Energy Retrofit Research Articles

Energy retrofits: Factors affecting a just transition to better indoor air quality

In comparison with other European countries, Ireland has a disproportionately high number of poorly performing energy-inefficient buildings. Consequently, Ireland has one of the most ambitious energy retrofit programmes in Europe. The aim of this study was to evaluate the impact of deep energy renovation measures i.e. (replacement of heating system and upgrade to building envelope) on indoor air quality, thermal comfort and ventilation in a sample of primarily social housing in Ireland. A mixed methods approach including measurement of indoor air quality and a thermal comfort questionnaire survey was employed. Indoor concentration measurements of PM2.5, carbon dioxide, formaldehyde, and radon along with measurements of air temperature and relative humidity were made (N=14). Occupants (n=56) completed a thermal comfort questionnaire survey pre- and post-retrofit. Data collection ran from autumn 2020 until autumn 2023.Thermal comfort improved post-retrofit along with occupant satisfaction with the indoor thermal environment and heating-systems. Post-retrofit, higher bedroom CO2, and higher PM2.5 concentrations were recorded in both living areas and bedrooms. Occupant behaviours e.g. blocking wall vents were significant predictors of poorer ventilation while smoking indoors was related to higher concentrations of PM2.5. In general, homes that had mechanical ventilation systems installed were better ventilated. Underventilation, as indicated by visible condensation or mould was observed in half of the social homes surveyed and reported by questionnaire respondents (26 %). Tailored communications to occupants regarding the important role of ventilation and indoor air quality is required as part of retrofit to optimise impacts on IEQ.

Evaluating Energy Retrofit and Indoor Environmental Quality in a Serbian Sports Facility: A Comprehensive Case Study

Evaluating Energy Retrofit and Indoor Environmental Quality in a Serbian Sports Facility: A Comprehensive Case Study

Green Campus Transformation in Smart City Development: A Study on Low-Carbon and Energy-Saving Design for the Renovation of School Buildings

In the context of increasingly deteriorating global ecological conditions and rising carbon emissions from buildings, campus architecture, as the primary environment for youth learning and living, plays a crucial role in low-carbon energy-efficient design, and green environments. This paper takes the case of Yezhai Middle School in Qianshan, Anhui Province, to explore wind environment optimization and facade energy-saving strategies for mountainous campus buildings under existing building stock renovation. In the context of smart city development, integrating advanced technologies and sustainable practices into public infrastructure has become a key objective. Through wind environment simulations and facade energy retrofitting, this study reveals nonlinear increases in wind speed with building height and significant effects of ground roughness on wind speed variations. Adopting EPS panels and insulation layers in facade energy retrofitting reduces energy consumption for winter heating and summer cooling. The renovated facade effectively prevents cold air intrusion and reduces external heat gain, achieving approximately 24% energy savings. This research provides a scientific basis and practical experience for low-carbon energy retrofitting of other campus and public buildings, advancing the construction industry towards green and low-carbon development goals within the framework of smart city initiatives.

An evaluation model for an optimal decarbonisation process in the built environment

PurposeThe goal is to deliver a decision-support framework to both public and private entities engaged in energy retrofit investments in the property market.Design/methodology/approachThe evaluation algorithm that is being offered takes an innovative approach to financial and economic analysis. Its foundation is a market-driven/cost-driven method, drawing logic from operational research and goal programming.FindingsThe algorithm is tested to a real estate portfolio yielding an optimal asset retrofitting schedule. The ranking list is determined by taking into consideration a variety of parameters, including investment costs and total CO2 emissions from energy retrofit initiatives. The Carbon Risk Real Estate Monitor’s (CRREM) emission targets for 2030 are employed as a reference point in the process of creating a ranking list of the assets that compose the real estate portfolio under examination.Practical implicationsThe evaluation algorithm will allow to determine, in a real estate portfolio, a priority list of assets to be enhanced. This is accomplished by taking into account the client’s financial resources, the overall cost of the intervention programmes for each asset, and the effects that each asset would have on the environment and the energy once the suggested retrofit programme is put into place.Originality/valueThe study proposes a methodological approach that seeks to balance the optimisation of energy performance, the reduction of environmental effect, the promotion of social well-being and economic sustainability in the context of managing the current property sector.

Applying machine learning algorithms to group the energy performance of existing buildings by different granularity level of energy data

ABSTRACT Recent technology advancement has extended smart-metering capability, enabling measurement of fine-grained building energy consumption. These massive energy data provide options to apply machinelearning in building energy analysis. However, the energy details needed depend on the building feature being analyzed. Unlike system faults and user-related inefficiencies, degradation in building thermal performance results in a steady energy increase that can be reflected even with coarse-grained energy data. This study assesses whether energy data of low temporal resolution can be used to provide insight into building energy efficiency. It evaluates the application of machine learning in clustering buildings based on their thermal characteristics using energy data of different time intervals. Through k-means clustering, buildings are clustered using their hourly, daily, and monthly heating energy. The results indicate that all three granularities can identify buildings with high window transmittances and infiltration rates. These findings present an opportunity for applying machine learning not only for modern buildings with advanced metering systems but also for aging buildings that makes the majority of the existing building stock. The study presents a practical method to identify and prioritize buildings for energy retrofit, an important step toward an effective energy upgrade of a large-scale building using machine learning.

Multi-objective assessment of the retrofit of traditional walls located in a historical city centre using an urban climate model

Historical city centres face two major challenges in the 21st century: heritage conservation and energy retrofitting. Wall insulation in traditional buildings is at the crossroads of these two issues. When studying the retrofit of the walls, other factors also need to be considered, such as the durability of the walls, the life cycle of the materials used for insulation, the indoor and outdoor comfort in summer. The aim is to propose a method for taking all these objectives into account when choosing the insulation technique for historical walls. To do this, the TEB (Town Energy Balance) urban climate model is used, because it considers the urban microclimate, the energy behaviour of buildings and moisture transfer through walls. A VTT model is integrated into TEB, to include the risk of mold growth. The medieval city centre of Cahors (France) was used as a case study. The retrofit of two types of wall was assessed: “massive” brick walls, and “light” walls with a timber-framed structure, filled with bricks. Six renovation scenarios were studied, including four insulation materials and both internal and external insulation positions. The results obtained underline the need to study the retrofit of the two types of building separately, because the recommendations made for insulation vary depending on the type of wall studied.

Evaluation of aerial thermography for measuring the thermal transmittance (U-value) of a building façade

In efforts to mitigate greenhouse gas emissions in the construction sector, policies promoting energy efficiency improvements in existing buildings are being implemented. Accurately assessing the impact of energy retrofit strategies requires precise determination of thermal envelope performance through energy audits. Aerial thermography, employing unmanned aerial vehicles (UAVs) equipped with infrared thermal cameras (IRT), is an underused method overcoming limitations in energy audits of large buildings or complexes. This approach offers an elevated perspective, providing an overview of the building’s thermal patterns, aiding in the identification of thermal envelope defects. By measuring temperature distribution, even in inaccessible envelope areas, the severity of identified defects can be estimated. Beyond detecting thermal bridges, air leaks, and moisture, aerial thermography is valid for estimating thermal transmittance (U-value) of enclosures. The aim of this research is to evaluate this method to calculate the U-value of the façade of an university building located in a Subtropical Mediterranean climate, during a typical full day in different seasons of the year. Concurrently with aerial thermography, the thermometric method (THM) was applied to compare results and refine the operational conditions during U-value measurement using different statistical indices and uncertainty analysis. The results demonstrated the validation of airborne thermography as a method for U-value calculation under specific meteorological and operational conditions, overcoming the common physical limitations of traditional building audit methods.

Energy audit based identification of energy efficiency improvement opportunities for existing houses

Energy efficiency in the building has two dimensions; efficient use of energy resources and energy conservation. Energy-efficient houses play a critical role in energy conservation and achieving sustainable built environment goals. The energy efficiency of a house depends on its building envelope (design, orientation, and energy properties of construction material) and operational characteristics appliance efficiency, energy consumption patterns). Rather than merely ensuring new houses are energy-efficient, it is vital to energy retrofit existing houses. Energy audits can assist in evaluating the energy efficiency of existing houses and identify improvement measures. The main objectives of this study were to identify efficiency improvement opportunities through an energy audit of houses and apartments in Karachi. A detailed energy audit checklist was prepared using literature, standards, expert review, and code requirements. Data was collected through physical and owner-assisted virtual audits of 58 houses in six districts of Karachi. Architectural plans, information about doors, windows, air ducts, thermal images, historical data, and material properties were collected. Audit tools included; an anemometer and thermal imagining camera during physical audits. Android applications were used during owner-assisted audits. Data were analyzed for developing descriptive graphs, U and R-values, Pareto charts, and district-wise mapping of energy properties of the material. As a result, energy improvement opportunities were proposed. These are focused on building envelope aspects, including; window orientation, minimizing air infiltration, and using heatresistant paint. Improvement measures were confirmed through thermal imaging of selected buildings.

Indoor thermal environment assessment of a historic building for a thermal and energy retrofit scenario using a CFD model

Research on retrofit scenarios for the energy efficiency of historical buildings is growing. Despite their potential to improve the energy consumption of a building, retrofit scenarios for indoor thermal environments and the thermal comfort of historical buildings has not been sufficiently studied. Therefore, in this study, indoor airflow, heat distribution, and thermal comfort levels of indoor residents were predicted using computational fluid dynamics (CFD) modeling of historic buildings based on measured values. Although the heating was turned on in the meeting room in winter, heat loss caused by low thermal performance, airtightness, and inflow of cold air caused local thermal discomfort. Individuals seated near the windows had a temperature difference of up to 2.6 °C between the head and ankle levels. Heat loss was identified from the exterior walls and windows, with air infiltration significantly affecting indoor thermal comfort. The airtightness of the window frames of historic buildings was low, thus necessitating related improvement in heat and energy retrofit scenarios. This study propose a suitable approach to resolve this problem.

Leverages of energy transition at home: a critical discussion of barriers and future trends

Abstract The transition of the residential sector to a more sustainable energy system is regarded as a crucial action. Thus, significant efforts have been spent to promote deep energy retrofitting of existing inefficient assets. In addition, in more recent times, academics have begun to consider the potential for behavioral change among households to generate energy savings for the sector. This has led to the emergence of a growing body of literature aimed at understanding how to mobilize energy demand reduction potential that can be prompted by households’ behavioral change. Based on findings from a systematic literature review by the Authors, the paper tries to speculate upon four main dichotomic approaches that are retrieved within. These include behavioral-driven versus technological-driven approaches, awareness-raising versus rewarding or incentive-based systems, structural measures such as home retrofitting or the shift to clean energy, and provisional measures such as subsidies and tax rebates for vulnerable consumers. The paper also considers individual/customized measures versus collective policies towards energy transition. Based on that, common grounds are sought to advance effective strategies enabling energy transition of the residential sector. The drivers and limitations of the various approaches are also discussed in this context.

Building retrofitting towards net zero energy under climate change

Abstract The challenge in Net-Zero Energy Building (NZEB) retrofitting is to identify the most effective measures to address energy performance issues. This paper presents a machine learning model for optimizing retrofit measures to achieve NZEB under the influence of climate change. Specifically, the non-dominated sorting genetic algorithm (NSGA-III) minimizes energy consumption and the predicted percentage of dissatisfaction (PPD) while achieving a NZE balance, thereby obtaining the Pareto front. The Order of Preference by Similarity to Ideal Solution (TOPSIS) ranking technique is then applied to the Pareto front to obtain an optimal solution. Various passive energy retrofit measures are investigated, and renewable retrofit measures are employed to cover the required energy. This process is repeated for different time frames to consider the impact of climate change on selecting retrofit measures. The results clearly indicate that, for retrofitting a residential NZEB, higher insulation values are needed for future scenarios compared to the present scenario due to the effects of climate change. Using the future scenarios defined by the Shared Socioeconomic Pathways framework, a higher level of envelope insulation and renewable retrofit measures are required to achieve NZEB in the Sustainable Future scenario compared to the Fossil Fuel-dependent Future scenario, with increases of 35% and 50%, respectively.

Assessing the Potential of Phase-Change Materials in Energy Retrofitting of Existing Buildings in a Mediterranean Climate

Assessing the Potential of Phase-Change Materials in Energy Retrofitting of Existing Buildings in a Mediterranean Climate

Upcycling EPS waste and mineral wool to produce new lightweight gypsum composites with improved thermal performance

Energy efficiency and waste management are crucial for sustainability of construction sector. In this research, a new gypsum composite material is presented in which traditional raw materials have been partially replaced by thermal insulation waste from facades energy retrofitting projects, using an innovative process to recover this waste. Consequently, a novel lightweight gypsum composite has been developed with a replacement of up to 14.7 % by weight of the original material with EPS waste, adding mineral wool as reinforcement fibres (0.375 %wt.). Thus, thermal behaviour analysis of these new composites has been conducted, both material itself and of its performance as part of a real construction system, including finite element analysis of the construction system. In addition, the physicochemical, physical and mechanical characterisation of the new composites has been carried out. Results show that the developed new material has a density 20.3 % lower than the traditional gypsum composite, resulting in a 30.4 % reduction in thermal conductivity. Furthermore, the use of these new lightened gypsum composites as finishing boards in lightweight steel frame (LSF) wall systems reduces the overall thermal resistance of the wall by up to 10.6 % with just 25 mm thickness. On the other hand, the mechanical resistance of this new material exceeds the reference values established by current standards, ranging between 4.18 and 1.87 MPa for flexural strength and between 7.87 and 4.27 MPa for compressive stresses. Additionally, the developed composites have shown a reduction in both total and capillary water absorption compared to traditional gypsum by 19.6 % and 40.0 % respectively, enhancing the material’s durability and its excellent thermal properties throughout its lifespan.

Equity-based energy retrofits to address energy poverty in Canada

Many energy efficiency and decarbonization retrofit programs aim to alleviate energy poverty by targeting low-income households, but these programs do not always address the multiple determinants of energy poverty. This study develops a vulnerability-based framework to explore the extent to which energy retrofit programs designed for low-income households comprehensively account for socioeconomic, demographic, and cultural structures that shape energy poverty experiences, employing Canada as an empirical case study using key informant interviews with program administrators. The framework conceptualizes energy poverty as the vulnerability to future housing-related harms, amplified by energy-related risk factors, and conditioned by a household's inability to adequately respond. The study finds several key issues limiting the capacity of low-income retrofit programs to address the overlapping and compounding determinants of energy poverty, including inadequate funding, exclusion of the poorest quality housing, limited retrofit options, and a narrow focus on energy efficiency gains. This study shows key opportunities to expand and deepen the current ecosystem of low-income retrofit programs by expanding existing policy innovations. The paper also offers suggestions for widening the policy arena to address energy poverty, both within retrofit programs and beyond.

Integrated optimization of the building envelope and the HVAC system in office building retrofitting

Increasing the energy efficiency of existing buildings is the major strategy to reach carbon neutral targets, given that the building sector is a major emitter. In particular, one major part of building energy usage is the building heating, ventilation and air-cooling system, which are highly depending on the thermal performance of building envelope and increase the challenge of selecting optimal packages of energy efficiency measures. This paper thereby presents a method for optimizing the building envelope and heating, ventilation and air-cooling system. The simulation-based NSGA-III approach developed in this paper is based on coupling the dynamic simulation models created in EnergyPlus software with the non-dominated sorting genetic algorithm, as the engine that performs an optimization process. A large domain of energy efficiency packages combined with heating, ventilation and air-cooling systems and building envelope are investigated to minimize energy consumption, retrofit cost and thermal discomfort in indoor environments, which including ideal loads air system, four pipe fan coil system and variable refrigerant flow system, insulation materials and insulation thickness for external walls and roof, different types of external windows, and window-wall ratio. An office building in Chongqing was chosen as a case study to demonstrate the practical implementation of the proposed method. The results show that the four pipe fan coil system was superior in the diversity and performance of the Pareto front. Then, the optimal packages were generated by a synthetic method, which have 58.57 kWh/m2 of energy consumption, 30.76 CNY/m2 of retrofit cost and 40.67 % of the percentage of thermal discomfort hours. The results also indicate that the yearly energy savings rates are 17.30 %, 23.05 % and 21.10 % separately for ideal loads air system, four pipe fan coil system and variable refrigerant flow system after performing optimization. These results highlight the importance and necessity of performing an optimization procedure for existing buildings to select the optimal retrofit measures.

The Practical Impact of Price-Based Demand-Side Management for Occupants of an Office Building Connected to a Renewable Energy Microgrid

This paper examined the practical impact of price-based demand-side management (DSM) for occupants of an office building connected to a renewable energy microgrid. There has been an absence of studies that have analyzed occupant reactions, in terms of perceived practicality, regarding the implementation of DSM in conjunction with factors including renewable energy generation, load shifting and energy costs. An increased understanding of the practicality of DSM will support future improvements in building energy efficiency and sustainability. Ten occupants of the National Build Energy Retrofit Test-bed (NBERT) were selected as a case study. The electricity consumption pattern of the NBERT occupants was derived over a period of two years. Five unique DSM schedules were developed for each of the NBERT occupants, and a survey was carried out to investigate the practicality of these DSM schedules. A real-time electricity pricing tariff, electricity CO2 intensity, three feed-in tariffs and two microgrid control methods were evaluated to assess the practicality of each DSM schedule on the ten NBERT occupants. The results showed that the incorporation of onsite renewable energy generation with price-based DSM had a positive impact (r = 0.69–0.75) on occupant practicality. Onsite renewable energy generation was able to offset the demand for expensive electricity from the grid during peak hours, which aligned with the occupants’ typical work schedules. However, the introduction of a feed-in tariff with a renewable energy microgrid made price-based DSM less practical (r = 0.15–0.64).

Integrating Technological Environmental Design and Energy Interventions in the Residential Building Stock: The Pilot Case of the Small Island Procida

The next decade will see severe environmental and technological risks, pushing our adaptive capacity to its limits. The EPBD Case Green directive, to counter this phenomenon, emphasizes accelerating building renovations, reducing GHG emissions and energy consumption, and promoting renewable energy installations. Additionally, it calls for deadlines to phase out fossil fuels and mandates solar system installations. This research provides a comprehensive perspective on the opportunities for and challenges of incorporating renewable energy into the built environment. It focuses on the 2961 residential buildings on Procida, a small island located south of Italy, to efficiently utilize energy resources and lay the groundwork for sustainability. Beginning with an analysis of the territorial, urban, historical–conservation, structural, and geological context, in addition to environmental assessments, the research develops a classification and archetypalization system using in-house software. This system aggregates data on the island’s residential buildings, analyzes their current state, and formulates various intervention scenarios. These scenarios demonstrate how integrating technological–environmental design interventions, such as upgrading the building envelope and enhancing bioclimatic behavior, with energy retrofitting measures, such as replacing mechanical systems and installing solar panels, can improve the overall performance of the existing building stock and achieve energy self-sufficiency.

Life Cycle Sustainability Assessment: An Index System for Building Energy Retrofit Projects

As a major contributor to global energy consumption and greenhouse gas emissions, the building sector is crucial in shaping energy and climate change policies. Understanding building energy consumption is essential for developing effective policies, and comprehensive datasets and analyses are increasingly important. This paper outlines a structured methodology for developing a sustainability assessment index for building energy efficiency retrofits throughout a building’s life cycle, covering the design, construction, use, and out-of-use phases. It highlights the interdependencies among these phases, with the design plan influencing energy efficiency and material selection, the construction plan ensuring these goals are met, and the plans for energy management, demolition, and resource recovery focusing on sustainable practices. The keys to energy-efficient retrofits are sustainable materials, energy-efficient equipment, and green technologies, which help reduce energy consumption, emissions, and operating costs. Oversight and regulation are necessary to maintain standards. This research combines a literature review, surveys, interviews, the Delphi method, and an analytic hierarchy process (AHP) to develop a comprehensive evaluation system, categorizing 20 factors across a building’s life cycle and assigning weights based on environmental, economic, and social dimensions. The system provides a scientific basis for assessing the sustainability of energy efficiency programs, validated through consistency testing.

Evaluating energy retrofit strategies in enhancing operational performance of mosques: A case study of Al-Imam Al-Hussein Mosque

Mosques are unique in terms of architectural design and operational efficiency. Architectural Design, building envelope characteristics, intermittent operating schedules, and occupancy patterns all impact the performance. Managing these factors poses challenges regarding reducing energy consumption and simultaneously achieving the occupants' thermal and visual comfort, especially in hot, arid climatic conditions. Also, the potential benefits of daylighting in reducing energy consumption in mosque buildings need to be addressed. Accordingly, this study evaluates the impact of various retrofit strategies on the operational performance of Al-Imam Al-Hussein Mosque, one of the large historic mosques in Cairo, considering the energy performance, thermal comfort, and daylighting performance. The current performance of the mosque has been analyzed using energy simulation software to determine the areas that affect its performance. Hence, five retrofitting strategies have been studied to assess their impact on improving the performance of the mosque. When changes are applied to the building envelope only by changing the glazing type, the visual discomfort is improved while sufficient daylighting is maintained inside the prayer area. By adding a cooling system and applying changes to the building envelope, thermal comfort was improved, and the visual discomfort decreased. However, this has led to an increase in energy consumption. Combining different strategies (as in strategy 5) by changing the glazing type, changing the operation scheme, adding LED lamps with dimmers, and adding a cooling system has improved the defined performance metrics. It has achieved a 23% decrease in the annual energy consumption, decreasing the visual discomfort by 30% while maintaining sufficient daylighting conditions inside the space, and enhancing occupants’ thermal comfort by 65%. The proposed approach aids in evaluating the retrofit strategies of mosque buildings, considering different criteria, including daylighting performance, to be energy efficient, sustainable, and maintain occupants’ visual and thermal comfort.

Energy retrofit and climate adaptive design of dwellings in the hot arid climate: Trends and future challenges

As long as buildings face various climate change impacts in recent decades, such as increased heat, particularly in the residential sector. Therefore, energy retrofit, and climate-adaptive designs may contribute significantly to climate change mitigation and adaptation strategies. At the same time, these strategies do not only improve the sustainability of dwellings/houses/residences but also contribute to broader goals of increasing energy efficiency, reducing environmental impact, offering economic benefits, and enhancing the community's resilience in the challenges they face impact from the effects of climate change. This study aims to examine and present the development of energy retrofitting, energy efficiency and climate-adaptive design for dwellings/ residential buildings in hot weather publications through bibliometric research. The research has been examined within the Web of Science™ Core Collection (W.O.S.) online database spanning from 2012 to November 2023 by using the "Title/Abstract/Keywords" category, and a comprehensive data visualisation has been conducted utilising the VOSviewer and CiteSpace programmes. The findings indicate the research trends in the literature and future challenges, and the results from these findings demonstrate the need for sustainable and energy-efficient buildings to preserve the environment and climate. These sustainable developments focus on improvements in energy retrofitting technologies, energy efficiency and saving targets, indoor thermal comfort, optimising passive design and minimising energy demand. This study will probably be a source to provide valuable insights for researchers, practitioners, experts, and policymakers to understand the implications of energy retrofitting and climate-adaptive design in hot arid climates. As well as it would offer theoretical and practical initiatives to be applied in this field.