Energy Retrofit Research Articles

Retraction Note: Energy financing for energy retrofit in COVID-19: Recommendations for green bond financing.

Retraction Note: Energy financing for energy retrofit in COVID-19: Recommendations for green bond financing.

Energy demand and air quality in social housing buildings: A novel critical review

Social housing buildings, throughout Europe, represent a consistent share of the existing building stock. Due to the increasing levels of urbanization, the social housing population in the cities has risen and, after the economic crisis following the subprime mortgage crisis and the pandemic, low-income families as well. The greatest part of social dwellings, those built in the previous century, is usually sub-standard from an energy and environmental point of view. This study reviews the existing literature documenting indoor environmental conditions and energy refurbishment interventions or programs to improve the energy efficiency of existing social buildings. By considering the high risk of energy poverty in social contexts, and the socio-economic conditions of tenants, the economic implications deriving from the energy retrofit were also evidenced. Relevant papers published between 2010 and 2024 were reviewed and were divided according to the reference scale, namely the building or the district scale. The review shows the need to improve the energy performances of social dwellings, both to reduce their energy demand and to improve the indoor microclimatic conditions and quality of life of tenants. Through a critical literature review approach, this study provides a contribution to the in-depth understanding of the role of social housing in the contemporary context, providing meaningful insights for formulating more effective and inclusive housing policies for the next future.

Improved energy retrofit decision making through enhanced bottom-up building stock modelling

Modelling the performance of building stocks is crucial in facilitating the renovation at the building stock level. Bottom-up building stock modelling begins by detailing individual buildings and then aggregates them into stock level. Its primary advantage lies in capturing the inherent heterogeneity among distinct buildings, which enables tailored retrofitting. Naturally, this approach requires a comprehensive dataset with detailed building information such as geometry and envelope thermal properties. However, a common challenge is the incompleteness of available data in individual datasets. To address this, previous bottom-up studies have filled the missing data with representative or statistical data. Such practice could lead to homogeneous modelling of distinctbuildings within the same statistical group. This limits the utilization of key ability of bottom-up building stock modelling in capturing heterogeneity, such as tailored retrofitting to explore potential retrofitting areas and strategies.To address this challenge of homogeneous modelling, we utilize data fusion framework for bottom-up building stock modelling, employing probabilistic record linkage and inverse modelling techniques to integrate multiple incomplete building performance datasets. This framework fills the missing data in one dataset with information from another, thus capturing inherent heterogeneity in the building stock. An empirical study was conducted in Umeå, Sweden, to investigate the framework’s effectiveness by modelling building stock with various retrofitting strategies. This study contribution lies in enhancing bottom-up building stock modelling by capturing inherent heterogeneity, to provide tailored retrofitting solutions.

CLIMATE‐JUST HOUSING: A Socio‐spatial Perspective on Climate Policy and Housing

AbstractFocusing on the nexus of climate and housing policy, this article analyzes the socio‐spatial consequences of urban climate mitigation policies and the resultant need to broaden the concept of climate justice. By using the example of energy retrofitting in a low‐income district in Kiel, Germany, the article examines cities’ dependence on real estate companies to reach low‐carbon goals in a privatized housing market and the (potential) need to provide incentives for investment. As the case study shows, this can lead to a highly sensitive confluence of climate policy, private real estate investment and neighborhood development policy, which leads to a higher financial burden as well as the potential displacement and further political marginalization of current tenants. In light of these results, the article argues for the application of a climate justice frame in analyses of urban climate policies that integrates housing justice with spatial justice. Specifically, it calls for the right to climate‐just housing; that is, for the right to affordable housing to be connected with the right to energy‐efficient housing in one's own neighborhood. This implies the right to information and to urban space as political space, which in turn means the politicization of the targets, strategies and, not least, spaces of urban climate policy.

Design, fabrication, and physical properties analysis of laminated Low-E coated glass for retrofit window solutions

The ever-growing demand for improved energy efficiency in buildings has stimulated a stream of research focused on innovative retrofit energy solutions. Laminated low emissivity (Low-E) type coated glass components can be used in retrofitting window systems for enhancing energy savings provided by the insulating properties of glass laminates containing these heat-mirror-type coatings. In particular, custom-designed double-silver low-E coatings embedded into the laminate structure (directly facing the polymer interlayers during and after the lamination) are of interest due to being protected from environmental exposure, enabling easy component transportation, storage, and window retrofits. In this study, we provide some details on the design of several reflector-type solar control low-E coatings of high environmental stability and demonstrate the feasibility of their fabrication on 3 mm thick glass substrates, followed by the lamination. We describe the optical properties of laminated structural glass components of potential usefulness for retrofitting window applications in new and existing buildings. Several thin-film coatings of a low-E type are deposited by using the RF magnetron sputtering technique and then subjected to lamination by using transparent epoxy and PVB materials, to be protected by a clear glass cover layer. The optical performance characteristics of these coatings (measured before and after lamination) elucidate the effects these lamination materials and cover glass thickness have on the final optical properties (leading to a slight reduction in the optical transmission in the visible spectral range, by around 8–10 % while retaining low thermal emissivity across the infrared spectral range). The outcomes of this research, if industrialized could contribute significantly to the development of sustainable building components and practices, and to acheiving a reduction in building energy consumption by way of enabling window retrofit operations at potentially reduced costs.

Energy optimization for Façade retrofit design of residential buildings in hot climates using advanced materials

Global warming has adversely affected the building sector in many countries. Energy retrofit strategies for existing buildings have been developed to combat this issue, including advanced facade system coatings. This study examines how advanced coatings such as PCMs, thermochromics, and cool materials can be effectively used to enhance the thermal behavior and energy performance of existing facades in hot climates. It aims to suggest the optimal combinations of such materials for the façade retrofit design of a typical low-rise residential building in hot climates. Using optimization, Design Builder software is utilized to assess the thermal behavior and energy performance of a combination of advanced materials used. The results revealed that the arrangement of exterior wall layers, thickness and placement of thermal insulation, and the material used in the façade outer layer have a significant effect on the annual energy consumption. Applying coatings with high reflective values as an outer layer of facades can reduce monthly surface temperatures by 2.62 °C in summer and annual cooling loads by 13.78 %. Using PCM coating as an inner layer of the façade improves indoor temperatures by 1.83 °C during different seasons and decreases annual cooling demands by 13.23 %. Finally, the optimal combination of such materials for the energy retrofit design of a typical residential building with three conventional façades has been defined.

Residential renovations: Understanding cost-disruption trade-offs

Disruption and mess associated with energy efficiency retrofits is one aspect that is rarely considered in studies investigating households’ preferences for energy renovations. Using a choice experiment, we estimate a price for residential retrofit disruption, finding it represents a substantial proportion of associated energy cost savings among some households. There is considerable variance in willingness to pay for both energy cost savings and disruption avoidance, consistent with experience of many households investing in energy retrofits but also of government retrofit schemes falling far short of policy targets. Just 1-in-4 households are actively receptive to retrofit policy supports, and disruption posing a significant barrier to undertaking energy retrofits, means both contribute to the slow progress against public policy targets to improve residential energy efficiency.

Examining building energy retrofit effects on indoor environmental quality before the Covid-19 era: a critical assessment

Examining building energy retrofit effects on indoor environmental quality before the Covid-19 era: a critical assessment

An Innovative, Lightweight, and Sustainable Solution for the Integrated Seismic Energy Retrofit of Existing Masonry Structures

A large percentage of existing building stock in Italy and throughout Europe is ageing and no longer complies with current regulations, particularly in terms of sustainability. For these reasons, an urgent consolidation plan is needed to ensure an increase in both seismic response and energy response. Indeed, these constructions were built before the actual technical codes, and currently, they are not able to withstand seismic actions. Meanwhile, they are subject to thermal dispersions that could be due to the use of materials with poor properties or construction errors. Among the numerous consolidation techniques, an innovative solution consisting of a coating system has appeared on the construction market in recent decades. It is an integrated solution that simultaneously improves the seismic and energy behaviour of the building. The paper proposes the evaluation of this lightweight and sustainable solution through some experimental tests which were performed at the National Institute for Research and Development in Constructions, located in the city of Timişoara (Romania). The tests were aimed to investigate the out-of-plane behaviour of a masonry wall (1.20 m × 2.40 m × 0.60 m) obtained by combining two smaller panels with mortar and subjecting them to constant vertical force and pushing by an increasing horizontal one. Its response was assessed before and after the application of extruded aluminium alloy base profiles belonging to the system under study.

Heating with justice: Barriers and solutions to a just energy transition in cold climates

Residential heat pumps could reduce greenhouse gas emissions, but increase energy burdens, the proportion of income households spend on utility bills. We analyze utility bills, thermostat settings and energy burdens for a sample of 51 households in Michigan, half below median income. We recruit a contractor to conduct energy assessments of these households and provide them with energy retrofit recommendations, including estimated costs and savings. We find that low-income households choose similar temperature setpoints to higher-income households, but live in less efficient homes. Below-median income households, which today experience a median energy burden of 6 %, would see it rise to 10 % if they shifted to electric heat pumps from natural gas. Weatherization could offset this increase, bringing burdens down to pre-electrification levels. However, median payback is 24 years, making retrofits infeasible for the poorest. Our results are indicative of an energy poverty trap that could hinder an equitable energy transition.

Balancing preservation and utilization: Window retrofit strategy for energy efficiency in historic modern building

In modern historic buildings, the decline in energy efficiency due to aging necessitates both the preservation of historical value and the need for energy retrofits. However, the windows cannot be altered due to the historical significance of the building's windows in terms of design and materials. Retrofitting windows in modern historic buildings require a more multifaceted improvement than other envelopes. This research examines the energy efficiency of a retrofit strategy that adds double-glazed windows to existing exterior windows. Through the application of retrofit technology, the performance of the windows and their impact on indoor temperature and relative humidity were analyzed. The research conducted an energy performance analysis using building energy simulations to assess energy savings. To ensure accurate energy efficiency evaluation, on-site indoor temperature and relative humidity monitoring, as well as non-destructive thermal performance assessments, were performed. The results revealed a 35 % improvement in airtightness with window retrofit. Based on these results, simulation results showed a 17 % reduction in annual cooling energy consumption and a 24 % reduction in annual heating energy consumption following the implementation of retrofit strategies. Thermal performance improvements proved effective in reducing cooling energy consumption, while airtightness improvements were more effective for heating energy consumption reduction. Consequently, for buildings requiring both heating and cooling, the double-glazed windows retrofit strategy emerged as an energy effective retrofit approach capable of enhancing both airtightness and thermal performance. This retrofit will unlock new possibilities for the preservation and revitalization of modern historic buildings, allowing them to continue their legacy.

Assessing the effectiveness of building retrofits in reducing GHG emissions: A Canadian school case study

This paper investigates the impact of energy retrofits on life cycle greenhouse gas (GHG) emissions across different electricity grid profiles in Montreal, Ottawa, and Halifax, using an existing school building as a case study. Using DesignBuilder for energy simulations and OneClick LCA for GHG emissions estimation, this study evaluates whether the reduction in the operational emission achieved by energy savings from retrofits can outweigh the increased embodied emissions from new envelope materials and equipment. In Montreal and Ottawa, where electricity is mainly generated from renewables and non-fossil fuels, retrofits involving electric heating and envelope improvements could decrease life cycle GHG emissions by up to 75 %. However, if the building initially used electric heating, the retrofits led to an increase in life cycle carbon emissions by 170 % in Montreal and 56 % in Ottawa, respectively, due to the embodied emissions of retrofit materials and equipment. In Halifax, where the electricity grid relies heavily on fossil fuels, all retrofit scenarios showed a positive impact on GHG reductions. Enhancing the building envelope and transitioning from natural gas to electric heating slightly reduced total emissions by 4 %, but retaining natural gas heating decreased the total life cycle GHG emissions by 27 %. This study emphasizes the importance of a comprehensive life cycle assessment in developing policies for achieving carbon neutrality. It demonstrates that the effectiveness of retrofits in reducing GHG emissions significantly depends on the local energy grid, suggesting tailored approaches based on regional energy profiles to optimize emission reductions and energy efficiency.

Under one roof: The social relations and relational work of energy retrofit for the occupants of multi-owned properties

In the UK a significant proportion of Multi-Owned Properties (MoPs) – characterised by buildings segmented into individually owned flats – must undergo retrofitting to achieve net zero emissions. Despite this requirement, advancement has been minimal, with existing government policy failing to consider a pivotal role of social dynamics among residents in the retrofit decision-making process. This research adopts an innovative perspective grounded in relational sociology, leveraging Viviana A. Zelizer's concept of ‘relational work’ and integrating two of the three types of social relations identified by Hargreaves and Middlemiss' (intimacy and institutions) to dissect the retrofit challenges faced by owners of historic MoPs in South Glasgow, UK. The study reveals that the necessity for heightened relational work among property owners acts as a barrier to retrofit initiative. Nevertheless, it identifies potential pathway to invigorate the retrofit sector by enhancing neighbourly connections and recognising the influential, yet underexplored, role of property managers in facilitating retrofit activities within MoPs. This inquiry not only underscores the significance of social relations in environmental retrofit projects but also suggests a re-evaluation of policy frameworks to accommodate the social intricacies inherent in MoPs, thereby fostering a more conducive environment for achieving net-zero targets.

Evaluation of cooling energy saving and ventilation renovations in office buildings by combining bioclimatic design strategies with CFD-BEM coupled simulation

Bioclimatic design knowledge and measures, including passive techniques and natural ventilation cooling, are urgently for building renovation to mitigate global warming. The performance of indoor airflow, energy, economic, and environmental aspects has been researched separately. However, developing a comprehensive framework to investigate bioclimatic strategies under the impact of climate change is challenging. This study aims to integrate bioclimatic design strategies with a coupled simulation approach using Fluent and EnergyPlus to evaluate retrofitting techniques for a single-room office in a university building in a hot summer and cold winter climate. A bioclimatic analysis was conducted to recommend cost-effective passive cooling strategies, including natural ventilation and window shading systems. Two passive measures, changing window types and furniture layouts, were included in renovation packages. Results indicated that the empty model is not valid compared to the fully furnished model when calculating room air change per hour (ACH). Natural ventilation was the most cost-effective strategy to mitigate climate change, with a net present value (NPV) ranging from USD 135.09 to 402.81 over 30 years. However, a higher ACH did not ensure a longer natural ventilation period. By changing the top-hung window to a vertical sash and implementing a movable furniture layout, can achieve better ventilation efficiency. The installation of window vertical shadings had the highest annual emission savings by 2080, while it performed negative economic viability in both the present and the 2050 climates. This research demonstrated how combining bioclimatic measures with a co-simulation approach can offer a thorough evaluation of building energy retrofitting. The results could support architectural and engineering design by integrating bioclimate measures to identify the most effective strategies.

Decarbonizing Affordable Housing in New York City

Buildings account for about 30% of global greenhouse gas emissions. Retrofitting existing buildings for electrification and energy efficiency is a necessary first step toward building decarbonization. For the City of New York to reach its ambitious decarbonization goals, the city must create market conditions to allow rapid scaling up of deep energy retrofits. RiseBoro Community Partnership delivered one such innovative deep energy retrofit project called Casa Pasiva. This case study reveals ways in which affordable housing developers are uniquely positioned with many supporting policies in New York to become early adopters of deep energy retrofits, given their need to improve both business operations and tenant health. However, future projects still face steep obstacles ranging from funding gaps, a lack of familiarity with new building technologies, and conservative investors. RiseBoro’s successful Casa Pasiva pilot project identifies many of the remaining challenges related to deep energy retrofit capital projects as well as further opportunities to scale necessary retrofits across the New York affordable housing market. Readers will learn about options for and obstacles to implementing and scaling up deep energy retrofits in the affordable housing industry.

Development and optimization of an energy saving strategy for social housing applications by water source-heat pump integrating photovoltaic-thermal panels

Residential buildings account for 84 % of Italy's built environment, playing a pivotal role in the EU's aim to cut GHG emissions by 55 % through enhanced energy efficiency and climate adaptation. This necessitates comprehensive energy retrofit initiatives, especially in sectors like social housing, which has been relatively overlooked in terms of energy efficiency strategies. This study focuses on a multi-story building from the 1980s in Rome, implementing an innovative energy system proposed by the RESHeat European project. This system, aimed at standardizing energy retrofits for late 20th-century social housing, leverages the underexplored potential of water-source heat pump (WSHP) systems. The novelty of this research extends to its examination of multi-family housing, a sector that has seen less attention compared to public spaces and smaller residential buildings. Through experimental validation and annual dynamic simulations using TRNSYS and Simulink, the research compares the existing heating system with a proposed upgrade that includes a WSHP and Photovoltaic-Thermal (PVT) panels. This upgrade demonstrated a significant efficiency improvement, achieving an annual COP of 6.1 for the WSHP and a 36 % Primary Energy Savings (PES) from the PVT panels, showcasing the effectiveness of these technologies in enhancing the energy profile of multi-family residential buildings.

Towards High-Efficiency Buildings for Sustainable Energy Transition: Standardized Prefabricated Solutions for Roof Retrofitting

Enhancing energy efficiency in buildings plays a pivotal role in realizing the ambitious objective of achieving carbon neutrality by 2050, as outlined in the European Green Deal. Roofs represent the technical element most affected by energy phenomena related to heat transfer: in winter, roofing can lose up to 35% of heat, and the summer heat flux can even be higher. This paper provides a catalogue of optimized and sustainable solutions, with a specific focus on standardization and prefabrication principles, for enhancing the energy efficiency of the most prevalent types of roofs that characterize the national residential building heritage. The methodological approach that guided the research presented in this article was based on the identification and study of the most common roofings in the diverse national residential building heritage, followed by their classification according to their construction era. In the context of essential energy retrofitting of deteriorated residential building stock, 21 optimized standardized solutions have been identified. The outcome of performance evaluations of the proposed solutions allowed the implementation of a matrix that can be a valuable support for designers in selecting the most efficient precalculated and prefabricated solutions for the national residential building heritage based on energy performance and sustainability criteria.

Challenges to energy retrofitting of existing office buildings in high-rise high-density cities: The case of Hong Kong

Achieving carbon neutrality by 2050 has become a global goal, sparking concerns regarding energy consumption and carbon emissions in building operations. Office buildings in high-rise high-density cities serve as central business districts, contributing significantly to the city’s economic activity and consuming a lot of energy. The process of retrofitting existing office buildings for energy efficiency in high-rise high-density cities tends to be challenging. However, there is a lack of comprehensive understanding of the challenges involved in office buildings’ energy retrofitting, as they have not been thoroughly explored. This study aims to investigate the challenges to the existing office building energy retrofitting (EOBER) in high-rise high-density cities with real cases in Hong Kong. Initially, a systematic literature review was undertaken to identify 49 potential EOBER challenges and categorized into seven groups: technical, financial, institutional, social, environmental, regulatory, and other categories. Afterward, 23 EOBER challenges were identified through 24 semi-structured interviews with 36 real office building energy retrofitting cases in Hong Kong. Moreover, these challenges were quantified by the Z-numbers-based Delphi survey and analysis. Results show that regulatory challenges are the primary challenges, followed by financial challenges. The lack of government incentives, policies, legislation and regulations significantly hinders practitioners’ ability to engage in energy retrofitting initiatives. The long payback period of building energy retrofitting poses a critical financial concern for practitioners embracing such initiatives. In the end, this research proposed integrated strategies to tackle these challenges and increase building energy efficiency, including launching financial and regulatory incentives, shortening the interval for mandatory energy audits, disseminating knowledge, and diversifying finance channels of building energy retrofitting. The findings contribute to the body of knowledge by employing systems thinking to identify and evaluate EOBER challenges in high-rise high-density cities through empirical methodologies. Moreover, this study provides valuable references for practitioners in navigating these challenges and minimizing risks associated with the retrofitting process.

Energy Performance of Buildings for Incentivisation in Energy-Efficient Structures: An Analysis of Secondary Data in Malta

High-performance green buildings mitigate the adverse environmental effects of energy consumption and carbon emissions while simultaneously demonstrating that sustainability does not mean compromising utility, productivity, or comfort. We need to address the identified gap in the evolution of energy-efficient structures facilitated in building applications to enhance energy usage without mitigating comfort. The aim of this study was to provide a review of the current methods used to assess energy efficiency in buildings in Malta through secondary data and to supplement this with qualitative data from interviews. The study investigated the importance of certification, compulsory legislation, and regulations implemented by local authorities and the European Union to incentivise energy performance measures. The findings, supplemented with qualitative data from representatives of public entities, show that most participants agreed that the current method of assessing needs requires a complete overhaul in order to promote a proactive approach to sustainable development. Recent public awareness has highlighted the limited understanding of sustainable practices implemented in buildings to capture and conserve energy. However, it is widely recognised that the building industry has significant potential for energy savings, which applies to both new constructions and existing structures, but the current level falls short of what is necessary in Malta. The study findings emphasise the primary energy users and pinpoint the obstacles in the implementation process. In conclusion, the use of software EPRDM, which may be applied to raise the importance of energy performance in building standards, lacks a value-driven focus, resulting in its full utilisation and potential being unexplored. Future applications of this study include the categorisation of old buildings for a possible bid in energy retrofit; campaigns to promote responsiveness; and the utilisation of advanced technological tools, such as DESIGNBUILDER and related software, to enable the simulation of an optimal building envelope. While increased energy efficiency may result in elevated rental and sale prices for buildings, this knowledge, when disseminated to prospective purchasers via the energy performance certificate (EPC) system, can catalyse investments in structures that are more energy efficient for the end user.

Who invests in energy retrofits? Mining Dutch homeowners’ data

Climate change and energy challenges necessitate a deeper understanding of the drivers behind household energy-efficient retrofitting (EER) to inform policy. This study dissects the determinants influencing homeowner investments in four EER measures—window double-glazing, insulation of roofs, walls, and floors, solar panel adoption, and heat pump installation—aimed at crafting targeted policy recommendations. We explored the determinants by employing a combination of three methods: a systematic literature review to pinpoint associated factors, principal component analysis to explore Dutch national survey data, and binary logistic regression on the principal components. Our findings indicate a lower propensity for EER adoption among older, long-term homeowners, suggesting the need for governmental financial incentives and technical assistance to bolster energy efficiency in this demographic. Conversely, homeowners engaged in their communities demonstrate a higher likelihood of investing in solar panels and insulation. Policymakers should, therefore, leverage community dynamics to enhance EER uptake, emphasizing information dissemination and collaborative initiatives. Our study underscores the importance of tailored support and the mobilization of community networks as critical to advancing household energy efficiency and broader sustainability goals. These and other insights can also inform energy policies in other countries.