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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 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.

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)

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.

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