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In order to reduce the contribution of the building sector to global greenhouse gas emissions and climate change, it is important to improve the building performance through retrofits from the perspective of carbon emission reductions. Data-driven methods are now widely used in building retrofit research. To better apply data-driven techniques in low-carbon building retrofits, a better understanding is needed of the connections and interactions in optimization objectives and parameters, as well as optimization methods and tools. This paper provides a bibliometric analysis of selected 45 studies, summarizes current research hotspots in the field, discusses gaps to be filled, and proposes potential directions for future work. The results show that (1) the building-performance optimization (BPO) process established through physical simulation methods combines the site, retrofit variables, and carbon-related objectives, and the generated datasets are either directly processed using multi-objective optimization (MOO) algorithms or trained as a surrogate model and iteratively optimized using MOO methods. When a sufficient amount of data is available, data-driven methods can be used to develop mathematical models and use MOO methods for performance optimization from the perspective of building carbon emission reductions. (2) The benefits of retrofits are maximized by holistically taking environmental, economic, and social factors into account; from the perspectives of carbon emissions, costs, thermal comfort, and more, widely adopted strategies include improving the thermal performance of building envelopes, regulating HVAC systems, and utilizing renewable energy. (3) The optimization process based on data-driven methods, such as optimization algorithms and machine learning, apply mathematical models and methods for automatic iterative calculations and screen out the optimal solutions with computer assistance with high efficiency while ensuring accuracy. (4) Only 2.2% and 6.7% of the literature focus on the impacts of human behavior and climate change on building retrofits, respectively. In the future, it is necessary to give further consideration to user behaviors and long-term climate change in the retrofit process, in addition to improving the accuracy of optimization models and exploring the generalization and migration capabilities of surrogate models. [ABSTRACT FROM AUTHOR]

This research investigates retrofitting strategies for multifunctional spaces within educational buildings, employing agent-based and performance-based modeling to support decision-making. An experimental matrix was developed, reflecting three usage scenarios (reading, exhibition, lecture) across four retrofitting schemes. An agent-based model was developed to delineate intricate human behaviors in space and examined the self-organizing behaviors of 30 agents for each scheme in every scenario, evaluating six metrics on spatial efficiency and visual experience. Calibrated models, derived from real data and processed through DesignBuilder software, evaluated three metrics: energy use, thermal comfort, and visual comfort. The research then incorporated metrics from the agent-based model and performance simulation to develop a method for discussing the decision-making process in retrofit strategies. The findings indicate that the optimal retrofitting solution for multifunctional spaces is heavily influenced by the distribution of usage scenarios. Given the substantial influence of space metrics on selecting the optimal retrofit scheme, the proposed framework effectively facilitates decision-making for building retrofits by providing a holistic evaluation of both spatial and energy criteria. [ABSTRACT FROM AUTHOR]

Building retrofit is an important strategy to reduce energy consumption and carbon emission in building industry. In order to optimize the design of building envelope retrofit, a multi-objective optimization method combining BP neural network and Monte Carlo-non-dominated ranking genetic algorithm ( MC-NSGA Ⅲ) was proposed. The DesignBuilder software was utilized for building performance simulation to obtain sample data. The BP neural network was utilized to establish prediction models between building envelope and building performance. The prediction models were used as the fitness function for each objective. Monte Carlo method was used for uncertainty analysis of crossover and variation probabilities. The MC-NSGA Ⅲ multi-objective optimization model was constructed to obtain the Pareto front. Then ideal point method was utilized to discover the optimal parameters combination. A case study of a school building in China was used to demonstrate the feasibility and effectiveness. The results indicate that the proposed method can find a comprehensive trade-off solution and provide references for building retrofit planning and design. [ABSTRACT FROM AUTHOR]

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Buildings' walls are covered to reduce environmental impact and esthetics, and cladding materials vary based on public preference and financial capacity. Metal sheets with glossy surfaces are commonly used, but researchers propose using aluminum sheets and filling gaps with commercial waste materials, like, fabric roll sticks or circular plastic hollow parts. A test room with internal dimensions of 1 × 1 × 2 m used in Baghdad (latitude 33.2° N) was used to study thermal behavior, with a window‐type air conditioner providing standard thermal conditions. The air gap attached to the top of the test wall was either left open or closed during the day. Results showed that double‐layer bamboo packing preserved 52.1% with a closed‐air gap and 49.5% with an open‐air gap, but no discernible difference was observed between the two situations. [ABSTRACT FROM AUTHOR]

To achieve climate and energy goals in the building sector, the current pace of renovating existing structures must double, overcoming prevailing barriers. Key Performance Indicators play a pivotal role in science-based decision making, emphasizing both direct and indirect benefits of building retrofits. The authors aim to contribute to proper metric identification for multi-perspective building performance assessment and formulate a methodology supporting energy planning decisions. They introduce the Global Cost per Emission Savings (GCES), an aggregated indicator encompassing both public (CO2 emissions) and private (global cost) perspectives of diverse retrofit technologies for building HVAC systems. Applied to the Italian residential building stock via the Reference Building approach, the methodology is tested using condensing gas boilers, biomass boilers, and electric heat pumps, revealing diverse environmental and economic performances. Addressing the establishment of effective decision-support tools for policymakers, the paper explores the potential impact of various policies on the favorability of technologies. Different policy scenarios are delineated to analyze how distinct approaches may influence the attractiveness of technologies. Notably, in the baseline scenario, biomass boilers hold an advantage over heat pumps according to the GCES index. However, scenarios involving technology-specific incentives or a greenhouse gases emission tax failed to alter the technological ranking, leaving heat pumps financially uncompetitive. In contrast, the TXPM scenario positions heat pumps as the most financially appealing option, penalizing biomass boilers for high particulate matter emissions. [ABSTRACT FROM AUTHOR]

When an energy rehabilitation of a building is planned, the aim is to achieve a significant energy saving. However, how to assess these savings can be difficult. A first idea may be monitoring the building before and after rehabilitation, but the climatic conditions can differ, which may mislead the conclusions. In this work, this problem was avoided by monitoring two similar buildings for a year, one of them energy retrofitted and the other not, sited in the same location (Zaragoza, Spain) and also with the same orientation and geometry, same climate, inner conditions as similar as possible but different materials in the enclosures: rehabilitated and original. This accurately compares energy consumption between the rehabilitated building and the non-renovated building. The yearly energy savings achieved were 58.42 % with the rehabilitation.

The retrofitting of buildings for improved energy efficiency has been recognized as crucial for achieving climate mitigation goals in Bosnia and Herzegovina (B&H). However, performing multi-objective optimizations for retrofitting existing buildings poses challenges, as it requires balancing conflicting objectives such as retrofit costs, energy savings, and CO2 reduction. To tackle this challenge, we employed a multi-objective analysis approach that aims to identify Pareto-optimal solutions for retrofitting, striking a balance between energy consumption, CO2 emissions, and retrofit costs. In this study, we utilized a combination of Full Factorial Design (FFD) and the state-of-the-art NSGA-III framework to evaluate energy-efficient (EE) retrofit strategies for residential buildings in B&H. The analysis was based on the existing building database from the national TABULA study, serving as a fundamental reference. By analyzing this data, we aimed to determine the optimal approach for EE retrofitting in single-family homes (SFH). Key results indicate that upgrading external walls and improving heating system efficiency are the most effective measures for reducing energy consumption and CO2 emissions. However, these measures come with higher retrofit costs. A multi-objective optimization approach identifies a set of non-dominated solutions representing energy efficiency retrofit measures with the lowest specific final energy for heating, specific CO2 emissions, and overall retrofit costs. The top-ranked set of measures achieves a Simple Payback Period (SPP) of 19.9 years. The insights gained from this study are intended to provide valuable guidance to decision-makers in formulating cost-effective and energy-efficient retrofitting strategies that simultaneously minimize annual energy consumption, CO2 emissions, and retrofit costs.

The urban building stock dataset consists of synthetic input and output data for the energy simulation of one million buildings. The dataset consists of four different residential types, namely: terraced, detached, semi-detached, and bungalow. Constructing this buildings dataset requires conversion, categorization, extraction, and analytical processes. The dataset (in .csv) format comprises 19 input parameters, including advanced features such as HVAC system parameters, building fabric (walls, roofs, floors, door, and windows) U-values, and renewable system parameters. The primary output parameter in the dataset is Energy Use Intensity (EUI in kWh/(m2*year)), along with Energy Performance Certificate (EPC) labels categorized on an A to G rating scale. Additionally, the dataset contains end-use demand output parameters for heating and lighting, which are crucial output parameters. jEPlus, a parametric tool, is coupled with EnergyPlus and DesignBuilder templates to facilitate physics-based parametric simulations for generating the dataset. The dataset can be a valuable resource for researchers, practitioners, and policymakers seeking to enhance sustainability and efficiency in urban building environments. Furthermore, dataset holds immense potential for future research in the field of building energy analysis and modeling.

In the framework of reducing carbon dioxide emissions and energy consumption, the energy retrofit of existing buildings plays a significant role and is often supported by numerical analyses of the planned activities and expected results. This study analyses a public building (a kindergarten) located in Bialystok (Poland) and aims to determine the building's energy performance prior to and after thermal modernization. The building was examined by employing two different software packages, Audytor OZC 7.0 Pro and Trnsys 18. The thermal efficiency improvement applied to the renovated building in Bialystok was also analyzed by virtually locating the building in Bologna (Italy). Moreover, a comfort analysis focused on the classrooms of the kindergarten was carried out employing Trnsys. As a novelty, in the analysis, particular attention is paid to ventilation losses and to the influence of envelope elements properties on the building energy demand. The results arising from analyses were compared to real consumption data for the heating season. The results obtained from the two software programs display excellent agreement, and they also match the real consumption data if the heating demand is considered, while some differences arise when the cooling demand is considered. [ABSTRACT FROM AUTHOR]

The LES Project (LES-Llavor Energètica i Salut. Del cole a casa i a la societat, in English: Energy and Health Seed. From school to home and society) is seen as an opportunity to increase the visibility of the role of science and women scientists in their actual contexts and to present architectural research as essential in mitigating climate change and improving people's health. The goal of this research was to reach the greatest range of people possible through intergenerational transfer. However, the main receptors and drivers were students aged between 8 and 10 years old who were responsible for transmitting energy and environmental conditioning concepts and their interrelations with strategic performance in buildings. Awareness was raised through scientific workshops implemented in primary schools that had energy and air quality deficiencies and opportunities, and the concepts were extrapolated to housing. Two schools in different socioeconomic districts (vulnerable and middle-income families) were selected as a strategy to provide details about the perceptions of energy benefits in both schools' families. The results of the experience were highly satisfactory. Children from 8 to 10 years old were interested and ready to understand and transfer key concepts about energy efficiency and health improvement through the transformation of the buildings surrounding them. The dissemination of the project and social awareness reached the primary students of the two schools selected for the project and the entire educational community (students, teachers, families and all of society). Currently, we are working on a second stage that will allow for a broad volume of replicability of the workshops, with schoolteachers taking the lead in these actions. For this purpose, LES has the support of the Department of Education of the Generalitat de Catalunya. [ABSTRACT FROM AUTHOR]

The decarbonisation strategy of the building sector, which accounts for 24% of national greenhouse gas (GHG) emissions, is important to achieve climate neutrality in Korea by 2050. In this study, a bottom-up model and four scenarios were developed for examining scenarios for the decarbonisation of the residential building by 2050. A comparative analysis of energy consumption, GHG emissions, and investment cost was performed. The result showed that building energy performance improvement and heating fuel electrification are key measures for decarbonisation. We concluded that an investment of KRW 6.2 trillion per year would be required to achieve the 2050 decarbonisation scenario. Policy strategies were proposed for increasing investment in accelerating building retrofit, mandating zero-energy building (ZEB), and prohibiting gas boilers.

Great potential for saving carbon emissions lies in modernizing European buildings. Multi-year modernization roadmaps can plan modernization measures in terms of time and are able to consider temporal interactions. Therefore, we have developed a mixed-integer program that determines modernization roadmaps. These roadmaps include changing the energy supply system, improving the envelope, and considering annually varying boundary conditions. High craftwork capacities are required to implement the necessary modernizations to meet climate goals. Unfortunately, studies showed that the current shortage of craftworkers will intensify in the next years. Other important limitations correspond to energy resources. Recent crises show that many energy systems need to handle these limitations. Therefore, we extended the mixed-integer program by a method to handle these limitations inside the roadmaps. By the use of data from 90 interviews with craftwork specialists about the time needed to realize modernization measures, the method is applied. The main purpose is to analyze how modernization strategies change under limited resources, especially in terms of craftwork capacities. Hence, the method is exemplified by a representative single-family dwelling. Within this use case, modernization roadmaps with different craftwork capacity levels were calculated. The results show that modernization roadmaps change comprehensively over these levels. Key findings are that costs and emissions rise with decreasing craftwork capacities. Furthermore, smaller storages and pv systems are implemented at low craftwork capacities. The electrification of the heat supply supported by medium insulation standards should also be implemented with limited craftwork capacities. [ABSTRACT FROM AUTHOR]

The transition from nearly zero-emission building (NZEB) to positive energy building (PEB) models is a new trend, justified by the need to increase the efforts to address the climate change targets and the ambition for a clean energy transition in the construction sector. In line with this scenario, this study assumes that PEB may be applied to meet climate change targets and promote new approaches to urban regeneration plans. It focuses on the functional and energy regeneration of abandoned buildings, considering that many abandoned European buildings are often located in a strategic part of the city. Therefore, the research question is as follows: to what extent can abandoned buildings be converted into a PEB? What would be the meaning of this new association? In order to answer this question, this study developed a procedure to transform an abandoned building into a PEB, implemented through a case study of a former Italian industrial site. Findings pointed out the variables impacting PEB configuration and were used to support a discussion, stressing how rethinking abandoned buildings as PEB may drive new trends to synchronise the socio-technical evolution of energy infrastructure and urban regeneration plans. [ABSTRACT FROM AUTHOR]

Mitigating CO2 emissions for space heating (SH) and hot water (HW) preparation in buildings is key to reaching climate protection targets. In this context, it is important to understand meaningful balances between CO2 reduction through thermal renovation activities and the change of heating systems. In this work, we develop cost-optimal balances for different system settings with the Invert/Opt model. This model optimises the measures applied in each building so that the system costs for SH and HW preparation are minimised under given constraints for a given country. About 500–1000 options are considered for each building. We calculate scenarios and sensitivities for all countries of EU-27, reflecting a 95% reduction in CO2 emissions for SH and HW with a mix of direct and indirect RES technologies. These differ in the settings related to the applicability and costs of building-shell-related measures and the costs and availability of resource potentials. The results show that probably a high share of thermal renovation on total upcoming refurbishment activities until 2050 is cost-efficient to reach a 95% CO2 reduction in the EU-27 building stocks. Assuming that up to 90% of the buildings in each EU-27 country is applicable for a thermal renovation in case a refurbishment activity is needed leads to around 4% lower system costs by 2050 (13 billion EUR/year) compared to assuming a maximum share of 35%. Energy needs are reduced on average more in older buildings than in newer buildings. Nonetheless, a combination of thermal renovation and heating system change is often the most cost-effective option to reduce system-wide CO2 emissions also in more recent buildings. The calculations lead to cost-optimal savings in final energy demand in the range of 29–47% between 2019 and 2050. Assuming less favourable conditions for thermal renovation (high capital recovery expectations, additional technical barriers and high availability of cheap fuels) the cost-optimal level of heat savings in buildings for overall EU-27 could be suspected at around 1/3 down to 1/4 of current final energy demand. [ABSTRACT FROM AUTHOR]

Nearly-zero energy buildings are standard for new constructions in the European Union. The challenge for decarbonized cities is retrofitting the existing buildings. Retrofitting the existing buildings provides considerable opportunities for improving occupants' comfort and reducing global energy consumption and greenhouse gas emissions. Building retrofit is being considered one of the main approaches to achieve sustainability in the built environment at relatively low-cost and high-uptake rates. Although a broad range of retrofit technologies are readily available, methods to ascertain the most suitable set of retrofit actions for specific projects are still a practical challenge. This article first aims to develop and present a simulation-based multi-objective optimization model, named RETROSIM, to quantitatively assess technology choices in a building retrofit project. RETROSIM is a combination of a building energy simulation model and RETROSIM proprietary optimization engine. Secondly, in this study, RETROSIM is used to evaluate a building retrofit project as a case study to show the functionality of the proposed method. The study initiates with the single optimization of objective functions focusing on the building's characteristics and performance: primary energy consumption, global costs and thermal discomfort hours. Then this methodology is used to study the interaction between these conflicting objectives and evaluate their trade-offs. [ABSTRACT FROM AUTHOR]

This study is focused on the feasibility of using energy performance contracting (EPC) for the retrofit of two apartment buildings constructed using precast concrete technologies in Slovakia decades ago. The retrofit packages were defined, and their suitability for EPC was evaluated through discounted payback. The uncertainties in the profitability calculations were covered by designing five possible economic developments and defining input ranges instead of just single inputs. The measures in the technical systems were shown to be more feasible than the retrofit of the building envelopes. The potential to finance the selected measures for technical systems through EPC was further evaluated. It was shown that, for at least one of the two buildings studied, the EPC was recommended only for the economic developments with a notable increase in energy prices compared to the baseline that referred to the situation before the Covid-19 pandemic. In the best case, the payback was four years for one building and seven years for the other; thus, both were potentially suitable for EPC. However, for a complex retrofit, the EPC must be combined with a different funding source to also finance other retrofit measures.

This work analyzed the thermal behavior of an existing building, considering different retrofitting strategies. The methodology starts with an in-situ survey that allowed for obtaining information about occupation, work schedules, envelope materials, lighting, and equipment, which was vital to develop an energy model of the building. Then, the thermal analysis, employing simulations, demonstrates a higher relevance of heat flows through the building's envelope than internal loads and higher cooling rather than heating demands. Afterward, several retrofit strategies focusing on modifying architectural elements were assessed. Finally, these strategies were compared based on their impact on the air-conditioning energy demand. A systematic review identified a lack of studies relating certification and energy policies to buildings retrofitting. Therefore, we assessed the energy performance of the building, when modified to meet the baseline requirements set on the Chilean certification requirements for sustainable buildings, to verify if the certification is a suitable method to assess the energy efficiency of an office building. Although the study only involves a single building, it aims to illustrate identified limitations using the energy policies for Chilean public buildings. The Chilean certification for sustainable buildings seems not to be suitable for the evaluation of energy consumption for the retrofit of existing buildings. Although this study does not demonstrate general trends, it presents a precedent for subsequent studies to evaluate the relevance of the Chilean certification guidelines. [ABSTRACT FROM AUTHOR]

The decarbonisation strategy of the building sector, which accounts for 24% of national greenhouse gas (GHG) emissions, is important to achieve climate neutrality in Korea by 2050. In this study, a bottom-up model and four scenarios were developed for examining scenarios for the decarbonisation of the residential building by 2050. A comparative analysis of energy consumption, GHG emissions, and investment cost was performed. The result showed that building energy performance improvement and heating fuel electrification are key measures for decarbonisation. We concluded that an investment of KRW 6.2 trillion per year would be required to achieve the 2050 decarbonisation scenario. Policy strategies were proposed for increasing investment in accelerating building retrofit, mandating zero-energy building (ZEB), and prohibiting gas boilers. [ABSTRACT FROM AUTHOR]

The LES Project (LES-Llavor Energètica i Salut. Del cole a casa i a la societat, in English: Energy and Health Seed. From school to home and society) is seen as an opportunity to increase the visibility of the role of science and women scientists in their actual contexts and to present architectural research as essential in mitigating climate change and improving people’s health. The goal of this research was to reach the greatest range of people possible through intergenerational transfer. However, the main receptors and drivers were students aged between 8 and 10 years old who were responsible for transmitting energy and environmental conditioning concepts and their interrelations with strategic performance in buildings. Awareness was raised through scientific workshops implemented in primary schools that had energy and air quality deficiencies and opportunities, and the concepts were extrapolated to housing. Two schools in different socioeconomic districts (vulnerable and middle-income families) were selected as a strategy to provide details about the perceptions of energy benefits in both schools’ families. The results of the experience were highly satisfactory. Children from 8 to 10 years old were interested and ready to understand and transfer key concepts about energy efficiency and health improvement through the transformation of the buildings surrounding them. The dissemination of the project and social awareness reached the primary students of the two schools selected for the project and the entire educational community (students, teachers, families and all of society). Currently, we are working on a second stage that will allow for a broad volume of replicability of the workshops, with schoolteachers taking the lead in these actions. For this purpose, LES has the support of the Department of Education of the Generalitat de Catalunya.

The traditional rammed earth houses sharing similar patterns in the Lingnan region, south China, and distributed in rectangular arrays, are gradually losing their vitality and becoming uninhabited under modern living conditions. This research examined a typical pattern called the "Four-point gold" house and analyzed the suitability of different retrofitting technologies by field measurements and building simulation. To optimize energy consumption, indoor thermal comfort, and the corresponding economic performance of the retrofitting measures for the prototypical house, five measures, including wall insulation, reflective roof coating, carpet, sunshade, and natural ventilation, are proposed after considering the status quo of the building envelope. It is found that the best performance in energy-saving, dynamic investment payback period, and annual indoor thermal comfort are 2192.27 kWh/a, 9.17 years, and 1766 h, respectively. Different parameters are included to be clustered by K means clustering technique, and the comprehensively optimized scheme consists of a regime of 30 mm XPS 30 mm, ZS-221 white coating, carpet, 0.5 m sunshade width, and turning off windows (doors). The proposed retrofitting strategy can be promoted to a wide range of traditional rammed earth houses in the Lingnan region in China and holds a conspicuous energy-saving potential for the suburban and rural residential sectors in the region. [ABSTRACT FROM AUTHOR]

High-quality data on building energy use and indoor pollution are critical to supporting government efforts to reduce carbon emissions and improve the population's health. This study describes the development of a city-representative housing stock model used for estimating space-cooling energy use and indoor PM2.5 exposure across the Hong Kong housing stock. Archetypes representative of Hong Kong dwellings were developed based on geographically-referenced housing databases. Simulations of unique combinations of archetype, occupation, and environment were run using EnergyPlus, estimating the annual space-cooling energy consumption and annual average PM2.5 exposure concentrations under both non-retrofit and retrofit scenarios. Results show that modern village houses and top-floor flats in high-rise residential buildings, on average, used 19% more space-cooling energy than other archetypes. Dwellings in urban areas had lower exposure to outdoor-sourced PM2.5 and higher exposure to indoor-sourced PM2.5 compared to those in rural areas. The percentage decrease in space-cooling energy consumption caused by energy efficiency retrofits, including external wall insulation, low-e windows, and airtightening, varied significantly based on archetype. The implementation of external wall insulation in the housing stock led to an average decrease of 3.5% in indoor PM2.5 exposure, whilst airtightening and low-e windows resulted in 7.9% and 0.2% average increases in exposure, respectively. [ABSTRACT FROM AUTHOR]

Building retrofits provide a large opportunity to significantly reduce energy consumption in the buildings sector. Traditional building retrofits focus on equipment upgrades, often at the end of equipment life or failure, and result in replacement with marginally improved similar technology and limited energy savings. The Integrated System (IS) retrofit approach enables much greater energy savings by leveraging interactive effects between end use systems, enabling downsized or lower energy technologies. This paper presents a case study in Hawaii quantifying the benefits of an IS retrofit approach compared to two traditional retrofit approaches: a Standard Practice of upgrading equipment to meet minimum code requirements, and an Improved Practice of upgrading equipment to a higher efficiency. The IS approach showed an energy savings of 84% over existing building energy use, much higher than the traditional approaches of 13% and 33%. The IS retrofit also demonstrated the greatest energy cost savings potential. While the degree of savings realized from the IS approach will vary by building and climate, these findings indicate that savings on the order of 50% and greater are not possible without an IS approach. It is therefore recommended that the IS approach be universally adopted to achieve deep energy savings.

Building retrofits provide a large opportunity to significantly reduce energy consumption in the buildings sector. Traditional building retrofits focus on equipment upgrades, often at the end of equipment life or failure, and result in replacement with marginally improved similar technology and limited energy savings. The Integrated System (IS) retrofit approach enables much greater energy savings by leveraging interactive effects between end use systems, enabling downsized or lower energy technologies. This paper presents a case study in Hawaii quantifying the benefits of an IS retrofit approach compared to two traditional retrofit approaches: a Standard Practice of upgrading equipment to meet minimum code requirements, and an Improved Practice of upgrading equipment to a higher efficiency. The IS approach showed an energy savings of 84% over existing building energy use, much higher than the traditional approaches of 13% and 33%. The IS retrofit also demonstrated the greatest energy cost savings potential. While the degree of savings realized from the IS approach will vary by building and climate, these findings indicate that savings on the order of 50% and greater are not possible without an IS approach. It is therefore recommended that the IS approach be universally adopted to achieve deep energy savings.

To improve energy efficiency—during new buildings design or during a building retrofit—evaluating the energy savings potential of energy conservation measures (ECMs) is a critical task. In building retrofits, occupant behavior significantly impacts building energy use and is a leading factor in uncertainty when determining the effectiveness of retrofit ECMs. Current simulation-based assessment methods simplify the representation of occupant behavior by using a standard or representative set of static and homogeneous assumptions ignoring the dynamics, stochastics, and diversity of occupant's energy-related behavior in buildings. The simplification contributes to significant gaps between the simulated and measured actual energy performance of buildings. This study presents a framework for quantifying the impact of occupant behaviors on ECM energy savings using building performance simulation. During the first step of the study, three occupant behavior styles (austerity, normal, and wasteful) were defined to represent different levels of energy consciousness of occupants regarding their interactions with building energy systems (HVAC, windows, lights and plug-in equipment). Next, a simulation workflow was introduced to determine a range of the ECM energy savings. Then, guidance was provided to interpret the range of ECM savings to support ECM decision making. Finally, a pilot study was performed in a real building to demonstrate the application of the framework. Simulation results show that the impact of occupant behaviors on ECM savings vary with the type of ECM. Occupant behavior minimally affects energy savings for ECMs that are technology-driven (the relative savings differ by less than 2%) and have little interaction with the occupants; for ECMs with strong occupant interaction, such as the use of zonal control variable refrigerant flow system and natural ventilation, energy savings are significantly affected by occupant behavior (the relative savings differ by up to 20%). The study framework provides a novel, holistic approach to assessing the uncertainty of ECM energy savings related to occupant behavior, enabling stakeholders to understand and assess the risk of adopting energy efficiency technologies for new and existing buildings.

To improve energy efficiency—during new buildings design or during a building retrofit—evaluating the energy savings potential of energy conservation measures (ECMs) is a critical task. In building retrofits, occupant behavior significantly impacts building energy use and is a leading factor in uncertainty when determining the effectiveness of retrofit ECMs. Current simulation-based assessment methods simplify the representation of occupant behavior by using a standard or representative set of static and homogeneous assumptions ignoring the dynamics, stochastics, and diversity of occupant's energy-related behavior in buildings. The simplification contributes to significant gaps between the simulated and measured actual energy performance of buildings. This study presents a framework for quantifying the impact of occupant behaviors on ECM energy savings using building performance simulation. During the first step of the study, three occupant behavior styles (austerity, normal, and wasteful) were defined to represent different levels of energy consciousness of occupants regarding their interactions with building energy systems (HVAC, windows, lights and plug-in equipment). Next, a simulation workflow was introduced to determine a range of the ECM energy savings. Then, guidance was provided to interpret the range of ECM savings to support ECM decision making. Finally, a pilot study was performed in a real building to demonstrate the application of the framework. Simulation results show that the impact of occupant behaviors on ECM savings vary with the type of ECM. Occupant behavior minimally affects energy savings for ECMs that are technology-driven (the relative savings differ by less than 2%) and have little interaction with the occupants; for ECMs with strong occupant interaction, such as the use of zonal control variable refrigerant flow system and natural ventilation, energy savings are significantly affected by occupant behavior (the relative savings differ by up to 20%). The study framework provides a novel, holistic approach to assessing the uncertainty of ECM energy savings related to occupant behavior, enabling stakeholders to understand and assess the risk of adopting energy efficiency technologies for new and existing buildings.

• An integrative literature review was carried out, with 269 papers reviewed. • Italy publishes the most on the subject, followed by China, Spain, and the USA. • Improving the envelope's thermal insulation is the most used strategy worldwide. • Other aspects of retrofits were discussed, including benefits and disadvantages. • Future retrofit assessments were suggested based on the conclusions. Given the high energy consumption and greenhouse gas emissions associated with buildings worldwide, sustainable strategies that provide conscious use of natural resources and suitable conditions of indoor environments for users are essential. In this sense, the objective of this paper was to present an overview of retrofit strategies aimed at improving energy efficiency and sustainability in buildings. The work is based on an integrative literature review of studies carried out in several countries over the last seven years. The main benefits of the retrofit strategies are reducing energy consumption, decreasing pollutant emissions, and improving the indoor environmental quality for the occupants. Active retrofit strategies are related to building systems and renewable energy sources, while passive strategies use natural resources more efficiently and generally at a lower cost. Methods and software can support the selection of the best retrofit strategies for each building. This paper compared and discussed the relevant results of the case studies, which comprised 72.9% of the papers selected for the integrative review. In all types of buildings and climates, the most discussed retrofit strategies were building envelope insulation, improving the climatisation and lighting systems, and using renewable energy sources – representing approximately 70% of the strategies. There was also a significant frequency of optimisation of natural lighting, natural ventilation, and ventilated façades in non-residential buildings or other types, mainly in semi-arid, temperate, and Mediterranean climates. Finally, recommendations for future studies were presented. [ABSTRACT FROM AUTHOR]

Electrification of heating is the main option for decarbonizing the residential sector, mainly through heat pumps, which are therefore widely considered both by local stakeholders and in energy outlook studies. However, site-specific estimation of heat pump performance is rarely available or requires extensive building data. This paper presents a generic modeling of heat pumps that can be used to estimate the performance of heat pumps in various configurations and with few data inputs. The developed methodology includes partial load, defrosting and weather compensation. Three operating regimes are considered: Full load, inverter-controlled operation and on/off cycles. In this way, a wide range of configurations can be simulated, including different heat emitters, heat pump technologies and operating modes, with the only inputs required being weather data and COP curves at full-load. As an application, the performance of air-to-air and air-to-water heat pumps for heating and cooling is mapped across Europe using a kriging approach. The methodology also allows quantifying the impact of oversizing on heat pump performance: a case study shows a possible new way forward for retrofit strategies with hybrid heat pumps. The datasets resulting from the simulations across Europe are made openly available for further use. • The modeling of heat pump only requires weather time-series to estimate the performance, and considers part-load and defrost. • A methodology is developed to map the performance of heat pumps across Europe. • The impact of oversizing on performance is quantified using realistic case studies. • Hybrid heat pumps are identified as an option to mitigate poor retrofit practices. • European datasets and local estimates are made available to the modeling community. [ABSTRACT FROM AUTHOR]

• Assessment of roof-PV potential and building retrofit needs for housing stock. • Building characteristics and profiles provide energy efficiency guidelines. • Self-consumptions between 8 and 30% can be achieved for Catalonia region. • Very relevant retrofit measures are required to approach self-generation. European Union policies are encouraging the implementation of renewable energies to reduce fossil fuels dependency. This is further motivated by the effects of global warming and the relevant temperature rise in large cities. Thus, it is increasingly important to analyze the large-scale potential of solar energy, making use of the roof availability for renewable energy generation in cities. Furthermore, it is important to couple this analysis with the energy demand of the buildings analyzing the self-consumption possibilities and help in the decision-making process in regional investments. The proposed methodology estimates and matches the roof potential for electricity generation by PV and the building's energy demand, including the building characteristics as a novelty. As a result, we calculate the self-consumption possibilities and the retrofit requirements of a selected housing stock. Our methodology starts with the quantification and classification of the residential stock. This includes the characterization of the types of dwellings in the regional residential stock, taking into account the size of the municipalities. Then the energy demand of the dwellings, depending on the characteristics of the buildings and the roof generation potential, is compared. Catalonia region (Spain), including the city of Barcelona is studied to show the contributions of this methodology to the energy transition. Results indicate that between 8 and 30% of the residential electricity demand of the municipalities can be covered by rooftop PV. Important energy retrofits (reductions of 80% of the energy demand) are required to approach the feasibility of self-consumption. Nevertheless, there is a limited potential impact in larger cities due to the reduced available roof area per habitant. [ABSTRACT FROM AUTHOR]

Retrofitting existing buildings to be a nearly zero energy building (nZEB) is an effective solution for greenhouse gas emissions and primary energy consumption reduction. A hybrid approach that integrates the building energy simulation method and orthogonal array testing (OAT) to renovate buildings to nZEB is proposed in this paper. Within a residential building in Changchun, Jilin of China, the total energy consumption index (TECI) and CO2 emission factor for heating are used as evaluation criteria. The reliability of the building energy model is validated and adopted to forecast the energy performance of different building renovation strategies. According to OAT, four passive measures can be ranked by their influence on TECI in descending order as follows: external wall heat transfer coefficient, airtightness, window heat transfer coefficient, and roof heat transfer coefficient. The optimal renovation solution of the studied building can reduce the TECI by 43.18% by only reducing the external wall heat transfer coefficient from 0.5 to 0.2 W/m2·K and the infiltration N50 from 3.6 to 0.4 ac/h. Besides, combined heat and power (CHP) utilities emit less CO2 than heat pumps in providing heating under the current CO2 emission factor of the power grid in China, making it impossible to give up district heating systems until carbon emissions of electricity generation have declined significantly. The results can provide a reference for the application of the nZEB standard in actual retrofitting projects. [ABSTRACT FROM AUTHOR]

Building's energy and water consumption and associated utility costs can be significantly reduced if proper energy and water-efficiency upgrades are applied. Due to the limitations of the upgrade budgets and the availability of a wide range of energy and water-efficiency measures, decision makers are always faced with a challenging task to identify optimal sets of building upgrade measures. This paper presents the development of a new model that is capable of identifying an optimum selection of building upgrade measures to minimize equivalent annual cost (EAC) while maintaining the performance of existing buildings and complying with available upgrade budgets. The model is developed in three main phases: (1) formulation phase, where decision variables, objective function, and constraints are identified and formulated; (2) implementation phase that performs the model computations and specifies the model input and output data; and (3) performance evaluation phase where two case studies of university buildings are analyzed to demonstrate the capabilities of the model. Furthermore, a case study from the literature is used to verify the model performance and document its new capabilities. The primary contributions that this research adds to the body of knowledge are: (1) developing new model that can identify optimal selection of building upgrades while complying with user-specified requirements for building operational performance and available upgrade budgets in short computation time, (2) modeling a wide range of upgrade measures for building fixtures and equipment as well as envelope components, and (3) integrating updatable databases from vendors and suppliers to generate up-to-date and practical recommendations. The model is designed to use OpenStudio to analyze combinations of feasible alternatives such as HVAC systems, wall and roof insulations, window types, and water heaters to calculate the corresponding building energy consumption. The model is designed to perform its computations using binary linear programming to identify global optimum solutions in short computational time. The results of the case studies illustrated the capabilities of the model in optimizing building upgrade measures to reduce the building utility costs up to 38% while complying with specified upgrade budgets. [ABSTRACT FROM AUTHOR]