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Building renovation is urgently required to reduce the environmental impact associated with the building stock. Typically, building renovation is performed by envelope insulation and/or changing the fossil-based heating system. Life cycle assessment and life cycle cost analysis are seen as suitable methods to evaluate the performance of a building in terms of environmental impacts and cost. However, the results are highly affected by uncertainty. The goal of this paper is to provide recommendations for robust renovation strategies considering uncertainties on future evolution of climate, energy grid, user behaviors. The method includes identifying optimal renovation options for the envelope and heating systems for building-representatives from all construction periods that are currently in need of retrofit in Switzerland. Conventional and bio-based materials are examined with inclusion of dynamic carbon storage potential. The results of the analysis show that heating system is a priority for building renovation for all the considered construction periods. The results also show that if only conventional materials are considered for building renovation, optimal solution does not prescribe deep renovation and higher energy consumption during life time is favored. However, when bio-based insulation materials can be used, the opposite conclusion is drawn and synergies between low environmental impact and low energy costs during life cycle are identified. Such renovation strategies pave the way for a just and low carbon transformation of the Swiss building stock.

Life cycle assessment can support decisions for improving the environmental performance of construction products. However, the amount of data required for developing life cycle inventories limits the adoption of LCA. This work associates the interpretation of the impact results of construction products at the unit process level with a quantitative definition for the foreground and background system, for guiding primary data collection towards foreground processes that can be affected by decision-makers in the construction sector. A set of construction products commonly used in Brazil is selected, and their cradle-to-gate life cycle inventories are modeled using the ecoinvent database (version 2). Life cycle impact assessment is performed using the ReCiPe Midpoint Hierarchist method. The contribution of each process during the life cycle of construction products for each impact category is quantified. These processes are associated with economic sectors, which are classified as belonging to the foreground or background system from the perspective of the construction industry. Foreground sectors are those controlled or influenced by the construction sector and are defined based on the production share consumed by the construction value chain. The elementary flows defining each impact category are also identified. Foreground processes show significant contributions to most impact results of construction products. Global warming, fine particulate matter formation, ozone formation, acidification, human carcinogenic toxicity, and terrestrial ecotoxicity are mainly caused by direct emissions and fossil fuel combustion in manufacturing processes. Land occupation for production activities contributes to land use change, while the consumption of fuels, raw materials, and water causes fossil and mineral resource scarcity and water consumption respectively. Freshwater and marine ecotoxicities and human non-carcinogenic toxicity have foreground contributions only for steel and copper products due to emissions from the landfilling of mining tails. Ionizing radiation and stratospheric ozone depletion are mostly driven by background processes. A reduced group of elementary flows covers a big share of the environmental impacts of most construction products. The results indicate priorities for life cycle inventory primary data collection of construction products, by focusing on foreground processes and the corresponding elementary flows that cause many of the potential embodied impacts of construction. Increasing the availability of primary data for these processes improves the reliability of LCA-based decisions in the construction sector, especially in countries which still lack local LCI databases.

Boosting building renovation is urgently needed to achieve carbon neutrality by 2050. Building retrofit can be achieved by energy-efficient measures such as thermal insulation or replacement of a fossil heating system. Currently, conventional materials that are mostly used for envelope insulation raising the risk of a lock-in situation where measures to mitigate climate change are actually contributing to it. Bio-based materials are a promising alternative as they can be used to not only reduce the energy consumption of a building but also temporarily store carbon. To evaluate the potential benefits of such materials, life cycle assessment (LCA) and life cycle cost analysis (LCCA) are commonly used. Such assessment allows the analysis of a building over its whole life. However, considering that buildings are very long lasting systems, many associated uncertainties can affect the outcome of LCA and LCCA. To account for all the uncertainty sources and provide a robust solution for building renovation, uncertainty quantification can be applied. In this paper, we use robust optimization under uncertainties to define the most cost-effective and climate-friendly solution. We apply bio-based materials and include carbon storage calculation in the integrated LCA and LCCA. For the robust optimization, we use a novel methodology combining a well-known non-dominated sorting genetic algorithm II (NSGA-II) with surrogate modeling to lower computational cost. The methodology is applied for a case study located in Switzerland. The results show that bio-based materials provide a robust solution for building renovation but to achieve the highest reduction potential, bio-based envelope insulation should be combined with the replacement of the existing fossil heating system., Applied Energy, 316, ISSN:0306-2619, ISSN:1872-9118

Purpose: The Life Cycle Assessment (LCA) has been applied in the construction sector since the 1990s and is now more and more embedded in European public policies, e.g., for Environmental Product Declaration regulation or for building labeling schemes. As far as the authors know, these initiatives mainly rely on background impact data of building products provided by different databases' providers. The new product-specific and company-specific EPD data allow having more than one data for describing a building material. But are these new databases really displaying similar LCA results compared to generic databases? Does it depend on which impact category (e.g., global warming, acidification, toxicity) is considered? Methods: To answer these research questions, this paper assesses numerical and methodological differences of two existing LCA databases for building LCAs: the ecoinvent generic database and one Environmental Product Declaration (EPD) database developed in France. After reviewing the main assumptions of these databases, numerical values of environmental impact are compared for 28 building materials using Life Cycle Impact Assessment (LCIA) indicators of the EN 15804 standard calculated based on cradle-to-gate ecoinvent and EPD Life Cycle Inventories (LCI). Results and discussion: Global results at the database level indicate deviations of different magnitudes depending on the LCIA indicators and the building materials. While indicators correlated to fossil fuel consumption, such as the ADP, the GWP, and the primary energy demand, exhibit a small deviation (approximately 25%), other indicators, such as the photochemical ozone formation (POCP), radioactive waste, and ADP elements, are found to be more variable between EPD and generic data (sometimes by more than 100%). Three indicators are found to be systematically different between EPD and generic data (i.e., the EPD value being either higher or lower for all materials). Similarly, five building materials show systematic differences for all LCIA indicators. Specific deviations for one indicator and one material are also reported. The application of the two databases on three building LCA case studies (brick, reinforced concrete, and timber frame structures) identifies deviations due to the most influential materials. Conclusions: Current generic and EPD databases can present very different values at the database scale which depend on the type of environmental indicator. For building LCA results, the situation is different as generally speaking a limited number of materials controlled the impacts. Finally, recommendations are presented for each environmental indicator to improve the consistency of the building assessment from generic to product- and country-specific information.

The performance gap, defined as the difference between the measured and the calculated performance of energy-efficient buildings, has long been identified as a major issue in the building domain. The present study aims to better understand the performance gap in high-energy performance buildings in Switzerland, in an ex-post evaluation. For an energy-efficient building, the measured heating demand, collected through a four-year measurement campaign was compared to the calculated one and the results showed that the latter underestimates the real heating demand by a factor of two. As a way to reduce the performance gap, a probabilistic framework was proposed so that the different uncertainties of the model could be considered. By comparing the mean of the probabilistic heating demand to the measured one, it was shown that the performance gap was between 20–30% for the examined period. Through a sensitivity analysis, the active air flow and the shading factor were identified as the most influential parameters on the uncertainty of the heating demand, meaning that their wrong adjustment, in reality, or in the simulations, would increase the performance gap.

This article presents the descriptive statistics of service life data of building elements, gathered through an international, European and Swiss literature review of LCA, LCC and other sources called “Real-Estate Management sources” that include building owners, banks, insurances, associations of tenants and owners, etc. Furthermore, the properties of the fitted lognormal distribution are given. The data are structured, using a hybrid decomposition (functional decomposition, according to the eBKP-H – SN506511 and material decomposition, as well). These data and the derived statistical distributions were used in a research study, in order to quantify the uncertainty and sensitivity of the LCA and LCC output, due to the variability of the building elements’ service lives., Data in Brief, 36, ISSN:2352-3409

Life Cycle Assessment (LCA) is increasingly used for decision-making in the design process of buildings and neighbourhoods. Therefore, visualisation of LCA results to support interpretation and decision-making becomes more important. The number of building LCA tools and the published literature has increased substantially in recent years. Most of them include some type of visualisation. However, there are currently no clear guidelines and no harmonised way of presenting LCA results. In this paper, we review the current state of the art in visualising LCA results to provide a structured overview. Furthermore, we discuss recent and potential future developments. The review results show a great variety in visualisation options. By matching them with common LCA goals we provide a structured basis for future developments. Case studies combining different kinds of visualisations within the design environment, interactive dashboards, and immersive technologies, such as virtual reality, show a big potential for facilitating the interpretation of LCA results and collaborative design processes. The overview and recommendations presented in this paper provide a basis for future development of intuitive and design-integrated visualisation of LCA results to support decision-making., Building and Environment, 190, ISSN:0360-1323

Building renovation is urgently required to decrease the energy consumption of the existing building stock and reduce greenhouse gas emissions coming from the building sector. Selecting an appropriate renovation strategy is challenging due to the long building service life and consequent uncertainties. In this paper, we propose a new framework for the robust assessment of renovation strategies in terms of environmental and economic performance of the building's life cycle. First, we identify the possible renovation strategies and define the probability distributions for 74 uncertain parameters. Second, we create an integrated workflow for Life Cycle Assessment (LCA) and Life Cycle Cost analysis (LCC) and make use of Sobol’ indices to identify a prioritization strategy for the renovation. Finally, the selected renovation scenario is assessed by metamodeling techniques to calculate its robustness. The results of three case studies of residential buildings from different construction periods show that the priority in renovation should be given to the heating system replacement, which is followed by the exterior wall insulation and windows. This result is not in agreement with common renovation practices and this discrepancy is discussed at the end of the paper. ISSN:0360-1323 ISSN:0360-1323

Current Topics and Trends on Durability of Building Materials and Components. Proceedings of the XV edition of the International Conference on Durability of Building Materials and Components (DBMC 2020) Barcelona, Spain 20 – 23 October 2020, ISBN:978-84-121101-8-0

This paper presents a new service life database (DUREE database) for building elements, based on international service life data. The database includes 7‘000 service life data, for more than 2‘000 building elements. In addition, the fitting of the data to a lognormal distribution is presented. The study contributes to the increasing demand of probabilistic building LCA and LCC and provides the possibility to define statistical distributions, with a systematic way, for a large number of building elements and different levels of details (LOD), appropriate for BIM-based assessments.

Building renovation is currently urgent in order to decrease the energy consumption of a building stock. In order to achieve robust renovation scenarios, uncertainty quantification is needed. Climate change scenarios are important factors and need to be included in the analysis. In this paper, three climate change scenarios are applied probabilistically for a renovation scenario using dimensionality reduction techniques and further uncertainty propagation. The results show that RCP2.6 provides more robust results and saves on average 2. 105 CHF and 2. 105kgCO2eq. in a building life cycle comparing to RCP 8.5. The analysis under climate change is also compared to the probabilistic calculations under current climate and the results show the underestimation of both costs and environmental impacts when climate change is not included. It can also be clearly seen that even under the best case of RCP 2.6, building renovation is urgently needed to decrease the environmental impacts and costs., IOP Conference Series: Earth and Environmental Science, 588 (3), ISSN:1755-1315, ISSN:1755-1307

Internal insulation is a typical renovation solution in historic buildings with valuable fa&ccedil, ades. However, it entails moisture-related risks, which affect the durability and life-cycle environmental performance. In this context, the EU project RIBuild developed a risk assessment method for both hygrothermal and life-cycle performance of internal insulation, to support decision-making. This paper presents the stochastic Life Cycle Assessment method developed, which couples the LCA model to a Monte-Carlo simulation, providing results expressed by probability distributions. It is applied to five insulation solutions, considering different uncertain input parameters and building heating scenarios. In addition, the influence of data variability and quality on the result is analyzed, by using input data from two sources: distributions derived from a generic Life Cycle Inventory database and &ldquo, deterministic&rdquo, data from Environmental Product Declarations. The outcomes highlight remarkable differences between the two datasets that lead to substantial variations on the systems performance ranking at the production stage. Looking at the life-cycle impact, the general trend of the output distributions is quite similar among simulation groups and insulation systems. Hence, while a ranking of the solutions based on a &ldquo, approach provides misleading information, the stochastic approach provides more realistic results in the context of decision-making.

Life cycle assessment (LCA) is a data-intensive methodology; therefore, experts usually focus collection efforts on a few activities, while generic data on remaining activities are taken from databases. Even though increased availability of databases has facilitated LCA takeoff, assuring data quality is fundamental to ensure meaningful results and reliable interpretation. Ecoinvent has become a global reference for inventory data. Its current version released three impact partition modeling options—the recycled content, “allocation at the point of substitution” (APOS), and consequential models—whose adequate choice is crucial for yielding meaningful assessments. Tutorials and manuals describe the distribution algorithm that backs each system model, to ground decision-making regarding the best fit to a study’s goals. We performed a systematic literature review to investigate—within the papers published on the International Journal of LCA (IJLCA)—how transparently authors addressed the system model choices. About 70% of LCA practitioners continued to use earlier versions of ecoinvent after version 3 was launched in 2013. The number of papers using versions 3.x only showed an increased growth trend 2 years later. Eighty-three papers actually adopted the newest version of the database. From those, only 29 papers clearly mentioned the adopted system model. Our SLR also suggests a trend regarding authorship profile of LCA-related studies: the number of studies conducted by practitioners aware of the intricacies of sound modeling of background and foreground data might have been surpassed by those conducted by non-LCA specialists who use LCA as a supporting tool for investigations in applied fields, and merely scratch the surface. Our results point to a need for a caveat: ecoinvent users must take time to understand the general concept behind each system model and practice one of the most important actions when performing an LCA—state methodological choices clearly.

The current study presents the CO2-eq emissions of the operational energy use of a single-family house, equipped with a micro-cogeneration unit. A back-up boiler and electricity from the grid cover the remaining energy demand, not covered by the micro-CHP. Two different technologies are evaluated, i.e. ICE and fuel cell systems, operating with a variable share of biomethane, while two different substrates were considered for the biomethane generation. A dynamic LCA was applied for the electricity mix, coming from the grid, using different time steps. The results show that producing biomethane from biowaste compared to conventional natural gas is beneficial, in terms of CO2-eq emissions, independently of the micro-CHP technology, while the total CO2-eq emissions of the fuel cell technology are higher than those of the ICE, independently of the substrate and the biomethane share.

Buildings are responsible for a large share of CO2 emissions in the world. Building renovation is crucial to decrease the environmental impact and meet the United Nations climate action goals. However, due to buildings’ long service lives, there are many uncertainties that might cause a deviation in the results of a predicted retrofit outcome. In this paper, we determine climate-friendly and cost-effective renovation scenarios for two typical buildings with low and high energy performance in Switzerland using a methodology of robust optmization. First, we create an integrated model for life cycle assessment (LCA) and life cycle cost analysis (LCCA). Second, we define possible renovation measures and possible levels of renovation. Third, we identify and describe the uncertain parameters related to the production, replacement and dismantling of building elements as well as the operational energy use in LCCA and LCA. Afterwards, we carry out a robust multi-objective optimization to identify optimal renovation solutions. The results show that the replacement of the heating system in the building retrofit process is crucial to decrease the environmental impact. They also show that for a building with already good energy performance, the investments are not paid off by the operational savings. The optimal solution for the building with low energy performance includes the building envelope renovation in combination with the heating system replacement. For both buildings, the optimal robust cost-effective and climate-friendly solution is different from the deep renovation practice promoted to decrease the energy consumption of a building., Energy and Buildings, 251, ISSN:0378-7788, ISSN:1872-6178

The selection of the most suitable Life Cycle Assessment (LCA) databases, and corresponding elementary processes, to be used in the modelling of raw materials and related processes, is of paramount importance and decisively conditions LCA results. The NativeLCA methodology is based on the selection and/or adaptation of a coherent LCA dataset to produce each building product to be used as generic data for a national context. The aims of this paper are: to test the plausibility of Portuguese LCA datasets of raw and construction materials used in reinforced concrete structures; to confirm the coherence and usefulness of the NativeLCA methodology; and to increase the number of case studies illustrating its application that are available for the scientific and academic community. In that sense, the NativeLCA methodology is briefly summarized; available databases for construction products are presented and characterized; and two case studies (representing a full and a simplified NativeLCA methodology application) are presented and discussed. The results include coherent LCA datasets for cement and steel rebars product stage (A1-A3), based on the adaptation of available European (foreign or national) LCA datasets, that can be used as generic in LCA studies in Portugal. This paper also contributes to: the development of the NativeLCA methodology by providing examples of its application in its full and simplified versions; demonstrate that, while further efforts are needed to develop regional and sector-specific LCA databases, adapted to each national context, the NativeLCA approach can be used to consistently choose available LCA datasets to be used as generic in a national context; lead practitioners to increase the reliability of building LCA studies according to their goal and scope definition.

The concept of urban metabolism has often been used to model and analyze urban regions to provide insights on their environmental sustainability. However, no consensus exists on the assessment methods that should be used to analyze the sustainability of these complex systems. This lack of consistency prevents data sharing and comparison between most studies. Past and current publications are therefore surveyed to identify key methodological aspects that could be favored to harmonize the sustainability assessment of urban metabolism. This investigation is structured around the common aspects of environmental assessment methods that have been used for the past forty years. It suggests that a network system modeling approach, a global life-cycle perspective, and a multi-criteria assessment are strategic choices for environmental sustainability assessment. While challenging in their implementations, these choices can offer common grounds to capitalize on the knowledge brought forth by new studies. The investigation also discusses basic principles to propose developments like the use of a functional equivalent as a basis of comparison and the use of specific uncertainty assessment methods. These propositions could help to improve the clarity of future studies that tackle the question of environmental sustainability in urban metabolism.

Recycled concrete is one of the most efficient answers to the shortage of natural aggregate in highly populated and protected regions, such as Switzerland. Although the technology has evolved and today a number of certified recycled concretes are available in the ready mix concrete market, there are still many barriers to its use for structural purposes. These are caused by early tests that, analyzing non-optimized or non-commercial products, reached the conclusion that the performances of recycled concrete would not match the ones of ordinary concrete. Furthermore, early studies on the environmental impact of recycled concrete seemed to confirm an identical environmental impact for recycled and ordinary concrete (Viviani 2011; Viviani 2014). In this paper, is presented a thorough Life Cycle Assessment (LCA) for a commercialized recycled concrete and a commercialized ordinary concrete of the same strength class, both certified, both deeply characterized, showing virtually identical physical and rheological properties and sold at the same price (recycled concrete price being slightly lower than the ordinary). This LCA study shows that recycled concrete is only slightly better than ordinary concrete in terms of greenhouse gases emissions. This difference is yet not enough significant (1%) as well as for the cumulative energy demand (4%). In opposite, it performs better with around 12% less environmental impacts according to the Swiss Ecological Scarcity 2006 Method. So, current actions taken to promote their use are fully in the direction of a more sustainable construction industry if the transportation distance to the construction site is minimized and below e.g., 25 km as recommended in the Swiss Minergie ECO label.

The IEA EBC Annex 72 focuses on the assessment of the primary energy demand, greenhouse gas emissions and environmental impacts of buildings during production, construction, use (including repair and replacement) and end of life (dismantling), i.e. during the entire life cycle of buildings. In one of its activities, reference buildings (size, materialisation, operational energy demand, etc.) were defined on which the existing national assessment methods are applied using national (if available) databases and (national/regional) approaches. The ?be2226? office building in Lustenau, Austria was selected as one of the reference buildings. TU Graz established a BIM model and quantified the amount of building elements as well as construction materials required and the operational energy demand. The building assessment was carried out using the same material and energy demand but applying the LCA approach used in the different countries represented by the participating Annex experts. The results of these assessments are compared in view of identifying major discrepancies. Preliminary findings show that the greenhouse gas emissions per kg of building material differ up to a factor of two and more. Major differences in the building assessments are observed in the transports to the construction site (imports) and the construction activities as well as in the greenhouse gas emissions of the operational energy demand (electricity). The experts document their practical difficulties and how they overcame them. The results of this activity are used to better target harmonisation efforts., IEA -International Association for the Evaluation of Educational Achievement(Slovenia)

To meet the national regulation on building energy needs while preserving the architectural heritage, the renovation of protected historic buildings implies to insulate internally their facades. However, it is a technically risky solution. This work is part of the European project RIBuild that develops guidelines to ensure moisture-safe solutions. For that purpose, historical buildings were monitored to confront the current state-of-the-art of hygrothermal simulations with in-situ measurements. To enforce these calculations, stones used in Swiss traditional construction were characterised, and materials’ modelling were investigated. The results of the study will be integrated into a probabilistic web-tool.

Buildings are one of the largest energy consumers and greenhouse gas emitters in the world. As the largest part of the energy consumed by the existing non-insulated buildings occurs during the operation stage, retrofitting the building stock is crucial to reduce the environmental impact. To guarantee that the retrofit measures provide economic and environmental benefits, the whole life cycle should be assessed. However, the identification of environmental and at the same time cost-effective solutions is difficult due to the complexity and the uncertainty involved. Currently, simplified approaches based on limited assumptions are used that can lead to inaccurate results. This paper proposes a method for identifying robust renovation scenarios for residential buildings in Switzerland. The method and the developed tool use 47 uncertain parameters and Sobol' indices to identify the most influential parameters. As such, robust renovation strategies can be identified in the early design stage., IOP Conference Series: Earth and Environmental Science, 323 (1), ISSN:1755-1315, ISSN:1755-1307, Proceedings of the 2019 Sustainable Built Environment Conference (SBE19)

The building sector contributes up to 40% of energy consumption and 30% of greenhouse gases emissions (GHG) worldwide [1] . One of the main driver to mitigate these energy and GHG emissions is the renovation of existing buildings. While the energy demand is reduced during an energy related renovation, investment costs and environmental impacts increase due to the materials and building integrated technical systems (BITS) replaced or added to improve its energy performance. To address these trade-offs, there is a need to consider a life cycle approach to avoid impacts’ transfer between the operational and embodied energy and impacts. In this paper, we present a pragmatic Life Cycle Assessment (LCA) methodology for energy related renovation measures of building developed in the framework of the IEA annex 56 “Cost effective energy and carbon emissions optimization in building renovation”. The approach is consistent with the existing building LCA's state-of-the-art but goes into a more applicable methodology by focusing only on the significant life cycle stages for energy related building renovation i.e. the production, transportation, replacement and end of life of new materials for the thermal envelope and building integrated technical systems (BITS) and the operational energy demand. In this paper, the methodology is applied on a Swiss multi-family residential building built in 1965 which was renovated in 2010. The LCA is presented using three indicators: the total and non-renewable cumulative energy demand (CED) and the global warming potential (GWP). Results show that embodied CED and GWP remain negligible in the renovated building compared to the energy savings. Further studies are needed to further apply this LCA methodology.

In Europe, low energy buildings become common for new constructions and life cycle assessment (LCA) is increasingly used to assess their environmental performance. The overall objective of this study is to investigate known challenges related to buildings LCA such as biogenic carbon accounting and dynamic and prospective aspects, and to discuss how they affect LCA results for low energy buildings and what developments are still needed. Three single family houses built respectively with timber frame, concrete blocks cavity wall, and cast concrete are used as a case study, focusing on the global warming impact category. When biogenic carbon is addressed, the timber house is the less impacting choice, whether it is landfilled or burned at the end-of-life. The cavity wall house is the second most favourable option, and the cast concrete house is the worst one. In the case of landfilling for the timber house, the biogenic carbon balance is not neutral and worth to be considered. When a dynamic approach and specific prospective scenarios are considered, the ranking between houses stays the same, but the gaps between options vary e.g. the gap between the landfilled timber house and the cast concrete house vary from 40 % to 60 % when optimistic changes in the electricity mix are considered. Dynamic LCA allows for a more consistent analysis of emissions flows and global warming impacts over time. Prospective LCA could provide more relevant LCA results but increases uncertainty and could be used as sensitivity analysis for long life span buildings.

Purpose Growing awareness of the environmental performance of construction products and buildings brings about the need for a suitable method to assess their environmental performance. Life cycle assessment (LCA) has become a widely recognised and accepted method to assess the burdens and impacts throughout the life cycle. This LCA-based information may be in the form of environmental product declarations (EPD) or product environmental footprints (PEF), based on reliable and verifiable information. All of these use LCA to quantify and report several environmental impact categories and may also provide additional information. To better understand on the one hand existing EPD programmes (EN 15804) for each country and on the other the recent developments in terms of EU reference document (e.g. PEF), the authors decided to write this review paper based on the outcomes of the EPD workshop that was held prior to SB13 Graz conference. Methods This paper presents the state of the art in LCA and an overview of the EPD programmes in five European countries (Austria, Belgium, France, Germany, Switzerland) based on the workshop in the first part and a comprehensive description and comparison of the PEF method and EN 15804 in the second part. In the last part, a general conclusion will wrap up the findings and results will provide a further outlook on future activities. Results and discussion The high number of EPD programmes underlines the fact that there is obviously a demand for assessments of the environmental performance of construction materials. In the comparison between and experiences of the different countries, it can be seen that more similarities than differences exist. A comparison between PEF and EPD shows differences, e.g. LCIA impact categories and recycling methodology. Conclusions Independent of raising awareness of the construction material environmental performance, the existence of so many environmental claims calls for clarification and harmonisation. Additionally, construction materials being assessed in the voluntary approaches have to follow the harmonised approach following the principles of the European Construction Products Regulation (regulated) not to foster barriers of trade. The authors therefore highly appreciate the most recent activities of the sustainability of construction works (CEN/TC 350 committee http://portailgroupe.afnor.fr/public_espacenormalisation/CENTC350/index.html) currently working on these issues at the EU level. Finally, the LCA community is further encouraged to increase the background life cycle inventory data and life cycle inventory modelling as well as the meaningfulness of certain environmental impact categories, such as toxicity, land use, biodiversity and resource usage.

The assessment of the environmental performance of buildings is now commonly using a life cycle approach, based on a growing number of databases and methods in Life Cycle Assessment (LCA). Recent studies have, however, highlighted the problems related to uncertainties in the LCA results. The aim of this study is to assess the sensitivity of construction materials to the different modelling choices in order to highlight their consequences at the building scale. In particular, we focused on the different modelling options in terms of database choices, system boundary definitions and replacement scenarios of building materials during the whole service life of the buildings. The assessment of uncertainties was conducted at two levels: the material or element level and the building level. The results clearly show the importance of these modelling choices. Variations on the overall assessment of buildings are significant, but the details at the material scale show that not all materials are similarly sensitive to these choices. We identified those materials that have a large contribution to the environmental impact of the buildings and which are also sensitive to different modelling choices. This can help for a better understanding of these modelling choices and can be used in upcoming regulations or public policies.

Purpose: In this study, life cycle assessment (LCA) is applied to a sample of 40 low-energy individual houses for the French context in order to identify guidance values for different environmental priorities (energy and water consumption, greenhouse gases emissions, waste generation etc.). Methods: Calculation rules for the LCA derived from EeBGuide guidance and HQE Performance specific rules for the French context. Data are based on Environmental Product Declaration (EPD for the impacts related to products and technical equipment while generic data are used for energy and water processes. The LCA is defined for the entire life cycle of a building from cradle-to-grave according to NF EN 15978 standard. It includes the products and equipment implemented in the building, the different uses of energy for heating, domestic hot water, lighting, ventilation and auxiliaries, and the different uses of water consumption. Results and discussion: Results for the 40 houses showed that the average life cycle non-renewable primary energy consumption is about 37 kWh/(m2*year) while the life cycle greenhouse gases emissions are of 8.4 kg CO2-eq/(m2*year). The embodied impacts represent between 40% and 72% for the following indicators: acidification, global warming, non-renewable primary energy, and radioactive waste. The net fresh water use is mostly determined by the direct use of the water in use, and the non-hazardous waste indicator is only linked to the materials and equipment. When integrating the variability of the different houses design, energy performance, climate requirements, it was found that those values can vary of an order of two between the 10 and 90% percentiles’ values. It was found that the results are also sensitive to the enlargement of the system boundaries (e.g. inclusion of the other uses of energy such as building appliances) and the modification of the reference study period. Conclusions and recommendations: This study provided a first set of LCA guidance values describing a range of environmental impacts for new low-energy individual houses in France. Results were also reported for different design parameters, system boundaries and reference study period. The outcomes of this study can now serve as a basis to guide and support new LCA-based labelling systems developed by public authorities and labelling schemes (e.g. the HQE Association).

Life cycle assessment (LCA) is widely used to evaluate the environmental impacts of buildings, but due to uncertainties, the final results can be unreliable. To increase the reliability of LCA results, this study identifies the building materials that have the largest relative contribution to buildings' impacts and uncertainties. To do so, the impacts of 15 single-family houses and 15 multi-family building projects situated in France are evaluated. Only the uncertainties related to input parameters for building materials are considered (service life, characterization factors and quantity). The results obtained in this study show that LCA will still be able to distinguish significantly between two projects if their difference is higher than approximately 20%. Furthermore, the impacts of the buildings' exploitation phase do not show any correlations with the impacts related to the construction materials. The exploitation phase dominates the non-renewable energy consumption while waste impacts are most influenced by building materials. The contribution to global warming potential is shared between both phases. Finally, reinforced concrete was identified as the largest contributor to the environmental impact of both building types. In contrast, insulation materials and non-structural wood were the largest contributors to the uncertainties of the final results for single-family houses and multi-family buildings, respectively.

The renovation of historic buildings is essential to meet the Swiss objectives for energy consumption in 2050. These buildings offer a great saving potential, however, the heritage preservation has to be considered in the renovation scenarios. While essential for the historic conservation, this consideration restricts the renovation possibilities to achieve the heating demand requirements according to the SIA 380/1 standard. This study introduces a framework for identifying the suitable historic buildings’ renovation schemes considering life cycle costs, energy and life cycle environmental impacts. With a case study, the feasibility of achieving the energy performance SIA 380/1 standard is then discussed.

International audience; Different Life Cycle Impact Assessment (LCIA) methods have been developed over the past twenty years. While the use of a single score indicator may, on the one hand, ease the decision making it may also induce a loss of information. On the other hand, the use of a large set of environmental indicators may increase the difficulty of decision making due to the high number of parameters. In this paper, a statistical methodology is used to identify a simplified set of environmental indicators. This methodology applies Principal Component Analysis (PCA) to five LCIA methods (CML’01, Eco-indicator99, IMPACT 2002+, ecological scarcity, EPD) using a building products database. For each method, the results show that only 4–6 dimensions are sufficient to explain at least 90–95% of the variance for each set of indicators. They refer to the following environmental themes: fossil-fuel consumption, ecotoxicity, ionising radiation, land use and mineral resources. The use of a selected set of five LCI flows is found to be as relevant as current LCIA methods from a statistical point of view. Furthermore, PCA applied to a building LCA case study shows similar trends as for the database results. Further studies are now needed to confirm these findings for going towards simplified structural relationships among LCIA indicators for building materials.

International audience; The simplification of life cycle inventories (LCIs) by reducing the number of elementary flows is a major issue regarding their use in sector-specific applications. It can ease the understanding of complete LCIs and focus on the most relevant elementary flows. Current LCIs that have been created for Environmental Product Declarations (EPDs) differ from databases provided by academics, in which more than a thousand flows are considered, as they contain a reduced list of substances. In this paper, we examine the consequences of these simplified LCIs on the accuracy of the life cycle impact assessment (LCIA) step. We consider the specific case of an LCI database for building products that was developed in France. Three environmental midpoint and endpoint indicators are analysed: the global warming potential (GWP), the photochemical ozone formation potential (POCP), and the disability-adjusted life years (DALY). The results for 110 building materials indicate that a simplification is not always relevant, as large uncertainties were detected in the final results, especially for the environmental indicators describing the photochemical ozone creation and the damage to human health that require a larger number of LCI flows. In the case of the GWP indicator, the simplification is relevant for approximately 95% of the building materials. The analysis of the key elementary flows for each indicator enables the identification of missing elementary flows in the simplified LCI. Perspectives and recommendations are provided to improve the level of details of simplified LCIs according to the impact assessment methods.

Purpose The objective of the paper is to discuss the role of a new guidance document for life cycle assessment (LCA) in the construction sector available as an online InfoHub.\ud \ud Methods This InfoHub derives from the EeBGuide European project that aimed at developing a guidance document for energy-efficient building LCA studies. The InfoHub is built on reference documents such as the ISO 14040-44 standards, the EN 15804 and EN 15978 standards as well as the ILCD Handbook. The guidance document was filled with expertise and knowledge of several experts. The focus was put on providing scientifically sound, yet practical guidance.\ud \ud Results The EeBGuide InfoHub is an online guidance document, setting rules for conducting LCA studies and giving instructions on how to do this. The document has a section on buildings—new and existing—and a section on construction products. It is structured according to the life cycle stages of the European standards EN 15804 and EN 15978, covering all aspects of LCA studies by applying provisions from these standards and the ILCD handbook, wherever applicable. The guidance is presented for different scopes of studies by means of three study types. For the same system boundaries, default values are proposed in early or quick assessment (screening and simplified LCA) while detailed calculation rules correspond to a complete LCA. Such approach is intended to better match the user needs in the building sector.\ud \ud Conclusions and recommendations This paper can be viewed as a contribution to the ongoing efforts to improve the consistency and harmonisation in LCA studies for building products and buildings. Further contributions are now needed to improve building LCA guidance and to strengthen links between research, standardisation and implementation of LCA in the construction practice.

The International Journal of Life Cycle Assessment, 18 (5), ISSN:0948-3349, ISSN:1614-7502

L’analyse de cycle de vie (ACV) est une approche reconnue d’evaluation de la performance environnementale des systemes sur l’ensemble de leurs cycles de vie. Bien que preconisee par les standards, la prise en compte de l’incertitude en ACV reste marginale. Nous presentons dans cet article une nouvelle proposition de classification des incertitudes ainsi qu’une representation systemique du processus de realisation d’une ACV. Ces deux resultats combines nous permettent de caracteriser et de suivre les incertitudes vehiculees durant ce processus. Ces resultats exploratoires nous laissent entrevoir de nouvelles orientations de recherche vers l’integration de l’incertitude en ACV.