《WBCSD&奥雅纳(Arup):净零建筑报告(英文版)(79页).pdf》由会员分享,可在线阅读,更多相关《WBCSD&奥雅纳(Arup):净零建筑报告(英文版)(79页).pdf(79页珍藏版)》请在三个皮匠报告上搜索。
1、Net-zero buildingsHalving construction emissions todayNet-zero buildings Halving construction emissions today 2Contents2Key high impact carbon reduction strategies|164Conclusion|733Building layers|253.1 Structure(sub-structure and super-structure)|27 3.2 Skin(faade)|413.3 Space plan|563.4 Services|6
2、23.5 Stuff|721Introduction|10Foreword|3Executive summary|6Net-zero buildings Halving construction emissions today 3ForewordThis report builds on our previous net-zero buildings work and aims to provide insight into potential strategies and measures that companies might deploy to halve embodied carbo
3、n emissions,those associated with building components,by 2030.As demonstrated in the previous Net-zero buildings:Where do we stand?report1,as buildings generally become more energy efficient,in some cases embodied carbon already accounts for more than 50%of a new projects whole life carbon footprint
4、.Importantly,a major component of this embodied carbon is the upfront carbon associated with the initial construction process and hence reaching the atmosphere at the very outset(figure 1).Although some of these carbon emissions are currently considered hard to abate,we can,and we must,aim higher an
5、d immediately develop buildings with significantly less embodied carbon if the sector is to achieve the overall net-zero targets we strive for.In the Where do we stand?report,we point to what we need to do.The aim here is to point out strategies that will highlight the possibilities of how we achiev
6、e the systemic changes we require.Time is running out,so it is essential to work with what is available today,without over-relying on major future technological advances.We must rethink the way we do things,questioning everything and adapting current practices under the lens of major reduction poten
7、tial.We must prioritize consumption reduction as a first principle doing more with less.We must all fully commit to making decarbonization of our buildings an absolute and clear priority on all new projects,working together across the value chain from the outset to make this happen.We hope that this
8、 report contributes to showing that when we are properly informed,motivated,and working in a singular collaborative environment from the very outset,we can already do significantly better than the current outcomes we are achieving.Figure 1:Estimated distribution of carbon emissions from Where do we
9、stand?report130%20%50%Embodied A1-A5Embodied B-COperational B6-B7Upfront embodied A1 A5KgCO2e/m2 Replacement B4 FF&EReplacement B4 FF&EEnd of life C1 C4Replacement B4 Services+FF&EReplacement B4 Structure+Faade+PartitionsReplacement B4 Services+FF&EIn use5803804802800YEARS4050600Net-zero
10、buildings Halving construction emissions today 4The building industry is not the same,or as advanced,in all parts of the world and we must recognize this while still driving toward the overall objective in terms of global emissions reductions.The mantra of doing more with less is valid in all geogra
11、phies.We must also recognize that in the immediate timeframe of the next decade,some more advanced parts of the industry will need to achieve beyond the advocated halving of emissions in order to achieve the change required globally.To succeed,we need to set our ambitions high.There are many barrier
12、s and competing agendas to achieving the immediate and systemic changes necessary yet,there are also untapped opportunities.We must radically collaborate as an industry and act as one to genuinely establish the principles set out in this report.Figure 2:Building and construction system value chains8
13、Building value chainInfluencer value chainCarbon:flow and hotspotsSegments of the system“We need and we can halve the emissions in the built environment by 2030.This report highlights the importance of radical collaboration across the entire value chain to achieve this goal.We identify practical and
14、 holistic measures that can be deployed in any building project around the world now because 2030 is today.”“To meet the immense global decarbonization challenge our industry faces,we need to immediately halve our consumption-based emissions.To achieve this goal,we must galvanize the whole of our hi
15、storically fragmented and slow to innovate value chain and support it with appropriate levels of governmental legislation.”Roland HunzikerDirector,Built Environment,WBCSDChris CarrollBuilding Engineering Director,ArupNet-zero buildings Halving construction emissions today 5For the built environment,
16、2030 is todayIt is possible to at least halve embodied carbon emissions immediately by using what is already available.But there is no single solution.Business leaders must put every decision they make under the spotlight of the goal to halve emissions and make well-informed choices that create genu
17、ine large-scale whole life carbon reductions.This report indicates strategies that,combined thoughtfully,should give the confidence to act to achieve this goal now.The world is facing a global crisis that requires urgency and immediate concerted action.Carbon must become a priority,equal to money in
18、 future decision-making.In developing this report,we have engaged with a wide number of WBCSD members,representative of the full built environment value chain(figure 2),to explore practical,implementable strategies that we can deploy now to gain significant upfront carbon reductions.We look forward
19、to the expansion of this work to explore in increasing detail how we can drive the rapid,widescale decarbonization of the whole built environment.Based on this work,we call on companies throughout the built environment and worldwide to implement systemic,not incremental,changes to achieve the shared
20、 goal of at least halving our emissions by 2030.We need this systemic change today,as we are already planning what will be built in 2030.For the built environment,2030 is today.Arup MUCEB Novated ScopeNet-zero buildings Halving construction emissions today 6This report is a follow-up to the WBCSD Ne
21、t-zero buildings:Where do we stand?1 publication which provided a detailed description of how to account for full life-cycle emissions of building projects based on six whole life carbon assessments(WLCA).That report framed the challenge in terms of the dramatic decarbonization of the built environm
22、ent.This Net-zero buildings:Halving construction emissions today report points to how to do it in relation to the systemic change requirements identified previously.This report focuses on embodied carbon as this is proving challenging to abate globally and represents an immediate concern over the ne
23、xt decade,a period in which companies need to significantly increase their efforts to stay on track toward a net-zero future.In this work,we focus on upfront embodied carbon as this represents a clear challenge in terms of reductions targeting the goals associated with 2030.However,we also point to
24、reduction strategies associated with life-cycle embodied carbon and we touch on the impact of operational carbon,which will be a specific focus in our next report in the Net-zero buildings series,on the inter-relationship between embodied and operational carbon.We ask,how do we halve?the current con
25、struction emissions of building projects by using and adapting currently available technology,materials,and products.Reducing emissions as much as possible will require a focus on all aspects of a building,from the earliest possible moment,by all players in the value chain.There is no“silver bullet”
26、and we do not intend for the report to be definitive but to raise awareness of the potential to achieve the significant reductions in carbon levels we can and must make.We aim to provide insight into strategies that,when brought together under the prioritized objective of driving carbon reductions,c
27、an begin to frame the possibility of how to at least halve current embodied carbon emissions.Executive summary3.2 Skin(faade)15%3.4 Services20%3.1 StructureSuperstructure40%Substructure10%3.5 Stuff(FF&E)5%3.3 Space plan(partitions and finishes)10%Figure 3:Upfront embodied carbon estimated(A1-A5)800
28、KgCO2e/m2400Net-zero buildings Halving construction emissions today 7Figure 4:Key overarching considerations whole-building decisionsThe first part of the report explores the impact of early-stage,whole-building decisions,and the major impact these can have on the carbon outcome of a particular proj
29、ect(section 2).For example,the decisions whether to build,what to build,what to re-purpose,and general building massing on a site might have a significant impact on the overall carbon outcome of a particular project(figure 4).The second part looks in more detail at the specific decisions and measure
30、s we might take within the individual building layers to maximize the reductions we can achieve(section 3).Gains at the individual building layer level(figure 5)may often seem insignificant in isolation,but when taken together across all the building layers,they may aggregate to major reductions.The
31、 report points to the importance of looking at every project,and all the decisions behind it,through the lenses of both the whole building and the individual buildings layers,to achieve the best possible carbon reduction outcomes.There are many parallels with how projects are assessed commercially,a
32、nd we urge companies to now consider carbon with the same rigor that is applied to cost.Figure 5:Examples of building layer specific decisions3.2 Skin(faade)Overall massing floor to wall ratio Use whole life carbon to inform design decisions Focus on most carbon intensive components Think circular3.
33、4 Services Use whole life carbon to inform design decisions What can we omit?Optimize distribution routes Reduce refrigerant impact Use low embodied carbon materials Adopt circular economy principles3.1 Structure 200kgCO2e/m2 or less!Minimize material use as a priority Use material to its best impac
34、t consider hybrid,modular and new forms of construction Explore emerging low-carbon alternatives Specify lowest carbon options Design for performance3.5 Stuff(FF&E)Consider replacement cycles Prioritize low carbon,circular procurement3.3 Space plan(partitions and finishes)What can we omit?Focus on m
35、ost carbon intensive components 800 KgCO2e/m2400Build nothingMaterials&systems selectionOverall building geometryArea efficiencyRepurpose/refurbishBuilding heightLoading assumptionsColumn grids/transfersLow-carbon specificationEfficient designBuild efficientlyFaade to floor ratioBasementFinishesMaxi
36、mize recycled contentFaade optimizationDesign for disassemblyTransport&construction emissionsImpact+-Building layer considerationHolisticSpecific Structure Skin Space plan Services Stuff Net-zero buildings Halving construction emissions today 8Key outcomes and messagesThe urgency and need to priorit
37、ize carbon should be a given.It is necessary to consider carbon as part of the new economics of all projects,an equal to money.Carbon accounting must be a transparent metric shaping all future projects.Given the urgency,business must fully support this prioritization and appropriate levels of suppor
38、tive legislation must drive it.Looking at the impact of key early decisions,such as what companies build and how they shape their briefs,an appropriate understanding of carbon impacts must drive the inception of all projects.Typically,architecture,engineering and construction(AEC)firms achieve the b
39、iggest impacts at the earliest stage of their projects.That is not to say we should not then try to squeeze everything we can in relation to carbon reduction out of all stages,as every reduction counts.To make substantiated reductions in carbon emissions,companies must be scientific in their scrutin
40、y of the numbers,and firms must collect,share,and analyze data rigorously.Industry players must review decisions systemically across multiple inter related parameters and evaluate the notion of carbon payback in reaching the right balanced solution across operational and embodied carbon.Genuine atmo
41、spheric carbon emissions reductions must be our goal.To be genuine projects should prioritize the general use of less resources over a reliance on a disproportionate share of scarce lower carbon resources.We must focus on the immediate potential big wins at scale and not get distracted by incidental
42、 reduction potential.It should seem obvious,but we point out that,generally,if the industry consumes fewer resources in delivering the same outcome,it lowers its carbon footprint in proportion to this reduction.Hence,we identify as a clear outcome throughout the report the prioritization of using le
43、ss.Aligned with this,a transition to a circular economy will clearly play a part in decarbonizing future building projects.Looking for the highest possible reuse value of everything from whole buildings to the systems and components within them will be a key part of using fewer resources,avoiding wa
44、ste and the need to keep expending embodied carbon during the life cycles of buildings.Arup Central Saint GilesNet-zero buildings Halving construction emissions today 9Key points to take from the report Data is key and will drive informed calculation,analysis,and consistent reporting as an enabler o
45、f the highest impact.Companies must quickly gain the confidence totreat carbon like money,setting clear budgetary targets.Early well-informed thinkingis essentialto gain the highest reduction potential.A systemic approach is required asthere is no single solution.Collaborativeengagement of the entir
46、e value chain isthe only way we will gain the required reductions.Urgent and decisive action is essential as for the built environment2030 is today.ActionOutcomeUrgent&collaborativeImmediate concerted action to adopt whole life carbon(WLC)measurement and reductions as standard practice within the in
47、dustry.All actors must collect,analyze,transparently report and openly share data on all projects.Design,planning and investment decisions,including value engineering made on the basis of carbon as cost.EarlyInformed consideration of WLC at the outset of all new or refurbishment projects including a
48、ll building elements/systems to determine strategic design decisions and procurement strategy.Increased potential to realize significant carbon reductions on individual assets.SystemicAdopting consistent data across all layers of a building to support resource reductions and the transition of the su
49、pply chain,addressing global supply limitations for low-carbon and recycled alternatives to steel and concrete,bio-materials and waste products.Genuine pathways for net-zero building transition that are aligned with science-based targets(SBTs).CircularMaximize the highest level of reuse;minimize was
50、te,limit life cycle replacement and reuse materials and components,and adopt products with the lowest carbon.Markets created for product-as-a-service;new and recycled materialsWith this report we call on all built environment companies throughout the entire value chain to come together around an agr
51、eed set of decisive actions.Actions to take todayNet-zero buildings Halving construction emissions today 10Introduction1Decarbonization trajectories in line with the 1.5 C Paris Agreement2 aim to halve global carbon emissions by 2030 and reach net-zero emissions by 2050.The United Nations backed Mar
52、rakech Partnership for Global Climate Action3 in its climate action pathway echoes the need for the built environment to halve emissions by 2030.Part of this goal is to reduce embodied carbon by at least 40%overall and for leading projects to achieve a reduction of at least 50%.4 It is imperative to
53、 hit these challenging 2030 goals to achieve a fully net-zero built environment across the whole life cycle by 2050 at the latest.The built environment is a critical sector to decarbonize as it represents close to 40%of global,energy related carbon emissions approximatively 14 gigatons of carbon eac
54、h year.5Understanding the whole life carbon emissions of buildings is a key step in meaningfully creating reductions and credible pathways toward net-zero emissions.Businesses need to more accurately understand where the industry is,where it wants to get to and,importantly,how to get there.Following
55、 the publication of our Building System Carbon Framework(July 2020)and the Net-zero buildings:Where do we stand?report(July 2021),we now aim to address the last of these questions:How to at least halve emissions by 2030.The Net-zero buildings:Where do we stand?report shows that around 50%of whole li
56、fe carbon emissions of new building projects stem from embodied carbon.Although it is necessary to consider carbon emissions holistically in a whole life-cycle context,operational energy consumption has been the focus of consumption reduction measures and legislation for some time.Embodied carbon ha
57、s only more recently started being part of the net-zero focus.As seen in our previous report,most of the embodied carbon is emitted upfront at construction stages A1-A5(figure 8).A1-A3 are product stages,including raw material supply,transport,and manufacturing;A4-A5 are construction process stages,
58、including transport to building site and installation in the building.Therefore,in this report we focus on promoting reduction measures for these upfront stages.Operational emissions reductions remain important,and we plan to focus specifically on this area of the net-zero agenda in our next Net-zer
59、o buildings publication.The need for more clearly defined targets for upfront embodied carbon thresholds,associated with a genuine industry commitment to supporting global and national net-zero pathways,is clear.Given where things stand currently,the industry needs to achieve the deepest reductions
60、in carbon emissions possible by using and adapting the technology,materials,and products currently available.In the short term,leaders cannot rely on the emergence of radically new technology within the next decade and must therefore support the level of reductions aimed for by adapting thinking via
61、 a prioritized focus on carbon.002004020505540Gt CO2eFigure 6:Past carbon emissions and remaining budget2Sources:Intergovernmental Panel on Climate Change(IPCC)6 and Global Alliance for Buildings and Construction7Current annual emissions level reaching+40
62、Gt CO2e/yearof which approx.+15 Gt CO2e/year=built environment400 Gt CO2e additional carbon budget to reach+1.5C2,400 Gt CO2e current level of atmospheric carbonNet-zero buildings Halving construction emissions today 11Crucially,leaders must think systemically and not rely on modest incremental or s
63、uperficial change to get the immediate and deep reduction levels needed.Companies must ensure emissions reductions claimed at a building level genuinely manifest themselves as a contribution to global atmospheric carbon reductions and are not merely a localized over-reliance on using an inequitable
64、and disproportionate amount of a particular rare low-carbon resource.Prioritizing consumption reductions should always be a primary objective before looking to use an equitable share of resources,such as cement replacements and recycled steel,for example.With this report,we look to support the notio
65、n that leaders can and must be much bolder and more impactful in terms of reducing the construction-stage embodied carbon emissions associated with projects.But to do this,companies must be fully committed to and focused on prioritizing carbon reductions.Firms must be holistic and rigorous about acc
66、ounting for the carbon impact of every decision made and be prepared to think differently and not rely on but continually challenge precedents.There is not a single answer or“silver bullet”to get the halving needed.In undertaking this work,we aim to play a part in helping engender more creative,prod
67、uctive,and impactful upfront dialogue between multiple parties in the value chain at the earliest stages of projects.This dialogue should focus on many of the strategies we outline in the subsequent chapters and that,when brought together,can make the deep reductions needed.Typically,companies can a
68、chieve the biggest impact in terms of construction-stage embodied carbon reductions by setting projects off in the right direction at the earliest possible opportunity.In many cases,buildings that will emit upfront construction carbon emissions in 2030 are already being designed.Figure 7:WBCSD focus
69、 on net-zero buildingsNet-zero buildings Where do we stand?Net-zero buildingsHalving construction emissions todayThe Building System Carbon FrameworkA common language for the building and construction value chainArup Coal Drops YardNet-zero buildings Halving construction emissions today 12ProductCon
70、structionUse stageEnd of lifeBeyondA1A2A3A4A5B1B2B3B4B5B6B7C1C2C3C4DRaw materialTransport to plantManufacturingTransport to siteConstruction&installationUseMaintenanceRepairReplacementRefurbishmentEnergy operationWater operationDemolitionTransportWaste processingDisposalReuseRecoveryRecycleSkinSiteS
71、ocialStructureSpace planServicesStuffFigure 8:Building Systems Carbon Framework(BSCF)Whole life cycle stages and building layersOur approachIn 2020,we published the Building System Carbon Framework(BSCF)8 to provide a simple approach to transparently allocate and report carbon emissions of buildings
72、 using a common metric and a whole life approach,enabling each user to identify the best emissions-reduction strategies for their part of the value chain and allowing stakeholders to make informed decisions based on clear and transparent information and a common language.In 2021,WBCSD and Arup publi
73、shed the Net-zero buildings:Where do we stand?report1 which presents the results of six case studies developed from Arup projects using whole life-cycle assessments based on the BSCF.The case study report indicated the potential for clearer,more ambitious carbon targets to emerge and the imperative
74、to halve global buildings-related emissions within the next decade.This Net-zero buildings:Halving construction emissions today report builds on our previous work and aims to provide a deep look into potential strategies and measures that companies might deploy to halve embodied carbon emissions tho
75、se associated with building components by 2030.Previous findings Where do we stand?As demonstrated in the previous Where do we stand?report,as buildings become more energy efficient in general,in some cases embodied carbon already accounts for more than 50%of a new projects whole life carbon footpri
76、nt.Importantly,a major component of this embodied carbon is the upfront carbon associated with the initial construction process and hence reaching the atmosphere at the very outset.Although some of these carbon emissions are classified as hard to abate,we can,and we must,aim higher and immediately d
77、evelop buildings Net-zero buildings Halving construction emissions today 13with significantly less embodied carbon if the sector is to achieve the overall net-zero targets we strive for.We explored in detail the whole life carbon emissions of six building projects.These building projects are all in
78、Northern Europe,generally had a sustainability focus,and hence considered at the advanced end of business-as-usual construction.However,the general conclusion of the report pointed to the urgent need to better collaborate across the whole value chain to drive systemic change and large-scale genuine
79、decarbonization if the built environment industry is to play its part in limiting global warming to a 1.5C increase in line with the Paris Climate Agreement.Embodied carbon represented an average of 50%of the total whole life carbon emissions of new building projects when considered across the 60-ye
80、ar life span of the six case study buildings we studied.Generally,national,and local legislation and predicted national grid decarbonization levels are driving improvements in operational energy.These developments push the balance of whole life-cycle emissions toward an ever-higher percentage of emb
81、odied carbon.Further,the largest part of this embodied carbon is in the immediately emitted upfront construction stage(A1-A5).Although it is essential to consider carbon impacts holistically(embodied and operational)in relation to the best whole life carbon outcomes for buildings,companies must be c
82、oncerned about the immediate impact of the construction stage over the next decade.In this report we focus on the global need to at least halve the business-as-usual impacts of A1-A5 construction stage emissions by 2030.560kgCO2e/m2SubstructureSuperstructureFaadeInternal walls and partitionsInternal
83、 finishesFittings,furnishings,and equipment(FF&E)Building servicesSite emissions11%5%43%15%18%2%5%1%Figure 9:Upfront embodied carbon(A1-A5)average distribution across all six case studiesFigure 10:Whole life carbon emissions through time average distributionConstruction A1 A5KgCO2e/m2 Replacement B4
84、 FF&EReplacement B4 FF&EEnd of life C1 C4Replacement B4 Services+FF&EReplacement B4 Structure+Faade+PartitionsReplacement B4 Services+FF&EIn use 5803804802800YEARS4050600Operational carbonEmbodied carbon50%50%Net-zero buildings Halving construction emissions today 14Business-as-usualThere
85、 is currently no unified consensus on what average business-as-usual construction stage embodied carbon numbers might be.As such,there is no firm and consistent view as to what a target number representing half might be.However,based on industry benchmarks,research,and a growing number of calculated
86、 building life-cycle assessments(LCAs)for embodied carbon,in this report we assume as a starting point a global average upfront(A1-A5)value for a typical new commercial building of around 800 kg CO2e/m2.Some studies focus on parts of the industry and regions where thinking about lower carbon designs
87、 is already developed7,9 and show average numbers below this figure.Numbers are also emerging without consistently covering the full building layer scopes outlined in this report.This highlights the necessity to define consistently derived,clear benchmarks and hence reductions targets at a regional
88、level to drive informed systemic reductions.Figure 11 is an extract from a recent One Click LCA report9 that assesses embodied carbon data for 3,737 European building projects summarizing average upfront structural and skin layer(baseline)embodied carbon results.For office buildings,there is an aver
89、age value for structure and skin layers of about 450 kgCO2e/m2,which would corollate with the overall assumption for all layers of about 800 kgCO2e/m2 referenced when also taking stages A4-A5(transport and construction)emissions into consideration.Figure 12 shows an estimated distribution of carbon
90、within the building layers for the same typical commercial building extrapolated from our previous report results.Halving whole building carbon emissions by 2030 would represent an upfront embodied carbon target around 400 kg CO2e/m2,which currently correlates with numbers pointed out by organizatio
91、ns such as the London Energy Transformation Initiative(LETI)10 in the UK and the Carbon Leadership Forum(CLF)11 in the US.Again,companies are beginning to conceive projects now that they will deliver in 2030.Figure 11:Impact of optional scopes on A1-A3 embodied carbon(EU)00600400kgCO2e/m2
92、CommercialEducationalIndustrialOffice buildingsResidentialBaseline(structure and skin layers only)Embodied carbon benchmarks for European buildings(2021)One Click LCAStructureSkinSpace planStuffServices800kgCO2e/m250%15%20%10%5%Figure 12:Estimated typical upfront embodied carbon(A1-A5)distributionNe
93、t-zero buildings Halving construction emissions today 15About this reportIn the report we break the building up into its different layers,as presented in the BSCF,and explore the drivers,opportunities,and barriers to significant carbon reductions in the individual building layers.A chapter looking a
94、t the more general decisions that are made in terms of planning the building from a holistic perspective will precede the chapters on the individual building layers.Often these key decisions,many made early in the overall delivery process,will straddle multiple building layers,and shape their outcom
95、es significantly.Figure 13:Building layers3.2 Skin(faade)External wallsWindowsExternal doors3.4 ServicesMechanicalElectricalPublic health3.1 StructureSuperstucture FrameUpper floorsRoofStairs and rampsSubstuctureFoundationsRetaining wallsLowest level slab3.5 Stuff(FF&E)Fittings,furnishings and equip
96、ment3.3 Space plan(partitions and finishes)Internal walls and doorsWall,floor and ceiling finishesArup 80 Charlotte StreetNet-zero buildings Halving construction emissions today 16Key high impact carbon reduction strategies2By focusing on major carbon reduction strategies from the earliest point in
97、every project,it is possible to create an environment where the systemic reductions required become possible.Consider carbon from the outsetThe biggest reduction opportunities take place at the earliest stages of a buildings conception.At the outset of all building projects,AEC firms should clearly
98、consider the necessity to build at all.When companies look at this decision and assess what they might be able to reuse and repurpose in terms of existing buildings,they must consider the whole life-cycle impact of all the decisions they From our previous Where do we stand?case study work,we estimat
99、ed the overall whole life carbon associated with the structure was an average of approximately 20%of the total 60-year whole life carbon emissions.If we add in the initial upfront embodied faade component,we average around 25%of the whole life carbon emissions.At around a quarter of the total whole
100、life carbon expenditure,this is clearly an important and significant deliberation at the start of any building project where there is the opportunity to retain or repurpose an existing building.make.They cannot simply assume it is always beneficial to save,for instance,an existing structure and/or f
101、aade if it compromises the buildings efficiency and performance beyond the savings in carbon it offers.Carbon payback periods must become a common metric they review fundamental early-stage decisions through as they already do under the lens of monetary cost.Figure 14 demonstrates one such analysis
102、through a particular outcome,although we note that another example may demonstrate a different outcome.The key point is companies must study this with appropriate rigor at the outset of all projects to frame the best carbon outcomes.Figure 14:Key overarching considerationsBuild nothingMaterials&syst
103、ems selectionOverall building geometryArea efficiencyRepurpose/refurbishBuilding heightLoading assumptionsColumn grids/transfersLow-carbon specificationEfficient designBuild efficientlyFaade to floor ratioBasementFinishesMaximize recycled contentFaade optimizationDesign for disassemblyTransport&cons
104、truction emissionsImpact+-Building layer considerationHolisticSpecificWhole buildingBuilding layerNet-zero buildings Halving construction emissions today 17Figure 15:Understanding carbon payback periods 2030Years40506002004006008000kgCO2e/m2 gross internal area(GIA)100Whole life carbon(em
105、bodied&operational)emissions over a 60-year life span for a notional commercial project in central LondonCumulative results comparing payback periods for a new build versus refurbishment optionsNew buildHeavy refurbLight refurbAssumes major decarbonization of the national grid Compensates for residu
106、al energy inefficiencyPayback 1Payback 2010%30%50%80%100%Embodied carbon reduction potentialFigure 16:Impact of decision-making in timeBuild nothing/re-assess the needBuild less/repurpose/refurbishDesign efficiently/specifyPrioritize low-carbon materialsBuild leanDefine key parameters:geometry/mater
107、ials/criteriaDesignManufactureConstructionBriefNet-zero buildings Halving construction emissions today 18Prioritizing carbon alongside costOften,real reductions in construction-embodied carbon mean a reduction in resource use.By extension,they should ultimately result in a reduction in cost.This is
108、not always the case as firms typically do not price carbon into the equation.For instance,in certain geographies the balance in labor costs and energy costs will drive the use of systems or solutions that are not the most optimum from a carbon perspective.As an example,in countries with high labor c
109、osts,companies will often prefer materially heavy construction solutions such as reinforced concrete flat slabs despite their carbon inefficiency as they can be built quicker,with less labor and less complexity in terms of fitting out around them.When valuing carbon appropriately,cost should also no
110、t drive the choice of materials and products toward poorer general quality,flexibility and longevity as companies will have to replace elements with a short lifespan more often throughout the buildings life.To drive thinking toward the highest level of decarbonization,companies must appropriately va
111、lue carbon in the decision-making process alongside cost.Figure 17:Reinforced concrete flat slabsFigure 18:Reinforced concrete waffle slabsTypically 180 kg CO2e/m2 for a 9x9 m grid with comparable loadingTypically 120 kg CO2e/m2 for a 9x9 m grid with comparable loadingArup 88 Wood Steet Daiwa Europe
112、 HouseNet-zero buildings Halving construction emissions today 19Carbon as a new appropriately priced cost parameterBuilding geometryThe overall initial planning of a buildings geometry can have a big impact on its carbon footprint.Companies need to assess the carbon impacts of the choices made on th
113、e geometric massing of buildings in terms of the floor layouts,core layouts,column grids,floor-to-floor heights and wall-to-floor ratios,among other considerations.Good,informed decision-making on these key building geometry parameters can put the industry on the way to the significant embodied carb
114、on reductions needed.Area efficiencyOne aspect to consider at the outset is the overall efficiency factor of net usable area to gross construction area achievable.Often what is commonly referred to as the net-to-gross ratio can vary by more than 20%in different versions of the same building typology
115、.This indicates that at the lower efficiency numbers companies are constructing more overall building to deliver Building heightAs buildings become significantly taller,they typically require more structure(thicker core walls,bigger columns,larger foundations,etc.)and more space and equipment associ
116、ated with vertical movement of people(lifts ad stairs)and building services(risers,interstitial plant provision,etc.).As well as requiring more material and systems,the net-to-gross ratio of tall buildings naturally starts to fall due to the addition of extra vertical circulation provisions and as s
117、uch there is a double hit when carbon intensity is measured against the effective usable(net)area of the building.Often this can mean an embodied carbon expenditure of more than 50%additional is required to provide the same net useable area between high-rise and low-rise construction.the same functi
118、onality.Often companies naturally optimize the net-to-gross ratio from a cost-efficiency perspective,but they should also consider it from a carbon efficiency perspective at the outset.Building height also impacts area efficiency for the reasons outlined below.Figure 19:High-rise vs low-rise floor e
119、fficiency108 floor levels above groundNet/gross 69%8 floor levels above groundNet/gross 87%9 floor levels above groundNet/gross 80%CoreOccupied areaFigure 20:High-rise benchmarking20304050607040060080012001000Carbon intensity(A1-A5 kgCO2e/m2 GIA)Number of storeys010Anonymous,Ruskin SquareAnonymous M
120、idrise,LondonAnonymous Midrise,LondonAnonymous,SouthbankAnonymous,City122 LeadenhallAnonymous Highrise,City8 Bishopsgate22 Bishopsgate(Published)Net-zero buildings Halving construction emissions today 20Wall to floor ratioA major influence in terms of the skin or faade of a building is related to th
121、e efficiency of the wall-to-floor ratio achieved via the general massing arrangement.This ratio can vary significantly for a wide number of reasons,often avoidably.Typically,the ratio can vary from about 0.3 to 0.5 and hence at its upper end represent more than 60%of additional faade area compared t
122、o the optimum lower end of the range,driving additional carbon into the design.Column grids and floor-to-floor heightsThe column grid and allowable floor-to-floor height can have a major impact on the embodied carbon outcome.The span of the building floor plate between columns and walls and the allo
123、wable depth the structure can occupy(span-to-depth ratio)can significantly impact the overall amount of material needed to effectively perform the same overall functional requirement,which in turn is directly linked to the overall carbon footprint.By considering the impacts of all the geometric para
124、meters outlined above holistically,there is obvious potential to optimize the embodied carbon at the earliest point possible in the decision-making process.To do this,companies need to better estimate and consider embodied carbon in relation to all the possible variables,to an appropriate degree of
125、accuracy,at the earliest point possible in the design process.Figure 21:Wall-to-floor(W2F)ratioWall to floor ration comparison showing in excess of 40%rangeW2F=0.35(good)W2F=0.50(poor)Embodied carbon kgCO2e/m2Range of carbon intensity potentially doubling the embodied carbonTypical span range for a
126、floor plateSpanFigure 22:Span vs carbon relationship for a typical floorplate systemFigure 23:Weight-to-depth relationships for a comparable composite floor plate designMinimum depth solution 9m x 9m grid100 kgCO2e/m2300mm600mmMinimum weight solution 9m x 9m grid50 kgCO2e/m2Net-zero buildings Halvin
127、g construction emissions today 21Transport and construction emissionsThe previous case study report shows that the majority(93%)of upfront construction carbon emissions are associated with the manufacturing of the products,components and systems used to build the building.For these typical building
128、projects,the construction emissions associated with transport to the site and construction and installation processes were by comparison relatively small(less than 7%).Companies should clearly aim to decarbonize as much of the construction(A4 and A5)activity as possible via the adoption of electric
129、vehicles(EVs),cleaner processes,less waste,more offsite fabrication,etc.We recognize that the ratio A1-3(manufacture)versus A4-5(placement)will also vary depending on the materials adopted in the construction process.For instance,the use of timber in the manufacturing process will be comparatively l
130、ess carbon intensive and companies should place greater emphasis on transport and construction compared to steel and concrete construction.Therefore,to make the most meaningful impact,companies need to clearly recognize and prioritize the biggest components of upfront embodied carbon and always focu
131、s attention on the largest opportunities for possible reduction.Figure 24:Stage A1-A5 steel product life cycle95%carbon emissions5%carbon emissions Raw material extractionIron oreLimestoneCoalRoad,rail or seaRoad,rail or seaSite waste and emissionsBlast furnaceBasic oxygen furnace&casterHot mill15-3
132、0%5-15%30-45%5-10%20-30%2-10%1-5%TransportTransportConstructionIronmakingSteelmaking and castingRollingSteel sections,rails and rolled billetsA1A2A3A4A5Distribution of carbon emissions per modules of A stage Example for steel elements(BOS)A1-A3 SSAB EPD A4 1000km by road A5 3.3%wastageArup 80 Charlo
133、tte StreetNet-zero buildings Halving construction emissions today 22Standards and codes of practice Standards,codes of practice and regulations that shape the development of building design and specification typically do not consider carbon as an outcome.Codes of practice and regulations,driven by t
134、he necessity to unify and homogenize approaches,are often by nature conservative and drive a certain level of redundancy and over-design beyond what companies might consider if they made each decision based on project-specific Design criteria Generally,the development of the most common criteria tha
135、t drive building designs does not consider minimizing embodied carbon.A particular example of this is perhaps the imposed(people)loads companies design structures to.Typically,the assumed loading criteria has taken a conservative approach,focusing on capturing all possibilities whether they are like
136、ly or even credible.Often the real scenario is a floor plate in a building will only ever see a small fraction of the maximum imposed design loads of its design specification,meaning much of the material used has been wasted.Criteria such as the real-time occupancy levels of buildings also dictate t
137、he design of building services and lifts,which companies typically design to codes that assume worst case scenarios.Perhaps moving forward,companies can be more thoughtful about the real maximum life-time criteria the designs will see and design for real performance,maybe even using modern digital s
138、ensor technology to enable this.first principles,as opposed to a prescriptive requirement.As codes of practice and regulations develop alongside the industrys ambitions to radically decarbonize,governments should give more consideration to carbon efficiency as an outcome.Developing codes to require
139、future designers to take more responsibility for balancing performance,safety,and carbon via better performance-based understanding would lead to more carbon-efficient designs.In the same project-specific performance design approach,designers might also consider future flexibility by designing it ex
140、plicitly into key elements,for example columns,walls,foundations at an appropriately minimal level of carbon impact that much leaner design can balance elsewhere,all of this supported via digital records in perpetuity.Figure 25:Typical prescriptive safety consideration factorEngineering judgement an
141、d general assumptionsDead load factor of safetyFactor associated with prescriptive deflection controlFactor of safety on applied actionsOverall factor of safety2+Importance factor of safetyMaterial factor of safetySuperimposed load factor of safetyLive load factor of safetyFigure 26:People density2.
142、0 kN/m210 people in 2x2 m space3.0 kN/m216 people in 2x2 m space5.0 kN/m226 people in 2x2 m space(usual public space allowance)Net-zero buildings Halving construction emissions today 23Design for manufactureThe development of building componentry and systems has the potential to lead to lower carbon
143、 solutions.Rather than designing each building as a bespoke proposition,if the company constructs it from a system of pre-developed and manufactured components it can continually refine,innovate and optimize the system in relation to its carbon footprint.Tracking and reporting the carbon associated
144、with modular systems should also ultimately be more rigorous as companies can establish environmental product declaration(EPD)documentation for each of the repeating components.Figure 27:Laing ORourke Explore Plant robotically manufacturing precision reinforced concrete building units.Figure 28:Cust
145、om made engineered timber components StoraEnso Sylva kit.Figure 29:Factory built volumetric modular housing Atlantic Yards B2 Towermodel and document production as well as enabling iterative and parametric design changes.The team used BIM to organize and visualize the building design and prefabricat
146、ion/construction sequencing of the project using 3D elements and 4D time/phase parameters.This virtual representation of Arups design and the fabrication and construction process enabled the client and project stakeholders to easily visualize and understand the intent.Communicating the data in this
147、way proved a powerful tool for client decision making in the early stages of the project,understanding spatial and tolerance requirements driving design and process decisions.Software Integration&Cloud Collaboration Successful efforts of integrating the BIM model with engineering calculations enable
148、d automating mechanical zoning diagrams and load modelling calculations.Success in data transfer and automation techniques enabled knowledge sharing for future projects through the establishment of guidelines and protocols for integrating BIM with Building Energy Modelling(BIM to BEM.)The team hoste
149、d live model data in the cloud using Autodesk BIM 360 Glue,at the time one of the industrys cutting edge cloud-based services.The team worked directly with the software developers providing feedback as an early adopter.Engineering details and interdisciplinary coordination were resolved using an inf
150、ormation-rich consolidated virtual model.Using the cloud collaboration members of the project teams continually accessed the most current model data,capturing comments and changes using built-in mark-up capabilities and enabling the client to be involved in the collaborative process,unhindered by so
151、ftware compatibility issues.SHoP ArchitectsStoraEnso Sylva kitNet-zero buildings Halving construction emissions today 24Whole life carbon&circularityFor the reasons presented above,this report focuses on upfront embodied carbon(A1-A5).However,it is also important to look at all embodied carbon stage
152、s,as well as operational carbon,ensuring the equal consideration of each and that companies do not compromise their reduction by decisions made at the outset.It will become increasingly important to understand the decarbonization trajectories of the built environment supply chain in terms of the rep
153、lacement of materials and products used at cyclic intervals throughout a buildings life.Figure 30 shows a typical set of life cycles across the various building layers.As well as looking for lower carbon solutions within these building layers,companies must consider more circular approaches to their
154、 provision.They need to be designing with minimal carbon impacts for life-cycle replacement,maximizing the potential to reuse building layer componentry at their highest possible reuse potential.Figure 30:Building layer life cycles0y10y20yServicesSpace planSkinStructureProject life cycle30y40y50y60y
155、Element life cycleFigure 31:Average whole life carbon breakdown of the six Where do we stand?case studies1,800kgCO2e/m232%Embodied upfront19%Embodied use/end of life(B&C)Design this impact out adopting circular design principles49%OperationalTo make the required systemic carbon impact reductions acr
156、oss our built environment we must collaboratively focus on shaping all future projects around the lowest possible carbon outcome from the earliest point in their inception.Net-zero buildings Halving construction emissions today 25Building layers3Our Where do we stand?study gave the following insight
157、 into where the average whole life carbon impact of the study buildings sat.Although based on the small case study sample it starts to give an indication of where the most impactful focus areas might be.We can also compare our findings with the growing body of published work being brought forward as
158、 referenced in chapter 1.We can see via the previous section that a limited number of key decisions at the outset of a project can have a major impact on the embodied carbon associated with the upfront construction stage(A1-A5).As we explore the subsequent building layers in more detail,we will expl
159、ore further upfront embodied carbon reductions and explore how we might make better decisions in relation to embodied carbon expended during building use via exploring more circular design principles.Business as usual estimates of total embodied carbon associated with upfront construction vary.Commo
160、nly quoted values sit in the range of 600-1,000 kgCO2e/m2.This suggests that an upfront construction stage total embodied carbon target associated with a halving of business as usual might sit around 400 kgCO2e/m2 as pointed to in the introduction.If we are asking“How do we halve construction emissi
161、ons?”,can the maximum bar for this question be at 400 kgCO2e/m2 or even lower?3.2 Skin(faade)Embodied upfront=95 kgCO2e/m2Embodied use&EoL=90 kgCO2e/m2Operational=0 kgCO2e/m2Total WLCA=185 kgCO2e/m23.4 ServicesEmbodied upfront=100 kgCO2e/m2Embodied use&EoL=190 kgCO2e/m2Operational=880 kgCO2e/m2Total
162、 WLCA=1,170 kgCO2e/m23.1 StructureEmbodied upfront=320 kgCO2e/m2Embodied use&EoL=10 kgCO2e/m2Operational=0 kgCO2e/m2Total WLCA=330 kgCO2e/m23.5 Stuff(FF&E)Typical WLCA=30 kgCO2e/m23.3 Space plan(partitions and finishes)Embodied upfront=45 kgCO2e/m2Embodied use&EoL=35 kgCO2e/m2Operational=0 kgCO2e/m2
163、Total WLCA=80 kgCO2e/m2Figure 32:Average carbon footprint across all six case studies per WBCSD framework distributionHow do we achieve a maximum upfront construction stage(A1-A5)embodied carbon of 400 kgCO2e/m2?We look in more detail at the 5 building layers within the WBCSD Building Systems Carbon
164、 Framework(BSCF),pointing to opportunities for and barriers to significant decarbonization.Net-zero buildings Halving construction emissions today 26Figure 33:Building systems carbon framework-building layers3.Space plan(10-30 years)The materials used for compartmentalisation:suspended ceilings,rais
165、ed floors and all internal surface finishes.4.Services(20-30 years)Services such as smart energy systems,lighting and air conditioning that support the internal climate in a building.5.Stuff(5-10 years)Everything else that comes in a building with the final tenants.The furniture,the electronics,the
166、decorations,etc.1.Structure(30-60 years)The construction of a building,which involves the structural skeleton and determines its basic shape.2.Skin(30-35 years)The outside layers of a building such as the faade,including windows,surface material and insulation.30-60 years30-35 years20-30 years10-30
167、years5-10 yearsTim Soar White Collar FactoryNet-zero buildings Halving construction emissions today 271 Structure(sub-structure and super-structure)3.1 StructureSuperstucture FrameUpper floorsRoofStairs and rampsSubstuctureFoundationsRetaining wallsLowest level slabStructureSkinSpace planStuffServic
168、es50%15%20%10%5%Figure 34:Structure and upfront embodied carbon(A1-A5)estimated typical distribution800kgCO2e/m2How do we halve construction emissions?Although the exact breakdown of embodied carbon across the building layers varies,the structural building layer(sub-structure and super-structure)can
169、 typically represent around 50%of the upfront construction stage embodied carbon.Given the above premise for limiting all upfront construction stage embodied carbon,this would create an immediate target for the structural layer of about 4003002001000A+A+ABCDEFGNet-zero buildings Halving construction
170、 emissions today 28Plan for low carbon from the startAs already seen,key decisions,often made very early in the design process,can have a major influence on the embodied carbon impact of the structure.To radically lower the embodied carbon in structures,it is essential to change the way companies un
171、derstand and prioritize carbon decisions associated with how they plan buildings from the outset.The structural grids,meaning the spans chosen for structures,can have a marked impact on the material used and hence the embodied carbon expended.Historically,companies have often prioritized excessive s
172、pans to create flexible column-free spaces because it is technically feasible.Perhaps companies have considered cost in this decision but have not typically considered the direct carbon impact.Figure 37 shows for a typical concrete flat slab structure the impact of span against carbon.As can be seen
173、,at a certain threshold a relatively modest increase in span can have a marked impact on the embodied carbon outcome.The figure also shows the potential impact of different assumptions in terms of the materials(reinforcement and cement)sourced.There is more on that later in this section.The structur
174、al layer results across the 6 case studies we explore in the Where do we stand?report range from 150 480 kgCO2e/m2,although it should be noted that the lower end of the values represents projects that had major structural reuse components.Often,early in a project,companies can identify areas of the
175、structural layer that contain a proportionally large component of the overall structural upfront embodied carbon,such as the floor plate.These areas should provide a particular focus for early reduction strategies.Vertical structure8%Basement structure7%Foundations5%Core/stability system12%Floor pla
176、te structure68%Figure 36:Typical breakdown across the structure layer (note varies according to overall building massing)Figure 37:Graph of span to carbon for a typical flat slabWorld valuesGeneral values Low carbon values6789000300400Embodied carbon kgCO2e/m2Median-25%+40%Span
177、45Carbon factor(kgCO2e/kg)ConcreteSteel reinforcedWorld values0.191.95General values0.151.5Low carbon values0.120.76Net-zero buildings Halving construction emissions today 29Often in framing structures at early design stages,companies will see the impact of changes in grid(column or wall locations)f
178、rom one floor to next,which will require elaborate transfer structures.Sometimes these are necessary for unavoidable functional reasons.However,at times excessive use of carbon-intensive transfer structures is simply the product of poor spatial planning and coordination.Another factor for considerat
179、ion early on is the provision of basement area.Experience shows that basement construction is typically twice the carbon intensity of the same area constructed above ground.One key driver for the additional carbon associated with basements is the necessity to have a perimeter retaining wall,typicall
180、y constructed from thick reinforced concrete.Given the carbon impact of the perimeter retaining wall,the shape of the basement plan as determined by the ratio of the wall length to the basement area contained is also a key factor.How far the basement extends below the ground water level,its overall
181、shape,and hence how complex the basement construction needs to be can have a notable impact on the carbon intensity of the structural layer.Significant carbon expenditure in relation to required reinforced concrete retaining wallGround water levelGround water levelFigure 38:Diagram showing open cut
182、basement with simple retaining vs bored secant type wall Basement constructed in a battered excavation above the water tableBasement constructed below the water table using a concrete cut-off retaining wallArup Citibank Plaza Hong KongNet-zero buildings Halving construction emissions today 30Materia
183、l choicesIn a global context,concrete and steel are the predominant structural construction materials by a large margin and will realistically continue to be so for the next decade and beyond.Companies should explore and develop timber and other lower carbon alternative materials but in doing this t
184、hey should be conscious of the supply-demand dynamics and use any alternative materials so that they give the maximum genuine benefit in terms of reducing atmospheric carbon.Companies should be conscious of the true impact of the decisions made at an individual project level,as the aim should be to
185、drive down overall consumption(demand)to levels to where a global carbon-free supply can meet them.Figure 39:Cement and steel contribution to global construction material carbon impactFigure 40:Global construction demand versus supply13,14,15,165%66%29%CementSteelOthersIn 20204Mm3Global engineered t
186、imber production493Mm3Global timber and wood-based panel production1.9GtGlobal steel production400MtGlobal reinforcing bar demand4.3GtGlobal cement productionWhatever material companies are using,they should aim to use as little of it as possible.5B+m2Building construction each yearNet-zero building
187、s Halving construction emissions today 31Reinforced concreteThere are several ways to reduce the carbon impact of reinforced concrete structures but the most immediately impactful way in real terms is to use less of the heaviest polluting elements,namely less cement and less reinforcing steel.16%1%1
188、%15%5%5%4%94%56%71%67%8%8%5%1%1%40%1%2%1%1%6,5mFigure 53:Hybrid reinforced concrete and timber frame proposal for an office building in LondonKLH Timber concrete compositesArupNet-zero buildings Halving construction emissions today 39Emerging low-carbon alternativesGiven the amount of time taken for
189、 new technologies to become mainstay construction techniques,companies cannot rely on the emergence of new materials that can be deployed at a global built environment scale over the coming decade.For the ones already established,they can be niche and the challenge sits with their scalability.There
190、are also some encouraging signs that more innovative new low-carbon intensity materials may emerge in the not-too-distant future.More research,innovation and investment are clearly required to develop genuine scalable alternatives to steel and concrete in the next few decades.Figure 54:Example of he
191、mpcrete houseFigure 55:Example of rammed earth wallUK Hempcrete LtdLaura Trilitzsch Port Philip Estate WineryNet-zero buildings Halving construction emissions today 40New forms of constructionThe construction industry by its nature is conservative and relies heavily on precedents.Relatively low prof
192、it margins drive this,which in turn drives poor levels of investment in developing new ideas.Companies are,for all intents and purposes,constructing buildings using the same structural techniques and systems that they have used for decades.Perhaps to meet the challenge of halving carbon emissions,co
193、mpanies need to drive a higher level of innovative new thinking in terms of the structural systems they design.Companies need to rethink preconceived concepts and systems from a carbon perspective and re-engineer them looking at the new imperative of optimizing the carbon footprint while still deliv
194、ering the required function.One example of this is a recent piece of work undertaken to look at how to reimagine a 9x9 meter standard reinforced concrete floor plate starting from the position of minimizing material consumption and hence carbon.The proposal is for a vaulted system instead of adoptin
195、g a planar concrete slab surface.The vaulted slab uses compression as opposed to bending action to resist the floor loads and as such is a much more materially efficient structure,a principle understood for millennia but disregarded as other influences took precedence over material efficiency in des
196、ign.As companies explore new ideas,preconceived norms will push back against them.But companies must strive to overcome all barriers that arise.If companies rapidly,and holistically,collaborate to evolve new ideas,a whole new generation of low-carbon solutions outside of preconceptions will emerge.A
197、1Do not scaleABCDEFGHIJKLMN11ClientProject TitleScale at A1RoleName ArupRevDateByChkdAppdArup Job NoRevSuitabilityDrawing Title31/07/202117:27:49077075-59The Arup VaultLaing ORourkeStructuralSequencingSheet 1S0-Work In ProgressSQ-S-501ScaleSequencing 1-ColumnsScaleSequencing 2-BeamsScaleS
198、equencing 3-Corner Panels1.2.3.This drawing should be read in conjunction with the Structural General Notes drawing:GN-S-001 and Structural SpecificationsAll dimensions are in millimetres and all levels are in metres(AOD)unless noted otherwise;Do not scale from this drawingThis drawing has been prod
199、uced electronically and may have been photo-reduced or enlarged when copied.Do not rely on any scale quoted.Work only to figured dimensions.Notes:C01DRTSMTCIssued for ConstructionScaleSequencing 4-Middle PanelsFigure 56:Prototype of a precast vaulted floor plate Laing ORourke Arup(approximately 1/3
200、of the CO2e of a more conventional flat slab).Figure 57:EMPA-ETH Zurich HiLo vaulted flooring systemLaing ORourkeEMPA HiLo constructionEMPA HiLo funicular floorNet-zero buildings Halving construction emissions today 412 Skin(faade)Figure 58:Skin and upfront embodied carbon(A1-A5)estimated typical di
201、stributionHow do we halve construction emissions?Although the faade designs can vary significantly based on the type of system adopted and performance requirements sought,upfront embodied carbon average per square metre of faade area from experience across a wide number of measured projects might be
202、 considered typically in the range of 150-300 kgCO2e/m2 when applied to the surface area.3.2 Skin(faade)External wallsWindowsExternal doorsStructureSkinSpace planStuffServices50%15%20%10%5%800kgCO2e/m2Hufton+Crow Central Saint GilesNet-zero buildings Halving construction emissions today 42Infill pan
203、el External finish Insulation Internal finishGlazing panelFrame(incl.gasket and thermal break)Unitized panelBracketsStructural frameStructural frameFigure 59:Aluminum unitized curtain wall(WT-02)Spandrel panel External finish Insulation Internal finishFrame Mullions TransomGlazing panelGasket and th
204、ermal breakBracketsStructural frameStructural frameFigure 60:Steel stick system curtain wall(WT-08)Net-zero buildings Halving construction emissions today 43Brickwork(and mortar)external claddingSecondary framingWindow and frameSheetingInsulation and faade frame(including gasket and thermal break)In
205、ternal finish plasterboard and vapour barrierBracketsStructural frameStructural frameFigure 62:Brickwork masonry wall steel frame system(WT-15)Aluminum rainscreenSecondary framingWindow and frameSheetingInsulation and faade frame(including gasket and thermal break)Internal finish plasterboard and va
206、pour barrierBracketsStructural frameStructural frameFigure 61:Aluminum rainscreen,steel frame panel(WT-13)Net-zero buildings Halving construction emissions today 44Figure 63:A1-A3 average contribution of faade components over 4 faade typologiesAs can be seen from Figure 63,breaking down four common
207、faade types(figs 59-62)the most impactful elements of the faade in relation to upfront embodied carbon are typically the metal framing,the glass and external finishes and shading applications.The previous Where do we stand?report concludes that,across the 6 case studies,the faade contributed on aver
208、age to 15%of the upfront embodied carbon of a building(A1-A5)and on average around 20%of the embodied whole life carbon(A-C).One individual case had a maximum faade contribution of around 30%of the whole life-cycle embodied carbon(A-C),which in turn equated to over 20%of the total whole life carbon.
209、Hence the contribution of the faade system is of significance and companies should consider it carefully at the outset.Faades both contribute directly to the embodied carbon of a building and have an influence on its operational carbon.Although there has been widespread focus and legislation on redu
210、cing operational energy use,and hence operational carbon,there has been little global focus on the embodied carbon contained within the faades of buildings.In some localized regions the awareness of embodied carbon benchmarks and targets to focus the industry on embodied carbon reduction is only jus
211、t now emerging.Faade systems,although not typically consuming operational energy,through their design can increase or decrease a buildings operational energy and associated carbon via their performance.It is necessary to assess the relationship between embodied and operational carbon impacts during
212、the development of the faade design,for example the addition of significant carbon-intensive shading elements(e.g.,aluminum bris Soleil)can,if not considered carefully,lead to a major increase in the total embodied carbon that,in some cases,improvements in operational energy performance do not pay b
213、ack.Understanding the relationship between embodied carbon of the skin and operational performance of the building(services layer)is key to making deliberate,carbon-conscious decisions to reduce emissions across supply chains and design processes.The operational performance of faades is related to t
214、heir orientation and the azimuth of the sun.Companies should develop their design to their specific exposure condition on the building,bringing an opportunity to further tune the relationship between embodied carbon and operational performance.Frame(including secondary elements)Gaskets&thermal break
215、sGlassExternal screen(sheet,rainscreen,brick&cement)InsulationInternal finish&vapour barrierFixing150-300kgCO2e/m249%18%4%3%6%18%2%Net-zero buildings Halving construction emissions today 45Figure 64:Diagram showing example of payback period study comparing double and triple glazed units.Reduced oper
216、ational carbonReduced embodied carbonSingle glazingDouble skinDouble glazingTriple glazingECCarbon payback periodOC1kgCO2eTimeEmission factors for glazing units were provided by Saint-Gobain Glass.CoatingGlass substratePVB interlayerDouble glazed unit(DGU)Build-up:8T-16-44.2Total embodied carbonA1-A
217、3 71kgCO2eq/m2Triple glazed unit(TGU)Build-up:8T-16-6-16-44.2Total embodied carbonA1-A3 96kgCO2eq/m2Closed cavity faade(CCF)or Double skin faade(DSF)Build-up:66.2+8T-16-44.2Total embodied carbonA1-A3 116kgCO2eq/m2The comparison of carbon data related to the building skin,across multiple projects,is
218、challenging as design decisions respond to a wide range of drivers,parameters and performance requirements that make each combination unique.It is also necessary to consider the faade in terms of its effect on the embodied carbon of other building layers as decisions made can have an impact on other
219、 building layers.For example,the skin layer is closely related to structural layer movements;if the faade is heavy or brittle it may require the use of more material in the structure that supports it.It is important that companies understand the actual impacts of these wider holistic building layer
220、decisions and consider them in terms of making the best overall outcomes.Azimuth of the sun as a design considerationNet-zero buildings Halving construction emissions today 46Figure 65:Faade typologiesTo answer the question of“How do we halve construction emissions?”holistically,companies need to lo
221、ok across building layers and across carbon stages(embodied and operational).Holistic payback studies assessing at what point in time the operational savings in the building services will offset the upfront carbon cost of a performance improvement to the skin is a good example of this holistic appro
222、ach.Examples of these studies are currently not widely available,do not follow a consistent methodology and will be unique to each skin-building combination.However,from what companies have studied to date,there are some emerging general trends to explore with regards minimizing the initial upfront
223、embodied carbon of faade designs.Figure 66 taken from a sample of 16 faade projects shows a wide range of operational performance outcomes(x and y axis)linked to non-corelating embodied carbon outcomes(z axis),suggesting these two carbon performance criteria are not currently considered together.Alu
224、minum unitized curtain wall(WT-02)Steel stick system curtain wall(WT-08)Aluminum rainscreen,steel frame panel(WT-13)Brickwork masonry wall steel frame system(WT-15)Net-zero buildings Halving construction emissions today 47Figure 66:Embodied carbon figures alongside thermal and solar performanceUpfro
225、nt embodied carbon(kgCO2e/m2)Solar gains(W/m2)Improved solar performanceU-value(W/m2K)Improved insulative performance0.9-1.01.0-1.15060WT-16WT-15WT-14WT-13WT-12WT-04WT-11WT-10WT-09WT-08WT-07WT-06WT-03WT-05WT-02WT-011351.2-1.31.3-1.51.4-1.61.3-1.4Overview of cladding systems and associated embodied c
226、arbonGenerally,faades are made up of a variety of systems,configurations and materials from a broad supply chain.The lack of information about the full material journey,together with the lack of an industry-wide faades methodology to calculate embodied carbon,makes comparison across sources a challe
227、nging exercise.Hence there is an urgent need for better,consistent faade system carbon data within the industry.Recent research from Arup and Saint-Gobain22 used detailed analysis to enable a comparison of popular cladding types for a range of key materials and design parameters.Some of the key find
228、ings were:Embodied carbon(A1 A5,B4 and C1 C4)ranged from 160 to 520 kgCO2e/m2 of faade area(significant variance depending on the system type and design).Often,from a material perspective aluminum is contributing to embodied carbon as much or closely followed by glass.Limited service-life of key mat
229、erials and components means they may need replacing two or three times over the typical life expectancy of a building(e.g.,insulated glazed units that may only have a useful service life of 25 years).This is a significant additional embodied carbon burden if not carefully considered as part of a del
230、iberate circular economy life cycle from the outset.Net-zero buildings Halving construction emissions today 48Figure 67:Example of embodied carbon/m2 comparison of some typical faade types Arup and Saint-Gobain Study 2022.23WT-01WT-02WT-03WT-04WT-05WT-06WT-07WT-08WT-09WT-10WT-11WT-12WT-13WT-14WT-15W
231、T-0500300600GlassAluminumSteelStainless steelMineral woolEPDMBrickConcreteStoneTimberRubberSiliconePolyamidePlasterboardFibrecementCementFigure 68:Diagram showing average embodied carbon distribution across WLC stagesTotal A1-A3Total A3-A4Total B4Total C0WT-01WT-02WT-03WT-04WT-05WT-06WT-0
232、7WT-08WT-09WT-10WT-11WT-12WT-13WT-14WT-15WT-500300600Aluminum unitized curtain wallStick curtain wallDouble skin curtain wallClosed cavity curtain wallPrecast concrete with windowsFramed systemNet-zero buildings Halving construction emissions today 49Design variables of significant impact
233、The Arup and Saint-Gobain study took 16 curtain wall system types,typical of modern residential and commercial buildings,and investigated the influence of key design and material decisions by analyzing the data from thousands of faade configurations and corresponding energy simulations across the 16
234、 typologies.It explored insights such as the influence of the window-wall ratio,the bay size and solar control products.Although the correlation between parameters in the study did not point at universal conclusions,some clear insights on carbon drivers emerged from the study:Window-to-wall ratio(WW
235、R):80%variation in embodied carbon,with a big impact on operational carbon(i.e.U-value,solar gains)Framing materials:40%variation in embodied carbon(industry average,highly sensitive to supply chain)Consideration of the above from the earliest opportunity should allow for considerable scope to make
236、better decisions in terms of driving much lower upfront embodied carbon designs.Cladding materials:30%variation in embodied carbon(industry average,highly sensitive to supply chain)Insulated glazing unit(double glazing DGU vs triple glazing TGU):10%variation in embodied carbon(depends on WWR),with i
237、mpact on operational carbon(i.e.U-value)Other trends and guidance on achieving lower carbon faade design also emerged from the study:Low MediumHighWindow-to-wall ratio(WWR)Orientation Framing materials Cladding materials Insulated glazing unit(double-glazing vs triple-glazing unit)Variations in faad
238、e design Good industry dataDecarbonized supply chain Increased service life System and material passports Glass coatings*Fabrication Shipping Installation*Application of glass coatings improves operational performance at a minimal embodied carbon costFigure 69:Key considerations in low-carbon skin d
239、esignArup 8 Chifley SquareNet-zero buildings Halving construction emissions today 50Plan for low carbon from the startReferencing the discussion above,low-carbon faades require good early understanding by all stakeholders in the design process to have the maximum overall impact.Companies should expl
240、ore all ways to achieve the projects overall aims fully at the outset.For instance,is new construction the best answer,can a refurbished faade facilitate the reuse of an existing building and deliver the required energy performance?Each project should look to set clear implementable targets with res
241、pect to the skin building layer(faade)that consider the basic overall relationship between the key drivers.Companies should consider project parameters such as the orientation,required service life,expected use conditions,building form factor,climate resilience measures,thermal performance and mass,
242、future flexibility,access requirements,faade system selection,coordination and optimization with the structure and mechanical systems and other functional requirements(architecture,acoustic,security,fire etc.)as holistically as possible at the earliest stage.At all points,they should review and cons
243、ider the carbon payback period.Faades are typically relatively complex systems of materials,and the emergence of clear environmental product declaration(EPD)documentation throughout the supply chain will help to drive transparency and demand for lower carbon designs within the industry.Designing out
244、 waste,maximizing off-site manufacture and minimizing weight are all ways to reduce the overall embodied carbon impact.Figure 70:Triton Square,London 3,000m2 of faade taken down and refurbished locally to improved performance criteriaArup 1 Triton SquareNet-zero buildings Halving construction emissi
245、ons today 51Companies should consider the impact on embodied carbon of all visual requirements of the faade system in relation to their carbon impact.For example,allowing a reduced finish quality on less visually prominent areas of the faade and relaxing glazing distortion limits and color variance
246、requirements can reduce the energy and the embodied carbon associated with rejected waste material.Companies should carefully consider the ease of access to parts of the faade that need to be more regularly inspected,cleaned,maintained and replaced.They should account for the carbon impact of the cl
247、eaning requirements of a faade in the project-wide embodied carbon assessment.Designers should consider if they can reduce the cleaning procedure to decrease the carbon emissions associated with the maintenance or if more frequent,targeted cleaning might enable materials,components and systems to ha
248、ve significant extra life and thereby reduce the additional embodied carbon associated with replacement.Accurate,accessible and structured as-built information,including detailed records of materials(digital twin)is fundamental to realizing future refurbishment options,reuse potential and recycling
249、capabilities of a project.Figure 71:Faade inspection and maintenance considered from the outsetFigure 72:Faade virtual twinArupArupNet-zero buildings Halving construction emissions today 52Material choicesAs already demonstrated,material selection and its supply chain have a significant impact on th
250、e embodied carbon that goes into the skin of a building.Designers should pay particular attention to the components and materials with the highest impact.Supply chainMany players within material supply chains are beginning to focus on trying to decarbonize their production.One example of this is the
251、 aluminum market.By increasing the recycled content of aluminum and using renewable energy supplies in production,it is possible to dramatically reduce the embodied carbon.The supply chain choice for this single material alone can halve the embodied carbon of a typical curtain wall.Figure 73:Carbon
252、intensity of all materials considered in faadesFigure 74:Potential range of typical aluminum unitized curtain wall02461012148kgCO2e/kgAluminumSteelGlassTimber*Blockwork(UK)Brick(UK)ConcreteStoneAluminumSteelGlassTimber*Blockwork(UK)Brick(UK)ConcreteStoneExtruded profilesSheetHot dip galvanized steel
253、 sheetStructural(closed sections)Structural(plate)13.213.02.72.52.52.01.61.71.50.50.5 0.40.40.30.10.20.2 0.20.1 0.1 0.1Reinforcement barsStructural(rolled open sections)ToughenedGeneralStructural glulamOSBStructural CLTStructural LVLLightweightDenseGraniteLimestoneSandstonePrecast C40/50(UK)In situ
254、C32/40(unreinforced excludes China)*No sequestration included0500300200kgCO2e/m2 SA40%recycled content93%recycled contentGlassAluminumEthylene propylene diene terpolymer(EPDM)rubberPolyamideMineral woolStainless steel20%69%11%84%Net-zero buildings Halving construction emissions today 53At
255、 current rates of aluminum scrap recycling versus global demand,companies should bear in mind that like the steel industry,the scrap market can only supply to approximately a third of demand.Hence,there should always be a drive to reduce consumption to an absolute minimum before relying on recycled
256、content to reduce the overall embodied carbon footprint of the faade.Glass manufacturers are also looking to develop lower carbon products via the use of significantly increased amounts of cullet(recycled glass)combined with the use of renewable electricity within their process to produce equivalent
257、 technical and aesthetic performance to conventional glazing products.Some materials and processes can have a significant impact in reducing the whole life carbon(WLC)of the faades by extending service life or offering operational savings with minimum upfront carbon cost.A clear example of the latte
258、r are glass coatings,where an additional 1 kgCO2e(2%of the carbon cost of a typical double glazing),can save 10 KgCO2e/m2 of faade each year.Figure 75:Embodied carbon involved in common glass processesFigure 76:Glass being recycled into cullet0246GWP(kgCO2e)Magnetron coatingTemperingPLANI
259、CLEAR 4mmLamination2 sheets of PVBDGUTGUSaint-GobainNet-zero buildings Halving construction emissions today 54Emerging low-carbon alternativesDesigners are exploring many experimental low-carbon materials,some of which have a history in building construction prior to modern architecture.These includ
260、e“biogenic”materials originating from plant or animal sources available in the biosphere,naturally occurring geological materials and composites of the two.In applications generally within the less-regulated parts of the construction industry,these experimental alternatives to current convention are
261、 demonstrating potential to create building skins or faades with significantly reduced upfront embodied carbon.The question is whether some of these alternatives can achieve the scale needed to address global demand in the short time frames required.It is worth noting that WLC data is often limited
262、for these alternative materials and companies should assess each building or refurbishment for material selection on an individual basis,in that the examples outlined below will not always be the most low-carbon option both solely in terms of up-front embodied and overall,when also considering opera
263、tional performance.See section 4 and figure 99 where the“balance point”between embodied and operational carbon is discussed.Another notable development in the faade industry is the growth of building integrated photovoltaic(BIVP)modules.The emergence and improved performance of BIVPs allows the pote
264、ntial for the building skin,if orientated well,to generate significant amounts of clean energy.Perhaps in the future combined with other measures above,it could lead to the faade system to potentially be a net-positive building layer over its life span.Figure 77:Example of hempcreteFigure 79:Bio-bas
265、ed cement tiles made from approx.85%aggregate combined with 15%biocement.Figure 80:Example of building-integrated photovoltaicsFigure 78:Bricks made from up-cycled construction waste and a lower temperature firing processUK Hempcrete LtdKenoteq K-BRIQZhou Ruogu GreenPix Media WallStoneCycling BioBas
266、edTilesNet-zero buildings Halving construction emissions today 55The use of timber and other combustible materialsFrom an embodied carbon perspective,timber offers potential in terms of reducing the impact of some of the more carbon-intensive faade framing and finishes.However,designers need to care
267、fully consider the use of combustible materials in faades.In some applications and geographies it is restricted.Figure 81:Example of timber faade construction in LondonArup Kings Cross 1Net-zero buildings Halving construction emissions today 563 Space planFigure 82:Space plan and upfront embodied ca
268、rbon(A1-A5)estimated typical distribution3.5 Stuff(FF&E)Fittings,furnishings and equipment3.3 Space plan(partitions and finishes)Internal walls and doorsWall,floor and ceiling finishesStructureSkinSpace planStuffServices50%15%20%10%5%800kgCO2e/m2How do we halve construction emissions?As defined in o
269、ur previous work,which adopted the WBCSD Building System Carbon Framework,space plans consist of internal walls and partitions and internal finishes,the breakdown of which we illustrate below.Overall,space plan elements can account for approximately 10%of the upfront embodied carbon(A1-A5)emissions
270、of new commercial buildings,according to analysis carried out by Arup.23 However,the contribution is expected to vary significantly due to the often bespoke and variable nature of the space plan.Considering the target discussed in section 3 to limit the total A1-A5 emissions of a commercial building
271、 to 400 kgCO2e/m2,this might translate into an immediate space plan target of 40 kgCO2e/m2 or less.Figure 77 illustrates the estimated upfront embodied carbon footprint of space plan elements for three scenarios:A typical current commercial building one that includes a demountable suspended ceiling
272、and traditional raised access floors;A more environmentally focused current commercial building based on case studies 2 and 3 from our previous Net-Zero Buildings:Where do we stand?report;An aspirational target for a commercial building in 2030. typical values2020 best in class2030 aspira
273、tional targetkg CO2/m2 GIA(A1-A5)Concrete slabSuspended ceiling4011Ceiling finishes11Wall finishes511Internal walls and partitions10105Internal doors1011Floor finishes101010Raised access floor403020Concrete slabFigure 83:The estimated upfront embodied carbon footprint of Space Plan elements per Gros
274、s Internal Area(GIA)for a commercial buildingNet-zero buildings Halving construction emissions today 57A significant proportion of the embodied carbon emissions in the space plan come from raised access floors and suspended ceilings.Reducing the embodied emissions of these elements has a large impac
275、t on the overall carbon footprint of the space plan when comparing the cases above.It is worth noting here that in some geographies it is common to have densely arranged internal walls and partitions.In these cases,the internal walls and partitions would contribute a significantly greater proportion
276、 of the space plan carbon footprint.The above 2030 target case aims to illustrate further possible savings to achieve the 40 kgCO2e/m2 gross internal area(GIA)target for the space plan.In addition to the upfront,product and construction stage emissions(A),the Space Plan elements outlined above gener
277、ally need to be upgraded or replaced during the lifetime of buildings,generating additional emissions during the use phase(B).The lifespan of typical finishes tends to be around 10-30 years while that of partitions is generally about 30 years,hence all elements of the space plan are expected to be r
278、eplaced at least once during the defined 60-year lifetime of a building.Architectural and commercial trends drive replacement but the durability of the materials chosen also influences it since the space plan elements are often those in direct contact with the building users.Given the above life spa
279、n and replacement periods,it is important that companies also consider circularity(repurposing,reuse)as well as carbon in the determination of the space plan design.As adopting a non-circular,business-as-usual scenario companies could in theory create a space plan life-cycle design that produced in
280、excess of 300 kgCO2e/m2 if companies replaced everything with no recycling considerationWe discuss the most effective methods of reducing emissions from these elements of the space plan in the following sections.Figure 84:Typical life span assumptions055Raised access floorFloor finishesIn
281、ternal doorsInternal walls and partitionsWall finishesSuspended ceilingCeiling finishesSpace plan elementExpected lifespanNet-zero buildings Halving construction emissions today 58Reducing resource consumptionThe biggest opportunities to remove embodied carbon comes from reducing resource consumptio
282、n.Omitting Suspended ceilings Building services systems are designed to be visibly exposed.Raised access floors Electrical and communication cables,small ducts and other floor mounted building services systems are integrated into other finishes or designed to be surface mounted.Non-structural intern
283、al walls and partitions where possible functionally Omitting internal walls and partitions wherever open floor plans might be achieved.This may include omitting most internal walls and partitions and including a limited number of modularized or flexible partitions that can be moved within a space to
284、 fit varying needs.Procuring Build less Procuring building materials with longer lifespans is of relevance to space plan elements due to their shorter overall lifespans,as is aligning with design for disassembly/replacement concepts.Note that this technically relates to operational replacement embod
285、ied(B4)emissions but due to the lifespans in question it is worth noting because the long-term savings will likely outweigh those made to the upfront embodied carbon from material choices.In this instance,the responsibility lies with the consumer(i.e.,the tenants)to choose materials with longer life
286、spans and to opt not to replace space plan elements only in order to keep up with architectural trends.Reuse Procure the raised floors and suspended ceilings from material banks(e.g.,old buildings)using circular principles.However,these circular markets are currently underdeveloped and require signi
287、ficant maturing to function at scale.These measures require early design integration.Further opportunities to remove embodied carbon in the space plan come from primary material choices and recycled content.Recycle Procuring recycled carpet,plasterboard(for wall and ceiling finishes),kitchen tops an
288、d floor panels.Low carbon space plan finish materials Some examples are:Linoleum as an alternative to vinyl Water-based eco paints(e.g.,limewash)Cork as an internal finish for walls and ceilings Bamboo for flooring Timber(misc.uses)Clay plasters as alternative to gypsum equivalentsFigure 85:Examples
289、 of exposed ceiling(no suspended ceiling)versus typical demountable suspended ceilingArup 80 Charlotte StreetArup 8 Fitzroy StreetNet-zero buildings Halving construction emissions today 59Emerging low-carbon examplesRaised floorsAs highlighted above,raised floors often contribute the largest proport
290、ion of the upfront embodied emissions within the space plan.Using recycled and low-carbon componentry within the system can significantly reduce carbon impact.The example in figure 86 uses recycled substrate floor panels,consisting of up to 95%calcium sulphate and recycled paper supported by steel p
291、edestals to form a raised floor system.In comparison with some more traditional flooring systems,which have an estimated upfront embodied carbon intensity of typically about 50 kg CO2e/m2,the flooring system has an intensity of 30 kg CO2e/m2.Internal walls and partitionsThere is a lot of potential i
292、n the market for emerging products,such those examples included below,to replace existing,more carbon-intensive metal and cement-based products with alternatives that are much lower in terms of their embodied carbon content and even have the potential to store or sequester carbon.It is worth noting
293、that companies should assess each building or refurbishment for material selection on an individual basis,in that the examples outlined below will not always be the most low-carbon option when compared with using,for example,plasterboard drywall with a high gypsum recycled content.In addition,there
294、is the question of whether some of these alternatives can achieve the scale needed to address global demand in the short time frames required.Figure 86:Technik flooring system with half tile finish01020305040kgCO2e/m2Traditional RAFTechnik RAFPedestalPanelStone tile finishArup 80 Charlotte StreetNet
295、-zero buildings Halving construction emissions today 60Internal wallsHempcrete is a non-structural,composite material made by mixing hemp shiv(the woody inner portion of the hemp stalk)with a wet lime binder.It provides a natural,vapor permeable insulation material that can be used in various forms
296、in internal walls and flooring.Earth bricks and blocks(i.e.,adobe)have been used for as long as humankind has been building.At their crudest,these materials are hand molded from clay rich soils and dried in the sun.It is possible to improve structural performance by mechanically pressing or extrudin
297、g the materials and stabilizing with a cement or hydraulic lime.Typically used in non-load bearing internal partition walls,they are a low-carbon alternative to concrete blocks or timber/metal stud walls.They also help regulate heat through their high thermal mass.Additionally,it is possible to rein
298、force earth bricks and blocks with natural fibers such as straw(e.g.,“strocks”or hemp shiv.)to create composite blocks.Clay rich soils and aggregates can be compressed by hand or hydraulic rams into shuttering to create rammed earth.Rammed earth has been used for thousands of years and more recently
299、 as a popular low-carbon alternative to cast concrete.Cob(compressed clay and straw)is another traditional walling method that has been used globally for centuries that is gaining popularity as a low-carbon alternative.Conventional straw bales can be connected with steel or timber spiked rods to pro
300、duce masonry infill walls,of which the durability and fire performance can be improved with lime renders(external),clay plasters(internal)or rainscreen cladding such as timber weatherboards.These are available as prefabricated timber cassette panels.Figure 87:Example of hempcrete wallFigure 89:Examp
301、le of rammed earth structureFigure 88:Example of adobe brickFigure 90:Example of straw bale modulesUK Hempcrete LtdTzou Lubroth ArchitektenModcell H.G Matthews LtdNet-zero buildings Halving construction emissions today 61PartitionsConventional straw bales can be connected with steel or timber spiked
302、 rods to produce masonry infill walls,of which the durability and fire performance can be improved with lime renders(external),clay plasters(internal)or rainscreen cladding such as timber weatherboards.These are available as prefabricated timber cassette panels.Some lower carbon new alternatives to
303、gypsum,cementitious based partitions are beginning to emerge.Compressed straw boards,manufactured by placing straw under heat and pressure creates a reaction in the natural resins within the straw that binds the materials together.The materials are bound at the edges with paper to create a board mat
304、erial that can be used for several applications,such as internal partitions.Other bio-material bi-products such as rice husks,an agricultural bi-product,can be used in a similar manner.Hemp,a rapid growth biomaterial can be formed into corrugated sheet via the use of farm bio-waste resin to form rig
305、id corrugated sheets.Mycelium,the vegetive filament root structure of mushrooms,again a waste byproduct,is also starting to be used in a similar capacity.It is also possible to replace gypsum-based plasters with emerging clay-based alternatives to further lower the embodied carbon of internal partit
306、ions.32About Durra PanelDurra Panel is a fully certified wall and ceiling panel that contains an engineered biomass panel core made entirely out of reclaimed wheat straw.Durra Panel is Australian owned and manufactured in Bendigo,Victoria from locally sourced materials.The manufacturing process conv
307、erts a wasted agricultural by-product into a strong and durable construction material which is 100%recyclable and biodegradable at the end of its useful life.Using processes and systems developed over 40 years,Durra Panel can be used to create simple and safe ceiling and wall systems along with non-
308、load bearing partition walls.Durra Panel is faster,safer and more economical than traditional building materials,providing cost effective savings on site and greatly reducing labour and build times.Figure 91:Example of compressed straw boardsFigure 93:Example of hemp corrugated sheetFigure 94:Exampl
309、e of mycelium building blocksFigure 92:Example of rice husk ash bricksDurra PanelMargent FarmArup HyFi TowerWatershed MaterialsNet-zero buildings Halving construction emissions today 624 ServicesFigure 95:Services Estimated typical distribution of upfront embodied carbon(A1-A5)Figure 96:Building ser
310、vices systems3.4 ServicesMechanicalElectricalPublic healthStructureSkinSpace planStuffServices800kgCO2e/m250%15%20%10%5%Building servicesMechanicalHeatingCoolingVentilationPublic healthGasCold waterHot waterDrainageNon-potable waterFire suppressionElectricalElectricalLightingRenewablesTelecommunicat
311、ionsVertical transportationHow do we halve construction emissions?The results across the six case studies we previously explored in Where do we stand?show that 75%of the emissions associated with the services layer are related to the operational energy consumed during the lifetime of the building(B6
312、 Operational Energy Use).However,it is important to note the relative contributions of embodied and operational carbon vary depending on building type and energy source.As the grid decarbonizes and companies switch to all-electric buildings,embodied carbon will represent a higher portion of the whol
313、e life carbon of the services layer,demanding attention now.It is essential that design decisions be made in a holistic way,following a whole life carbon approach to consider both operational and embodied carbon impacts.According to several available sources,24,25 building services can represent 4-1
314、6%of total upfront(A1-A5)embodied carbon emissions for residential buildings,15-20%for commercial buildings and 11-13%for schools.Net-zero buildings Halving construction emissions today 63Figure 97 illustrates how the embodied carbon of the services layer is split into the different mechanical,elect
315、rical and plumbing systems for an Arup commercial case study in London.Note the difference between the contribution of cooling to A1-A5 embodied carbon(23%)and to A-C(30%).This is primarily due to the impact of refrigerant leakage in cooling systems,which is captured in stage B1.Taking a whole life
316、carbon approach to reduce the impact of services As with other building layers,designers should consider carbon as a key parameter throughout the development of a building project,from the earliest opportunity.Although the focus of this report is A1-A5 upfront embodied carbon,B1 which captures the i
317、mpact of refrigerant leakage and B4 which captures equipment replacement should not be ignored(see figure 98).As illustrated in our previous report,Where do we Stand?case studies,when considering A-C whole-life embodied carbon,the services layer can represent as much as 30%of the buildings total emb
318、odied carbon,only marginally less than the structural layer.The services layer contributes significantly to a buildings whole life carbon emissions,so it is necessary to look holistically at how companies can make significant reductions in an effective way.Figure 97:Embodied carbon contribution of b
319、uilding services systems to A1-A5 and A-C,based on an Arup case study for a newly built,mid-rise office building in LondonCoolingHeatingVentilationElectricalLightingVertical transportCold waterFire protectionHot waterDrainage23%30%4%27%15%4%27%17%6%7%5%7%3%2%12%5%3%A1-A5 embodied carbonA-C embodied
320、carbonFigure 98:Embodied carbon of a mechanical cooling system illustrating the high contribution of refrigerant(R410A)leakage in B1 and equipment replacement in B4 to A-C embodied carbon0204060tCO2eA1-A34.5%1.7%0.9%12.4%0.0%0.0%0.0%0.0%0.3%80.2%A4A5B1B2B3Lifecycle stageB4B5C1C2C3C40.0%0.
321、0%DistributionChillerFCUNet-zero buildings Halving construction emissions today 64Companies need to be careful not to shift emissions from one whole life carbon stage to another or from one layer to another,so that the decisions designers make lead to the most significant carbon reductions overall.F
322、or design decisions where there might be a compromise between embodied and operational carbon,companies should look for the whole life-cycle balance point as illustrated in Figure 99.For example,as companies increase insulation thickness to improve faade performance and thus reduce operational carbo
323、n(in green),they increase the embodied carbon by adding more material(in blue).If companies increase insulation thickness beyond the balance point,the embodied carbon cost becomes higher than the operational carbon saving.Therefore,companies must consider where the balance point lies to optimize who
324、le life carbon.The balance point will vary depending on the building and type of intervention,so it is necessary to evaluate it on a case-by-case basis.When assessing these design options,it is also important that companies look beyond whole life carbon,keeping in mind other factors such as the impa
325、ct on energy use intensity and building running costs.Figure 99:Whole life carbon balance points.Example on wall insulation thickness.Insulation thicknessOperationalEmbodiedBalance pointWhole-lifeCarbon emissionsJack Hobhouse 80 Charlotte StreetNet-zero buildings Halving construction emissions today
326、 65Embodied carbon hotspotsCalculating the embodied carbon of building services systems is complex due to the high number of components making up each system and the limited data available from manufacturers.Enabling the identification of the biggest contributors to embodied carbon will require wide
327、r manufacturer and industry engagement.The rapid development of standardized DistributionDistribution accounts for a significant portion of services A-C embodied carbon and should be considered alongside primary plant.Figure 101 shows data from an Arup study that compares the embodied carbon of seve
328、ral HVAC strategies.Results highlight the high contribution of pipework and ductwork to the overall embodied carbon of all HVAC systems assessed.carbon intensity data,such as internationally accredited environmental product declarations(EPDs)or CIBSE TM6526 forms as a minimum,is essential.Some key o
329、pportunity areas to reduce embodied carbon impacts are starting to emerge.Refrigerants within chillers,heat pumps or other heating and cooling equipment:Figure 100 illustrates the impact of switching R410A refrigerant with R32 and R1234ze on the embodied carbon of a 100kW air cooled chiller.The stud
330、y assumed the same chiller can use all three refrigerants.In practice,there are other considerations(such as efficiency,flammability,etc.)when selecting heating and cooling equipment but companies must strive to reduce refrigerant charge and select low GWP refrigerants.Figure 100:Embodied carbon of
331、a 100kW air cooled chiller using different refrigerants;R410A,R32 and R1234ze0500tCO2e(2088)(677)Refrigerant type(GWP in kgCO2e/kg)(1)A1-A3A4A5B1B2B3B4B5C1C2C3C4Figure 101:A-C embodied carbon contribution of pipework and ductwork to HVAC systems,based on an Arup case study for a newly bui
332、lt,mid-rise office building in London050001000tCO2eChilled ceilingsFan coil unitsPassive chilled beamsActive chilled beamsPipework and insulationDuctwork and insulationAHUTerminal unitsTrench heatersHeat pump and chillerNet-zero buildings Halving construction emissions today 66An Arup stu
333、dy looking at six commercial buildings found the embodied carbon of distribution to range from 25 to 70 kgCO2e/m2 depending on the services density.Figure 102 shows the embodied carbon contribution of the various components.This study highlighted the notable contribution of ductwork and associated insulation to the embodied carbon of distribution,both for A1-A5 and A-C embodied carbon.Note:Arup ex