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Introduction: In Switzerland, heating accounts for 70% of a building’s energy consumption, mostly fueled by fossil sources. Recently, cantonal regulations have mandated the use of renewable energy in heating, making heat pumps more significant. This study examines how public and private actors can create or transform a business ecosystem to facilitate heat pump adoption in multifamily houses and which business models, resources, and activities are most effective to support this transformation. Methods: We conducted a literature review and 13 semi-structured interviews with experts in heat pumps and contracting business models. The interviews were analyzed using an ecosystem framework. Results: Our findings revealed three primary barriers to the adoption of heat pumps in MFHs: technical challenges, lack of expertise, and regulatory issues. In terms of contracting business models, high transaction costs and customer acceptance are significant obstacles. Additionally, we discovered that in Switzerland, contracting is predominantly offered by public-oriented organizations with ready access to capital. Discussion: The study emphasizes the necessity for collaboration among various actors to facilitate the implementation of contracting solutions with the goal of accelerating the adoption of heat pumps in multifamily housing. Key activities include generating the necessary expertise and standardizing large heat pumps in MFHs, central government efforts to harmonize and facilitate HP regulations across cantons, as well as active communication and sensitization of building owners and users. [ABSTRACT FROM AUTHOR]

K-12 schools are the largest energy consumers in the public sector, with their HVAC energy consumption representing the largest portion of their total energy use. While transitioning these schools to grid-interactive HVAC system operation through advanced controls offers significant financial and environmental benefits, and model predictive control (MPC) has been identified as a promising solution to achieve that, very few MPCs are affordable and have been deployed in K-12 schools. This situation raises concerns about the unclear real-world benefits of MPC technology among facility managers and industries. To address this gap, this paper presents a low-cost MPC solution that requires minimal control infrastructure costs and a unique field demonstration at a K-12 school, conducted for both cooling and heating seasons. This work adopted a previously developed MPC and extended it for use in the school application. The MPC aims to coordinate multiple packaged units to eliminate unnecessary peaks and shift cooling or heating loads in response to grid signals based on load conditions, while maintaining thermostat temperatures within school-defined bounds. Throughout the field tests, the MPC achieved a 24% reduction in peak demand during the cooling season and shifted cooling or heating loads by up to 16% in response to the school's utility tariff, considering load conditions, while also allowing end-users to override thermostat setpoints. The paper also discusses the limitations of this study and future research directions for better performance of the MPC at K-12 schools.

Rapid electrification of buildings at the district scale is needed for cities to achieve climate change mitigation goals. However, most electrification studies focus on either the single building level or the city/region building stock level, and depend on the slow and uncertain process of requesting personally identifiable customer energy usage data from utilities. To answer a key question facing local policymakers: “Where can electrification proceed at scale without first upgrading the grid?” this study aims to quantify and inform building electrification impacts at the district scale using detailed building energy modeling and based on public records datasets. We explore how energy efficiency retrofits can help mitigate increased peak electric demand, and quantify impacts to energy use and carbon emissions. Building energy models of a baseline, and scenarios of simple electrification, energy retrofits, and electrification in combination with retrofits were created and simulated for 54 commercial buildings in two contiguous districts of San Francisco. A simple electrification scenario increased annual electricity consumption but reduced annual site energy usage by 15% to 17%, mainly due to replacing inefficient gas furnaces and boilers with more efficient heat pumps. Peak demand increased 7.4% for Fisherman's Wharf (e.g. within the capacity of the existing power grid), while the Design District showed a marginal decrease. Annual carbon emissions were reduced by 46% and 37%. Combining electrification with efficiency upgrades reduced peak demand by 26% and 40%, and annual carbon emissions by 63% and 64% for the two districts. These results indicate that impacts of electrification depend on the mix of building uses within a district, and coupling electrification with energy efficiency upgrades is an effective strategy to decarbonize buildings while maintaining or reducing the peak electric demand.

Based on program analysis, literature review, expert interviews, and an October 2022 expert roundtable, this report identifies a set of conclusions and recommendations for California policymakers. We offer recommendations in distinct but overlapping areas:• Expanding consumer energy financing programs• Addressing the needs of lower- and moderate-income residents• Accelerating building decarbonization toward California’s 2045 goal• Ensuring equity in program revenue sources• Improving program design through learningThese recommendations all reflect a core insight developed from the research and outreach process: that the enormous size of California’s building decarbonization need calls for significant infusions of private capital, and financing programs can be a mechanism to attract some of this capital. However, consumer energy finance programs are not yet operating on a scale that matches the challenge. Even at their most robust and effective these programs will likely only fund a portion of the needed retrofits and are not always appropriate for lowerincome residents, who will require access to alternative measures involving minimal or zero repayment obligations. And effectively taking advantage of newly available federal Inflation Reduction incentives will rely on state programs that facilitate layering of funds from an array of sources.A central recommendation across this report’s sections is that state legislators and financing program administrators consider alternatives to utility ratepayer funds as the core revenue source for credit enhancement. Shifting from ratepayer funds to alternative sources including taxpayer funds, federal funds, and philanthropic sources could potentially help scale up the GoGreen Financing programs’ reach and flexibility across utility service territories, fuel sources, and eligible measures; facilitate more seamless integration with other state programs; reduce procedural barriers to rapid adaptation to market and technology developments; and advance equity by relying on a more progressive revenue source

IntroductionIn Switzerland, heating accounts for 70% of a building’s energy consumption, mostly fueled by fossil sources. Recently, cantonal regulations have mandated the use of renewable energy in heating, making heat pumps more significant. This study examines how public and private actors can create or transform a business ecosystem to facilitate heat pump adoption in multi-family houses and which business models, resources, and activities are most effective to support this transformation.MethodsWe conducted a literature review and 13 semi-structured interviews with experts in heat pumps and contracting business models. The interviews were analyzed using an ecosystem framework.ResultsOur findings revealed three primary barriers to the adoption of heat pumps in MFHs: technical challenges, lack of expertise, and regulatory issues. In terms of contracting business models, high transaction costs and customer acceptance are significant obstacles. Additionally, we discovered that in Switzerland, contracting is predominantly offered by public-oriented organizations with ready access to capital.DiscussionThe study emphasizes the necessity for collaboration among various actors to facilitate the implementation of contracting solutions with the goal of accelerating the adoption of heat pumps in multifamily housing. Key activities include generating the necessary expertise and standardizing large heat pumps in MFHs, central government efforts to harmonize and facilitate HP regulations across cantons, as well as active communication and sensitization of building owners and users.

Building decarbonization strategy with Distributed renewable energy sources (DRES) is applied and extended worldwide for its climate change mitigation benefits, however, it generates debate regarding equity in sharing electric system operation costs. To analyze DRES effects on equity, it is conducted a case study, in which same residential consumer is evaluated in three different markets (Spain, Mexico, Colombia). We analyze not only electrical system technical variables, but we also include society's economic, social, technological, and environmental characteristics. Next, energy, economic, and environmental benefits are obtained in each the three case studies, analyzing the impact of using DERS on equity to recover electric system operating costs. We also evaluate whether tariff mechanisms are equitable to motivate all consumers participation, as well as whether all consumers have equal opportunity for using DERS. We conclude that tariff mechanisms in Mexico and Colombia lead to inequity to recover market operating costs, favoring large consumers with high incomes. Furthermore, tariff mechanisms discourage the use of DERS by small and medium consumers due to economic, social, and technological aspects. In Spain, inequity arises due to increased difficulty for some consumers to use DERS, i.e., consumers in apartment buildings. [ABSTRACT FROM AUTHOR]

This study examines the impact of low-income assistance and electrification programs on a disadvantaged community in Southern California. An urban building energy model is paired with an AC power flow and electric distribution system degradation model to evaluate how the cost of energy, carbon emissions, and pollutant emissions change after applying building weatherization, energy efficiency, and electrification measures to the community. Results show that traditional weatherization and energy efficiency measures (upgrading lighting and appliances, improving insulation to current building code standards) are the most cost-effective, reducing the cost of energy and carbon emissions by 10–20 % for the current community. Heat pump water heaters offer a 40 % average reduction in carbon emissions and almost 50 % decrease in criteria pollutant emissions, but at a cost increase of 17–22 %. Appliance electrification also reduces carbon emissions 5–10 % but increases cost by 7 % to 25 %. For reducing carbon, government programs that support building electrification are most cost-effective when they combine switching from natural gas to electricity with high efficiency system. Electrifying hot water and appliances effectively reduces emissions but must be paired with improved low-income assistance programs to prevent increased energy burden for low-income families. The urban building energy model and electrical distribution simulations used in this study can be replicated in other low-income communities.

In this study, we investigate methods to reduce carbon emissions from existing large commercial buildings with central natural gas-fired boilers used for space heating. This research explores opportunities to reduce natural gas use through improved building operations and through building decarbonization. We conducted one-hour interviews with 17 mechanical HVAC designers, together having over 350 years of industry experience, professional tenures at engineering consulting firms and design/build firms, and project work in California, New York, Texas, Alaska, the United Kingdom, and Canada. We asked a mix of quantitative and qualitative questions, covering four topic areas: General Background, Peak Heating Load and Boiler Selection, Boiler Controls, and Existing Building Decarbonization. The interviews yielded insight into industry practices, including determining peak heating load, equipment redundancy, boiler staging controls, Heating Hot Water temperature resets, challenges of building electrification, and design considerations for building decarbonization. From the interview results, we developed five key findings: (1) New boilers are oversized, (2) Actual building load distributions are not available, (3) Heating Hot Water temperatures are too high, (4) Boiler end-of-life is not the best electrification opportunity, (5) Reduce building emissions even if all-electric is infeasible. There are many challenges to reducing carbon emissions from existing buildings, but we conclude there are also many opportunities to make immediate positive change.

To reduce the carbon footprint of buildings, the concept of virtual prosumers (consumers who both consume and produce) using remote solar energy parks represents a novel method in Europe. In 2019, Lithuania became the first country in Europe to introduce a digital platform that enables the buying or renting of parts of a remote solar park, making it the first such platform in the world to operate on a national scale. This study examines the effectiveness of this model in Lithuania, assessing the model’s success, public engagement, and success factors. The main study focus is on evaluating the impact of remote solar parks on the decarbonization of buildings, particularly through the prism of virtual prosumer participation. This study integrates both qualitative and quantitative data. The quantitative analysis includes a detailed case study, evaluating the amount of energy produced by two selected remote solar parks in Lithuania, as well as their impact on the carbon dioxide emissions and primary energy use of the two individual houses (a detached house and a unit within an apartment building) connected to these remote power plants. In Case Study A, the renewable primary energy usage was 22.19 kWh/m2 compared to a minimal 0.22 kWh/m2 of non-renewable energy (CO2 emissions 0.0 kgCO2/kWh). Case Study B showed 181.38 kWh/m2 of renewable energy versus 3.63 kWh/m2 of non-renewable energy (CO2 emissions 6.17 kgCO2/kWh). Concurrently, qualitative methods involve analysing the existing legal and economic frameworks in Lithuania and Europe, which either facilitate or impede the prosumer model, in addition to examining the necessary technological infrastructure. Key findings of this study highlight the potential of remote solar energy parks to significantly reduce the carbon emissions of buildings. This model is especially beneficial for structures where onsite solar energy solutions are impractical. It fosters greater inclusivity in adopting renewable energy, enabling a variety of stakeholders to participate in and benefit from clean energy production. However, the study identifies several major challenges, including regulatory restrictions, the need for infrastructure development, a shortage of developers, state contributions, public awareness, and the creation of a unified platform.

This research conducted investigations of buildings equipped with radiant systems and expert interviews in 2021–2022 with manufacturers and mechanical, electrical, and plumbing (MEP) engineers in Japan who had experience designing radiant heating and cooling systems for non‐residential buildings. In total, interviews were conducted with 56 respondents from 16 companies. Results from the building investigation showed that 69% of the identified buildings had radiant ceilings, and 30% had radiant floors. In terms of working fluid, 56% were water‐based, and 43% were air‐based. For the expert interview, 79% of all respondents answered that the use of radiant systems will continue to increase in the future. In total, 54% of all respondents answered that it has become easier to design radiant systems at present compared to the 2010s. Based on the results, knowledge gaps and challenges in the design of radiant systems were summarized in terms of design method, room temperature control, auxiliary systems, and their relevance to building decarbonization. [ABSTRACT FROM AUTHOR]

California requires all new residential buildings to meet near-net zero energy building (near-NZEB) targets in its building energy efficiency standards (Title 24) starting January 2020. For the first time, rooftop solar PV is required in new homes under three stories tall. While individual technologies are available for energy efficiency and renewable energy, significant challenges exist for scaling up NZEB homes across the State of California. This study presents a novel and holistic modeling and cost-effective analysis of new single-family homes in California to inform the design of cost-effective near-NZEB homes, as well as to guide future updates of Title 24. California's NZEB homes are defined using the time dependent valuation methodology to evaluate their cost-effectiveness. A comprehensive set of energy efficiency measures, solar PV, and battery storage are considered in the modeling and analysis as well as different net-metering policies for rooftop PV compensation rates for exported power. The BEopt tool with the EnergyPlus simulation engine is used to model and optimize, based on cost, the building designs for all-electric and mixed-fuel single-family homes across all 16 California climate zones. Results show that optimal designs of near-NZEB single-family homes have lower lifecycle costs for both all-electric and mixed-fuel cases in all California climate zones than the 2020 baseline code-compliant homes. Cost-optimal designed all-electric homes are comparable in lifecycle costs to mixed-fuel homes in most climate zones in part because no natural gas infrastructure is needed. For battery storage, electricity rates with a greater degree of time-dependence will improve cost-effectiveness of near-NZEB or full NZEB homes. These findings provide technical and investment insights into the scale up of cost-effective near-NZEB home design in California. The methodology and models can be adopted for other U.S. states or international cities to inform policy making and design of near-net zero energy residential buildings.

To achieve climate neutrality by 2050, decarbonizing the building sector is crucial, as it currently contributes 36 % of greenhouse gas emissions in Europe. Monitoring decarbonization progress is essential for evaluating our trajectory towards long-term goals, facilitating informed decision-making. However, monitoring this issue is currently unfeasible due to a lack of real data. Despite challenges in data gathering, directives like Infrastructure for Spatial Information in Europe (INSPIRE) and the Energy Performance of Buildings Directive (EPBD) promote open data accessibility. To overcome this barrier, this paper suggests using georeferencing and automated cross-referencing of open building data to obtain data to monitor progress towards decarbonization effectively. This approach materializes in the proposal of a national-scale Urban Building Energy Model (UBEM) for Spain, which leverages data from Energy Performance Certificates (EPC) and potentially Digital Building Logbooks (DBL) to enhance it. The study demonstrates the considerable potential of this approach, not only in characterizing the energy performance of Spanish buildings based on location, type, and age but also in estimating energy consumption, carbon dioxide emissions, monitoring renovation progress, assessing energy savings, and identifying energy-inefficient building segments. Finally, this study compares the information obtained using the proposed model with the set of progress indicators of the EPBD recast for the new national building renovation plans, concluding that the UBEM model manages to provide data to collect 29 of the progress indicators and, when combined with a DBL, it would be able to provide 59. This framework holds promise for replication in other MS, offering valuable insights into the decarbonization of the European building stock.

Abstract This research conducted investigations of buildings equipped with radiant systems and expert interviews in 2021–2022 with manufacturers and mechanical, electrical, and plumbing (MEP) engineers in Japan who had experience designing radiant heating and cooling systems for non‐residential buildings. In total, interviews were conducted with 56 respondents from 16 companies. Results from the building investigation showed that 69% of the identified buildings had radiant ceilings, and 30% had radiant floors. In terms of working fluid, 56% were water‐based, and 43% were air‐based. For the expert interview, 79% of all respondents answered that the use of radiant systems will continue to increase in the future. In total, 54% of all respondents answered that it has become easier to design radiant systems at present compared to the 2010s. Based on the results, knowledge gaps and challenges in the design of radiant systems were summarized in terms of design method, room temperature control, auxiliary systems, and their relevance to building decarbonization.

The building sector accounts for a significant proportion of global energy usage and carbon dioxide emissions. It is important to explore technological advances to curtail building energy usage to support the transition to a sustainable energy future. This study provides an overview of emerging and sustainable technologies and strategies that can assist in achieving building decarbonization. The main technologies reviewed include uncertainty-based design, renewable integration in buildings, thermal energy storage, heat pump technologies, thermal energy sharing, building retrofits, demand flexibility, data-driven modeling, improved control, and grid-buildings integrated control. The review results indicated that these emerging and sustainable technologies showed great potential in reducing building operating costs and carbon footprint. The synergy among these technologies is an important area that should be explored. An appropriate combination of these technologies can help achieve grid-responsive net-zero energy buildings, which is anticipated to be one of the best options to simultaneously reduce building emissions, energy consumption, and operating costs, as well as support dynamic supply conditions of the renewable energy-powered grids. However, to unlock the full potential of these technologies, collaborative efforts between different stakeholders are needed to facilitate their integration and deployment on a larger and wider scale. [ABSTRACT FROM AUTHOR]

The building sector is responsible for approximately 40% of global energy consumption and carbon emissions, making it a key area of focus in addressing the urgent global challenge of climate change and in achieving the 1.5-degree target. This study concentrated on building decarbonization, using bibliometric and network visualization analyses based on a dataset of 2494 publications retrieved from the Web of Science up to 25 June 2023. Findings revealed a rapid growth in publications, with China being the largest contributor (approximately 31%). Notably, the journals of Cleaner Production and Applied Energy emerged as the most influential journal in this field. Although leadership teams and authors have gained prominence, cross-national collaboration and communication among them remain limited. Furthermore, an analysis of keywords and co-citations revealed that the main research themes and hotspots encompass "energy", "life cycle assessment", "storage", and related "models" and decarbonization "strategies". As the field progresses, a clear trend toward multidisciplinary integration and diversified research directions and content was observed. Researchers can further concentrate their efforts on countries with historically limited research but substantial emissions, and enhance international collaboration and interdisciplinary integration. Overall, this study offers valuable insights for researchers and facilitates future investigations in the field of building decarbonization. [ABSTRACT FROM AUTHOR]

The significant share of the building sector in Greenhouse Gas (GHG) emission and final energy consumption makes it a significant target for decarbonization programs. Different standards and technological roadmaps propose several technical solutions to mitigate buildings’ climate change impact, such as improving existing and new buildings’ energy and environmental performance by utilizing Renewable Energy Sources (RES) and Energy Storage Systems (ESS). This study aims to examine and quantify the potential of two recommended solutions with a Life Cycle Assessment (LCA) approach, including Building-Integrated Photovoltaic (BIPV) and Thermal Energy Storage (TES) systems, to achieve the building decarbonization targets. Therefore, a residential building is analyzed under three different scenarios, and the CO2equivalent emission alongside the avoided carbon emission and Environmental Payback Period (EPBP) of each scenario are assessed and compared.The result shows that applying a coupled BIPV-TES system in a residential building equipped with electric heat pumps can reduce CO2 eq emission by 21.42% over 30 years of the building service life.

This data article relates to the paper "Review of the cost-optimal methodology implementation in Member States in compliance with the Energy Performance of Buildings Directive". Datasets linked with this article refer to the analysis of the latest national cost-optimal reports, providing an assessment of the implementation of the cost-optimal methodology, as established by the Energy Performance of Building Directive (EPBD). Based on latest national reports, the data provided a comprehensive update to the cost-optimal methodology implementation throughout Europe, which is currently lacking harmonization. Datasets allow an overall overview of the status of the cost-optimal methodology implementation in Europe with details on the calculations carried out (e.g., multi-stage, dynamic, macroeconomic, and financial perspectives, included energy uses, and full-cost approach). Data relate to the implemented methodology, reference buildings, assessed cost-optimal levels, energy performance, costs, and sensitivity analysis. Data also provide insight into energy consumption, efficiency measures for residential and non-residential buildings, nearly zero energy buildings (NZEBs) levels, and global costs. The reported data can be useful to quantify the cost-optimal levels for different building types, both residential (average cost-optimal level 80 kWh/m2y for new, 130 kWh/m2y for existing buildings) and non-residential buildings (140 kWh/m2y for new, 180 kWh/m2y for existing buildings). Data outline weak and strong points of the methodology, as well as future developments in the light of the methodology revision foreseen in 2026. The data support energy efficiency and energy policies related to buildings toward the EU building stock decarbonization goal within 2050. Datasets: Data directly related to this article are provided in the Supplementary Materials. Dataset License: CC-BY 4.0. [ABSTRACT FROM AUTHOR]

Building decarbonization strategy with Distributed renewable energy sources (DRES) is applied and extended worldwide for its climate change mitigation benefits, however, it generates debate regarding equity in sharing electric system operation costs. To analyze DRES effects on equity, it is conducted a case study, in which same residential consumer is evaluated in three different markets (Spain, Mexico, Colombia). We analyze not only electrical system technical variables, but we also include society’s economic, social, technological, and environmental characteristics. Next, energy, economic, and environmental benefits are obtained in each the three case studies, analyzing the impact of using DERS on equity to recover electric system operating costs. We also evaluate whether tariff mechanisms are equitable to motivate all consumers participation, as well as whether all consumers have equal opportunity for using DERS. We conclude that tariff mechanisms in Mexico and Colombia lead to inequity to recover market operating costs, favoring large consumers with high incomes. Furthermore, tariff mechanisms discourage the use of DERS by small and medium consumers due to economic, social, and technological aspects. In Spain, inequity arises due to increased difficulty for some consumers to use DERS, i.e., consumers in apartment buildings.

Retrofitting buildings to achieve improved levels of energy performance is a key strategy in the transition to a low-/net zero carbon future. In China, there has been an enormous growth in residential construction in recent decades in response to the country's economic development and population growth. However, although these buildings are structurally solid and have long functional life spans, most have very poor thermal performance. Therefore, they would be very suitable for energy retrofitting. Because of the variety of retrofitting options, it is important to review the retrofit measures, regulations and possible outcomes to find effective, long-term solutions that strike a balance between the energy saved, the carbon emitted and the financial costs over a building's lifetime. This paper reviews suitable retrofit measures for the hot summer–cold winter region of China, because this is an area with huge numbers of residential buildings that are suitable for energy retrofitting. The study explores the current conditions of targeted residential buildings, retrofit schemes, building regulations, and policy gaps towards achieving China's 2060 carbon neutrality goal. The review indicates that current mandatory building energy regulations in this region are not ambitious enough to achieve a significantly lower carbon future, and one-step deep Passivhaus retrofit schemes are recommended to achieve decarbonization goals. [ABSTRACT FROM AUTHOR]

The building sector accounts for a significant proportion of global energy usage and carbon dioxide emissions. It is important to explore technological advances to curtail building energy usage to support the transition to a sustainable energy future. This study provides an overview of emerging and sustainable technologies and strategies that can assist in achieving building decarbonization. The main technologies reviewed include uncertainty-based design, renewable integration in buildings, thermal energy storage, heat pump technologies, thermal energy sharing, building retrofits, demand flexibility, data-driven modeling, improved control, and grid-buildings integrated control. The review results indicated that these emerging and sustainable technologies showed great potential in reducing building operating costs and carbon footprint. The synergy among these technologies is an important area that should be explored. An appropriate combination of these technologies can help achieve grid-responsive net-zero energy buildings, which is anticipated to be one of the best options to simultaneously reduce building emissions, energy consumption, and operating costs, as well as support dynamic supply conditions of the renewable energy-powered grids. However, to unlock the full potential of these technologies, collaborative efforts between different stakeholders are needed to facilitate their integration and deployment on a larger and wider scale.

The building sector has a central role in achieving the European goals of a zero-emission and fully decarbonized stock by 2050. Among the provisions of the Energy Performance of Buildings Directive (EPBD) recast, the implementation of the cost-optimal methodology marked a novel approach in the establishment of minimum energy performance requirements for new and existing buildings. Member States must develop cost-optimal calculations every 5 years to verify and accordingly update the national requirements in force. This paper analyses the latest national cost-optimal reports, providing an updated assessment of the implementation of the cost-optimal methodology throughout Europe. It quantifies the progress in reaching cost-optimal levels in comparison with the previous assessment. It focuses on the conformity and plausibility of calculations in compliance with the policy framework. Furthermore, it evaluates the gap with national requirements, showing that the gap is higher than 15% only in a few Member States. The results provide a comprehensive review of the European progress towards cost-optimality in both the residential sector (average cost-optimal level 80 kWh/m2y for new, 130 kWh/m2y for existing buildings) and the non-residential sector (140 kWh/m2y for new, 180 kWh/m2y for existing buildings). An overall positive development can be inferred from the analysis of the Member States' progress in the methodology's implementation. The review also gives inputs for the cost-optimal methodology update foreseen for 2026 (e.g., cost-optimality for districts and historical buildings). The outcomes assume a crucial relevance for the ambitious energy efficiency targets established by Europe. [ABSTRACT FROM AUTHOR]

The building sector is responsible for approximately 40% of global energy consumption and carbon emissions, making it a key area of focus in addressing the urgent global challenge of climate change and in achieving the 1.5-degree target. This study concentrated on building decarbonization, using bibliometric and network visualization analyses based on a dataset of 2494 publications retrieved from the Web of Science up to 25 June 2023. Findings revealed a rapid growth in publications, with China being the largest contributor (approximately 31%). Notably, the journals of Cleaner Production and Applied Energy emerged as the most influential journal in this field. Although leadership teams and authors have gained prominence, cross-national collaboration and communication among them remain limited. Furthermore, an analysis of keywords and co-citations revealed that the main research themes and hotspots encompass “energy”, “life cycle assessment”, “storage”, and related “models” and decarbonization “strategies”. As the field progresses, a clear trend toward multidisciplinary integration and diversified research directions and content was observed. Researchers can further concentrate their efforts on countries with historically limited research but substantial emissions, and enhance international collaboration and interdisciplinary integration. Overall, this study offers valuable insights for researchers and facilitates future investigations in the field of building decarbonization.

[Display omitted] • Digital Twins (DT) are crucial in decarbonizing operating buildings (DOBs). • Scientometrics mapping revealed limited DT-based trajectories for DOBs. • SLR highlighted a lack of dynamic carbon criteria tailored for operating buildings. • Established the Dynamic Operational Carbon Reduction Guide (DOCReG). • Developed a DT-driven Decarbonization Framework for Operating Buildings (DT-DeFOB). Digital Twin (DT) technology presents a transformative approach to retrofitting practices, with the potential of decarbonizing operating buildings (DOBs) by up to 30 %. However, the fragmented nature of the extensive International Organization for Standardization (ISO) guidelines for carbon assessment and the complexity of DT systems, hinder practitioners' efforts to fully realize DT's potential in achieving the 2050 zero-emission target for operating buildings. This is evident in the continuous increase in operational carbon emissions from buildings, which reached an all-time high of 10 gigatonnes (GtCO 2) in 2022, and the mere 13 % global adoption rate of DT in building retrofitting. The aim of this review study is to develop a DT-driven Decarbonization Framework for Operating Buildings (DT-DeFOB) – a pathway for cohesive implementation of complex DT systems for DOBs. Using the inclusion and exclusion method, 243 relevant studies from 2018 to 2023 were selected for scientometrics mapping and systematic literature review (SLR). Furthermore, 20 ISO guidelines were selected for comprehensive document analysis. The findings indicated a growing trajectory in DT literature; however, a limited definitive trend in its effectiveness for DOB was evident. The SLR highlighted a lack of dynamic carbon criteria tailored for operating buildings, as well as a notable absence of a cohesive pathway for implementing multifaceted DT systems in DOBs. Hence, the critical components of DT-DeFOB were established, including a Dynamic Operational Carbon Reduction Guide (DOCReG) – a crucial component of DT-DeFOB developed via document analysis of the 20 selected ISO, Technology Interconnections, Human Engagement, Data Integration, and Lifecycle Management. DT-DeFOB provides a pioneering blueprint to help achieve the construction sector's 2050 net-zero carbon target, presenting a ground-breaking approach for impactful climate change mitigation strategies. [ABSTRACT FROM AUTHOR]

Building electrification is the movement to shift building operational energy use from fossil fuels toward electricity. It has been pursued mainly to reduce greenhouse gas (GHG) emissions from the building sector. We present here ten questions concerning building electrification and attempt to answer them in the context of the existing literature. Our questions span dimensions of policy, life cycle impacts on energy and environment, technological advances and challenges, indoor and outdoor air quality, health, economics, and social-behavioral factors. We find that while much of the extant research predicts that building electrification will provide benefits in terms of GHG emissions, pollutant exposures, and economic impacts, it remains limited to a narrow set of geographic regions and typically fails to capture the full extent of life cycle environmental impacts. Additionally, despite logical inferences for likely health benefits, we were unable to identify explicit studies of the health impacts of building electrification. We also find a common theme that, for building electrification to be successful in reducing GHG emissions, costs, and adverse grid impacts, it should be approached in parallel with increased building energy efficiency, grid renewable power, and smart grid infrastructure. Finally, we find that people hold strong opinions about fuel options in their homes, and the relationship between preferences and energy use is complicated. To shift people's beliefs around electrification, government-originating communications can highlight the benefits, but one must still account for heterogeneous household conditions. We conclude by suggesting key research areas needed to approach building electrification effectively and equitably. • Comprehensive LCAs are needed to understand building electrification impacts. • Electric grid resilience is a key research area for a successful transition. • People hold strong opinions about fuel options, especially for cooking in homes. • Social-behavioral research is needed to promote building electrification across communities. • Studies should consider broad geographic locations and diverse populations. [ABSTRACT FROM AUTHOR]

The building sector has a central role in achieving the European goals of a zero-emission and fully decarbonized stock by 2050. Among the provisions of the Energy Performance of Buildings Directive (EPBD) recast, the implementation of the cost-optimal methodology marked a novel approach in the establishment of minimum energy performance requirements for new and existing buildings. Member States must develop cost-optimal calculations every 5 years to verify and accordingly update the national requirements in force. This paper analyses the latest national cost-optimal reports, providing an updated assessment of the implementation of the cost-optimal methodology throughout Europe. It quantifies the progress in reaching cost-optimal levels in comparison with the previous assessment. It focuses on the conformity and plausibility of calculations in compliance with the policy framework. Furthermore, it evaluates the gap with national requirements, showing that the gap is higher than 15% only in a few Member States. The results provide a comprehensive review of the European progress towards cost-optimality in both the residential sector (average cost-optimal level 80 kWh/m2y for new, 130 kWh/m2y for existing buildings) and the non-residential sector (140 kWh/m2y for new, 180 kWh/m2y for existing buildings). An overall positive development can be inferred from the analysis of the Member States’ progress in the methodology’s implementation. The review also gives inputs for the cost-optimal methodology update foreseen for 2026 (e.g., cost-optimality for districts and historical buildings). The outcomes assume a crucial relevance for the ambitious energy efficiency targets established by Europe.

California requires all new residential buildings to meet near-net zero energy building (near-NZEB) targets in its building energy efficiency standards (Title 24) starting January 2020. For the first time, rooftop solar PV is required in new homes under three stories tall. While individual technologies are available for energy efficiency and renewable energy, significant challenges exist for scaling up NZEB homes across the State of California. This study presents a novel and holistic modeling and cost-effective analysis of new single-family homes in California to inform the design of cost-effective near-NZEB homes, as well as to guide future updates of Title 24. California's NZEB homes are defined using the time dependent valuation methodology to evaluate their cost-effectiveness. A comprehensive set of energy efficiency measures, solar PV, and battery storage are considered in the modeling and analysis as well as different net-metering policies for rooftop PV compensation rates for exported power. The BEopt tool with the EnergyPlus simulation engine is used to model and optimize, based on cost, the building designs for all-electric and mixed-fuel single-family homes across all 16 California climate zones. Results show that optimal designs of near-NZEB single-family homes have lower lifecycle costs for both all-electric and mixed-fuel cases in all California climate zones than the 2020 baseline code-compliant homes. Cost-optimal designed all-electric homes are comparable in lifecycle costs to mixed-fuel homes in most climate zones in part because no natural gas infrastructure is needed. For battery storage, electricity rates with a greater degree of time-dependence will improve cost-effectiveness of near-NZEB or full NZEB homes. These findings provide technical and investment insights into the scale up of cost-effective near-NZEB home design in California. The methodology and models can be adopted for other U.S. states or international cities to inform policy making and design of near-net zero energy residential buildings.

[Display omitted] • Natural gas heating has the lowest environmental impact but high economic cost. • Direct electric heating will cause more carbon emissions than soft coal heating. • Soft coal heating has the lowest economic cost but the worst user experience. • Biomass pellet heating and air source heat pump are suggested to be promoted. • Clean heating will reduce 260 Mt carbon dioxide emissions at 2020 level by 2030. Winter heating related carbon emissions is a significant contributor to climate change. Coupled with the soaring energy price, low-carbon transformation of residential heating is being carried out worldwide. China recently introduced a clean heating policy that could impact more than 100 million people living in the countryside. However, a series of issues, such as high economic cost, insufficient fuel supply, and poor heating effect, have seriously hindered its implementation. To help address these issues, this study employs life cycle assessment, equivalent annual cost, and multiple attribute decision-making to evaluate the environmental impact, economic cost, and user experience of the following eight typical rural heating methods: soft coal, hard coal, clean briquette, biomass pellet, natural gas, air conditioner, air source heat pump, and electric boiler. As a result of field tests, three optimal methods are recommended, i.e. biomass pellet, air source heat pump, and air conditioner, depending on the resources, climate, economy, and living habitat in different regions. Although using any one of the optimal heating methods will increase residents' heating costs by 30%-80%, the total environmental impact of rural winter heating will be reduced by 80% by 2030. And annual carbon dioxide emissions will be cut by 260 million tons in 2030 at 2020 levels. This is of great significance for China in its effort to control air pollution and fight climate change. Findings from the study will provide a useful reference for residential heating problems in other regions of China and the world. [ABSTRACT FROM AUTHOR]

Building energy codes—policies that traditionally set minimum requirements for buildings' energy use—have proven effective and efficient for building decarbonization. As researchers and policymakers increasingly recognize the limitations of prevalent building energy codes, discussion turns to innovative designs that could overcome such limitations. Therefore, this study aims to advance the implementation and development of innovative designs of building energy codes by exploring which challenges policymakers face when implementing these designs and, subsequently, by identifying how general code development might learn from these challenges. Evaluating the building energy codes of Denmark, France, England, Switzerland, and Sweden, we present six innovative designs of building energy codes and highlight how they advance building decarbonization by increasing energy efficiency and renewable energies, considering embodied energy, closing the performance gap, and accelerating retrofits. Based on 19 expert interviews with practitioners, regulators, and researchers, we identify real-world challenges that policymakers face when implementing innovative designs of building energy codes. Synthesizing these challenges across the countries, we derive six policy principles for advancing the development and implementation of building energy codes. Policymakers can thus learn valuable lessons from front-runners' experience and steer clear of avoidable pitfalls. • Current building energy codes fall short of advancing the required decarbonization of the building sector. • We present six innovative designs of building energy codes and assess how they overcome current design limitations. • Based on 19 in-depth expert interviews, we identify real-world challenges of implementing innovative building energy codes. • Synthesizing implementation challenges, we derive six design principles that support future code development. [ABSTRACT FROM AUTHOR]

Significantly reducing building sector greenhouse gas emissions is necessary to meet state and local climate stabilization goals. Initiatives to decarbonize home and building energy use are enabled by a new generation of advanced air source heat pumps (ASHPs) that provide efficient, comfortable heat even at low outdoor temperatures as well as highly efficient air conditioning in the summer. Coupled with thermal improvements to building envelopes and smart controls responsive to grid reliability needs, ASHPs are displacing the use of fossil fuels for comfort heating while providing a range of economic benefits. Investments to decarbonize buildings are most economical in natural market cycles of building construction, renovation and equipment replacement, and as part of community development initiatives to improve and preserve affordable housing. A growing number of state and local policies and programs are accelerating the rate of efficient electrification of home and building heating to replace fossil fuel heat with increasingly carbon-free renewable electricity. [ABSTRACT FROM AUTHOR]