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The European Union (EU) has introduced a range of policies to promote energy efficiency, including setting specific targets for energy-efficient renovations across the EU building stock. This study provides a comprehensive environmental and economic assessment of energy-efficient renovation scenarios in a large-scale multifamily building project that is district-heated, considering both the building and the broader urban energy system. A systematic framework was developed for this assessment and applied to a real case in Sweden, where emission factors from energy production are significantly lower than the EU average: 114 g CO2e/kWh for district heating and 37 g CO2e/kWh for electricity. The project involved the renovation of four similar district-heated multifamily buildings with comparable energy efficiency measures. The primary distinction between the measures lies in the type of HVAC system installed: (1) exhaust ventilation with air pressure control, (2) mechanical ventilation with heat recovery, (3) exhaust ventilation with an exhaust air heat pump, and (4) exhaust ventilation with an exhaust air heat pump combined with photovoltaic (PV) panels. The study's findings show that the building with an exhaust air heat pump which operates intermittently with PV panels achieves the best environmental performance from both perspectives. A key challenge identified for future research is balancing the reduced electricity production from Combined Heat and Power (CHP) plants within the energy system.

Transitioning towards a more circular economy is crucial to tackle the urgent challenges of climate change, depletion of primary raw materials, and waste in our society. Focusing particularly on multi-storey wood building construction in Scandinavia, this study aims to identify the primary challenges for maximizing circularity potential. Through a series of workshops and in-depth interviews with stakeholders across the construction industry value chain, this research seeks to uncover insights into enhancing circular practices. The study shows that time and cost constraints pose the main limitations to the reuse of materials and use of techniques to further improve material reuse in the future. Reusing materials is often at least as costly as using new virgin materials. However, by breaking down the constraints of "time and money" into more specific aspects opportunities for cost-effectiveness and efficiency emerge. According to the stakeholders in this study, the two most important aspects to focus on to make circular timber constructions more feasible and cost and time effective are “Logistics chain for reused materials” and “CE-labelling and warranties of reused materials”. © 2025 Elsevier B.V., All rights reserved.

Warming up incoming fresh air can account for half the space heating demand of a well insulated residential building. Variable air supply (e.g. by demand control) and energy recovery with an air-to-air heat exchanger reduce that demand. However in real-world settings, expected cost and environmental impact savings may not arise, leading to a so-called performance gap. This long-term study followed the building occupancy and electricity consumption of a modern family home in central Sweden, heated using a ground-source heat pump. Over three winters, three mechanical ventilation systems were trialled. Two had heat recovery – flat-plate or rotating wheel – while one was an exhaust system equipped with sensors for demand control of individual rooms. Variable airflow by simple schedule was also evaluated. In consistently subzero temperature conditions, the rotating wheel offered energy savings of at least 11 % compared to the flat-plate device. There was however no evidence (within a warmer temperature range) of a clear difference in heat demand between the exhaust system trials and those with heat recovery. The timing of electrical demand periods suggested that this apparent heat recovery performance gap related to temperature regulation and frost protection within the air handling units. In this real-world setting, with a ground-source heat pump providing baseload warmth, heat recovery ventilation provided limited electrical energy savings, and appeared to align the timing of power demand peaks more closely with falling outdoor air temperature.

Careful selection of construction materials and the efficient management of post-use materials are vital for resource-efficient buildings with lower environmental impacts. This study explores the implications of circular economy practices, entailing efficient post-use materials recovery for reduced environmental impacts of cross-laminated timber (CLT) multi-storey construction. The global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP) of a CLT building are explored in a life cycle perspective, including include all building materials-related activities in the product, construction, end-of-life stages, with a focus on circularity strategies - cascading, reuse, and recycling of post-use building materials. The results show that the building's end-of-life stage represent a significant share of the total life cycle GWP impacts. However, the stage represents a relatively smaller share of the AP and EP impacts. The implementation of circularity significantly reduces the life cycle climate impacts of the building. The end-of-life stage, which represents about 20% of the total material-related GWP impact, can be effectively mitigated through these circularity strategies. Cascading proves to be a better option compared to reuse and recycling, offering a GWP benefit of 70 kgCO<inf>2eq</inf>/m2. Comparatively, the GWP benefit from cascading is 64% and 72% higher than that of the reuse and recycling options, respectively. This study highlights the importance of life cycle perspective and circularity strategies at the end-of-life stage of CLT buildings to reduce environmental impacts. © 2025 Elsevier B.V., All rights reserved.

Background and aim. The Intergovernmental Panel on Climate Change (IPCC) reported in 2019 that the building sector accounts for 21% of global greenhouse gas (GHG) emissions, with 18% originating from producing construction materials such as cement and steel. This highlights the urgent need to address embodied carbon in construction to align with climate goals. This study examines the potential of reusing structural materials, primarily concrete elements, to significantly reduce embodied emissions in the construction sector, which has increasingly focused on embodied carbon alongside operational energy efficiency.

Methods and Data. A lifecycle analysis compared the Global Warming Potential (GWP) of concrete elements reclaimed from an old building, conventional concrete, and timber construction for the structural frame of a row house.

Findings. Reclaimed concrete demonstrated the lowest GWP, achieving a 77% reduction compared to traditional concrete and surpassing timber. These findings indicate that reclaimed concrete elements can rival timber as a sustainable building material.

Theoretical / Practical / Societal implications. Prioritizing sustainable material choices and resource efficiency is crucial for the construction sector to meet increasingly stringent global climate targets. This study emphasizes the importance of reusing structural materials to lower carbon emissions during construction, contributing to a more sustainable built environment.

Background and aim: The construction industry contributes approximately 19% of global greenhouse gas (GHG) emissions and accounts for one-third of worldwide energy consumption, underscoring its pivotal role in addressing climate change. This study evaluates the environmental impact of preserving an existing concrete structure versus constructing a new one with cross-laminated timber (CLT) or virgin concrete.

Methods and data: The effectiveness of environmental comparison in mitigating carbon emissions and reducing resource consumption is investigated through a comparative lifecycle analysis of reuse and replacement scenarios. Utilizing the Life Cycle Assessment (LCA) framework, three scenarios were analysed: (1) preserving existing concrete floors on-site and adding two cross-laminated timber (CLT) extensions, (2) demolishing the existing concrete structure to construct an entirely new five story building using CLT, and (3) demolishing and constructing a new five story structure with cast-inplace virgin concrete. The analysis comprehensively quantifies the Global Warming Potential (GWP) across the production, operational, and end-of-life stages.

Findings: Results demonstrate that reusing existing concrete floors reduces approximately 40 kg CO₂e/m² gross floor area compared to a new timber construction and 121 kg CO₂e/m² tons compared to new concrete construction.

Theoretical/practical/societal implications: The results highlight the environmental benefits of implementing circular economy principles into construction practices.

What are the main findings?

• An overview of sustainable renovation practices in Sweden's multi-family buildings was provided
• Energy use and investment costs are key evaluation methods.

What is the implication of the main finding?

• Standardized decision-making tools are needed.
• Findings highlight areas for improvement in current practices.

Abstract Energy-efficient renovation of the existing building stock is essential for achieving the ambitious sustainability goals set by the European Commission for 2030. However, implementing sustainable renovation has proven challenging, as numerous studies have concluded. Multi-family buildings are a significant part of Sweden's building stock and require renovations to meet energy efficiency standards. This study aims to provide an overview of sustainable renovation practices in Sweden's multi-family buildings. A semi-open structured questionnaire was developed to examine the adoption of these practices, with data collected from 11 housing companies. The responses reveal that Swedish housing companies are well aware of the three key aspects of sustainability and actively consider them in their renovation projects. Notably, specific energy use and investment costs are the most commonly used methods for evaluating the environmental and economic aspects, respectively. However, there is a lack of a common method for assessing the social aspects of renovation projects. Additionally, this study highlights the need for standardized decision-making tools in multi-family building renovations.

In this study, we critically examine the potential of recycled construction materials, focusing on how these materials can significantly reduce greenhouse gas (GHG) emissions and energy usage in the construction sector. By adopting an integrated approach that combines Life Cycle Assessment (LCA) and Material Flow Analysis (MFA) within the circular economy framework, we thoroughly examine the lifecycle environmental performance of these materials. Our findings reveal a promising future where incorporating recycled materials in construction can significantly lower GHG emissions and conserve energy. This underscores their crucial role in advancing sustainable construction practices. Moreover, our study emphasizes the need for robust regulatory frameworks and technological innovations to enhance the adoption of environmentally responsible practices. We encourage policymakers, industry stakeholders, and the academic community to collaborate and promote the adoption of a circular economy strategy in the building sector. Our research contributes to the ongoing discussion on sustainable construction, offering evidence-based insights that can inform future policies and initiatives to improve environmental stewardship in the construction industry. This study aligns with the European Union's objectives of achieving climate-neutral cities by 2030 and the United Nations' Sustainable Development Goals outlined for completion by 2030. Overall, this paper contributes to the ongoing dialogue on sustainable construction, providing a fact-driven basis for future policy and initiatives to enhance environmental stewardship in the industry.

This study takes a unique approach by investigating the integration of Brain–Computer Interfaces (BCIs) and Building Information Modeling (BIM) within residential architecture. It explores their combined potential to foster neuro-responsive, sustainable environments within the framework of Construction 5.0. The methodological approach involves real-time BCI data and subjective evaluations of occupants’ experiences to elucidate cognitive and emotional states. These data inform BIM-driven alterations that facilitate adaptable, customized, and sustainability-oriented architectural solutions. The results highlight the ability of BCI–BIM integration to create dynamic, occupant-responsive environments that enhance well-being, promote energy efficiency, and minimize environmental impact. The primary contribution of this work is the demonstration of the viability of neuro-responsive architecture, wherein cognitive input from Brain–Computer Interfaces enables real-time modifications to architectural designs. This technique enhances built environments’ flexibility and user-centered quality by integrating occupant preferences and mental states into the design process. Furthermore, integrating BCI and BIM technologies has significant implications for advancing sustainability and facilitating the design of energy-efficient and ecologically responsible residential areas. The study offers practical insights for architects, engineers, and construction professionals, providing a method for implementing BCI–BIM systems to enhance user experience and promote sustainable design practices. The research examines ethical issues concerning privacy, data security, and informed permission, ensuring these technologies adhere to moral and legal requirements. The study underscores the transformational potential of BCI–BIM integration while acknowledging challenges related to data interoperability, integrity, and scalability. As a result, ongoing innovation and rigorous ethical supervision are crucial for effectively implementing these technologies. The findings provide practical insights for architects, engineers, and industry professionals, offering a roadmap for developing intelligent and ethically sound design practices. © 2024 by the authors.

The European Union (EU) has implemented several policies to enhance energy efficiency. Among these policies is the objective of achieving energy-efficient renovations in at least 3% of EU buildings annually. The primary aim of this study was to offer a precise environmental comparison among four similar district-heated multifamily buildings that have undergone identical energy efficiency measures. The key distinguishing factor among them lies in the HVAC systems installed. The chosen systems were as follows: (1) exhaust ventilation with air pressure control; (2) mechanical ventilation with heat recovery; (3) exhaust ventilation with an exhaust air heat pump; and (4) exhaust ventilation with an exhaust air heat pump with a Photovoltaic (PV) panel. This study involved a life cycle assessment that relied on actual material data from the housing company and energy consumption measurements. This study covered a period of 50 years for thorough analysis. A sensitivity analysis was also conducted to account for various future scenarios of energy production. The findings revealed that the building with an exhaust air heat pump exhibited the lowest greenhouse gas emissions and the shortest carbon payback period (GBPT), needing only around 7 years. In contrast, the building with exhaust ventilation without heat recovery showed the highest emissions and the longest carbon payback period (GBPT), requiring approximately 11 years. Notably, the results were significantly influenced by future scenarios of energy production, emphasizing the crucial role of emission factors in determining the environmental performance of distinct renovation scenarios.