Search Results (496)

The urban housing sector plays a significant role in global energy consumption and carbon emissions, making the sustainable transformation of domestic buildings essential to achieving climate goals. Urban housing is also linked to the energy transition, social equity, public health, and environmental resilience. The UK’s Warm Homes Plan (WHP) is seen as a key policy initiative that aims to improve energy efficiency and living conditions, and to promote the transition to a low-carbon future. This study provides an integrated review of retrofit assessment, policy mechanisms, and socio-environmental factors in the context of urban housing decarbonization. This study adopts a structured critical review approach to analyze retrofit strategies, low-carbon heating systems, renewable energy integration, and smart control technologies. The study highlights that retrofit assessment is not limited to technical performance but also includes social acceptability, affordability, and urban infrastructure compatibility. Furthermore, case study comparisons show that decarbonization outcomes are improved when technical measures are integrated with effective governance, stakeholder engagement, and local policy support. This study presents an integrated conceptual framework that links technical retrofit measures, policy coordination, and socio-environmental indicators. The results show that isolated technical solutions are insufficient for decarbonizing urban housing. Rather, a multi-dimensional planning approach is necessary to enable a sustainable, resilient, and socially inclusive housing transition. Full article

This study evaluates the economic feasibility of retrofitting split-type air-conditioning systems in a university administrative building in a hot-humid tropical climate in Colombia, addressing the need for cost-effective energy-efficiency strategies in such contexts. A measurement-calibrated building energy model was developed using DesignBuilder and EnergyPlus, and a baseline scenario with low-efficiency fixed-speed split units was compared against three retrofit scenarios with higher-efficiency units defined by market-available COP levels. A 10-year life-cycle cost (LCC) analysis was conducted using a discounted cash flow approach, incorporating investment costs, operation and maintenance expenses, electricity tariff escalation, and equipment performance degradation, complemented by a parametric sensitivity analysis. The results show that air-conditioning systems account for the majority of total building electricity consumption, and that retrofit scenarios reduce cooling energy use by approximately 45–53% relative to the baseline. All retrofit options yield lower life-cycle costs despite higher initial investments, achieving total LCC reductions of up to 30%. Sensitivity analysis indicates that the economic ranking of alternatives remains stable under significant variations in electricity prices. Overall, the proposed framework provides a robust and transferable approach for assessing HVAC retrofit strategies, supporting informed decision-making for energy and cost optimization in buildings located in tropical climates. Full article

This study investigates integrating an air-to-water heat pump (HP) into an existing office building served by a district heating (DH) system to improve energy performance and reduce environmental impact. The system was modelled using Polysun software, considering two operating scenarios: a conventional configuration based solely on DH and a hybrid configuration combining DH with a HP. The analysis was performed using hourly simulations over a typical meteorological year, allowing a detailed evaluation of system behaviour under varying climatic conditions. The results indicate that the hybrid system reduces total energy consumption by approximately 24%, while natural gas consumption decreases by about 36%. Although electricity consumption increases due to HP operation, the overall energy performance is significantly improved. The HP operates efficiently within the analysed temperature range, with COP values ranging from 1.8 to 3.0 and a seasonal performance coefficient of approximately 3.6. The system ensures full coverage of the heating demand, with a negligible deficit, confirming appropriate sizing and control strategy. From an environmental perspective, the hybrid configuration results in approximately 29 t CO₂ per year less than the conventional system. These results demonstrate that integrating HPs into existing DH systems can represent a viable solution for similar buildings under comparable operating conditions. Beyond the quantified energy and environmental benefits, the novelty of the study lies in evaluating a hybrid solution under real operating conditions affected by DH instability. The results highlight practical implications for system resilience, operational flexibility, and the applicability of this retrofit strategy to existing buildings connected to conventional DH networks. Full article

Efforts to improve the energy performance of historic buildings have attracted growing attention from both policymakers and researchers over the past few decades. Based on 318 publications from the Web of Science database, this study conducts a review analysis in the field of historic building energy retrofit. Bibliometric analysis shows a remarkably increasing trend in research on this topic since 2015 and reveals a research imbalance between developed regions (e.g., Europe) and developing regions. This review examines the retrofit approaches of historic buildings using both passive and active strategies and synthesizes the understanding of life cycle assessment carbon emissions across different systaem boundaries, emission stages, and carbon accounting approaches. The results show that previous studies tend to focus primarily on energy performance, yet predominantly rely on simulation studies of individual cases, limiting cross-regional comparisons and the broader transferability of findings. Therefore, a multi-objective evaluation framework is proposed, considering thermal comfort, energy use, and carbon emissions, enabling identification of suitable retrofit measures across different contexts. By examining the problems and strategies in this field, this study highlights the substantial potential of historic building energy retrofit and provides a basis for future evaluation and decision-making. Full article

The seismic retrofit of existing reinforced concrete (RC) buildings equipped with dissipative bracing systems requires not only a global performance-based assessment, but also a rigorous verification of the local behavior of critical structural connections. In this context, the present study focuses on the numerical seismic performance of a beam–column connection extracted from a retrofitted RC hospital building located in Italy. The investigated joint represents a central node where two orthogonal steel bracing systems converge and transfer seismic forces to an RC column strengthened with heavy steel jacketing and anchorage devices. A detailed three-dimensional finite element model of the connection is developed using solid elements for concrete and steel components, explicit modeling of reinforcement bars, bolts, and anchor rods, and advanced nonlinear constitutive laws for both materials. Two modeling strategies are considered, including the explicit simulation of contact interfaces between steel components, in order to capture local stress redistribution and potential interaction effects. The connection is subject to seismic demand derived from the global structural analysis, corresponding to different values of the behavior factor, thus ensuring consistency between global design assumptions and local verification. The results highlight the progressive activation of nonlinear mechanisms within the steel components, the development of cracking and compression damage in the concrete core, and the preservation of a clear hierarchy of resistances under design-level seismic actions. The numerical outcomes allow a critical discussion on the role of local connection behavior in supporting the global dissipative strategy and provide quantitative insights into the evaluation of the behavior factor from a local-response perspective. The study emphasizes the importance of detailed connection-level analyses in the seismic retrofit of strategic facilities and supports a more consistent integration between global performance objectives and local structural design. Full article

Energy efficiency retrofits are widely promoted for public buildings, yet evidence from large-scale real-world projects remains limited compared with simulation-based assessments. This study leverages measured pre- and post-retrofit operational data from 530 public building retrofit projects across 11 provinces/municipalities in China to quantify realized energy-saving performance and screening-level cost-effectiveness across building types and climate zones. Wilcoxon and Kruskal–Wallis tests were employed to ensure statistical rigor. Retrofit measures were grouped into seven categories (e.g., HVAC, lighting, envelope, monitoring/management), and a median-based four-quadrant framework was employed to characterize investment–savings profiles by climate zone and building function. Across the full sample, mean energy use intensity decreased by 19.1%, with 99.2% of projects achieving positive savings. Savings varied markedly by building type: commercial and hotels achieved the highest savings intensities (26.5–28.0 kWh/(m²·a)), while education and cultural buildings generally showed lower gains, with some projects having < 10 kWh/(m²·a). Technology performance exhibited distinct climate and building suitability. Envelope retrofits were most effective in the Cold and Hot Summer–Cold Winter zones (13.30–22.06 kWh/(m²·a)) but yielded limited benefits in the Hot Summer–Warm Winter zone (~1.73 kWh/(m²·a)). HVAC and lighting upgrades delivered comparatively stable savings across climates and building types and dominated retrofit portfolios. Based on these findings, we propose a tiered strategy: prioritizing HVAC and envelope upgrades for high-load sectors while focusing on low-cost optimizations for educational facilities to mitigate investment risks. The findings provide large-scale empirical evidence to support climate- and building-specific retrofit prioritization and investment decision-making under real-world operating conditions. Full article

Heritage buildings constitute a significant element of the United Kingdom’s (UK) built environment, with 460,000 listed buildings across England, Scotland, Wales and Northern Ireland. These assets present substantial challenges for national decarbonisation due to statutory constraints on fabric alteration and the need to consider whole-life carbon impacts. This study evaluates the impact of conservation-compatible retrofit strategies on the operational energy and carbon performance of Fitzroy House, a Grade II listed late-modern office building in Nottingham. Dynamic building simulation (IES Virtual Environment) was used to assess baseline performance and to develop two retrofit scenarios incorporating improvements to glazing, airtightness, roof insulation, and the introduction of mechanical ventilation with heat recovery (MVHR). Climate resilience was evaluated using future weather files for the 2080s. Results are derived from comparative scenario-based modelling rather than calibrated predictions of absolute performance. Within this framework, the proposed measures can reduce annual heating demand by up to 68%, cooling demand by 60%, and operational carbon emissions by approximately 41% (district heating) to 64% (natural gas), relative to the as-built baseline under the most advanced retrofit scenario. Performance remains broadly robust under future climate scenarios, although cooling loads increase modestly. The findings demonstrate that, while meaningful reductions in operational carbon are achievable, retrofit outcomes are fundamentally shaped by conservation constraints, which act as an interpretive framework defining the limits and possibilities of intervention. However, results should be interpreted as indicative of relative performance improvements rather than fully generalizable or predictive outcomes, and embodied carbon impacts are not included within the scope of this study. The research provides an evidence-based pathway for improving similar late-modern listed office buildings while highlighting the limits imposed by conservation requirements and existing building fabric. Full article

The growing demand for sustainable energy solutions in the built environment has increased interest in hybrid envelope retrofits that integrate vegetation systems with on-site photovoltaics (PVs). This study presents a comparative assessment of two integrated vegetation–PV envelope retrofit strategies for an educational building in a cooling-dominated hot-humid climate relevant to Nearly Zero Energy Building (NZEB) applications. A calibrated dynamic simulation model was developed to quantify annual net electricity savings, operational CO₂ emission reductions, and cost-effectiveness using the levelized cost of saved electricity (LCOS). Two configurations were assessed: a solar green roof and a façade system combining green walls with glazing-integrated photovoltaics (GIPVs), enabling a consistent evaluation of roof-based and façade-based hybrid systems under identical conditions. Both strategies deliver comparable energy and environmental performance. The solar green roof achieves annual net electricity savings of 231.0 MWh and avoids 163.3 tCO₂, while the green walls–GIPV system provides 228.3 MWh and 161.4 tCO₂. However, significant differences are observed in economic performance. The LCOS of the solar green roof is approximately 0.07 $/kWh, compared with 0.28 $/kWh for the façade-integrated system. The results demonstrate that vegetation–PV hybrid retrofits can effectively support NZEB pathways in hot-humid climates, while highlighting that the solar green roof provides a more cost-effective solution under the studied conditions. The study contributes a consistent, decision-oriented comparison of integrated vegetation–PV strategies, linking energy, environmental, and economic performance within a unified modeling framework. Full article

Recent earthquakes have underscored the significant seismic vulnerability and poor energy performance of existing reinforced concrete (RC) buildings, with particular deficiencies observed in non-structural components such as masonry infill walls. Conventional retrofit strategies typically address seismic and thermal deficiencies separately, often leading to increased costs and invasive interventions. This study explores the development of an innovative plaster that combines seismic strengthening with thermal insulation. The proposed plaster is produced using natural raw materials of local Calabrian origin and reinforced with broom fibers to enhance both ductility and mechanical strength. Experimental investigations included mechanical characterization through compressive and flexural strength tests, toughness, and ductility evaluation, as well as thermophysical analyses and further complementary tests. The results demonstrate that fiber reinforcement ensures adequate strength and significantly improves deformability, making the material suitable for seismic retrofitting of infill walls. In fact, the results show that the fiber insertion improves the post-critical behavior of the plaster through a significant increase in its ductility. Moreover, the thermal tests confirm a notable reduction in heat transfer, enhancing the energy performance of building envelopes. The complementary tests have demonstrated the suitability of the designed plasters for the intended applications. Full article

With growing health awareness and an increasing preference for indoor exercise among the elderly, the demand for community indoor activity spaces is rising in the northern regions of China with cold winters and hot summers. While previous community studies have primarily focused on residential buildings, limited attention has been given to indoor activity spaces for the elderly. Moreover, field measurements expose critical thermal deficiencies in these spaces, where indoor temperatures remain substandard in both winter and summer, particularly falling substantially below the WHO health-based threshold (≥18 °C) in winter. Recognizing that transitional spaces are effective for improving indoor thermal conditions, this study explored their potential to enhance the indoor thermal environment, leading to targeted retrofitting schemes. The results showed that although additional transitional spaces effectively enhance the thermal performance, the strategies for winter and summer often conflict. Specifically, enclosed transitional spaces are effective for winter insulation but are prone to overheating in summer, whereas semi-outdoor configurations on the south and west facades are beneficial for summer heat prevention. Based on these findings, optimal retrofitting schemes were identified: for Site A, the existing interior corridor is transformed into a semi-outdoor transitional space; for Site B, an Adaptive Façade system is proposed for the south façade. Furthermore, despite the passive benefits, auxiliary HVAC systems remain necessary to maintain temperatures strictly within the comfort range during extreme weather. This study provides a scientific basis for research on transition spaces and offers a reference for retrofitting buildings in similar climatic regions. Full article

Sustainable renovation of existing residential building stocks is essential to reduce greenhouse gas emissions, improve energy performance, and support long-term climate-neutral housing strategies. However, decisions based only on operational indicators may overlook important product-stage embodied impacts, especially in highly integrated renovation solutions. This study evaluates how alternative renovation pathways for a public residential building portfolio in the Comunitat Valenciana (Spain) perform from a stock-level sustainability perspective, comparing five INFINITE industrialised retrofit kits (Kit 1–Kit 5) with five paired conventional renovation scenarios (S1–S5). A bottom-up building stock modelling workflow is applied, combining building-energy simulation to quantify operational performance and emissions (B6) with a screening life-cycle assessment of product-stage embodied carbon reported as GWP (A1–A3). To relate upfront and in-use impacts, the study computes carbon payback, cumulative emissions avoided, and a horizon-based partial life-cycle climate indicator, PLC(H), assessed for 2030, 2035, and 2050. The results show a clear sustainability trade-off: renovation packages that sharply reduce operational emissions often require higher upfront embodied carbon, shifting net climate benefits towards longer time horizons. Low-embodied options provide earlier benefits, with Kit 1 reducing PLC(H) by 15.5% by 2030, whereas deeper decarbonisation packages achieve stronger long-term outcomes, with S5 reducing PLC(H) by 70.7% by 2050. A bounded electricity-decarbonisation sensitivity further shows that these long-horizon rankings are affected by lower grid-emission factors, particularly for highly electrified pathways, although the strongest 2050 pathways remain robust across the tested cases. Overall, the findings show that sustainable stock-level renovation planning should jointly consider operational and embodied carbon, carbon payback, and milestone-based cumulative impacts in order to support balanced portfolio sequencing between broadly deployable fast-payback measures and selective deep retrofits. Full article

Artificial lighting accounts for roughly 30% of total electricity use in supermarkets and significantly affects product perception, customer experience, and purchasing behavior. Increasing the availability of natural light, combined with appropriate architectural energy retrofitting strategies, offers a major opportunity to reduce electricity demand. This study proposes a data-driven framework for evaluating energy retrofit strategies in commercial buildings, integrating Building Information Modeling (BIM) and Building Energy Modeling (BEM). A parametric methodology is used to evaluate multiple architectural retrofitting scenarios aimed at enhancing daylighting and reducing artificial lighting demand, while improving energy efficiency and environmental performance. The scenarios investigated include variations in skylight geometry and orientation, glazing type, photovoltaic integration, and advanced lighting controls. Three Key Performance Indicators (KPIs)—real energy effectiveness, lighting control performance, and environmental impact—are used to assess how design modifications influence energy use, indoor lighting quality, and environmental performance. The methodology is applied to three real food-retail buildings in Italy. Results show that lighting energy consumption can be reduced by up to 60% in scenarios combining LED technology with smart control systems, while total building electricity savings vary across case studies depending on building characteristics and usage patterns. Environmental impact reductions of approximately 15–20% are achieved, reflecting both operational and life-cycle improvements. The study demonstrates the potential of parametric architectural retrofitting to support multi-criteria decision-making for sustainable refurbishment of food-retail environments. Full article

The construction industry is one of the major sources of carbon emissions, and green retrofitting of buildings is an effective pathway to promoting sustainable development in the sector. However, existing research and implementation strategies often struggle to reconcile the needs of governments, businesses, and residents. Therefore, this study proposes a comprehensive research framework that employs bibliometric and text analysis methods to examine implementation barriers in retrofitting projects across four dimensions: policy, cost, technology, and resident satisfaction. The results indicate that retrofitting costs are the primary factor, while technology is a secondary factor. Furthermore, existing policies feature vague technical standards, insufficient incentives, and a lack of differentiation. Conflicts of interest and challenges regarding cost allocation persist throughout the renovation life cycle. Decision-support tools and renovation technologies face limitations and issues regarding applicability. Residents face constraints from multiple factors, including their knowledge base and economic capacity. Based on these findings, the government urgently needs to improve a differentiated policy system and encourage technological R&D and knowledge dissemination. Enterprises must actively respond to policies and optimize their technologies and management practices. Residents need to enhance their energy-saving awareness, participate in retrofitting efforts, and improve their energy consumption behaviors. Full article

Improving the energy performance of existing multi-apartment residential buildings is critical for reducing energy consumption and greenhouse gas emissions in Central and Eastern Europe, where large stocks of post-war buildings with limited insulation are connected to district heating systems. This study evaluates façade insulation retrofit strategies for two representative typologies in Novi Beograd, Serbia—a high-rise tower and an elongated slab-type (‘lamella’) building—using calibrated dynamic energy models and cradle-to-use lifecycle assessment (LCA) over a 50-year service life. Models were calibrated against measured 2023–2024 heating consumption data (NMBE < 1%, CVRMSE < 15%) and normalized with Typical Meteorological Year weather for consistent scenario comparison. Retrofit scenarios applied expanded polystyrene (EPS) and cellulose insulation at 10, 12, and 15 cm thicknesses. Results show that external insulation reduces annual heating demand by approximately 19–20% compared to the uninsulated baseline (192 kWh/m²·a), with the majority of savings achieved at 10 cm and only marginal gains from additional thickness. Insulation thickness has a stronger influence on operational energy reduction than material choice, as differences between EPS and cellulose remain below 0.5%. LCA indicates 23.6–26.0% lower climate change impacts and 23.6–25.8% reduced cumulative energy demand in retrofit scenarios, with cellulose offering modest advantages due to lower embodied emissions and biogenic carbon storage. These findings support targeted envelope retrofits as an effective strategy for decarbonizing district-heated residential buildings in the region. Full article

Building retrofit optimization has gained increasing attention as a pathway to improve energy performance and support sustainability. This review examines 162 studies and synthesizes simulation-based (SBMOO) and metamodel-based (MBMOO) multi-objective optimization techniques for building retrofit across climatic conditions. The review also analyzes passive, active, and combined retrofit strategies and evaluates how climatic context influences their suitability and performance. Passive strategies typically involve envelope- or material-related upgrades, whereas active strategies focus on building systems. Energy efficiency, comfort, cost-effectiveness, and environmental impact are identified as the major performance metrics for retrofit evaluation. Sustainability metric such as life cycle assessment (LCA) has yet to be used adequately to evaluate retrofit measures, while social objectives are also less explored. SBMOO provides robust optimization but can be computationally intensive, whereas MBMOO improves computational efficiency through surrogate modeling but depends strongly on dataset quality, sampling strategy, and surrogate model selection. In contrast to earlier reviews that usually emphasize either optimization techniques or retrofit measures independently, this study integrates optimization pathway comparison with climate-based analysis of retrofit strategies. The review also finds that most studies are highly case-specific, limiting transferability across climates, building types, and retrofit contexts. Therefore, this work proposes a synthesized framework to support structured selection of baseline modeling and optimization pathways for future retrofit studies. Overall, the review identifies current methodological trends, key research gaps, and future directions for more consistent and climate responsive retrofit decision-making. Full article