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PurposePrevious life cycle assessments (LCAs) of buildings and building components show a broad range of values for the impact of maintenance and replacement, some highlighting these operations as major hotspots while others consider them insignificant. This article highlights methodological aspects explaining this discrepancy. The influence of three aspects is investigated further in a case study of façade materials: the reference study period (RSP), service life data, and the use of a round-up number of operations or annualized impacts.MethodsA 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 from industry practitioners and low, standard and high values from a generic database), and two possible calculation methods (round-up or annualized impacts).Results and discussionWhile the same façade alternative had the lowest GWP in all cases, different methodological choices significantly affected the GWP and respective ranking of other alternatives. Some alternatives showed a significant increase in GWP over longer RSPs, while others were still dominated by the impact of initial production after 200 years. In nearly all cases, generic service life data lead to a higher GWP than data from industry practitioners. Major discrepancies were found between generic and practitioner data in some cases, e.g., for the brick façade. In most cases, annualized impacts led to a slightly lower (or equal) GWP than using a round-up number of operations. However, when a major operation happens shortly before the end of the RSP, the annualized method leads to considerably lower GWP.ConclusionsMaintenance and replacement are rarely significant over a 50-year RSP but sometimes become hotspots over longer RSPs. Using round-up operations or annualized impacts does not make much difference in average, but leads to significantly different results in specific cases. As building LCA enters certification and regulation, there is a need to harmonize such methodological choices, as they affect LCA results, hotspot identification, and recommendations. Discrepancies in service life data also call for the gathering of reliable data.

This paper explores how opportunities for reducing the total use of office space can be identified, investigates how the benefits in terms of energy savings from space efficiency measures could be calculated, and gives a first estimate of such values. A simple method to measure office space use is presented and tested at two university departments, and very low space efficiency is found. A variety of reasons for the low space efficiency are identified via interviews with property managers and heads of the concerned departments. These include the fact that the incentives for using space efficiently are small for the decision-makers, and the costs in terms of time and trouble are perceived as high. This suggests that interesting results can be achieved without large efforts. Moreover, we present a proof of concept of how to estimate the amount of energy that can be saved by reducing space use. We find a rough estimate of the potential energy savings of 2 MWh/m2 in embodied primary energy intensity (assuming that more efficient use of space leads to a decrease in new construction) and 200 kWh/m2/year in final energy intensity. Those numbers should be useful as rough estimates when looking at opportunities for saving energy by using space more efficiently.

The urgent need to reduce greenhouse gas emissions and the increasing share of embodied carbon in life-cycle impacts underscore the necessity of mitigating construction and demolition impacts to align with the Paris Agreement. Urban planning significantly influences material flows, with a substantial portion of construction occurring in planned urban development areas (UDAs), such as 76% in Copenhagen, Denmark. However, research on UDAs is limited, with most life-cycle assessments (LCAs) focusing on individual buildings. This study examines the embodied CO2e emissions from buildings and infrastructure in a newly developed UDA, using an archetype-based LCA approach that combines both on-site and average data, which can serve as a stepping stone for a more comprehensive analysis. The study shows that most emissions in the studied UDA occur upfront and are attributed to new building construction. The studied UDA featured several refurbished buildings, repurposed into housing and offices, but their reuse only made a small difference when considering embodied emissions for the entire UDA. Other UDAs may exhibit a different emission profile. Lastly, the study compares neighbourhood and city-scale impacts to absolute environmental boundaries, highlighting the significant climate impacts of urban planning, particularly in UDAs. Policy relevance Urban planning has a significant influence on climate impacts. The substantial amounts of embodied CO2e attributed to planned UDAs, particularly emissions occurring upfront and relative to absolute environmental boundaries, suggest the need to rethink current urban planning frameworks to better align with absolute environmental boundaries and the goals of the Paris Agreement. The results offer insights for developing contextual mitigation measures; the large share of CO2e emitted by new buildings underscores the potential of low-carbon technologies and materials and the broader impact of regulatory targets. Moreover, the limited relative impact of reuse in the studied UDA suggests the need for planning models that prioritise existing building inventories over new construction. Ultimately, the findings may also suggest the need to reconsider the overall scale of permissible building rights altogether.

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 relevanceImproving 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.

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. Grant support: This work is part of the research programme \"E2B2 - Research and innovation for energy-efficient construction and housing\", funded by the Swedish Energy Agency.

Life-cycle assessment (LCA) is widely used in certifications, regulations, and voluntary declarations covering the climate impact of buildings over their entire value chain. However, biodiversity impacts and other environmental impact categories are often disregarded. Conversely, there is a trend towards more systematic assessments of the biodiversity impacts that occur on-site as part of development projects (e.g. land transformation on the project site). However, off-site biodiversity impacts occurring throughout the rest of the value chain (e.g. from forestry activities, mining, manufacturing, heat and electricity production) are rarely considered. To bridge this gap, this article introduces the Doughnut Biotool, an open-source calculation tool to assess biodiversity impacts throughout the entire life cycle of development projects. The tool was initially developed to help implement Doughnut Economics and absolute sustainability principles in development projects. It constitutes a first step towards a better consideration of biodiversity impacts related to material- and energy use in building and construction projects. This paper presents the design of the tool and the method and data it relies on. The tool is applied to two separate case study projects, and used as a basis to discuss hotspots of biodiversity impacts within the building’s life cycle. Finally, the paper includes a discussion of the main challenges and opportunities for the future development and use of the tool, as well as for biodiversity impact assessments in the building sector as a whole.

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 CO 2 e/m 2 /y, whereas reference values are found between 20-80 kg CO2e/m 2 /y. Possible embodied target- and reference values are found between 1-12 kg CO 2 e/m 2 /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.

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.

The epithelial–mesenchymal transition (EMT) plays a crucial role in the differentiation of many tissues and organs. So far, an EMT was not detected in the development of the auditory organ. To determine whether an EMT may play a role in the morphogenesis of the auditory organ, we studied the spatial localization of several EMT markers, the cell–cell adhesion molecules and intermediate filament cytoskeletal proteins, in epithelium of the dorsal cochlea during development of the rat Corti organ from E18 (18th embryonic day) until P25 (25th postnatal day). We examined by confocal microscopy immunolabelings on cryosections of whole cochleae with antibodies anti-cytokeratins as well as with antibodies anti-vimentin, anti-E-cadherin and anti-β-catenin. Our results showed a partial loss of E-cadherin and β-catenin and a temporary appearance of vimentin in pillar cells and Deiters between P8 and P10. These observations suggest that a partial EMT might be involved in the remodelling of the Corti organ during the postnatal stages of development in rat.

Auditory attention decoding (AAD) algorithms exploit brain signals, such as electroencephalography (EEG), to identify which speaker a listener is focusing on in a multi-speaker environment. While state-of-the-art AAD algorithms can identify the attended speaker on short time windows, their predictions are often too inaccurate for practical use. In this work, we propose augmenting AAD with a hidden Markov model (HMM) that models the temporal structure of attention. More specifically, the HMM relies on the fact that a subject is much less likely to switch attention than to keep attending the same speaker at any moment in time. We show how a HMM can significantly improve existing AAD algorithms in both causal (real-time) and non-causal (offline) settings. We further demonstrate that HMMs outperform existing postprocessing approaches in both accuracy and responsiveness, and explore how various factors such as window length, switching frequency, and AAD accuracy influence overall performance. The proposed method is computationally efficient, intuitive to use and applicable in both real-time and offline settings.