediate scenario’ uses net zero targets for 2025 to
represent buildings that are in, or will soon be in, design, and
a ‘stretch scenario’ uses net zero targets for 2030 to represent
design changes that may be seen as challenging today but
will need to become the norm over the next decade.
The project teams’ brief was to deliver the same building
that had achieved planning approval (i.e. same overall
volume, external massing, site conditions), with free reign
to alter all other design parameters (e.g. structure, HVAC
system, tenant requirements etc.) to achieve, or get as close
to achieving, the net zero performance targets. Given this
brief, some net zero targets have not been achieved as
these would have required radical changes to the original
building design.
2. Cost changes
In parallel, an analysis of the effect on cost across the design
scenarios has been undertaken to estimate the changes
required in the fnancing of new net zero buildings. The focus
of this analysis has been on changes to capital cost and does
not seek to make the value case for net zero buildings. The
value case is signifcant when considering current market
trends, such as investor pressure through the Task Force on
Climate-related Financial Disclosure (TCFD), stranded asset
risks, corporate ESG drivers, and increasing occupier interest
in net zero. Future studies could explore this context further
and the wider benefts of net zero buildings.
The cost uplift for the intermediate scenarios were calculated
as 6.2% for offce and 3.5% for residential compared to the
baseline scenarios. This cost uplift can be considered feasible
today given these costs will likely be offset by the value
benefts, including increased rental premiums, lower tenancy
void periods, lower offsetting costs, and lower operating/
lifecycle costs.
However, the cost uplift for the stretch scenarios were more
signifcant at 8-17% for offce and 5.3% for residential. This
is perhaps not surprising as the net zero targets for 2030 are
substantially more demanding and the marketplace is not
yet geared up to delivering them at scale. To overcome this,
we need a long-term consistent regulatory trajectory that
tightens standards over time so as to provide the certainty
and level playing feld required for the supply chain to
innovate and costs to come down.
Foreword
It’s time we see net zero buildings as an opportunity
to innovate, explore better building techniques
and collaborate on a joint vision. We will face
challenges. The supply chain needs to make and
install materials and systems differently. We need to
build skills and capacity. Buildings will look slightly
different to how they do now, but not much. Using
materials with lower embodied carbon may be
unfamiliar to us but there are lessons and shared
from successful design solutions. We also need to
be better at measuring and monitoring building
performance when buildings are handed over.
Outcomes matter.
Ashley Bateson
Partner, Hoare Lea,
Advancing Net Zero
Programme Partner
This report represents a step towards building the case for net zero buildings. It provides the facts and fgures for two typical
developments, whilst signalling broader structural changes required for the buildings sector. A supplementary publication will
examine the market transformation in detail, and future studies could branch into other relevant areas, such as different building
types, retroft of existing buildings, and enabling green fnance mechanisms.
Carbon
2020 2025 2030
Time
Baseline
Intermediate
Stretch
Figure 1: A representation of the step change in building
performance required to meet future net zero targets and
drastically reduce carbon
The report’s fndings are separated into two main sections:
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Snapshot of fndings
NET ZERO OFFICE NET ZERO RESIDENTIAL
0
200
400
600
800
1,000
Baseline Intermediate Stretch
Embodied Carbon
(kgCO2e/m2)

350 (LETI)
Target
155

57
0
20
40
60
80
100
120
140
160
Baseline Intermediate Stretch
Energy intensity
kWh/m2/yr (GIA)
Upfront embodied carbon*
(LCA module A; kgCO2e/m2)
Energy performance
(whole building; kWh/m2 (GIA) / year)
Results See pages 20-27
Upfront embodied carbon*
(LCA module A; kgCO2e/m2)
Energy performance
(whole building; kWh/m2 (GIA) / year)
Results See pages 30-37
£3,125 6.2% increase
(£3,320)
8-17% increase
(£3,370 to £3,660)
Cost change (shell and core; £/m2 GIA) See pages 40-46
*Not including sequestration (capture of carbon in timber building materials)
£2,715 3.5% increase
(£2,810)
5.3% increase
(£2,860)
Cost change (shell and core; £/m2 GIA) See pages 47-51
*Not including sequestration (capture of carbon in timber building materials)
2. Introduction of mixed
mode ventilation: Relaxing
the internal comfort
conditions helped to reduce
heating and cooling loads by
over half (compared to the
baseline) and allowed the
introduction of openable
windows for passive cooling
in the spring and autumn.
1. Replacement of
steel and concrete in
structure: Incorporating a
fully timber structure along with
the removal of a concrete
basement helped reduce total upfront
carbon by 39%, compared to the
baseline. However, the larger-sized
timber beams and columns did
result in one floor being lost to
maintain the same building
height, which would impact the
building’s value.
3. Dematerialisation
of fitout and removal of
server room: By simply not
installing a suspended ceiling, a
14% saving in embodied carbon
was made. Utilising offsite servers
helped achieve a 78% decrease in
IT energy usage, however shifting
some energy use to a scope 3
emission.
Key design changes for stretch scenario See pages 18-19
2. Reduction of glazing
areas to reduce heat loss:
The glazing ratio is reduced
from 51% to 29% through
reducing bedroom window
sizes and removing bedroom
balconies. This is in addition
to incorporating triple glazing
and reducing the wall u-value.
1. Replacement of
concrete structure
with timber frame: The
use of a timber frame (beams,
decking and columns) helped
reduce total upfront carbon by 21%,
compared to the baseline. However,
given the increased depth of timber
beams, two floors had to be
removed to maintain the overall
building height.
3. Replacement of gas
boiler with air source
heat pump: The switch to an
air source heat pump
significantly reduces operational
energy demand. Approximately
half of the final energy demand in
the stretch scenario comes from
unregulated loads.
Key design changes for stretch scenario See pages 28-29
The baseline design is for a new 16 storey city offce building – see “Project overviews” on page 13 The baseline design is for a new 18 storey city residential building – see “Project overviews” on page 13
Baseline Intermediate Stretch

Target
Baseline Intermediate Stretch
Embodied Carbon
(kgCO2e/m2)
Energy intensity
kWh/m2/yr (GIA)
0
100
200
300
400
500
600
700
0
20
40
60
80
100
120
140
160

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UK Green Building Council | Building the Case for Net Zero UK Green Building Council | Building the Case for Net Zero
Introduction
SCOPE AND METHODOLOGY
In April 2019, UKGBC published the Net Zero
Carbon Buildings Framework which aimed to build
industry consensus on a defnition for net zero
carbon buildings. It set out high-level principles for
achieving net zero carbon for construction and for
operational energy, with the noted intention that
further detail and stricter requirements would be
developed over time, including energy performance
targets. For new buildings, the framework sets
out how net zero carbon can be achieved for
construction whilst designing for low energy to
ensure net zero carbon for operational energy can
be achieved when in use.
The scope and methodology of this feasibility
study is aligned with that of the framework – to
achieve net zero carbon in construction and follow
the high-level principles for reducing operational
carbon emissions. The high-level principles for
new buildings are broadly: designing to reduce
whole life carbon; designing for low energy
use; installing on-site renewable energy (where
possible); and offsetting all remaining carbon
related to the building’s construction stage (termed
‘upfront carbon’). Once these steps have been
completed, and following the verifcation of data,
the building is deemed to achieve ‘net zero carbon
– construction’.
The past few years have seen a surge of interest in net zero carbon and how new buildings can be
designed to achieve this outcome. A growing body of guidance is helping the buildings sector better
understand the key requirements for new buildings, such as performance targets developed by LETI7
and RIBA8 and the net zero outcomes defned in UKGBC’s net zero framework.5 However, there is
currently a limited understanding of the practical implications for designing and delivering these
buildings including, critically, an evaluation of the cost impacts.
This report presents the fndings of a feasibility study
that shines a light on the real-world implications
for achieving new net zero buildings. It provides an
evidence base for designing net zero buildings and
the cost of delivering them, whilst also beginning to
outline the market transformation required for this
to occur at scale. The fndings should help to build
confdence in the market that new net zero buildings
are possible by removing signifcant unknown
variables, such as cost uplift.
The UK’s 2050 net zero carbon target, corporate
ESG drivers, and increased occupier interest in
net zero are just three reasons why developers
and investors are becoming acutely aware of the
need to deliver new net zero buildings. The recent
publication of energy performance and embodied
carbon targets for net zero carbon buildings have
started to illustrate the increasing levels of building
performance that will be expected in the future,
representing a step change for the buildings sector.
This report shows how theoretical net zero targets
can practically be achieved by setting out the design
changes required for two typical buildings.
By examining the design changes required to
an offce building and residential block – both in
concept design stage at time of publishing – the
fndings provide a greater level of appreciation
and insight into the fundamental changes required
to the way buildings are currently designed and
delivered. The study uses the building designs
as a ‘baseline’ representing good practice today
and iterates these designs to achieve two net zero
scenarios. An ‘intermediate’ scenario uses net zero
targets for 2025 to represent buildings that are in,
or will soon be in, design, and a ‘stretch’ scenario
uses net zero targets for 2030 to represent design
changes that may be seen as challenging today but
will need to become the norm over the next decade.
In parallel, an analysis of the cost impacts resulting
from these design changes has been undertaken
to estimate the changes required in the fnancing
of new net zero buildings. The focus of the analysis
has been on changes to capital cost, however future
studies could examine changes across the life of
net zero buildings to appreciate their increased
value. This could include building on recent fndings
which show that sustainable buildings can result
in increased rental value of 6-11% and lower void
periods9 which could potentially balance increases
in capital costs.
Recognising that these changes will only be made
possible within a supportive market, the report
also begins to explore key themes for the buildings
sector to address to mainstream new net zero
buildings. Over the course of the study it became
clear that structural changes will be required in the
market, and so a supplementary publication is due
to follow in the fall of 2020 which will delve deeper
into these topics. In this way, a catalogue of future
studies can be undertaken which continue to ‘build
the case’ for net zero buildings, including examining
other building types.
This report is a step on the path to achieving new
net zero buildings, however the fndings will require
wide engagement across all stakeholders within the
buildings sector, from designers and developers,
to investors and occupiers. Critically, fndings that
breakdown technical hurdles and demonstrate
the achievability of net zero buildings will help
show the art of the possible. Given the signifcant
opportunities to decarbonise the UK’s buildings
sector3 and the pressing need for all new buildings
to be net zero by 2030,10 there is an urgency to
take the fndings from this study and use them to
accelerate the delivery of new net zero buildings.
Building
construction
Building
operation

Construction
products
and
processes
Modules A1
to A5
Module B6 Modules Module C Module D
B1-B5 & B7
Operational
energy e.g.
heating,
lighting and
applicances
Maintenance,
repair,
refurbishment
and water use
Carbon
savings from
material
re-use
All Modules referred to are from EN15978 Sustainability of construction works – Assessment
of environmental performance of buildings – Calculation method
Demolition,
waste and
disposal
Net Zero Carbon – Construction (1.1)
Net Zero Carbon – Operational Energy (1.2)
Net Zero Carbon – Whole Life (future development) (1.3)
Figure 2: UKGBC’s framework sets out two defnitions for net zero carbon buildings that can
be achieved today for construction and operational energy
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UK Green Building Council | Building the Case for Net Zero UK Green Building Council | Building the Case for Net Zero
The study is based on comparing different design
scenarios for two new buildings – an offce tower
and a residential block. The design scenarios
compare current business as usual levels of
building performance (the baseline) with two
sets of ambitious net zero designs. Developing
these net zero design scenarios helps to illustrate
potential design routes to achieving net zero
targets, and the resulting cost impacts.
The net zero designs are based on targets for
embodied carbon and operational carbon
(emissions related to all regulated and unregulated
energy use in the building) that have been
developed by various industry bodies, including
RIBA, LETI and UKGBC. By combining these targets
across increasingly ambitious design scenarios,
this study aims to illustrate their achievability when
combined and the overall reduction on a building’s
whole life carbon.
2. Reduce Construction Impacts
2.1 A whole life carbon assessment should be
undertaken and disclosed for all construction projects
to drive carbon reductions
2.2 The embodied carbon impacts from the product and
construction stages should be measured and offset at
practical completion
3. Reduce Operational Energy Use
3.1 Reductions in energy demand and consumption
should be prioritised over all other measures.

4. Increase Renewable Energy Supply
4.1 On-site renewable energy source should be
prioritised
4.2 Off-site renewables should demonstrate additionality
5. Offset Any Remaining Carbon
5.1 Any remaining carbon should be offset using a
recognised offsetting framework
5.2 The amount of offsets used should be publicly
disclosed
1. Establish Net Zero Carbon Scope*
1.1 Net zero carbon – construction
1.2 Net zero carbon – operational energy
New buildings and major refurbishments targeting net zero carbon for construction should
be designed to achieve net zero carbon for operational energy by considering these
principles.
* Please also note, a further scope for net zero whole life carbon (1.3) will be developed in
the future.
Figure 3: Steps to achieving a net zero carbon building
Figure 4: Methodology for net zero feasibility study
1. Select representative buildings
The study examines two typical new development schemes: an office
tower and residential block. The schemes were selected as
representative of typical building types so that the study’s findings
can be broadly applied. The schemes have been anonymised for the
purposes of this study but were in development at time of publishing.
2. Select design targets
The study involved iterating the existing design of each scheme to achieve
increasingly ambitious design targets. The targets selected were drawn from
work undertaken by RIBA, LETI and UKGBC covering embodied and
operational carbon. Three scenarios were developed for each scheme:
baseline, intermediate and stretch.
5. Identify market implications
The project teams’ findings were presented to an external team of
consultants and advisors to assess the implications of taking the theoretical
net zero building designs through to practical delivery. This discussion is
intended to signal to the property and construction sector the key barriers
and potential solutions for increasing the uptake of new net zero buildings,
and a further report on these issues will be published later in 2020.
3. Develop design scenarios
The project teams involved in the real-world schemes led on the
development of these design iterations, given their working knowledge
of each project. Their brief was to deliver the same building that had
achieved planning approval (e.g. same overall volume, external
massing, site conditions, etc.), with free reign to alter all other design
parameters (e.g. structure, HVAC system, tenant requirements, etc.).
4. Cost scenarios
The projects’ cost consultants assessed the three different design scenarios to
understand the capital cost impacts for each. For comparability, all scenarios
achieve the same net zero carbon for construction outcome, so any costs for
offsetting the remaining upfront carbon have also been applied.
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UK Green Building Council | Building the Case for Net Zero UK Green Building Council | Building the Case for Net Zero
PROJECT OVERVIEWS
The fndings from this study are intended to be generally applicable across the industry. They should
help to inform project teams on different design strategies to achieve net zero and to set budgets
for new projects targeting net zero outcomes. They should not however take the place of proper
planning and due diligence undertaken by clients and teams for specifc projects. Both of the case
studies analysed were selected on the basis that they were considered representative of common
new developments, allowing the fndings to be applied to other similar projects. Further consideration
of the fndings will always be required based on project-specifc parameters including, for example,
location, size, local planning rules, developer specifcation etc.
PROJECT TEAMS
UKGBC convened both project teams working on the real-world schemes to help develop the net zero
design scenarios and would like to offer a special thanks to them for contributing their time and expertise to
this study. It is only due to their voluntary efforts that this report has been made possible.
Office team

Alinea
Cost consultant
Tom Atkinson, Matt Orford
Review by JLL: Kenny Man, Emma Hoskyn
Landsec
Developer
Nils Rage
Hoare Lea
LCA, MEP
Ashley Bateson, Tom Spurrier, Will Belfeld, Owen Boswell
Heyne Tillett Steel
Structural engineer
Tom Watson, Will Johnson
Residential team
EPR Architects
Architect
Alex Potter
Cast
Cost consultant
Nick Jackson-Brown, Kojo Mensah
Review by JLL: Kenny Man, Emma Hoskyn
Legal & General
Developer
Stephen Murden
Hoare Lea
LCA, MEP
Ashley Bateson, Greg Jones, Tom Wigg, Tom Brown
LCA review by Cundall: Simon Wyatt
Robert Bird Group
Structural engineer
Jessica Lovell, Freya Summersgill, Cormac Ennis, Camilla Cabria,
Maria Pia Stasi, Simon Nicholas
Project supporters
The original idea for the study was developed by Hoare Lea and JLL, as Partners to UKGBC’s Advancing Net
Zero programme. UKGBC is grateful for their support and contribution of signifcant team resources to make
this study a reality.
Office
The original design of the offce scheme is for a
new 16 storey building on an urban infll site. The
developer’s specifcation is for a BCO Grade A
offce, which is typical of a new city offce building,
and had strong environmental aims. The design
is considered better performing compared to the
market average and this is reflected in the fgures
provided in the cost analysis. The original design
included some non-offce space, however for the
purposes of this study, these spaces have been
excluded from the analysis.
Residential
The original design of the residential scheme is for
a new 18 storey building on an urban site. Due to
strict environmental planning requirements, the
design is considered better performing compared
to the market average and this is reflected in the
fgures provided in the cost analysis. The project
plans to deliver 208 high-quality residential
apartments, ranging from studio to three-bedroom
units. The build-to-rent apartments and mixed-use
nature of the project (including some retail and
communal spaces) is considered typical of new highrise apartment buildings. The focus of the study
is the apartment design, so any commercial/retail
spaces have been excluded from the analysis.
Figure 5: Section through offce development; the
offce tower is the focus of this study
Figure 6: Artist’s depiction of original residential
design
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UK Green Building Council | Building the Case for Net Zero UK Green Building Council | Building the Case for Net Zero
GUIDE TO THIS REPORT
The fndings in this report are presented across two main sections:
1. Design changes
This section begins with a comparison of whole life carbon results across the three
design scenarios, including whether net zero targets were achieved and a summary
of key design changes. The design changes are expanded on further within four
subsections:
• Structure;
• Facade;
• Building systems; and
• Fitout design (for offce), apartment design (for residential).
These subsections provide a narrative of how the building’s design evolves from
the ‘baseline’ to ‘intermediate’ and ‘stretch’ scenarios. All design scenarios are
assumed to build upon and retain the previous design unless otherwise stated.
2. Cost changes
This section begins with a table summarising the overall cost changes between the
three design scenarios, including a percentage change from the baseline scenario.
The cost models have been developed using feasibility design documentation
and as a result estimates or ranges have been used to demonstrate cost effects.
Commentary further explaining the costs effects is provided on an elemental basis
to provide greater insights.
Market transformation
Over the course of the study it became clear that, given the scale of changes required to achieve the
changes needed in building design, the discussion about market implications and transformation deserved
its own publication which will be released as a supplement to this report later in 2020. The report summary
outlines the 10 key themes to signal what the future publication will address.
Specifc topics within the design and cost narrative sections in the report that were identifed as critical
to support the uptake of new net zero buildings have been tagged with the icon on the left. In this way,
readers are made aware of current approaches used in the study which may not be market norms, but
which will need to be addressed to remove barriers for net zero buildings.
NET ZERO TARGETS
UKGBC’s net zero framework was developed to
provide the buildings sector with clarity on the
processes and outcomes required for achieving
net zero carbon buildings. Complementary pieces
of work, undertaken and published in RIBA’s 2030
Climate Challenge,8 LETI’s Climate Emergency
Design Guide7 and UKGBC’s Energy Performance
Targets for Offces,6 sought to provide clarity on the
level of building performance required for buildings
to claim to be net zero. These ‘net zero targets’ can
be overlaid on UKGBC’s framework to ensure any
net zero building is highly effcient, uses only its ‘fair
share’ of available resources and limits the reliance
on offsets.
The approaches used to determine the targets have
varied between these three organisations. This is
mainly due to the inherently variable nature of the
‘top-down’ calculations (based on decarbonisation
trajectories to reach the UK’s 2050 net zero target),
which consider a range of interdependent and
economy-wide factors, such as, future renewable
energy generation and decarbonisation of heat. The
calculation of net zero targets is not an exact science
but it does offer the buildings sector insights into
the scale of reductions required to achieve a net
zero carbon built environment.
This study aims to contribute to the growing bank of
research on net zero buildings by examining what it
will take to meet these published net zero targets.
It does this by using the targets as performance
requirements that both project’s design teams were
required to deliver against. In this way, the study
highlights the key changes required to the way we
design, deliver and operate buildings to achieve net
zero buildings.
The targets selected are a blend from RIBA, LETI
and UKGBC to create a comprehensive set of
performance requirements that cover embodied
and operational carbon, for both the offce
and residential building typologies. As these
performance requirements become stricter over
time, two net zero scenarios have been developed
to align with a 2025 and 2030 time horizon. The
different design scenarios and net zero targets used
for this study are set out in Table 1.
Table 1: Design scenarios and net zero performance targets used in this study
Baseline scenario Intermediate scenario Stretch scenario

*These targets are based on LETI’s ‘best practice 2020’ target as there is no LETI target aligned with 2025.
UK Green Building Council | Building the Case for Net Zero
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Section 1:
Design Changes
This section provides an analysis of the upgrades made
to the baseline design to achieve the higher levels of
performance under the intermediate and stretch scenarios.
An overview is provided, with subsections adding further
detail by building element – structure, facade, building
systems and interior design. All design scenarios are
assumed to build upon and retain the previous design unless
otherwise stated.
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Net zero ofce
KEY DESIGN CHANGES TOWARDS NET ZERO
1. Replacement of steel and concrete in structure
Cement and steel are two of the most carbon intensive materials used in buildings, with steel making up
around 7%11 and concrete 7-9%12 of global carbon emissions. The change from a conventional steel and
concrete structure in the baseline design to a full timber structure (columns, beams and flooring) along with
the removal of the concrete basement in the stretch design helped reduce total upfront carbon by 39%,
compared to the baseline. However, to maintain the same building volume across all designs, one floor was
lost due to the larger-sized timber columns and beams, which would affect the building’s fnal value.
2. Introduction of mixed mode ventilation
City offce buildings typically need to meet a standard level of specifcation (BCO Category A) which can often
result in a blanket provision of heating/cooling and increased energy use intensity. The stretch design relaxes
comfort conditions in the specifcation and introduces openable windows to enable passive cooling in the
spring and autumn. The relaxation of comfort conditions down to 20°C in heating mode and up to 27°C in
cooling mode helped to contribute to a 38-55% reduction in heating and cooling energy loads.
3. Dematerialisation of ftout and removal of server room
Offces delivered as shell and core can typically include a large degree of applied fnishes which, at the
discretion of tenants, can be removed during the ftout process. By not installing these fnishes, embodied
carbon savings can be made. An example is the 14% saving in embodied carbon in the intermediate design
compared to the baseline design, simply by not installing a suspended ceiling due partly because of its
regular need for replacement during the life of an offce building. A similar approach to dematerialisation is
to utilise offsite servers and reduce the level of on-floor IT and small power equipment,, which reduced the
IT and server loads by 78% in the stretch design compared to the baseline design. As a result of the energy
saving on-site, this energy would become a scope 3 emission.
* Please note, the lifecycle assessment was undertaken for all major building elements within a developer’s base build scope.
For this reason, the following modules were not included within the assessment: B1-B3, B6-B7. The operational energy
strategy and results are provided in subsequent sections.
The baseline scenario for the ofce project represents a current standard practice ofce building. This
building was modelled to meet the LETI embodied carbon targets for the three scenarios, as well as
RIBA and UKGBC operational energy targets. The study’s design team was instructed to attempt to
meet these targets while keeping as close as possible to the project brief that had achieved planning
approval (e.g. same overall volume, external massing, site conditions, etc.) as possible. The team had
free reign to alter all other design parameters (e.g. structure, HVAC system, tenant requirements, etc.).
The results below represent the design team’s best attempt to meet the targets.
RESULTS
The following two tables provide a summary of results for the three design scenarios alongside a comparison
with relevant net zero targets. A tick or cross has been applied depending on whether the target has been met.
Table 2: Embodied carbon (module A; kgCO2e/m2)
Baseline Intermediate Stretch
Target
(excluding sequestration)
1,000
(LETI – business as usual)
600
(LETI – 2020 target)
350
(LETI – 2030 target)
Achieved
(excluding sequestration) 930 755 570
Achieved
(including sequestration)
N/A
(no timber used) 625 305
Whilst LETI explicitly state that sequestration from timber is excluded from their embodied carbon targets,
the results here show that the intermediate and stretch targets are diffcult to achieve without either
accounting for sequestration or signifcantly changing the baseline design.
Table 3: Operational energy (whole building; kWh/m2 (GIA)/year)

90
(UKGBC – 2025 target)
70
(UKGBC – 2030 target)
Achieved 156 115 56
The intermediate scenario does not meet the target as more signifcant changes to the baseline design
would have been required potentially impacting the project brief. The stretch scenario does meet the target,
and the removal of the on-site server and reduction of IT loads helps to bring energy use within reach of
UKGBC’s 2050 net zero target of 55kWh/m2.
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
Stretch
Other
Glulam sequestration
Glulam frame
Omit basement
Intermediate
Other
CLT sequestration
CLT upper floors
Omit suspended ceiling
Baseline

42,608 Embodied Carbon
(modules A1-A5, B4-B5 & C1-C4*; tCO2e)
Figure 7: Reductions in embodied carbon across the three design scenarios
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• Increase in column size due to lower strength
and stiffness of glulam, which along with the
increased number of columns and larger core
structure, resulted in a loss in floor space;
• Large services are not able to pass through the
structure, requiring either increased ceiling build
ups or a change in servicing strategy (although
structural floor depth is reduced compared with
the intermediate design).
However, the change to a full structural timber
frame allowed for several savings in embodied
carbon, including:
• Removal of all steelwork (other than connection
plates and fxings);
• Reduction in building weight leading to smaller
foundations (in addition to the removal of the
basement);
• Increase in carbon sequestration.
The fre risk for buildings with internally exposed
timber is potentially greater than for a traditional
steel and concrete frame. Specialist fre engineering
input would be required, and it is likely that
a specifc burnout analysis would need to be
undertaken to satisfy Building Control and building
insurers.
Additionally, timber structures have a reduced
density when compared with concrete. As such,
additional noise and vibration treatment is likely
to be required, which should be considered in the
overall building design. Nevertheless, international
examples show that timber commercial buildings
can be constructed safely to comply with building
regulations.
The LCA calculations for carbon sequestration in the timber structure have been made in line with the RICS
Professional Statement (Section 3.4.1). This includes recognising the benefts of carbon sequestration in module
A on the basis that end-of-life impacts are accounted for in module C, and that the timber originates from
sustainable sources (certifed by FSC, PEFC or equivalent). This takes a conservative approach to calculating carbon
sequestration across a building’s whole lifecycle given the unknown treatment of the timber structure at end-of-life.
For this study, an allowance has been made for the disassembly of the timber structure, and the anticipated
end-of-life scenario is local re-use within the built environment. Within a net zero carbon built environment it will
be crucial that landfll or incineration of timber products is avoided at end-of-life to avoid the re-release of the
biogenic carbon (or worse, methane in the case of landfll), through application of circular economy principles. This
discussion topic is due to be addressed in a supplementary report – please see “Market transformation” on page
58 for further information.
STRUCTURE
Baseline Intermediate Stretch
Superstructure Steel frame and
composite floor
Steel frame and crosslaminated timber floor
Glulam frame and crosslaminated timber floor
Substructure Concrete basement Concrete basement No basement
The BASELINE design represents the conventional
design of high-rise offce buildings using a steel
framed superstructure with composite concrete
floors on profled metal decking. A double-height
basement constructed from reinforced concrete
was included in the design. Lateral stability to the
structure is provided by reinforced shear walls at the
stair and lift cores. Concrete and steel are carbon
intensive materials and contribute a total of 49%
(460 out of 930kgCO2e/m2) to upfront carbon in this
design scenario.
The INTERMEDIATE design retains the steel
superstructure, however replaces the composite
concrete floors with cross-laminated timber (CLT)
panels. The double height reinforced concrete
basement and shear walls are retained. The use of
CLT floors requires a larger structural floor build up,
however provides several benefts that reduce the
embodied carbon in the structure, including:
• Ability of CLT to span further lengths enables
steel beam piece count and tonnage to be
reduced;
• Approximately 20% reduction in structural dead
load allows steel column tonnage to be reduced;
• Reduction in embodied carbon (kgCO2e/m2) of
CLT compared with composite concrete floor;
• Inherent carbon sequestration of CLT.
The STRETCH design incorporates a full structural
timber frame, with CLT floors supported on glue
laminated timber (glulam) beams and columns.
The reinforced concrete shear walls are replaced
with a combination of internal and external glulam
bracing. To achieve further carbon savings, the
double height basement is removed, and the
structure is founded on concrete pile caps and
piles, with a suspended concrete slab forming the
ground floor.
These measures reduce the upfront carbon of the
structural elements in the stretch design by 64%
compared to the intermediate design (from 357 to
129kgCO2e/m2). While there is relatively limited
commercial value attached directly to a basement
area, there may be other impacts which need to
be considered for projects such as the re-location
of services and amenities such as waste and cycle
storage. For this project, mechanical plant could
relatively easily be relocated to the roof space, with
the compromise that PV panels could no longer be
installed.
The use of a full structural timber frame required
some concessions in the building design,
including:
• Shorter spans achievable with glulam compared
to steel, leading to additional structural columns;

Non-structural
-400
-200
0
200
400
600
800
1,000
Baseline Intermediate Stretch
Embodied Carbon
(modules A1-A5; kgCO2e/m2)
Figure 9: Chart showing the reduction in upfront carbon across all three scenarios based on changes to the structural design
Figure 8: Typical upper floor plate for the baseline, intermediate and stretch designs
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FAÇADE
Baseline Intermediate Stretch
Building fabric Solid U-value of 0.2
Infltration 5 m3/hm2@50Pa
Solid U-value of 0.2
Infltration 3 m3/hm2@50Pa
Solid U-value of 0.15
Infltration 1.5 m3/hm2@50Pa
External
shading
None Some external shading Some external shading
Glazing ratio 80% glazed (floor to
ceiling)
50-60% glazed average
(south 40%, east/west 60%,
north 80%)
40% glazed (all elevations)
Glazing U-value of 1.4
G-Value of 0.32
U-value of 1.4
G-Value of 0.32
U-value of 1.2
G-Value of 0.28
Windows Sealed Sealed Openable (to allow mixed
mode ventilation)
The BASELINE DESIGN represents current
standard practice in high-rise offce buildings and
assumes a conventional BCO-type specifcation.
The structure is a steel frame and composite steel/
concrete deck, with a floor-to-floor height of 3.6m,
and the floorplates are column free. As is typical
for such projects, it includes a basement that
contains back-of-house (BOH) functions, as well as
signifcant items of plant (machinery, equipment and
appliances) with some also located at roof level.
The façade consists of floor-to-ceiling aluminium
curtain walling, with a solar control coating and a
glazing ratio of 80% to all elevations.
The INTERMEDIATE DESIGN switches the
structure to a hybrid steel-frame and CLT deck.
The deeper steel beams require a higher floor-tofloor height of 3.85m, which results in one less floor
within broadly the same volume as the baseline
design. The floorplates remain column free and the
basement is retained.
The façade design more signifcantly incorporates
orientation considerations, with lower glazing ratios
of 60% to the east/west and 40% to the south.
In addition, those elevations also have external
shading to further reduce solar heat gains.
Appropriate glazing percentages and feasibility
of facade openings will vary between buildings
as they require consideration of local air quality
and acoustic conditions, as well as the depth of
floor plates. Approaches to facade design may
also be influenced by site specifc factors such as
overshading from surrounding buildings in dense
inner-city locations, and internal daylight levels from
a health and wellbeing perspective.
The STRETCH DESIGN changes to a full timber
structure, with glulam beams/columns and a CLT
deck. The floor-to-floor height is the same as
the intermediate version (3.85m), but the timber
structure requires a central column within the
floorplate. The columns are also larger in plan area
than the steel versions.
The most signifcant change to the façade is the
introduction of mixed-mode ventilation. This will
enable free cooling in the spring and autumn,
with the chilled beams used for cooling only in
the warmest weather. The opening windows are
assumed to be manual operated, but with indicators
telling people when they are better kept closed.
This has allowed the limit for comfort cooling to
be lifted to 27°C. In addition, the glazing ratios are
further reduced to 40% all around the building.
However, given the heat losses are predominantly
from ventilation, the fabric U-values did not
require increasing as much as originally assumed.
As such, in order to not increase the embodied
carbon signifcantly, the glazing remains double
rather than triple.
Baseline scenario
Intermediate scenario
Stretch scenario
Key: Structure Cladding Finishes Mechanical & electrical
• Steel frame and
composite deck
• Hybrid steel frame
and CLT deck
• Timber frame
and CLT deck
• Floor to ceiling glazing
• Lower glazing ratios
• External solar shading
• Lower glazing ratios
• External solar shading
• Opening windows
• Suspended aluminium ceiling
• Raised access floor
• No suspended aluminium ceiling
• Raised access floor made
from reclaimed materials
• No suspended aluminium ceiling
• Timber floor build-up without floor
access for services (power and IT
distribution to be surface mounted)
• Fan coil units
• Chilled beams
• Mixed mode ventilation/
chilled beams
• Task lighting
• Wider range of indoor
temperatures (due to
reduced comfort cooling)
Figure 10: Illustration of the upgraded facade and internal ftout spaces
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BUILDING SYSTEMS
Baseline Intermediate Stretch
Heating and
cooling
Gas boiler
Air cooled chiller
Air source heat pump Air source heat pump
Ventilation
system
Fan coil units Active chilled beams Active chilled beams
Ventilation
strategy
Constant volume fresh air
supply
Demand-controlled variable
volume fresh air supply
Demand-controlled variable
volume fresh air supply
Comfort
conditions
22 to 24°C, with a +/- 2°C
control band
22 to 24°C, with a +/- 2°C
control band
20 to 27°C, with facade
openings and mixed mode
ventilation
The BASELINE DESIGN represents the
conventional design approach to high-rise offce
buildings in recent years, with heating and domestic
hot water provided by a gas boiler with an effciency
of 90%, and cooling provided by an electric chiller,
with a seasonal effciency of 4.5. Heating and
cooling is delivered to the offce floors via fan coil
units, with constant volume fresh air provided by
centralised air handling plant, with a heat recovery
effciency of 75% (included for all iterations). Internal
design conditions for occupant comfort are 22°C for
heating and 24°C for cooling, with a +/- 2°C control
band.
The INTERMEDIATE DESIGN responds to grid
decarbonisation and shifts thermal demands to
an all-electric solution, utilising a (reversible) air
source heat pump for heat generation, moving away
from the combustion of fossil fuels on site and the
associated carbon, nitrous oxide and particulate
emissions. The heat pump also provides cooling,
reducing the overall quantity of plant compared to
the boiler and chiller scenario. Anticipated seasonal
effciencies are 3.5 for heating and 4.5 for cooling.
Domestic hot water for core uses such as cycle
showers is generated via the central heat pump
plant, with on-floor hot water (i.e. kitchenettes)
generated via point-of-use electric heating.
An active chilled beam solution is preferred to
fan coil units, with demand controlled ventilation
enabled, to allow fresh air provision to ramp back
when CO2 concentrations in the space allow. Offce
lighting is enhanced to represent best practice
effciencies whilst still delivering 400lux to the
working plane and providing a holistic lighting
design in conjunction with exposed soffts.
The fundamental change in the STRETCH DESIGN
is the introduction of openings in the facade,
which enables a mixed mode ventilation regime,
with suitable controls linking the facade to the
HVAC systems allowing them to be deactivated
when external conditions allow (including the
consideration of condensation risk). The reduction
in glazing percentage on the facade assists in
this regard by reducing solar gain and improving
thermal comfort.
Internal comfort conditions within the stretch design
are relaxed down to 20°C in heating mode, and
up to 27°C in cooling mode to control the risk of
overheating. Consideration was given to removing
cooling altogether and adopting a free-running
naturally ventilated design. Dynamic thermal
analysis indicated that the stretch design could
meet natural ventilation comfort standards based on
current climate data, however its ability to provide
comfort conditions decreased when considering
future climate projections. The lack of thermal mass
in the stretch design CLT slabs is another factor, and
a degree of comfort cooling was therefore retained
within the stretch design.
Offce lighting total power density is limited to
4W/m2, through a combination of background and
task lighting, reduced lux levels, and/or emerging
technology such as power over ethernet.
Figure 11: Design schematic for net zero offces (including additional features not addressed within this study)
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Offce occupancy density is assumed to relax
to 1 per 10m2 representing slightly less intense
occupation than the baseline and intermediate
design. Tenant on-floor small power is limited to
9W/m2, with out-of-hours usage reduced from 25%
to 5%.
Like the intermediate design, most fnishes have
not been applied. The most signifcant change is
moving from a recycled raised access floor to a
simple floating timber build-up. The floor fnish will
endure much longer than a carpet, thereby reducing
replacement rates in-use.
The shift from hardwired, onsite servers towards
cloud computing and Wi-Fi will also mean that
the much-reduced hardwiring will either be drawn
through ducts or dropped from the sofft, as is
already common in much of the rest of Europe.
FITOUT DESIGN
Baseline Intermediate Stretch
Specifcation Aligned with BCO Aligned with BCO Not fully aligned with BCO
Occupancy 1 person per 8m2 1 person per 8m2 1 person per 10m2
Fresh air
supply
16l/s/p (constant) Up to 16l/s/p (demand
controlled)
Up to 16l/s/p (demand
controlled) and with mixed
mode operation
Small power
(installed)
15W/m2 12W/m2 9W/m2
On-site server
rooms
10W/m2 7.5W/m2 0.5W/m2
Finishes Suspended aluminium
ceiling
Raised access floor
Exposed ceiling
Recycled raised access floor
Exposed ceiling
Timber floor build-up
The BASELINE DESIGN represents a Class A offce
specifcation typical of new city offce buildings,
with the design brief meeting or exceeding the
BCO Guide to Specifcation13 in most instances.
The building’s operation is reasonably intense,
with the base assumption that the entire building
is fully occupied by tenants at a density of 1
person per 8m2, with fresh air supplied at a rate
of 16l/s/p. Tenants small power is assumed to be
15W/m2 installed load. This represents the level
of equipment installed by tenants, rather than the
maximum allowance the building power and cooling
systems can accommodate (i.e. the design brief)
which would typically be higher, i.e. up to 25W/m2.
Occupancy schedules have been aligned with
NABERS14 modelling guidance, and represent
standard offce hours with minimal out-of-hours
working. Outside normal hours, small power is
assumed to operate at 25% of the installed capacity,
with lighting operating at 5%. Tenant IT provision
(server rooms with associated cooling) are included,
equivalent to 10W/m2 power consumption across
the offce floors.
The fnishes for the baseline design assumes a full
suspended aluminium ceiling and a new raised
access floor, which together contribute signifcantly
to embodied carbon. It is also assumed that all the
surfaces within the cores are dry-lined.
The INTERMEDIATE DESIGN varies from
the baseline design in that the tenant installed
small power is limited to 12W/m2, and tenant IT
installation is limited to the equivalent of 7.5W/m2
across the floor-plates.
Additionally, there is no suspended ceiling, no
dry-lining within the cores, and the raised access
floors are recycled, all of which reduces the impact
on embodied carbon. The increased floor-to-floor
height, when combined with the omitted ceilings,
results in a much greater perceived internal volume.
The STRETCH DESIGN makes fundamental
changes to the ftout to signifcantly drive down
tenant energy usage. Tenant energy use is a
signifcant portion of total building energy,
specifcally IT server room operation. The stretch
design adopts off-site cloud computing, with onsite server room usage limited to 0.5W/m2. This
effectively shifts the associated energy and carbon
emissions from buildings i.e. from scope 2 (direct
energy usage) to scope 3 (supply/value chain).
It is recognised that to some degree this is
simply moving energy usage form one building
sector (offces) to another (data centres), however
studies15 have found that cloud-based operations
are signifcantly more effcient than local server
rooms, due to increased IT operational effciency
(aggregating resources and using less hardware
to do more), IT equipment effciency (using the
most energy effcient hardware), and data centre
infrastructure effciency (dedicated buildings which
are able to utilise advanced cooling technologies).
.
0
20
40
60
80
100
120
140
160
Baseline Intermediate Stretch
Energy intensity
(kWh/m2(GIA)/yr)
Landlord total
Server
Pumps and fans
Lighting
Cooling
Heating
Hot water
Lifts
Tenant total
Server room + cooling
IT/Small power
DHW
Lighting

UKGBC 2025 benchmark
UKGBC 2030 target
UKGBC 2050 target
Key:
156
Figure 12: Whole building energy use across three scenarios
28 29
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Net zero residential
KEY DESIGN CHANGES TOWARDS NET ZERO
1. Replacement of concrete structure with timber frame
While low carbon concrete and post-tensioned concrete slabs helps to reduce embodied carbon
from fully concrete structures, the use of a timber frame (beams, decking and columns) in the stretch
scenario achieves the most signifcant upfront carbon reduction: a 74% reduction of the structural
elements compared to the baseline design (from 273 to 70kgCO2e/m2). However, given the increased
structural zone required with the use of timber, two floors had to be removed to maintain the current
building height which resulted in the loss of eight units, likely affecting the building’s fnal value.
2. Reduction of glazing areas to reduce heat loss
Reducing heat loss when designing residential buildings is critical to tenant operational energy savings.
In addition to incorporating triple glazing and reducing the wall u-value, the stretch design sees
the glazing ratio reduced from 51% in the baseline and intermediate scenarios to 29% in the stretch
scenario through reducing the bedrooms’ window sizes and removing the balconies. Decreasing this
ratio further could have negative quality of life impacts given potentially inadequate daylighting levels.
While reducing the glazing ratio was necessary for achieving the stretch design targets, it is noted that
this could be controversial in build to rent schemes where there may be greater dwell times in different
rooms and thus increased daylighting requirements.
3. Replacement of gas boiler with air source heat pump
Most residential buildings today are equipped with a traditional gas boiler. The replacement of a
gas boiler with an air source heat pump immediately achieves the intermediate design operational
targets and contributes signifcantly to the energy savings in the stretch design. Given the increasing
decarbonisation of the UK electricity grid, air source heat pumps are a relatively easy and costeffective change that enable design teams to reduce a building’s operational emissions with little
lifestyle intrusion. Introducing additional energy recovery mechanisms help to further reduce
regulated operational energy loads. Given the diffculty in achieving the 2030 operational target due
to unregulated loads, regulation of minimum effciency standards of domestic appliances, incentives
for their adoption and strategies to encourage energy conscious behaviour would help facilitate the
pathway to zero carbon homes.
The baseline scenario for the residential project represents a current standard practice mid-rise
development. This building was modelled to meet LETI embodied carbon targets for the three
scenarios, as well as RIBA operational energy targets. As with the ofce team, the study’s residential
design team was instructed to attempt to meet these targets while keeping as close as possible to
the project brief that had achieved planning approval (i.e. same overall volume, external massing,
site conditions). The team had free reign to alter all other design parameters (e.g. structure, HVAC
system, tenant requirements, etc.). The results below represent the design team’s best attempt to
meet the targets.
RESULTS
The following two tables provide a summary of results for the three design scenarios alongside a comparison
with relevant net zero targets is provided. A tick or cross has been applied depending on whether the target
has been met.
Table 4: Embodied carbon (module A; kgCO2e/m2)
Baseline Intermediate Stretch
Target
(excluding sequestration)
800
(LETI – business as usual)
500
(LETI – 2020 target)
300
(LETI – 2030 target)
Achieved
(excluding sequestration) 615 500 485
Achieved
(including sequestration)
N/A
(no timber used)
N/A
(no timber used) 315
These results show that the intermediate target is just achievable. It is however extremely challenging for the
stretch target to be met, especially when sequestration from timber is not accounted for.
Table 5: Operational energy (whole building; kWh/m2 (GIA)/year)

70
(RIBA – 2025 target)
35
(RIBA – 2030 target)
Achieved 112 63 43
The stretch scenario falls short of the RIBA target despite an 80% reduction in regulated loads (74kWh/m2 in the
baseline, 15kWh/m2 in the stretch design). The target can only be met with reductions in unregulated loads.

-7.4 0
20
40
60
80
100
120
Domestic hot water
(air source heat
pump + immersion)
Other
Domestic hot water (lower
storage temperature, low
flow fittings)
Unregulated
Energy intensity
(kWh/m2(GIA)/yr)
Figure 13: Reductions in operational energy across the three design scenarios
30 31
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Whilst it would be possible to develop a crosslaminated timber wall panel structure that replaces
the current glue laminated timber (glulam) columns
and eliminates the concrete core, this was not
considered viable for the 16 storey residential
building height with current fre and safety
regulations. This option would remove the need
for a primary/secondary beam system, reducing
floor tonnages, and also providing suffcient lateral
stability to remove concrete in the cores.
While signifcant carbon savings were achieved, any
use of timber is caveated with the expectation that
safety of such structures has been frmly established
and planning regulations are updated to allow for all
timber structures.
The foundations have been reduced further in size
for the stretch design, benefting from an even
lighter structure, low carbon concrete and assuming
preliminary and working pile tests will be carried out.
STRUCTURE
Baseline Intermediate Stretch
Superstructure Reinforced concrete frame
with flat slab construction
Concrete core
Reinforced concrete frame with
post tensioned (PT) flat slabs
Concrete core
Full timber structure
Concrete core
Substructure Reinforced concrete frame
basement
Piled foundation
Reinforced concrete frame
basement
Piled foundation with pile tests
Reinforced concrete
frame basement
Piled foundation with
pile tests
Concrete mix Standard mix with some
cement replacements
Low carbon concrete Low carbon concrete
The BASELINE DESIGN represents the
conventional design of mid-rise residential
buildings using a using a concrete substructure and
superstructure. There is a one storey basement with
the structure supported by piled foundations. The
concrete grade assumed to be used in the design is
a typical London mix. This concrete mix has a high
carbon impact and, along with rebar, contributes
to 45% (273 out of 613kgCO2e/m2) of the upfront
carbon in this scenario.
The INTERMEDIATE DESIGN retains a similar
structure as the baseline design but replaces the
standard concrete mix with low carbon cement
alternatives. The volume of the slabs and piles
decrease when using post tensioning, thereby
reducing the overall amount of concrete needed
and the associated embodied carbon.
For the piled foundations, the number of piles are
reduced, in part due to a reduction in structural
loads and more signifcantly due to the adoption
of pile tests (preliminary and working). Pile tests
provide confdence in the performance of the

method, allowing the designer to assume a higher

initial investment of time and cost, however, in this
scenario pile tests alone resulted in a 14% reduction
in concrete and spoil volumes.

The STRETCH DESIGN retains a concrete
foundation and core, however the beams, decking
and columns have been replaced with crosslaminated timber (CLT) and glulam. The use of
timber achieves a 74% reduction in upfront carbon
of the structural elements over the baseline
scenario (from 273 to 70kgCO2e/m2 not including
sequestration), however required further adaptation
to the structural design.
The use of timber in the superstructure does come
with several important caveats:
• The overall structural zone size is increased from
190mm to 520mm, with some local beams at
640mm, which requires the removal of two floors
to maintain the current building height. This
resulted in a loss of eight residential units (out
of 209) which would directly impact the project’s
viability, unless a compromise pathway could be
negotiated.
• Penetrations for services through beams are
assumed to be a limited number of 150mm
diameter penetrations, which would need to be
excluded from the tonnages as they will require
• Columns will need to be encased in freboard or
similar to achieve the two-hour fre rating. This
will have an associated increase in embodied
carbon. Additionally, all connections are required

Embodied Carbon
(modules A1-A5; kgCO2e/m2)
-200
-100
0
100
200
300
400
500
600
700
Baseline Intermediate Stretch
Figure 14: Chart showing the reduction in upfront carbon across all three scenarios based on changes to
the structural design
Figure 15: Section drawings for the baseline and stretch scenarios
CLT Slab Options
Timber Beams and Timber Columns
3370mm
CLEAR FLOOR TO
CEILING HEIGHT
STRUCTURAL
BEAM DEPTH
150DIA
penetrations for
services
STRUCTURAL
SLAB ZONE
150mm
FLOOR FINISHES ZONE

150mm
3150mm
CLEAR FLOOR TO
150mm 225mm
FLOOR FINISHES ZONE
2575MM
2500mm 520mm 200mm
STRUCTURAL
SLAB ZONE
STRUCTURAL ZONE
Limited 150DIA
service penetrations
through timber beam
200mm
CLT Slab Options
Timber Beams and Timber Columns
3370mm
CLEAR FLOOR TO
CEILING HEIGHT
STRUCTURAL
BEAM DEPTH
150DIA
penetrations for
services
STRUCTURAL
SLAB ZONE
150mm
FLOOR FINISHES ZONE
3150mm
200mm
CLEAR FLOOR TO
CEILING HEIGHT
200mm
STRUCTURAL
SLAB ZONE
150mm
FLOOR FINISHES ZONE
2600mm min
3150mm
CLEAR FLOOR TO
150mm 225mm
FLOOR FINISHES ZONE
2575MM
SERVICES ZONE
STRUCTURAL
2500mm 520mm 200mm
STRUCTURAL
SLAB ZONE
STRUCTURAL ZONE
Limited 150DIA
service penetrations
through timber beam
200mm
SERVICES
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The STRETCH DESIGN reduces the glazing U-value
to 0.8, further minimising heat loss. This is achieved
through:
• Reducing the wall U-value to 0.13, compared to
0.15 in the intermediate scenarios.
• Reducing the glazing ratio to 29%. Designers
are likely to be reluctant to decrease this further
as it is important to keep adequate daylighting
levels for quality of life. The living room has
been protected from losing a signifcant amount
of view outside as each living room maintains
a minimum of one fully glazed double door.
As a result of the reduced window size, juliette
balconies are removed from all bedrooms.
• Increasing levels of insulation in the building
fabric, which does create a reduction of 120m2
net saleable area over the whole building.
However, this was considered to be an
appropriate design choice given the benefts of
reducing operational energy requirements.
The reduction in glazing area can be considered
a downside of the stretch scenario, as the glazing
areas are less than current market expectations.
However, with early analysis of daylight on projects
it can be maintained to acceptable levels in high
performance buildings.
With careful consideration of how windows are
confgured and positioned the compromise on
daylight can be minimal. For example, horizontal
windows, positioned in the centre of a room
generally provide better daylight distribution than a
vertical window of a similar area on the same wall.
In all cases overheating risk should be assessed
and minimised. Solar shading may be appropriate
to mitigate overheating risk and reduce tenant
requirements for comfort cooling.
FAÇADE
Baseline Intermediate Stretch
Cladding Full brick
U-Value of 0.22
Infltration 5m3/hm2@50Pa
Masonry wall construction
U-Value of 0.15
(with insulation)
Infltration 2m3/hm2@50Pa
Masonry wall construction
U-Value of 0.13
(with insulation)
Infltration 1m3/hm2@50Pa
Insulation None Roof: 150mm
Wall: 50mm at slab edge
Ground: 25mm
Roof: 150mm
Wall: 50mm overall wall depth
Ground: 25mm
Glazing ratio 51% glazed 51% glazed 29% glazed
Glazing Double glazing
U-value of 1.6
G-Value of 0.4
Triple glazing
U-value of 1.1
G-Value of 0.5
Triple glazing
U-value of 0.8
G-value of 0.6
The BASELINE DESIGN for the façade represents
a standard mid-rise residential scheme as
specifed within the original project brief. The
design decisions maximise the product value
from an aesthetic, resident comfort and usability
perspective. This results in large areas of double
glazing that enable a signifcant quantity of
bedrooms to have juliette balconies and each living
room a bolt-on balcony.
Current standard practice allows the façade to be
designed as a fully brick exterior. A rainscreen is
used on a light steel frame with a 50mm clear cavity.
The glazing and wall U-values achieve current Part L
requirements.
The INTERMEDIATE DESIGN has a similar glazing
ratio to the baseline scenario, however incorporates
triple glazing into the wall envelope. To ensure
insulation is improved and heat loss is reduced, a
decision was made to move to traditional masonry
construction. This results in a decrease in the
U-value by allowing for a smaller wall cavity, thereby
increasing the overall performance of the wall.
Without this move to masonry construction, it would
be diffcult to achieve the required U-value over
the whole wall without substantially impacting net
saleable area.
The following design considerations were required:
• Installing insulation at the roof required an
increase in the height of the building by 800mm
and at ground required the addition of a 25mm
insulation layer.
• Hand-laid brick was used as it is a robust and
long-lasting material. The mortar was changed
from a cement base to a lime base in order to
increase the likelihood of reuse if the building
were ever to be partially or wholly demolished.
• Powder coated aluminium panels were selected
given these are recyclable, improving the carbon
impacts of the building at end of life. However,
the specifcation of aluminium should be carefully
assessed given the range of product’s embodied
carbon dependent on where the aluminium is
sourced.
• Whereas the baseline design decreases the
glazing ratio and increases the G-value, the
intermediate design retains the same glazing
ratio but increases the G-value of the windows.
This means that there is a greater risk of
overheating without additional solar control
measures, such as external shading or the
inclusion of interstitial blinds in the windows. A
positive impact on resident wellbeing, however,
is the reduced acoustic transmission when using
triple glazed windows which blocks out external
noises such as traffc.
Figure 16: The original design included juliette balconies to most bedrooms (left), however this has been
removed for the stretch design to reduce glazing areas (right)
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Improving the effciency of generating domestic
hot water by storing it at lower temperature is
the primary gain in improving the regulated
energy effciency within the building systems. The
improvements to building services and fabric lead
to a 49kWh/m2 reduction in regulated energy
consumption for the intermediate scenario, with a
further 10kWh/m2 reduction for the stretch scenario.
A total energy consumption, including residents’
small power appliances, is anticipated to exceed the
RIBA 2030 target, suggesting further strategies will
be required to reduce regulated and unregulated
energy consumption.
A ground source heat pump system could be
considered as an alternative to air source heat
pumps to further reduce energy consumption at
sites with suitable ground conditions and space.
Ground source heat pump systems should be
appraised at an early stage in future housing
projects so that an appropriate evaluation can be
made for this low carbon technology.
BUILDING SYSTEMS
Baseline Intermediate Stretch
Heating Gas boiler
Radiators
Air source heat pump with
electric immersion heater
for domestic hot water
Radiators
Air source heat pump with suitable
treatment to deal with legionella
compliance
Radiators
Ventilation Mechanical
ventilation with
heat recovery
Mechanical ventilation
with heat recovery
Mechanical ventilation with heat
recovery
Other Low flow water fttings Low flow water fttings
LED lighting improvements
Reduced small power consumption
through occupant selection of
effcient electrical appliances
The BASELINE DESIGN uses a traditional gas
boiler to produce low temperature hot water at 70°C
with an effciency of 95% for both space heating
and domestic hot water. Mechanical ventilation
with heat recovery (MVHR) with a heat recovery
effciency of 85% is included for all scenarios. This
design represents a conventional approach given
the majority of UK homes are still powered by gas
boilers and new homes continue to be ftted with
gas systems.
The INTERMEDIATE DESIGN utilises an air source
heat pump (ASHP) in place of the gas boiler; the
decarbonisation of the UK electricity grid means
electric heating systems are, and will increasingly be,
a lower carbon solution than fossil fuel alternatives.
The air source heat pump generates low
temperature hot water at 45°C. This is distributed
to the dwellings for space heating and is typically
uplifted to 60°C for domestic hot water by an
electric immersion heater in the hot water cylinder.
This system is anticipated to result in an annual
weighted effciency of heat generation, or
‘coeffcient of performance’ (CoP), of 3.22 for space
heating and 2.06 for domestic hot water. These have
been calculated using manufacturer’s effciency
profles, local weather data, and room side demands
for heating and domestic hot water. Low flow water
fxtures and fttings are also included, reducing
domestic hot water demand.
Installing an ASHP instead of a gas boiler was an
effective way to reduce carbon with limited cost,
design, and occupant behaviour changes. The
intermediate net zero targets were achieved with
this change alone.
The STRETCH DESIGN includes the same ASHP
as the intermediate design, introduces additional
energy recovery technologies, and assumes
improved lighting and appliance effciencies. A
chemical treatment method, such as a chlorine
dioxide dosing system, is incorporated which allows
the storage of domestic hot water at 45°C (negating
the need for temperature-based legionella control).
This greatly improves the overall generation
effciency; an annual effciency (CoP) of 3.77 is
anticipated for the domestic hot water system.
Whilst a chlorine dioxide system has been costed,
other forms of legionella control enabling lower
temperature domestic hot water, such as UV
treatment or ionisation, as well as phase change
storage, could be deployed. Note, that these
systems have associated costs and maintenance
requirements above and beyond a typical domestic
hot water system which were not modelled in this
study.
0
20
40
60
80
100
120
140
160
Baseline Intermediate Stretch
Lighting
Space heating
DHW
Auxiliary
Small power
RIBA benchmark
RIBA 2025 target
RIBA 2030 target
Annual energy consumption
(kWh/m2/year)

Key:
Figure 17: Annual operational energy consumption per square meter of floor space
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APARTMENT DESIGN
Baseline Intermediate Stretch
Appliances Occupier choice of whitegoods
and appliances
Occupier choice of whitegoods
and appliances
AAA- whitegoods
and best appliances
Unregulated
loads
38kWh/m2 38kWh/m2 29kWh/m2
The BASELINE DESIGN assumes occupiers
choose their own white goods and appliances. This
represents current market average levels of energy
performance, and is unlikely to consist of many
high-effciency whitegoods or appliances factoring
in affordability and other product considerations.
The INTERMEDIATE DESIGN assumes the same
unregulated load demand.
The STRETCH DESIGN optimises the building
fabric and building systems to achieve 15kWh/m2 for
all regulated energy uses. This involves exhausting
nearly all interventions the building designer can
make to achieve the RIBA 2030 overall target of
35kWh/m2, leaving the balance in the hands of the
occupier’s unregulated loads.
Given the steady improvement in the energy
effciency of whitegoods and appliances, it was
considered reasonable to assume that occupiers’
unregulated loads can be reduced to 29kWh/m2
for new buildings. This results in total energy use
equalling 44kWh/m2 with unregulated loads making
up 65%, however, this still falls short of the RIBA
2030 target. This outcome could suggest that
energy performance targets should be separated
so that designers focus on the building energy uses
that they have full control over (regulated energy)
and allow other mechanisms (e.g. policy, effciency
ratings) to address what is out of their control
(unregulated energy use).
The designer’s influence on unregulated loads
in homes is particularly challenging as domestic
equipment is not controlled by building regulations.
Consequently, residents are free to operate
appliance in their home as they wish. Whilst design
solutions can go a long way to providing the
reductions in energy demand needed, ultimately
the responsibility for reducing unregulated loads,
such as white goods, kitchen equipment and TVs,
will sit with the occupier. Build-to-rent developers
can demonstrate best practice by installing very
high effciency appliances to keep consumer energy
loads to a minimum.
From a policy perspective, regulation of minimum
effciency standards of domestic appliances,
incentives for their adoption and strategies to
encourage energy conscious behaviour would help
facilitate the pathway to zero carbon homes. Smart
meters and intelligent controls will also have a role
in helping consumers to optimise the performance
of electrical appliances. Such changes will be crucial
in meeting future net zero building targets to
address energy uses that fall outside of the building
designer’s control.
A more radical approach was considered for this
study which was to remove access to individual
whitegoods and instead rely on communal facilities,
including washing and drying rooms. These
communal facilities could have the highest effciency
whitegoods and eliminate large unregulated energy
loads within apartments. Given the signifcant
departure from current market practice and occupier
preferences, this approach was not modelled.
Figure 18: Annual operational energy consumption per square meter of floor space.
UK Green Building Council | Building the Case for Net Zero
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39
Section 2:
Cost changes
As this report has shown, buildings can be designed
today to achieve future net zero targets. However, a
better understanding of the associated cost is necessary
to appreciate the changes required to the investment
and financing of net zero buildings. This section provides
estimates of the key cost changes from the baseline scenario
to the intermediate and stretch scenarios, for both the office
and residential projects.
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Net zero ofce
Table 7: Cost change by building element (£/m2 GIA) for offce design scenarios
Baseline Intermediate Stretch
£/m² £/m²
% change
from
Baseline
£/m²
% change
from
Baseline
1. Substructure £325 £365 12% £160 to 185 -44 to -50%
2. Frame, upper floors &
stairs
£450 £625 39% £730 to 820 63 to 82%
3. Roof
£75 £75 – £75 –
4. External walls, windows &
doors
£495 £445 -10% £495 to 550 0 to 11%
5. Internal walls & doors
£95 £95 – £95 2%
6. Finishes & fttings £235 £235 – £235 1%
7. Mechanical, electrical &
plumbing (MEP)
£730 £745 2% £745 to 820 2 to 12%
8. Lifts
£110 £120 9% £130 to 140 17 to 27%
9. Preliminaries; overheads &
proft; design & build risk £610 £610 – £700 to 775 15 to 27%
Total Shell & Core
£3,125 £3,320 6.2% £3,370 to 3,660 8 to 17%
It is important to note that costs are presented on a £/m² of GIA. Differences in the overall GIA will have a
knock-on effect on the price per m² where some elements remain constant. For example, the external walls
appear to have signifcantly increased in cost, and whilst some of this effect is the adoption of opening
windows, a large proportion is attributed to costs being spread over a lower GIA following the removal of
the basement.
OVERVIEW
The following section illustrates the effect on construction costs of embracing low carbon design and
achieving ambitious net zero targets. The change in cost is broken down by building elements on a
pounds per square metre basis to enable a direct comparison between the three design scenarios.
The cost models have been developed using feasibility design documentation and therefore ranges
have been utilised to demonstrate cost effects. Commentary explaining the rationale behind each
range is provided below. These costs are representative of a market that is yet to fully embrace low
carbon strategies, and this is reflected in the preliminary and on-costs.
Table 6: Design economics for three design scenarios
Baseline Intermediate Stretch
Gross Internal Area (m²) 28,516 26,975 24,650
Net Internal Area (m²) 19,391 17,997 16,035
NIA:GIA overall effciency 68% 67% 65%
Total floors (excl. roof) 17 16 15
Above ground floors (excl. roof) 16 15 15
Below ground floors 1 1 0
Slab to slab height (m) 3.60 3.87 3.85
Structural frame Steel frame and
composite floor
Steel frame and CLT
floor
Glulam frame and
CLT floor
The baseline design is benchmarked using a number of BCO compliant commercial buildings within central
London. These projects are aligned in size however, represent a mid-high shell and core specifcation. A
benchmark effciency of 68% is achieved on the net to gross internal floor area.
In this study, it is assumed that the baseline design would beneft from an additional floor where slab to slab
heights can be reduced due to the concrete and steel construction. The timber frame in the stretch design
dictates greater slab to slab depths to enable services to pass under the CLT beams, rather than through
them in a more conventional frame. The CLT beam depths are also deeper than steel beams.
The stretch design removes the basement and relocates plant to the upper floors whilst retaining the above
ground building envelope (the same building height is maintained). Whilst this attracts a reduction in overall
costs for the substructure, the loss of NIA is signifcant and reduces the building’s overall area effciency.
The reduction in total floors from 17 to 15 between the baseline and stretch scenarios has a compound
impact on the commercial viability of the project. Capital costs have increased and the yield has decreased
given total net internal area has reduced by 17%. Whilst out of scope of this study, future studies could
examine other contributing factors to building value, including stranded asset risks, investor pressure
through the Task Force on Climate-related Financial Disclosure (TCFD), and running costs. The latter could
build on recent JLL fndings showing that sustainable buildings can result in increased rental value of 6-11%
and lower void periods, which could potentially balance increases in capital costs. “Even with a potential
increase in construction costs, we estimate that the rental premium and yield compression could take a
typical scheme from 15% proft on cost to over 20% proft on cost,” from the JLL report.9
Additionally, the study did not consider whether a compromise pathway could be negotiated to improve
the project’s viability, for example, for an improved planning consent to increase building height, based
on the net zero credentials of the development. In any case, the market will need to clearly examine the
fnancial returns for full structural timber frame buildings to better understand the full implications. This
discussion topic is due to be addressed in a supplementary report – please see “Section 3: Conclusion” on
page 55 for further information.
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Baseline Intermediate Stretch
5. Internal walls & doors £95 £95 £95
6. Finishes & fttings £235 £235 £235
Costs for these elements are subject to minor change and remain constant in this study.
Baseline Intermediate Stretch
7. Mechanical, electrical &
plumbing (MEP)
£730 £745 £745 to 820
8. Lifts £110 £120 £130 to 140
The baseline MEP is for a high specifcation developer and therefore costs are considered higher than
industry benchmarks. Numerous specifcation and scope enhancements were costed, such as:
• Supplementary cooling systems to MER, Transformer & UPS rooms
• On floor hydraulic separation of LTHW & CHW services
• Power system monitoring – PMS, PLC, EMS requirements
• Standby generation provision for tenants
• Inclusion of a passive/active network
• Inclusion of mobile phone enhancement
• Smart enablement
The baseline allows for this increased level of specifcation at £730/m² and lifts at £110/m².
The stretch design sees a £20/m² cost increase over the intermediate design. This is attributed to a fully
automated temperature system, linked to window openings and the HVAC system

Industry benchmarks at the time of writing expect preliminaries to be between 14-15% of the construction
cost of the project. Overheads and proft for new builds were observed at 5%, and design and build risk at a
range of 2-3%.
The baseline and intermediate scenarios allow for industry benchmark percentages and therefore the
majority of cost uplift is attributed to an increase in construction costs.
In the stretch design the anticipated level of preliminaries, overheads and proft, and risk are increased to
reflect the current appetite in the market, lack of precedence and greater perceived risk relating to timber
frames. In time, it is anticipated that these on-costs will become more competitive as the adoption of timber
buildings becomes more commonplace.
KEY COST DRIVERS
Baseline Intermediate Stretch
1. Substructure £325 £365 £160 to 185
The concrete substructure for the baseline and intermediate designs remain the same. The costs, however,
are lower for the baseline to remain consistent with the benchmarked analysis which are typically single
storey, whereas the intermediate design is double height.
The removal of the basement in the stretch design omits costs for secant piling and basement excavation,
generating a saving of £190/m² across the reduced GIA of 24,650m².
Baseline Intermediate Stretch
2. Frame, upper floors & stairs £450 £625 £730 to 820
The baseline design is based on a steel frame with concrete slabs on a metal deck, and a concrete core.
The baseline is observed as the lowest cost of all three specifcations at £450/m² which is expected; the
market at the time of writing is well suited to respond to this specifcation and over time has increased the
performance of the frame and gained effciencies in construction methods and speed.
The intermediate design introduces CLT slabs in lieu of the concrete slabs on metal deck. This results in a
cost increase of £175/m² to £625/m² which is because of CLT slabs being more expensive, and an overall loss
of GIA.
In the stretch design, the frame and upper floors are entirely constructed from timber. A suitable range for
adopting this design was considered to be £730-820/m². The quantum of timber has been calculated using a
typical floorplate with marginal adjustments for ground and plant areas.
Baseline Intermediate Stretch
3. Roof £75 £75 £75
Whilst the roof slab is changed to CLT in the stretch design, no signifcant cost increase cost is expected
between all three scenarios.
Baseline Intermediate Stretch
4. External walls, windows &
doors
£495 £445 £495 to 550
The baseline external walls benchmarked in this scenario typically have greater levels of articulation than the
intermediate design. For this reason, the cost is slightly more expensive for the baseline design, allowing for
a variety of performance and architectural specifcations.
For the intermediate design, the external walls have been rationalised, reducing articulation and simplifying
the number of cladding types. The simplifcation of the cladding accounts to a £50/m² reduction compared
to the baseline design.
The stretch design takes the same façade as the intermediate design, however adds opening vents. The
integration of these into the façade adds £80/m², which is partially driven by the reduction in GIA.
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WHOLE LIFE COSTING
The scope of the main cost analysis for this study has been limited to changes in the buildings’ capital cost,
rather than whole life cost. This was considered reasonable given confdent assumptions can be made for
capital costs based on the feasibility stage design documentation, whereas these costs would have become
less reliable when modelling across the life of the building. A whole life cost analysis, however, is benefcial in
painting a fuller picture, allowing stakeholders to appreciate not only immediate cost changes, but also the
influence design changes can have on cost throughout the life of a building.
Some examples of whole life cost changes for low carbon buildings include:
• Lower energy costs due to higher energy effciency,
• Lower maintenance and replacement costs due to designing for durability,
• Higher rental premiums due to leading environmental attributes,
• Lower demolition costs due to designing for circularity,
• Lower offset cost due to effcient design and operation.
Whilst the previous section of this report provides the overall capital cost changes for the offce design
scenarios, a whole life costing analysis has been undertaken for a small selection of building design changes.
This is intended to provide a sample of whole life cost fndings which, ideally, should be undertaken as
standard practice across the overall design of a building, similar to lifecycle carbon assessments.
The three building elements for which the whole life costing analysis has been undertaken is provided in
Table 7 for both the baseline and stretch scenarios. A period of 30 years has been selected for the analysis
as this is considered to be the point at which a major retroft may be undertaken. The fndings highlight the
importance of assessing the feasibility of net zero buildings based on whole life cost, not only capital cost,
and future studies could provide this analysis across the overall design of a net zero building.
Table 8: A limited whole life costing analysis was undertaken for three building elements

Gas boiler vs. air source heat pump
The optimisation of the building’s design between the baseline and stretch scenarios, combined with the
change from gas boiler to air source heat pump, results in a 72% reduction in heating and co–ling loads –
from 1,450,000kWh/yr to 410,000kWh/yr. This improved energy performance in-use results in a 30-40% cost
saving over 30 years of operation. These calculations have been based on component lives derived from
CIBSE Guide M and JLL’s in-house benchmark data.
In addition to these cost savings, any costs to retroft the building to meet future net zero legislation or
market expectations should also be considered. This could include signifcant costs to remove any on-site
fossil fuel use from gas boilers and replacement with either a hybrid (hydrogen/gas) system or air source heat
pump. Designing new buildings that achieve net zero outcomes today would future-proof the building from
future unknown costs such as these.
£3,100
£3,150
£3,200
£3,250
£3,300
£3,350
£3,400
£3,450
£3,500
£3,550
£3,600
Prelims / OHP / D&B risk
MEP & lifts
External walls, windows & doors
Frame, upper floors & stairs
Substructure
MEP & lifts
External walls, windows & doors
Frame, upper floors & stairs
Substructure

Cost change
(£/m2 GIA)
Baseline scenario £3,125/m2
Intermediate scenario £3,320/m2
Stretch scenario £3,540/m2
175
130
Figure 19: Building element adjustments from baseline through to intermediate and stretch scenario
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Net zero residential
OVERVIEW
The following section illustrates the effect on construction costs of embracing low carbon design and
achieving ambitious net zero targets. This has been done by modelling costs on a residential build-to-rent
project in the south east with 209 units. The scheme is mixed-use with elements of retail, amenity, and
workspace. The retail and workspace elements were discounted from the exercise to give a true reflection of
the residential costs.
The change in cost is broken down by building elements on a pounds per square metre basis to enable
a direct comparison between the three design scenarios. The cost models have been developed using
feasibility design documentation and therefore values have been estimated and rounded. These costs are
representative of a market that is yet to fully embrace low carbon strategies, and this is reflected in the
preliminary and on-costs.
Table 9: Design economics for three design scenarios
Baseline Intermediate Stretch
Gross Floor Area (m²) 18,216 18,216 17,536
Net Internal Area (m²) 12,117 12,117 11,513
NIA:GFA overall effciency 67% 67% 66%
Total floors 18 18 16
Number of units 209 209 201
Structural frame Reinforced concrete
frame
Reinforced concrete
frame, with posttensioned slabs
Timber frame and CLT
floors, with retained
concrete cores
It is important to note that the stretch scenario has eight less residential units than the baseline and
intermediate scenarios which would have a direct impact on the viability of the scheme. This is due to the
requirements for the structural zone for this option increasing from 190mm to 640mm and the resulting two
floors being lost to maintain the current building height. This has caused a reduction to the gross internal
floor area and net internal area for this scenario.
Suspended ceiling vs. exposed soffit
The ftout for the stretch scenario has been designed to reduce, or remove entirely, any excessive material
fnishes. This approach, also known as ‘dematerialisation’, helps to reduce embodied carbon from the
building’s construction and use (i.e. maintenance, repair, refurbishment, replacement) stages. The change
from a standard suspended ceiling system to an exposed sofft with foil wrapped services not only helps to
reduce embodied carbon but also results in a cost saving of 50-60% over a period of 30 years.
These calculations assume a rate of £85/m² for installing the suspended ceiling and £35/m² for foil wrapped
services to the exposed sofft (to maintain aesthetics), with a 2% allowance for replacement every 5 years in
both scenarios. Additional benefts of the exposed sofft include easy access to building systems and greater
floor-to-ceiling heights, however further consideration would be required for the layout and provision of
services without a ceiling void.
Raised access flooring vs. solid timber flooring
A similar dematerialisation approach that was applied to the ceiling has also been applied to the flooring.
The change from raised access flooring with carpet tile to solid timber flooring saves the replacement of
carpet tiles at the assumed rate of every 12 years, with commensurate reductions in embodied carbon. The
calculations assume £60/m² for installing the raised access flooring with an allowance of 5% to be replaced
every 20 years for planned and reactive maintenance churn; £30/m² for the carpet tiles, with a replacement
life at every 12 years; and £120/m² for installing a timber floor cradle and batten system.
Unlike the cost savings for the exposed ceiling, the low carbon flooring option does result in a slight 3.5%
cost increase over a period of 30 years. This points to the importance of accounting for multiple product
and material life cycle costs as in some cases, cost increases will be balanced out by savings in other areas
though this principle is subject to further project specifc analysis. When considering solid timber flooring,
one also cannot disregard the carbon savings from eliminating multiple carpet replacements and utilising
wood instead.
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KEY COST DRIVERS
Baseline Intermediate Stretch
1. Substructure £130 £130 £125
Moving from the baseline design to the intermediate resulted in cost savings of (£3/m2) due to the reduction
in weight moving to post-tension slabs, reinforcement reduced from 150kg/m3 to 85kg/m3. This saving was
increased by a further £3/m2 moving to the timber frame option in the stretch design.
The volume of concrete required for the piling reduced by 17% from the baseline to intermediate design,
and a further 8% between the intermediate and stretch designs. For both the intermediate and stretch
design a preliminary pile test and three working pile tests have been allowed for. For all three scenarios CFA
piling was used.
An additional 25mm of excavation was allowed for to increase the thickness of the ground insulation by
25mm for the intermediate and stretch designs. This was reviewed and the cost impact was negligible.
Baseline Intermediate Stretch
2. Frame, upper floors & stairs £250 £265 £285
The baseline design cost is based on a traditional reinforced concrete (RC) frame with concrete cores. This is
the most common type of construction for mid-rise residential buildings in the UK due to its effciency, speed
of construction and general familiarity of the UK supply chain with this method of construction.
The intermediate design moved to a post-tensioned (PT) concrete slab which resulted in a cost increase
of £17/m2, despite reductions in the volume of concrete and reinforcement required. PT slabs generally
become more cost effcient than traditional RC frame on projects where large spans are required (over 6m),
with a simple and repetitive floor plate shape.
The stretch design (timber frame and CLT) was the most expensive of the three scenarios. Cost data was
notional given the limited amount of cost data available for medium to high rise timber residential buildings
in the UK. Additional costs which are not required for the other two scenarios were also factored into these
costs, including encasement of all columns in fre boarding to achieve a two hour fre rating, and similar
within the floor build-up. Due to current Building Regulations and the requirement for non-combustible
materials in the façade, further work and development will be required to better understand the risks with
timber and CLT and thus make it more cost-effective for project delivery.
A key issue which also impacted the stretch design was the fact that the overall structural zone had to be
increased from 190mm to 640mm when moving to a timber structure. This required the removal of two floors
to maintain the current building height and has resulted in the loss of eight residential units, 680m2 of gross
internal floor area and 484m2 of net saleable area.
Baseline Intermediate Stretch
3. Roof £85 £85 £90
150mm of roof insulation was added to the intermediate and stretch scenarios which resulted in a slight
cost uplift.
Table 10: Cost change by building element (£/m2 GIA) for residential design scenarios
Baseline Intermediate Stretch

0. Demolition & enabling £35 £35 – £35 –
1. Substructure £130 £130 – £125 -4%
Shell & Core
2. Frame, upper floors & stairs £250 £265 6% £285 14%
3. Roof £85 £85 – £90 6%
4. External walls, windows & doors £460 £510 11% £475 3%
Finishes
5. Internal walls & doors £200 £200 – £200
6. Finishes & fttings £340 £340 – £350 3%
7. Mechanical, electrical & plumbing
(MEP); lifts £580 £590 2% £625 8%
8. External works £60 £60 – £65 8%
Measured Works Total £2,140 £2,215 3.5% £2,255 5.4%
9. Preliminaries; overheads & proft;
design & build risk £575 £595 3% £605 5%
Construction Total £2,715 £2,810 3.5% £2,860 5.3%
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Baseline Intermediate Stretch
7. Mechanical, electrical &
plumbing (MEP); lifts
£580 £590 £625
The major change from the baseline design is the addition of air source heat pumps (ASHP) to provide heat
in lieu of a gas boiler system. This cost has been based on analysis explored by the cost consultant on the
current scheme’s design development. The provision of gas on-site has been removed, as well as specifc
equipment for gas boilers only, such as flues. It has been assumed that the structure can accommodate the
ASHP at roof level.
The LED improvements included for the stretch design are assumed not to demonstrate a cost uplift i.e.
reflect similar progress in the market as has been seen over the last decade.
Wastewater heat recovery systems (WWHRS) has also been included in the stretch design. This would require
a system on each shower/bath drain and the costing has been based on one unit per apartment using the
Showersave system.
The addition of the chlorine dioxide (ClO2) system for domestic hot water (DHW) to allow lower water
temperatures and therefore much higher water generation effciencies from the heat pump provides an uplift
in cost. This would necessitate an electric zip tap (or similar) to the kitchen sink of each apartment to provide
higher temperature water. The costing has been based on one unit per apartment.
The stretch design sees a £35/m² increase in cost over the intermediate design, attributable to the items
highlighted above.
Value engineering options would be explored on all design scenarios and costs could be reduced via MMC
options, such as bathroom pods and prefabricated MEP systems, although has not been explored in this
study.
Baseline Intermediate Stretch
9. Preliminaries; overheads &
proft; design & build risk
£575 £595 £605
Preliminaries have been benchmarked at 15.5% in line with current tender returns received for similar
residential projects; overheads and proft have been allowed at 5.5%; design and build risk has been
benchmarked at 5% on shell and core works, and 3% on ftout rates. All three scenarios make use of these
rates.
In the stretch design, it would be anticipated that for timber framed buildings the preliminaries costs may
be slightly lower, however due to the perceived risks around timber at present it was deemed prudent to
maintain the same level of on costs as the baseline and intermediate scenarios. In the future, as timber is
more widely adopted and the risks are better understood, this should in turn make pricing more competitive.
Baseline Intermediate Stretch
4. External walls, windows & doors £460 £510 £475
The baseline design included a solid:glazing ratio of 51:49 and masonry wall construction (metsec inner skin)
without insulation.
The intermediate design maintained the same solid:glazing ratio, however with a specifcation uplift to
triple glazing, 250mm glass wool insulation and blockwork inner skin. Lime mortar was also introduced. This
change in specifcation increased costs by £50/m2.
The stretch design increased the solid:glazing ratio to 71:29 (whilst maintaining triple glazing). This reduction
in the proportion of glazing brought costs down by £32/m2 and brought the capital value broadly in line with
the baseline design. It is to be noted that in this fnal scenario the amount of light entering the apartments is
reduced and may have a knock on effect on their desirability.
The insulation is increased to 300mm in the stretch design and, importantly, this results in 120m2 of net
internal area being lost throughout the building, due to the increased wall thickness build-up.
Baseline Intermediate Stretch
6. Finishes & fttings £340 £340 £350
Changes for costs for these elements were kept constant in this study and any movements are due to
changes in GIA/NIA. For the stretch design, additional costs were included for the introduction of freboard
to the floor build-up to achieve a two-hour fre rating.
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Carbon offsetting
OFFSET COSTS
Using the offset price of £64/tCO2, the additional capital cost for offsetting to achieve net zero carbon –
construction for all three scenarios is provided in the tables below.
Table 12: Offce breakdown of costs to achieve net zero carbon – construction for all three scenarios

Total upfront carbon
(module A; tCO2e)
25,125 20,419 16,857 14,036 7,625
Price of offset unit
(£/tCO2)
£64
Price to offset
total carbon for
construction (£)
£1,608,000 £1,307,000 £1,079,000 £898,000 £488,000
Offset price
(£/tCO2e/m2 GIA)
£59.61 £48.45 £40.00 £36.43 £19.80
Table 13: Residential breakdown of costs to achieve net zero carbon – construction for all three scenarios

Total upfront carbon
(module A; tCO2e)
13,538 11,009 10,347 6,750
Price of offset unit
(£/tCO2)
£64
Price to offset
total carbon for
construction (£)
£866,500 £704,600 £662,200 £432,200
(£/tCO2e/m2 GIA) £39.25 £31.91 £30.95 £20.20
* Unlike the intermediate scenario for the offce design, the intermediate scenario for the residential design does
not include a timber structure, so sequestration is not considered.
These results demonstrate the importance of including offset payments within the capital cost appraisal for
new buildings. Developers and investors that account for offsetting help to future-proof the business case
for new buildings where offsetting could become a requirement, for example, through planning or market
expectations. A current example, is the requirement to offset regulated emissions in the new London Plan,
which is due to be extended to major non-residential developments.19
This analysis demonstrates that higher performing, lower carbon buildings will have to pay less for offset
payments. Whilst these buildings will require an overall initial increase in capital cost compared to the baseline,
this can help to reduce the true cost of a building, including its environmental impact and cost to achieve net
zero. Carbon prices will only increase over the next decade and this will impact the absolute values.
In line with the scope and methodology of this study, all three design scenarios were intended to
meet UKGBC’s defnition of ‘net zero carbon – construction’. This involves calculating the total upfront
embodied carbon for each scenario and offsetting this in full to achieve a net zero carbon balance at
practical completion. Each design scenario has placed different levels of emphasis on reducing the
building’s whole life carbon, so this fnal step helps to provide comparability across all three scenarios
for achieving a net zero carbon outcome.
There is a growing recognition among leading developers that the embodied carbon from construction
can account for a large portion of their scope 3 emissions, and voluntary reporting initiatives such as TCFD
and SBT are increasingly encouraging businesses to measure and mitigate these impacts16. Concurrently,
leading city authorities such as London and Greater Manchester are beginning to require embodied
carbon assessments of new developments through planning, in the expectation that targets or offsetting
requirements will be required in the future. These corporate and policy drivers mean that there are likely to
be growing pressures on developers to mitigate and offset embodied carbon impacts in the coming years.
A UKGBC Task Group has been convened to develop guidance further detailing best practice in this
area, including the potential inclusion of an explicit carbon price for use in conjunction with the hierarchy
in UKGBC’s net zero framework.17 This guidance has a targeted publication date of spring 2021 so the
methodology and pricing outlined for carbon offsetting within this report may be superseded once the
updated guidance is released.
Setting a carbon price
There are a range of reference carbon prices utilised or proposed within the industry18. These can be
implicit, such as the voluntary carbon offset market, or explicit, such as the £95/tCO2 for the new London
Plan (currently only for regulated emissions)19. Explicit prices typically focus on a specifc range of emissions,
most often scope 1 and 2, which is reflected in their pricing. As a result, there is limited existing guidance
on what might be considered an appropriate carbon offset strategy for embodied carbon. A range of offset
prices were therefore reviewed to inform this study:
Table 11: Carbon price examples

(/tCO2)
Comments
Implicit
International
voluntary market,
e.g. Gold Standard
£2.4020 Range of project types including renewable energy, fuel
switching, waste disposal, etc.
UK Woodland
Carbon Code –
Pending Issuance
Units (PIUs)
£7 – 2021 PIUs are based on predicted sequestration and therefore
cannot be used to report against UK-based emissions until
verifed. Reasonable level of assurance of actual carbon
sequestration is not available until Year 15 onwards. A
Woodland Carbon Unit (WCU) is a tonne of CO2 that has
been verifed to be sequestered but given the current UK
market only a small number of verifed WCUs have been
sold. Consequently, an average price range cannot yet be
determined.
Explicit
World Bank; HighLevel Commission on
Carbon Prices (2017)
US $40 – $8022 The Commission concluded that the explicit carbon price
level consistent with achieving the Paris temperature target
is at least US $40–80/tCO2 by 2020.
The World Bank outlines the minimum carbon price range to be consistent with the Paris Agreement in 2020
as £32 – £64/tCO2 (US $40-$80/tCO2), therefore a conservative value of £64 is proposed for this analysis.
Note that the carbon price levied can be used to purchase carbon units from the voluntary carbon offset
market or WCUs. Any PIUs bought must be matched with the equivalent amount of accredited carbon units
to report against any embodied carbon emissions or to use in claims of net zero emissions.
UK Green Building Council | Building the Case for Net Zero
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55
Section 3:
Conclusion
Net zero buildings will play an important role in the UK’s
goal to decarbonise by 2050. Whilst there has been a
proliferation of guidance which set out the key requirements
for net zero carbon buildings, the practical design and cost
implications have yet to be fully explored. This report begins
to shine a light on the design and cost changes required for
buildings to achieve net zero performance targets and helps
to reduce some of the currently unknown variables.
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Summary of fndings
This study has shown that building to net zero
does result in a cost uplift but, nonetheless, there
is a strong case for these designs given shifting
market demands and future requirements to meet
operational and embodied carbon targets. Cost
increases of 6.2% for the offce tower and 3.5%
for the residential block under the intermediate
scenarios can be considered feasible today. While
the capital costs may be higher, this is likely to
correspond with an increase in the value of the
buildings, higher rental premiums, lower tenancy
void periods, potentially lower life cycle costs, and
more. From a tenant’s perspective, there can be
reputational benefts, positive health and wellbeing
impacts, lower operational costs, and other benefts.
Given these targets will be necessary to meet net
zero goals in the future, a strong argument can
be made for attempting to meet the intermediate
targets as soon as possible.
The cost increases of 8-17% for the offce tower and
5.3% for the residential block may be considered
unfeasible today without widespread market
transformation and adequate consideration of
the value proposition of net zero buildings. The
unavoidable loss of floor area and corresponding
loss of sellable NIA under the two stretch scenarios
is acknowledged as a negative impact on the
building’s value. This could also be partially offset by
an increase in rental premiums and decreased void
periods, as well as avoiding the risk that the building
will become a stranded asset in future. While there
was only limited analysis conducted on the life cycle
costing of some components in the offce tower,
accounting for life cycle savings shows promise in
increasing the value of net zero buildings. A similar
analysis could be conducted for residential buildings
in the future.
Whilst all of the scenarios achieved signifcant
reductions across both carbon and energy, some of
the specifc targets were not met due to limitations
of the study (e.g. adhering to the project briefs),
limitations of the building design (e.g. building
orientation and massing), slower uptake of low
carbon materials in the UK, and more. Some
additional potential implications of these fndings
could include: needing to allow greater deviations
and flexibility from project briefs to improve project
viability; more research into achieving the targets,
particularly for embodied carbon; occupant lifestyle
changes; exploration of regulatory and policy
changes needed, such as for unregulated loads in
residential buildings; and more.
The industry will likely need to transform over the
next few years to be better able to deliver net
zero buildings. It is expected the supply chain will
adapt over the next few years to better provide the
skills and materials needed for net zero buildings,
decreasing the construction costs and project times.
Innovative technologies will continue to make it
easier to achieve targets.
In this way, this report is the frst step towards
‘building the case for net zero buildings’. It provides
the facts and fgures for two typical developments,
whilst signalling broader structural changes
required for the buildings sector. A supplementary
publication will examine the market transformation
in detail (see below), and future studies could
branch into other relevant areas, such as different
building types, retroft of existing buildings, and
enabling green fnance mechanisms.
Figure 20: 10 key themes to enable net zero buildings
1. Set the net zero carbon vision
Clients need to show leadership and set the ambition for net zero carbon buildings. By working towards an ambitious
outcome, all stakeholders are inspired to step up to the challenge.
2. Effectively communicate the net zero carbon vision
The vision should be marketed in a positive way to emphasise the whole life benefts of to all stakeholders, including
end-users. Market recognition of net zero carbon buildings, using certifcation or other recognised schemes, can help
realise value. General upskilling across the value chain – including local authorities, design teams, construction workforce,
end-users (tenants, residents) – can help improve the holistic understanding and benefts of net zero buildings. Often
terminology can become ‘jargon’ and lead to disengagement.
3. Adopt an evidence-based approach to net zero design
It is critical to understand the carbon impact of design decisions to make informed decisions about net zero buildings.
The use of modelling and cost assessments, as conducted in this study, are benefcial but this will differ based on project
specifcations and locations.
4. Improve end-user perception of net zero buildings
Net zero buildings should be considered high-performing across other dimensions, not just environmental aspects, e.g.
amenity, health and wellbeing, aesthetics. They should not be seen as compromising other building qualities.
5. Rethink fnancing of net zero carbon projects
It is critical to unlock fnancing opportunities early in the project to guarantee their development. This would include both
green fnance options (e.g. preferential borrowing rates for green developments) and approaches to carbon offsetting.
6. Increase design innovation at scale
Innovation across all aspects of building design and construction is needed to deliver net zero carbon buildings at scale.
This needs to be supported by a favourable regulatory environment that favours a climate frst approach to design and
construction. Rapid innovation and accelerated uptake is also key to reducing cost.
7. Transform the supply chain to build capacity and capability
Designers will need skills in energy effcient design and specifcation of low carbon materials; constructors and product
suppliers will need skills in the installation of low carbon materials and technologies; all stakeholders will need to
embrace the circular economy.
8. Change project timescales
The design and construction of the project should be focused on the net zero carbon outcome, taking care not to ‘value
engineer’ and compromise the vision. A soft landings approach should be used, including adequate time programmed in
throughout construction and into aftercare.
9. Post occupancy is as important as the design stage
Comprehensive testing and commissioning will be necessary to achieve the intended outcome. Careful handover,
user-training and post-occupancy evaluation should be implemented. Regulators and end-users should be taken on the
journey, so they are comfortable with the result and how to use the building as it was designed.
10. Building management should maintain the net zero carbon vision
Appropriate building management and maintenance routines should be in place, to ensure the performance is
optimised, including low carbon repairs and refurbishment. Occupants should fully understand how to get the best
outcomes for the building to sustain effcient operation and comfort.
MARKET TRANSFORMATION
Achieving new net zero buildings at scale will require
the buildings sector to re-imagine the current
design and delivery process. Wider collaboration
and buy-in from stakeholders across the value chain
will be needed to ensure net zero carbon outcomes
are embedded throughout all stages of a building’s
lifecycle.
As this report has shown, the transition to a net
zero built environment is becoming achievable with
effective design changes and adequate investment.
However, a better understanding of current market
conditions is necessary to appreciate the challenges
and opportunities to enable a rapid transition to new
net zero buildings.
Over the course of this study, a series of topics
requiring further industry research and discussion
to enable this shift were identifed. These were
developed in collaboration with JLL where views have
been fed-in from a cross-section of teams – including
development, planning, construction, letting and
management – to gain important market insights
throughout critical stages of a building’s lifecycle.
It became clear throughout the project that these
topics are just as important to address for the net
zero transition as the design and cost implications
outlined in this report. As such, a supplementary
publication has been planned which will focus on
market transformation which will delve deeper into
each of the below themes, with publication due later
in 2020. The next page has a non-exhaustive list of
themes from the series of topics identifed thus far.
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References
Next steps
Whilst the focus of this report has been on two specifc building types, it starts to shed light on the
approaches that will be needed for the design, construction and delivery for all net zero carbon buildings.
UKGBC considers this report to potentially be the frst in a catalogue of studies that ‘build the case for net
zero’. In line with this, two planned future publications are:
• Market transformation for net zero carbon buildings
This report is intended to expand on the 10 key themes outlined above to stimulate discussion about the
ways that the supply chain, building owners and tenants will need to adjust their activities and behaviours
to enable net zero carbon buildings. This report is due to be published later in 2020.
• Large-scale housing case study
The delivery of large-scale housing developments that meet net zero carbon standards presents another
set of challenges. A future study could apply the same methodology used in this report to understand the
design and cost implications for this type of development. UKGBC is eager to explore options for further
analysis on other building types, and invites members to contribute their suggestions.
1. IPCC (2018), Special report on the impacts of
global warming of 1.5°C: https://www.ipcc.ch/
sr15/
2. WorldGBC (2019), Whole-life Carbon Vision:
https://www.worldgbc.org/advancing-net-zero/
whole-life-carbon-vision
3. Committee on Climate Change (2020),
Reducing UK emissions: 2020 Progress Report
to Parliament: https://www.theccc.org.uk/
publication/reducing-uk-emissions-2020-
progress-report-to-parliament/
4. RICS (2017), Whole life carbon assessment for
the built environment: https://www.rics.org/
uk/upholding-professional-standards/sectorstandards/building-surveying/whole-life-carbonassessment-for-the-built-environment/
5. UKGBC (2019), Net Zero Carbon Buildings:
A framework defnition: https://www.ukgbc.
org/ukgbc-work/net-zero-carbon-buildings-aframework-defnition/
6. UKGBC (2020), Net zero carbon: energy
performance targets for offces: https://www.
ukgbc.org/ukgbc-work/net-zero-carbon-energyperformance-targets-for-offces/
7. LETI (2019), Climate Emergency Design Guide:
https://www.leti.london/cedg
8. RIBA (2019), 2030 Climate Challenge: https://
www.architecture.com/about/policy/climateaction/2030-climate-challenge
9. JLL (2020), The Impact of Sustainability on Value:
https://www.jll.co.uk/en/trends-and-insights/
research/the-impact-of-sustainability-on-value
10. WorldGBC (2019), Net Zero Carbon Buildings
Commitment: https://www.ukgbc.org/wpcontent/uploads/2020/02/UKGBC-NZCBCommitment-Detailed-Guidance-Document.pdf
11. International Energy Agency (2018), Technology
Roadmap: Low-Carbon Transition in the
Cement Industry: https://www.iea.org/reports/
technology-roadmap-low-carbon-transition-inthe-cement-industry
12. Stockholm Environment Institute (2018), Lowemission steel production – decarbonising heavy
industry: https://www.sei.org/perspectives/lowemission-steel-production-hybrit/
13. British Council for Offces (2019), Guide to
Specifcation: http://www.bco.org.uk/Research/
Publications/BCOGuideToSpec2019.aspx
14. National Australian Built Environment Rating
System (2019), Handbook for Estimating
NABERS Ratings: https://www.nabers.gov.au/
ratings/commitment-agreements
15. US Department of Energy (2013), Study:
Moving Computer Services to Cloud Promises
Big Energy Savings: https://crd.lbl.gov/newsand-publications/news/2013/study-movingcomputer-services-to-the-cloud-promisessignifcant-energy-savings/
16. UKGBC (2019), Guide to Scope 3 Reporting in
Commercial Real Estate: https://www.ukgbc.org/
ukgbc-work/scope-3-reporting-in-commercialreal-estate/
17. UKGBC (2020), UKGBC Task Group for
Renewable Energy Procurement and Carbon
Offset Guidelines: https://www.ukgbc.org/
news/ukgbc-task-group-for-renewable-energyprocurement-and-carbon-offset-guidelines/
18. Carbon Pricing Leadership Coalition (2018),
What is carbon pricing?: https://www.
carbonpricingleadership.org/what
19. Greater London Authority (2019), Carbon Offset
Funds Survey Results 2019: https://www.london.
gov.uk/sites/default/fles/2019_cof_survey_
results_fnal_0.pdf
20. Forest Trends’ Ecosystem Marketplace (2019),
Financing Emissions Reductions for the Future:
https://www.forest-trends.org/wp-content/
uploads/2019/12/SOVCM2019.pdf
21. Woodland and Carbon Code (2019), What are
PIUs, WCUs and what can I say about them?:
https://www.woodlandcarboncode.org.uk/buycarbon/what-are-woodland-carbon-units
22. Carbon Pricing Leadership Coalition (2017),
Report of high-level commission on carbon
prices: https://static1.squarespace.com/
static/54ff9c5ce4b0a53decccfb4c/t/59b7f2409f8
dce5316811916/1505227332748/CarbonPricing_
FullReport.pdf
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Acknowledgments
The idea for this feasibility study into the design, delivery and cost of new net zero carbon buildings was
developed by Hoare Lea and JLL, as Advancing Net Zero Programme partners. Landsec and Legal &
General also provided their projects for use in the study. This study would not have been possible without
their support and contribution of signifcant team resources to bring this study to life.
Project Supporters
UKGBC would like to sincerely thank all design team participants, alongside all involved stakeholders for
their feedback, assistance and contributions over the course of the project. The design teams included
representatives from the following organisations:
• Alinea
• Bennetts Associates
• Cast
• Cundall
• EPR Architects
• Heyne Tillet Steel
• Hoare Lea
• JLL
• Robert Bird Group
Report Authors
UKGBC: Karl Desai, Richard Twinn, Alexandra Jonca
With special thanks to the UKGBC Advancing Net Zero Programme Partners
Lead Partner: The Redevco Foundation
Programme Partners: BAM Construct UK, Berkeley Group, Grosvenor Britain & Ireland, Hoare Lea and JLL.
QUESTIONS & FEEDBACK
This study aims to explore design
and cost implications of building to
net zero. We welcome input from any
interested stakeholders on the content
and potential future iterations.
If you have any questions on the
guidance or would like to provide
feedback, please email
[email protected]
UK Green Building Council
The Building Centre
26 Store Street
London WC1E 7BT
T 020 7580 0623
E [email protected]
W ukgbc.org