Wood and bio-based construction products are perceived as a way to use renewable resources, to save energy and to mitigate greenhouse gas (GHG)-emissions during production and to store carbon during the entire service life of the building. This article compares the carbon footprint per kilogram of wood products (softwood beams, plywood, oriented strand board panel, and fibre board) from the perspective of the life cycle assessment methodology for greenhouse gas (GHG) emissions of practitioners from 16 countries participating in the IEA Annex 72. These materials are used in PAL6 softwood structure multi-residential building. This article aims at comparing the carbon footprint accounting methods from 16 countries for PAL6 multi-residential building. Each national team applied the reference study period (RSP), life cycle modules covered, modelling rules, the geographical scope of inventory data as well as the LCA database according to its specific national method. The results show that there are three types of methodology to assess a building with biogenic content (0/0, -1/+1, -1/+1*). The results were more variable plywood, oriented strand board, and fibreboard than the softwood beams due to the variability in the wood transformation processes among the countries. A net negative carbon balance was obtained for the softwood beam for the countries using -1/+1* with a clear assumption of the fraction of the carbon permanently stored at the end-of-life (EoL). The carbon storage is only possible if it is secured at the EoL. Participating countries apply different definitions of permanence and EoL scenarios. Guideline on assessing, monitoring, and legally reporting carbon storage at the EoL are needed, based on concertation between standard, life cycle assessment, wood industry, and climate experts.

Wood and other bio-based building materials are often perceived as a good choice from a climate mitigation perspective. This article compares the life cycle assessment of the same multi-residential building from the perspective of 16 countries participating in the international project Annex 72 of the International Energy Agency to determine the effects of different datasets and methods of accounting for biogenic carbon in wood construction. Three assessment methods are herein considered: two recognized in the standards (the so-called 0/ 0 method and-1/+1 method) and a variation of the latter (-1/+1* method) used in Australia, Canada, France, and New Zealand. The 0/0 method considers neither fixation in the production stage nor releases of biogenic carbon at the end of a wood product's life. In contrast, the-1/+1 method accounts for the fixation of biogenic carbon in the production stage and its release in the end-of-life stage, irrespective of the disposal scenario (recycling, incineration or landfill). The-1/+1 method assumes that landfills offer only a temporary sequestration of carbon. In the-1/+1* variation, landfills and recycling are considered a partly permanent sequestration of biogenic carbon and thus fewer emissions are accounted for in the end-of-life stage. We examine the variability of the calculated life cycle-based greenhouse gas emissions calculated for a case study building by each participating country, within the same assessment method and across the methods. The results vary sub-stantially. The main reasons for deviations are whether or not landfills and recycling are considered a partly permanent sequestration of biogenic carbon and a mismatch in the biogenic carbon balance. Our findings sup-port the need for further research and to develop practical guidelines to harmonize life cycle assessment methods of buildings with bio-based materials.

Sustainable building design practices are influenced by requirements, guidelines, criteria for green procurement and certification, assessment tools such as life cycle assessment, etc. This study investigates how such artefacts support or define aspirations towards sustainability, through case studies of public housing projects in Sweden and Cyprus. The study first illustrates how constraints mediated by artefacts set boundaries to the range of available sustainable design options. On one hand, fulfilling sustainability requirements conveyed in regulations, certifications and directives is a major driver of designers' involvement with sustainable design. On the other hand, cost calculations, procurement laws and development plans exclude certain design options. Moreover, default solutions and standardised design guidelines within the organisation streamline and simplify the design process, indirectly determining what sustainable design options are considered. However, these demands and default options are also bent and adapted on a case-by-case basis. The ways in which sustainable design arises from the interplay between artefacts and actors' agency differed significantly between the Swedish and Cypriot cases. Swedish actors' operational definition of sustainability is strongly codified and enforced through inter-connected artefacts. The Miljo center dot byggnad certification is often a de facto definition of sustainability used by actors to set sustainability criteria and targets. Environmental databases for construction products act as black boxes, implicitly determining what aspects of sustainability are addressed in design decisions. Conversely, Cypriot designers' work with sustainability depends to a larger extent on their motivation, experience and ability to convince their peers.

Life cycle assessment (LCA) is increasingly being used as a tool by the building industry and actors to assess the global warming potential (GWP) of building activities. In several countries, life cycle based requirements on GWP are currently being incorporated into building regulations. After the establishment of general calculation rules for building LCA, a crucial next step is to evaluate the performance of the specific building design. For this, reference values or benchmarks are needed, but there are several approaches to defining these. This study presents an overview of existing benchmark systems documented in seventeen cases from the IEA EBC Annex 72 project on LCA of buildings. The study characterizes their different types of methodological background and displays the reported values. Full life cycle target values for residential and non-residential buildings are found around 10-20 kg CO2e/m2/y, whereas reference values are found between 20-80 kg CO2e/m2/y. Possible embodied target- and reference values are found between 1-12 kg CO2e/m2/y for both residential and non-residential buildings. Benchmark stakeholders can use the insights from this study to understand the justifications of the background methodological choices and to gain an overview of the level of GWP performance across benchmark systems. 

The building sector is responsible for about a fifth to a third of global greenhouse gas (GHG) emissions. Therefore, a successful mitigation of GHG emissions over the entire life cycle of buildings is particularly important to achieve climate targets such as the Paris Agreement. This requires measures at multiple levels and from multiple actors, including broad roadmaps for the building sector, policies and regulations, certification and green procurement criteria, and new practices among property owners, architects, developers and manufacturers. Such initiatives are sometimes supported by the introduction of tools and methods to quantitatively assess environmental performance. Life cycle assessment (LCA) is one such tool, used in certification and increasingly in procurement and regulation. To reliably steer towards lower environmental impacts, environmental performance assessment tools need to be precise, accurate and well-adapted to the decision contexts in which they will be used. While a tool like LCA can provide valuable decision support, some methodological issues remain unresolved, and its effect in real decision situations remains understudied.

This thesis aims to support decisions and initiatives to mitigate environmental impacts in the building sector, with a particular focus on fulfilling ambitious climate targets. The thesis addresses two facets of this overarching issue. First, it investigates challenges to the implementation of relevant sustainable practices, at various levels and in various decision contexts. Second, the thesis considers to what extent environmental performance assessments could steer towards low environmental impacts (and in particular low global warming potential (GWP)).

The thesis is based on a combination of quantitative and qualitative approaches. At a strategic level, a quantitative model of buildings’ GWP linked to four backcasting future scenarios is used to spotlight issues for the fulfilment of ambitious climate targets. This helps challenging existing paradigms and images of the future about how buildings are constructed and operated. At a more operational level, multiple qualitative studies explore barriers to specific practices to mitigate environmental impacts, and the roles played by environmental performance assessments. An interview- and workshop study explores important factors for the adoption of space sharing, as a way of optimizing the use of indoor space. A survey- and interview study highlights challenges to the use of requirements by Swedish municipalities to promote low-GWP construction. A third interview study shows how various artefacts mediate work with sustainable design in housing projects. Finally, the thesis addresses more directly the accuracy of environmental performance assessments, and investigates how choices of data and method related to maintenance and replacement affect LCA results, exemplified for façade materials.

The modelling of buildings’ GWP in backcasting scenarios helps challenge current paradigms by drawing attention to some less-discussed issues, such as reducing embodied emissions (including by avoiding new construction) as well as the demand for indoor space. Space sharing can help optimizing the use of indoor space, but several factors limit its adoption. It requires different practices among building users and property managers, including different business models and performance metrics considering occupancy. Ambiguities in national legislation and municipal plans regarding the status of shared and multifunctional buildings also hinder space sharing initiatives (e.g. unclear rights and responsibilities of tenants and property owners, conflicting requirements for fire safety or ventilation, etc.). Similarly, the thesis highlights important regulatory ambiguities regarding to what extent municipalities can set requirements to promote low-GWP construction. Environmental performance requirements in construction also entail barriers related to limited in-house skills, access to data, time and resources. Using such requirements would first require bridging skill and data gaps. Similar barriers are highlighted regarding the use of LCA in public housing projects. In such projects, artefacts such as national regulations, local development plans and internal requirements of the housing organization enforce a certain level of work with sustainable design while limiting the range of design options. Other artefacts simplify the design work and provide standardized default options. In such cases, design choices that strongly influence environmental performance are taken upstream of the project, when these criteria, requirements and default options are developed.

The thesis highlights ways in which quantitative assessments of environmental performance could directly influence building design and management, e.g. through the introduction of environmental performance criteria in regulation and procurement. Besides challenges related to skill, data, time and resources mentioned above, the thesis draws attention to the variability of LCA results due to choices of method and data sources. In the particular case of maintenance and replacement processes, the choice of reference study period (RSP) influences the relative significance of these processes, and longer RSPs favor more durable products. Discrepancies exist between different sources for service life data, indicating a need for more reliable data. The use of a round-up or annualized number of replacements makes little difference in average, but can lead to different outcomes in specific cases. This shows a need to carefully harmonize methodological choices as LCA becomes used more and more broadly in procurement and building regulation.

Furthermore, the thesis also draws attention to more complex effects of environmental performance assessments in housing projects. Widespread certification systems can become de-facto definitions of sustainability for actors, influencing design even in projects that are not certified. Environmental performance assessments can hide or reveal certain aspects of sustainability. Widely used assessment tools can act as “black boxes”, where criteria for what constitutes a sustainable building are hidden and no longer contested. This process helps operationalize sustainability in building projects. However, it can lead to some important aspects being disregarded. For instance, conventional energy performance metrics are often normalized for floor area, ignoring occupancy and space efficiency. On the other hand, quantitative assessments can also highlight important aspects of the multifaceted issue of sustainability. The thesis exemplifies this by using a quantitative model of buildings’ GWP to draw attention to key mitigation strategies, and by reviewing energy metrics highlighting occupancy and space efficiency.

Byggsektorn står för mellan en femtedel och en tredjedel av globala växthusgasutsläppen. En framgångsrik minskning av växthusgasutsläppen under byggnaders hela livscykel är därför väsentlig för att uppnå klimatmålen, såsom Parisavtalet. Detta kräver åtgärder på olika nivåer och av olika aktörer, inklusive övergripande färdplaner för byggsektorn, policies och regelverk, kriterier för certifiering och grön upphandling, samt ny praxis bland fastighetsägare, byggherrar, arkitekter och byggmaterialtillverkare. Ibland stöds sådana initiativ av verktyg och metoder för kvantitativ miljöbedömning. Livscykelanalys (LCA) är ett sådant verktyg som används för certifiering, och i ökande grad i upphandling och regelverk. För att styra mot lägre miljöpåverkan på ett robust sätt måste miljöbedömningsverktyg ha god precision och vara väl anpassade till de beslutssammanhang där de ska användas. LCA kan ge värdefullt beslutsstöd, men vissa metodfrågor återstår fortfarande, och det saknas kunskap om hur användning av LCA kan få effekt i verkliga beslutssituationer.

Denna avhandling syftar till att stödja beslut och initiativ för att minska miljöpåverkan inom byggsektorn, med särskilt fokus på ambitiösa klimatmål. Avhandlingen undersöker två aspekter av denna övergripande fråga. För det första utreder den utmaningar i relation till genomförandet av relevanta hållbarhetsinitiativ inom byggsektorn, på olika nivåer och i olika beslutssammanhang. För det andra utforskar avhandlingen i vilken utsträckning  kvantitativa miljöbedömningar kan styra mot lägre miljöpåverkan (och särskilt klimatpåverkan).

Avhandlingen bygger på en kombination av kvantitativa och kvalitativa studier. En kvantitativ modell av byggnaders växthusgasutsläpp nyttjas på en strategisk nivå i fyra framtidsscenarier med backcastingmetodik, för att belysa viktiga aspekter för att nå ambitiösa klimatmål. Modellen bidrar med att ifrågasätta befintliga paradigm och framtidsbilder om hur byggnader byggs, förvaltas och används. Ett antal kvalitativa studier  undersöker hinder för några specifika hållbarhetsinitiativ på en mer operativ nivå, samt vilken roll miljöbedömningar kan ha för dessa. I en intervju- och workshopstudie undersöks viktiga faktorer för delning av byggnadsytor, för att optimera deras användning. En enkät- och intervjustudie understryker utmaningar för svenska kommuners användning av miljökrav för att främja byggande med låg klimatpåverkan. En tredje intervjustudie visar hur olika artefakter medierar arbetet med hållbar design i bostadsprojekt. Slutligen undersöker avhandlingen precisionen i miljöprestandabedömningar och visar hur osäkerheter och metodval relaterade till beräkning av underhåll och utbyte påverkar LCA- resultat, exemplifierat för fasadmaterial.

Modellering av byggnaders växthusgasutsläpp i backcasting-scenarierna bidrar till att ifrågasätta befintliga paradigm genom att peka på ett antal mindre diskuterade klimatstrategier, såsom behovet att minska inbyggd klimatpåverkan (bland annat genom att undvika nybyggnation) samt minska efterfrågan på byggnadsytor. Delning av ytor kan bidra till att optimera användningen av byggnadsytor inomhus, men flera faktorer begränsar sådana initiativ. Det kräver ändrade rutiner bland byggnadsanvändare och fastighetsförvaltare, såsom nya affärsmodeller och prestandamått som bättre kan synliggöra hur byggnader används. Otydligheter i regelverk och kommunala planer när det gäller hur de hanterar delade och multifunktionella byggnader hindrar också delningsinitiativ (till exempel otydlighet kring  rättigheter och ansvar för hyresgäster och fastighetsägare, motsägelsefulla krav på brandsäkerhet eller ventilation, och så vidare). På samma sätt finns det regulatoriska oklarheter kring i vilken utsträckning kommuner, som myndigheter, får ställa krav för att främja låg klimatpåverkan. Miljöprestandakrav på byggprojekt medför också hinder i form  av att de kräver mer intern kompetens, tillgång till data, tid och resurser. För att kunna ställa klimatkrav för nybyggnation, krävs att kommuner först löser kompetens- och dataluckor. Liknande hinder visades när det gäller användningen av LCA i offentliga bostadsprojekt. I sådana projekt upprätthåller artefakter, såsom regelverk, detaljplaner och interna krav hos beställarorganisationen, en viss nivå av hållbarhetsarbete samtidigt som de också kan begränsa designmöjligheter. Andra artefakter förenklar designarbetet och skapar standardiserade basalternativ. I sådana fall tas, för miljöprestandan, kritiska designbeslut utanför projektet, det vill säga när dessa kriterier, krav och standardalternativ utvecklas.

Avhandlingen visar också hur kvantitativa miljöbedömningar kan påverka byggprojekt och fastighetsförvaltning, till exempel genom införande av miljöprestandakriterier i regelverk och upphandling. Förutom utmaningar relaterade till kunskap, data, tid och resurser som nämns ovan, understryker avhandlingen variationer i LCA-resultat på grund av val av metod och datakällor. När det gäller klimatpåverkan från underhåll och utbyte av byggnadsmaterial påverkar valet av referensstudieperiod (RSP) den relativa betydelsen av dessa processer, där en längre RSP gynnar produkter med längre livslängder. Livslängsdata skiljer sig mellan olika källor, vilket tyder på ett behov av mer tillförlitliga data. Användningen av ett avrundat eller årligt antal operationer  gör dessutom liten skillnad i genomsnitt, men kan leda till tydligt olika resultat i specifika fall. Detta visar på att det finns ett behov av att harmonisera och förfina detaljer i metodval nu när LCA i allt högre grad börjar komma in i upphandling och regelverk för byggnader. 

Vidare uppmärksammar avhandlingen också mer komplexa effekter av miljöprestandabedömningar i bostadsprojekt. Populära certifieringssystem kan bli de facto definitioner av hållbarhet för vissa aktörer, och påverkar designval även i projekt som inte är certifierade. Dessutom kan miljöbedömningssystem dölja eller synliggöra vissa aspekter av hållbarhet. Allmänt använda verktyg kan fungera som "svarta lådor", där kriterier för vad det betyder för en byggnad att vara hållbar döljs och inte längre ifrågasätts. Denna process bidrar till att operationalisera hållbarhet i byggprojekt, men kan leda till att viktiga aspekter också ignoreras. Till exempel är konventionella energiprestandamått vanligen normaliserade för golvarea, vilket ignorerar hur ytan används och hur yteffektiv byggnaden är. Å andra sidan kan kvantitativa bedömningar också belysa viktiga aspekter av den mångfacetterade hållbarhetsfrågan. Avhandlingen exemplifierar detta genom kvantitativ modellering av backcasting-scenarier för att synliggöra viktiga klimatstrategier, och genom att visa på energimått som tar hänsyn till användning och yteffektivitet.

Purpose

Previous life cycle assessments (LCAs) of buildings and building components show a broad range of values for theimpact of maintenance and replacement, some highlighting these operations as major hotspots while others consider theminsignificant. This article highlights methodological aspects explaining this discrepancy. The influence of three aspects isinvestigated further in a case study of façade materials: the reference study period (RSP), service life data, and the use of around-up number of operations or annualized impacts.

Methods

A comparative LCA of seven façade alternatives is carried out as an illustrative case study. For each alternative,global warming potential (GWP) is calculated using three possible RSPs, four possible material service lives (one fromindustry practitioners and low, standard and high values from a generic database), and two possible calculation methods (round-up or annualized impacts).

Results and discussion

While the same façade alternative had the lowest GWP in all cases, different methodological choicessignificantly affected the GWP and respective ranking of other alternatives. Some alternatives showed a significant increasein GWP over longer RSPs, while others were still dominated by the impact of initial production after 200 years. In nearlyall cases, generic service life data lead to a higher GWP than data from industry practitioners. Major discrepancies werefound between generic and practitioner data in some cases, e.g., for the brick façade. In most cases, annualized impacts ledto a slightly lower (or equal) GWP than using a round-up number of operations. However, when a major operation happensshortly before the end of the RSP, the annualized method leads to considerably lower GWP.

Conclusions

Maintenance and replacement are rarely significant over a 50-year RSP but sometimes become hotspots overlonger RSPs. Using round-up operations or annualized impacts does not make much difference in average, but leads to significantlydifferent results in specific cases. As building LCA enters certification and regulation, there is a need to harmonizesuch methodological choices, as they affect LCA results, hotspot identification, and recommendations. Discrepancies inservice life data also call for the gathering of reliable data.

Energianvändningen i byggsektorn – samlat, alltså energi till allt från utvinning av råvaror, till produktion av byggmaterial och inbyggnad av dem, till användning av byggnaderna och slutligen rivning och avfallshantering – utgör den största enskilda klimatbelastningen globalt. Det innebär att det är nödvändigt att göra så bra val som möjligt ur klimatsynpunkt. Man behöver då se till hela byggnadens livscykel, och inkludera både initiala klimatbelastningar och sådan som uppstår under byggnadens operativa tid – ett bra verktyg för att göra det är att göra en livscykelanalys, LCA.

Utvändiga material, såsom fasadmaterial som utsätts för väder och vind, kan ha ett betydande underhållsbehov och begränsad livslängd, vilket genererar klimatbelastningar. Om man gör en LCA för en kortare period än byggnadens livstid så kommer de initiala belastningarna få en oproportionerligt stor inverkan, och finns det risk för att man försummar alternativ som har fördelar på längre sikt. I denna studie har 6 olika fasadkonstruktioner undersökts i en LCA och en LCC för analysperioderna 50, 100 och 200 år, och resultaten visar att det för vissa material är speciellt viktigt att ta både påverkan från produktion och underhåll i beaktande. Av de studerade materialen var en fjällpanel av cederträ över tid mest gynnsam, pga av att den innehöll den allra minsta mängden material respektive att den inte hade någon ytbehandling. Den fasad som uppvisade minst klimatpåverkan i underhållsskedet var tegelfasaden – som dock genom sin stora mängd material och en tillverkningsprocess som kräver höga tempera-turer vid tillverkning hade den överlägset högsta klimatbelastningen initialt. Därmed kunde transport och tillverkningsprocessen i det fallet identifieras som de mest givande processerna att reducera miljöpåverkan av.

Ekonomiskt sett dyrast i alla tidsperspektiven var den målade granpanelen, och initialt var fibercementskivfasaden billigast. Men efter 100 år var tegelfasaden nästan lika prisvärd, och i ett 200-årigt perspektiv så var teglet det mest ekonomiska alternativet. I livscykelkostnads-analysen var det underhållsfasen som stod för de väsentliga skillnaderna mellan alternativen, och ytskiktens underhållsbehov var avgörande framför allt för de långsiktigare analys-perioderna.

Studien visar att olika tidshorisonter ger olika bilder av både klimatpåverkan och kostnader, och att samtidig analys av flera analysperioder, varav minst ett som någorlunda motsvarar en potentiellt förväntad livstid för byggnaden, kan ge ett bättre besluts-underlag genom att belysa både klimatbelastning över tid, inverkan av alternativens underhållsbehov och potentiella förbättringsmöjligheter.

Introduction: The international research project IEA EBC Annex 72 investigates the life cycle related environmental impacts caused by buildings. The project aims inter alia to harmonise LCA approaches on buildings. Methods: To identify major commonalities and discrepancies among national LCA approaches, reference buildings were defined to present and compare the national approaches. A residential high-rise building located in Tianjin, China, was selected as one of the reference buildings. The main construction elements are reinforced concrete shear walls, beams and floor slabs. The building has an energy reference area of 4566 m2 and an operational heating energy demand of 250 MJ/m2a. An expert team provided information on the quantities of building materials and elements required for the construction, established a BIM model and quantified the operational energy demand. Results: The greenhouse gas emissions and environmental impacts of the building were quantified using 17 country-specific national assessment methods and LCA databases. Comparisons of the results are shown on the level of building elements as well as the complete life cycle of the building. Conclusions: The results of these assessments show that the main differences lie in the LCA background data used, the scope of the assessment and the reference study period applied. Despite the variability in the greenhouse gas emissions determined with the 17 national methods, the individual results are relevant in the respective national context of the method, data, tool and benchmark used. It is important that environmental benchmarks correspond to the particular LCA approach and database of a country in which the benchmark is applied. Furthermore, the results imply to include building technologies as their contribution to the overall environmental impacts is not negligible. Grant support: The authors thank the IEA for its organizational support and the funding organizations in the participating countries for their financial support.

Recent life cycle assessments (LCAs) of buildings highlight the importance of global warming potential from construction materials, in particular in energy-efficient buildings. It is therefore important to address the influence of methodological choices related to materials on LCA results. This paper focuses on scenarios for the maintenance and replacement of building elements. Methods: A literature review is carried out to summarize the state of the art regarding scenarios for maintenance and replacement in building LCA, their influence on LCA results and related methodological issues. Additionally, a case study is carried out to investigate whether assumptions about service lives in LCA could significantly influence the recommended design for a building's roof, using a Monte Carlo analysis considering service lives as stochastic variables. Results: The literature review reveals a broad range of impacts from maintenance and replacement in case studies. There is therefore no consensus about the relative impact of these processes. These differences can be partly explained by differences in scope (e.g. what elements are considered to be replaced and what kinds of processes are included), in methods for service life estimation and in future scenarios for the production and recycling of materials. Relative impacts from maintenance and replacement seem to be highest for energy efficient buildings with a long service life, and for elements such as carpets, paint, insulation, doors and windows. The case study of roofing materials exemplifies a case where assumptions about service lives could influence design decisions. Both the ranking of alternatives and the relative significance of maintenance and replacement processes depend on assumptions about service lives. An asphalt roof cover is preferred when considering only initial installation, but a clay tile roof cover is preferred over asphalt in roughly two thirds of the cases when considering maintenance and replacement. Metal roofs almost always had a poorer environmental performance under the assumptions considered. Conclusions: Results from the case study are compared with previous studies of maintenance and replacement processes, and methodological issues deserving further consideration are highlighted. In particular, the case study is used to discuss the issue of whether a modelling based on independent service lives for various building elements accurately reflects industrial practices. Moreover, the relevance of including maintenance and replacement in regulations and climate declarations for buildings is discussed.

The sharing of indoor space can improve space and energy efficiency. The drivers and barriers to space-sharing initiatives are investigated from the perspectives of building users and building sector practitioners, based on interviews and a workshop. The role of energy performance metrics in promoting space efficiency is further analysed through a literature review. From the users’ perspective, space sharing can be understood through the interplay between tangible aspects (e.g. concrete benefits derived from sharing), organisational aspects (e.g. common decision processes and conflict resolution) and social aspects (e.g. group identity and consensus on appropriate behaviours). From the perspective of architects and property owners, shareable spaces require features such as flexibility and multifunctionality. The design of such spaces is limited by regulatory issues (e.g. building regulations poorly accommodate shared facilities) and business-related issues. One such issue is that building performance metrics normalised based on floor area do not incentivise the efficient use of space. A review of complementary metrics is provided, covering parameters such as number of users, layout, time of use, etc. Each metric serves a particular purpose; therefore, a set of complementary metrics can be used to support decisions at different phases of the building’s life cycle.

Practice relevance

Improving space efficiency (e.g. by sharing indoor space) is a key strategy to meet simultaneously the future demand for facilities in cities and fulfil environmental objectives such as a reduction of climate change impact in the building sector. A clearer understanding of the specificities of space sharing is provided from the perspectives of building users and practitioners. This will assist practitioners to understand the needs of other stakeholders. Regulatory and business-related barriers to space-sharing initiatives are highlighted as a first step towards overcoming these barriers. Guidance is provided on complementary energy performance metrics appropriate for space efficiency. These metrics can be used to support various decisions during the different stages of a building’s life cycle.