The Evolution and Future Directions of Green Buildings Research: A Scientometric Analysis

Abstract

Economic development and urbanization naturally give rise to expanding demand for new buildings, whose construction and operation inevitably lead to significant increases in energy consumption and greenhouse gas emissions. To better conserve resources and protect the environment, technologies for green buildings have evolved significantly in the past two decades. In this study, a scientometric analysis of green buildings research from 2003 to 2023 was performed using CiteSpace. A total of 1986 articles retrieved from the Web of Science (WoS) core collection database were used as the data source for an in-depth analysis of research trends, hotspots, and future directions, showing changes in publication numbers, core journals, key countries, and institutions that have made remarkable contributions in this field. The results showed that the field of green buildings research is in a phase of rapid growth. The current research hotspots include the adoption of the green buildings paradigm, rating systems, energy performance, greenhouse gas emissions, indoor environmental quality, and green roofs/walls. Based on the keywords citation bursts and literature review, we believe that government promotion measures, use of renewable energy, integration with plants, and application of artificial intelligence (AI) in green buildings will be the most promising development directions in the future.

1. Introduction

With the continuous expansion of the global economy, urbanization and infrastructure development have led to an increase in energy consumption and greenhouse gas emissions in buildings, roads, etc. The construction activities involved require substantial energy input for materials production, transportation, and on-site operations including heating, cooling, and lighting during construction. Energy consumption also continues into the operational phase after building completion. According to UNEP’s data, the buildings and construction industry is one of the sectors with the largest energy footprint and a substantial contributor to carbon emissions worldwide. For example, in 2021, the buildings and construction industry contributed to approximately 37% of energy- and process-related CO₂ emissions and accounted for more than 34% of global energy consumption [1].

Green buildings, also known as sustainable or eco-friendly buildings, emerged as a response to the energy crisis in the 1970s and environmental challenges posed by traditional construction practices back in the 1980s. In 1990, the world’s first green building standard BREEAM was introduced by the United Kingdom, followed by the formation of the U.S. Green Building Council (USGBC) in 1993. Green buildings encompass various definitions, all rooted in the incorporation of environmentally friendly and resource-efficient practices throughout a building’s life-cycle. These measures aim to reduce adverse effects and enhance positive contributions a building can make to its natural surroundings and the well-being of its inhabitants [2,3]. For example, in terms of environmental impact, green buildings can significantly reduce energy consumption, carbon emissions, and resource depletion. According to USGBC, a 2014 UC Berkeley study [4] showed that buildings adhering to Leadership in Energy and Environmental Design (LEED) standards exhibited a remarkable 50% reduction in greenhouse gas emissions (GHGs) compared to conventionally constructed buildings. This reduction was attributed to a 48% decrease in GHGs resulting from water consumption, a 48% decrease due to solid waste management, and a 5% decrease in GHGs related to transportation. In terms of economic benefits, green buildings often result in lower operating costs, increased property value, and potential eligibility for government incentives. As shown by the Weerasinghe et al. [5] study, while the initial construction cost of a green industrial building is 29% higher compared to that of a traditional building, the operational and maintenance expenses for green buildings yield savings of 23% and 15%, respectively. This ultimately results in a 17% lower total cost over the building’s life-cycle (life-cycle cost, or LCC) compared to traditional buildings. Furthermore, with improved indoor air quality and natural lighting, green buildings also provide benefits to the occupants’ health and well-being. Based on the World Economic Forum’s analysis on Europe’s market in 2020 [6], a 20% shift in heating towards heat pump applications running on clean electricity would reduce GHGs by 9%. When coupled with smart solutions, EUR 3 billion in human health benefits could be saved from decreased air pollution between now and 2030. From all of the above, we can see that the importance of green buildings has extended beyond immediate economic gains, offering long-term sustainability benefits. They are thus increasingly receiving more attention from governments, owners, operators, as well as occupants of the buildings. With the signing of the Paris Agreement and the proposal of net-zero carbon emissions, many regions have adopted green building standards, making sustainable practices a legal requirement in some cases.

In the past few decades, the field of green buildings has developed quickly. It is therefore important to efficiently navigate the large collection of research work produced by scientists around the world. With the development of bibliometrics and scientific knowledge graphs, several software solutions were designed to help researchers in visualizing and analyzing scientific literature quickly and accurately. One such software is CiteSpace. By creating co-citation networks, co-authorship networks, keyword co-occurrence maps, etc. using advanced algorithms, CiteSpace is very helpful in uncovering hidden patterns, collaborations, and research hotspots, as well as generating a quick understanding about the dynamics and trends in a specific research field or academic domain. It is thus a great efficiency booster for researchers in deciding on research directions, identifying funding opportunities, as well as finding and establishing academic partnerships [7,8].

Based on the above, the purpose of this study was to use CiteSpace in combination with a literature review to provide a visual analysis on the development of green buildings research worldwide from the year 2003 to 2023. A total of 3317 publications on this topic were collected from the Web of Science (WoS) core collection database, out of which 1986 belonged to the “article” category, and were imported into CiteSpace 6.2.R4 Advanced for bibliometric analysis, including co-citation networks, keywords citation bursts analysis, etc. Development trends and research hotspots in this field were thus identified, and a detailed discussion was presented. Finally, promising development prospects, namely government promotion measures, use of renewable energy, integration with plants, and the application of artificial intelligence (AI) in green buildings, were proposed.

2. Research Data and Methods

2.1. Data Collection and Search Strategy

The Web of Science (WoS) core collection database was selected as the data source for this study, as it is the world’s leading citation database containing records of articles from the journals with the highest impact worldwide [9]. As the subscription from the authors’ institution only covered a subset of WoS core collection, the following indexes are included in this study: Science Citation Index Expanded (SCI-EXPANDED), 1984-present; Social Sciences Citation Index (SSCI), 1984-present; Arts and Humanities Citation Index (AHCI), 2012-present; Conference Proceedings Citation Index—Science (CPCI-S), 2001-present; Emerging Sources Citation Index (ESCI), 2019-present; Current Chemical Reactions (CCR-EXPANDED), 1985-present; and Index Chemicus (IC), 1993-present. To obtain publications on green buildings research, the following search term was used on 7 September 2023: Title = “green*” and “building*”. A total of 3390 publications including articles, proceeding papers, review papers, and others were retrieved. Based on the analysis of these articles, 2003 was found to be a point starting from which a stable growth trend in terms of publication numbers per year was observed. Therefore, the time span was set from 2003 to 2023 (around 20 years) for the second search. A total of 3317 papers were published on this topic during that period, among which, 1986 were categorized as “articles”, 171 as “review articles”, 996 as “proceeding papers”, and the remaining as “others”. Since the purpose of this study was to analyze the development trends and hotspots of the green buildings research, review articles with wide coverage and high citations may skew the analysis results for hotspots, etc. [10]; thus, only peer-reviewed articles were selected as the data source for the bibliometric analysis in this study [11,12].

2.2. Scientometric Analysis Methods

CiteSpace is a Java-based software that utilizes graphical analysis to detect and summarize transformations or trends within a given field. In this study, version 6.2.R4 Advanced was used, and different node types including “Institutions”, “Country”, “Keywords”, “Reference”, and “Cited journal” were selected separately based on the purpose of the analysis. Other parameters were set as follows: years per slice was set as 1, k in g-index was set as 25, Top N was set as 50, and Top N% was set as 10. Relation graphs of countries, institutions and cited journals were generated to highlight countries, institutions, and journals which made outstanding contributions in the field; meanwhile, co-citation network analysis and keywords citation bursts were generated to uncover the research hotspots. Co-citation network analysis of CiteSpace was built on the methods pioneered by Henry Small (1973) [13], but extended from a single-slide equivalent to multiple-slice network analysis. Burst detection in CiteSpace is based on Kleinberg’s algorithm. It aims to identify an entity that is associated with a numeric function, whose value surges at least within a short period of time during the time frame observed. For example, keywords with a burst of occurrences are indicators of hot topics [8,14,15].

3. Results and Discussions

3.1. Basic Characteristics

3.1.1. The Number of Published Articles

Based on the number of publications in a field, the development stage and trend of the field can be predicted. As can be seen from Figure 1, few publications on this topic were published from 1984 to 1994. However, according to Liu’s [16] research, this result may have some bias since the Web of Science core collection could have some limitations in old literature retrieval, thus influencing historical bibliometric analysis [16]. From 1995 to 2002, there was a small peak in article numbers on green buildings, with 11 related articles published in 2001, but the total number was still very small. Since 2003, the publications on green buildings increased rapidly. Since the data were collected in the middle of 2023, the year 2022 ended up being the one with the highest number of published articles, with a publication count of 300. The increase in the number of published articles reflects the fact that green buildings have continued to attract attention from a wide range of researchers and have become an international hotspot over this period. However, it is worth noting that the WoS core collection database used in this study included several indexes covering different time spans (based on the subscription of the authors’ institution); for example, AHCI: 2012-present, CPCI-S: 2001-present, ESCI: 2019-present, CCR-EXPANDED: 1985-present, and IC: 1993-present. In addition, it should also be recognized that the WoS database has a history of expanding its coverage to more journals [17]. Therefore, a sudden growth of publications at or after the specific year (for example, in 2013, 2020) may be partly due to the inclusion of new indexes [18,19].

3.1.2. The Core Cited Journals

In CiteSpace, “Cited journal” was selected as the node type to map the most cited journals in the field of green buildings. As shown in Figure 2, 975 nodes with 6151 rows and a density of 0.0134 were obtained. The color bar legend on the lower left corner represents the chronological order, with redder colors corresponding to closer years. The top five most cited journals are “Energy and Buildings”, “Renewable and Sustainable Energy Reviews”, “Journal of Cleaner Production”, “Sustainability-Basel” and “Sustainable Cities and Society” (as shown in

Table 1. Top 10 published articles by countries/institutions and co-citation by journals.

Rank	Countries	Number of Published Articles	Institutions	Number of Published Articles	Journals	Number of co-Citation Frequency
1	China	661	Hong Kong Polytechnic University	59	ENERG BUILDINGS	1043
2	United States	291	National University of Singapore	43	RENEW SUST ENERG REV	831
3	Australia	167	Tongji University	34	J CLEAN PROD	797
4	Malaysia	99	Chongqing University	34	SUSTAINABILITY-BASEL	560
5	United Kingdom (England)	95	Shenzhen University	31	SUSTAIN CITIES SOC	510
6	Italy	87	Egyptian Knowledge Bank (EKB)	27	APPL ENERG	469
7	Republic of Korea	76	Universiti Teknologi Malaysia	26	ENERG POLICY	463
8	Canada	69	Tianjin University	25	BUILD RES INF	459
9	India	59	University of Hong Kong	23	ENERGY	383
10	Singapore	56	Kwame Nkrumah University Science & TechnologyRecherche Agronomique (INRA)	22	RENEW ENERG	335

). Among them, “Energy Buildings” has been cited the most, totaling 1043 times, and thus has great influence and impact in the field of green buildings.

3.1.3. The Major Countries and Institutions

With “country” and “institution” each selected as the node type in CiteSpace, the generated network maps were analyzed, as shown in Figure 3 and Table 1.

(1) Country analysis

The 1986 publications in this study came from 94 countries, with 94 nodes and 555 connecting lines in the map, of which the top five countries in terms of number of publications are China (publication numbers = 661; betweenness centrality = 0.47), United States (291; 0.33), Australia (167; 0.09), Malaysia (99; 0.13), and United Kingdom (England) (95; 0.19). The number of publications in China is ahead of other countries, and the betweenness centrality is the highest, which is similar to the results from other publications [20,21]. For Malaysia, its publication numbers on green buildings ranked 4th among all the countries. This may be because it is one of the major energy consumers in Southeast Asia, and had a dramatic increase in energy consumption from 1994 to 2014 [22,23]. In particular, from 1990 to 2014, the energy consumption of buildings in Malaysia displayed a notable and consistent linear growth. Construction activities have had a significant impact on nearly 67.5% of Malaysia’s ecosystem. Consequently, there is a pressing need to advance the development of green and energy-efficient buildings in Malaysia to foster sustainable development [22].

According to the instructions on how to use CiteSpace provided by Dr. Chaomei Chen, betweenness centrality scores are standardized to the range of [0, 1]. A node with high betweenness centrality typically acts as a bridge connecting two or more sizable groups of nodes, with the node itself situated in between these groups. In CiteSpace, nodes with elevated betweenness centrality are distinguished by purple outlines, and the thickness of the purple outline corresponds to the strength of their betweenness centrality. As can be seen in Figure 3a, besides China, United States, Malaysia, and United Kingdom (England), there were two other countries with purple rings, namely Saudi Arabia (44, 0.11) and Belgium (12, 0.12), who had relatively high betweenness centrality (larger than 0.1), indicating their importance in connecting different countries for collaborations.

(2) Institutional analysis

From 2003 to 2023, a total of 462 institutions have participated in green buildings research, with a mapping density of 0.0058, indicating that the connection between institutions is not close, the degree of co-operation is low, and the institutions are all in their own systems. Among them, the top five institutions in terms of number of publications are Hong Kong Polytechnic University (59), National University of Singapore (43), Tongji University (34), Chongqing University (34), and Shenzhen University (31).

3.2. Research Hotspots

To better discern research hotspots in the field of green buildings, co-citation network and keywords citation bursts were generated using CiteSpace and the results are shown in Figure 4 (cluster view of network) and Figure 5 (time-based view of network) and Figure 6 (keyworks citation bursts), respectively. As can be seen from Figure 4, the network consisted of 894 nodes and 3535 lines, clustered in eight main categories: spatial distribution (0#), project management (1#), green buildings rating system (2#), Ghana (3#), greenhouse gas (4#), energy performance (5#), indoor environmental quality (6#), and green roof (7#). From the time-based view in Figure 5, we can also see other older or smaller clusters like bridge construction (#8), environmental indicators (#20), etc.; among them, life-cycle assessment (#19), green façade (#26), and multi-objective genetic algorithm (#14) clusters are relatively new and interesting. From the keywords citation bursts in Figure 6, we can observe that keywords related to energy including “embodied energy”, “energy consumption”, “energy conservation”, etc. are long-term concerns in the field of green buildings. In particular, “renewable energy” has received a lot of attention in the past two years. In addition, “life cycle assessment”, “model”, “plant” related to “green wall”, etc. are also worth paying attention to. Based on the above, research hotspots in the field of green buildings will be discussed from the following aspects.

3.2.1. Factors Affecting Green Buildings Adoption

In the “spatial distribution (0#)” cluster, most articles were focused on discussing the barriers [24], drivers [25,26], and promotion strategies [27,28], etc. on green buildings adoption. For example, Zou, et al. [29] showed that following the introduction of China’s Three-Star Green Building Rating System, there had been a significant surge in the number of certified green buildings, but their spatial distribution in the country was not even. The underlying determinants included local economic fundamentals, subsidy-based incentive policies, real estate market, energy efficiency, public awareness, etc. Feng, Chen, Shi, and Wei [28] found that offering government subsidies to construction firms could effectively encourage the advancement of green buildings. Conversely, providing subsidies directly to homebuyers may not necessarily have a positive impact on the purchase of green buildings. Therefore, the government should consider implementing alternative measures aimed at stimulating demand for green buildings among buyers. In Darko et al. [30]’s research, a quantitative model known as Partial Least Squares Structural Equation Modeling (PLS-SEM) was employed to assess the impact of various barriers, drivers, and promotion strategies on the adoption of Green Building Technologies (GBTs) in Ghana. Data for this analysis were collected through a questionnaire survey conducted among 43 professionals with experience in green building practices. The barriers examined included government-related barriers (GRB), encompassing factors such as the absence of government incentives, policies, and regulations. Other categories of barriers comprised human-related, knowledge and information-related, market-related, and cost and risk-related barriers. The drivers considered consisted of environment-related, company-related, economy and health-related, cost and energy-related, and industry-related drivers. Additionally, promotion strategies were examined, which included government regulations and standards (GRS), incentives and R&D support (IRDS), awareness and publicity programs (APP), education and information dissemination (EID), as well as awards and recognition (AR). The results of the analysis revealed that government-related barriers (GRB) had a significant negative impact on GBTs adoption. In contrast, company-related drivers demonstrated a significant positive influence on GBTs adoption. Furthermore, two promotion strategies, specifically “government regulations and standards” (GRS) and “incentives and R&D support” (IRDS), were identified as having significant positive effects on GBTs adoption.

3.2.2. Project Management

As can be seen from the time-based view of the network in Figure 5, although “project management” (1#) is the second largest cluster among all, most of the related publications occurred before 2015. Project management in green buildings involves the planning, coordination, and execution of construction projects with a strong focus on sustainability and environmental responsibility [31,32]. It plays an essential role in meeting the sustainability goals of reducing environmental impact, improving energy efficiency, conserving resources, and creating a healthy indoor environment for occupants throughout the entire life-cycle of green buildings [33,34].

In recent years, several new tools and methods have been adopted in green buildings project management; for example, life-cycle assessments (#19). A life-cycle assessment (LCA) is a theoretical evaluation method that has been widely used in green buildings assessments worldwide, which primarily target the environmental effects of a building over its entire life-cycle, encompassing stages such as raw material extraction, production, utilization, and disposal. It quantifies various environmental aspects such as energy consumption, greenhouse gas emissions, water usage, and resource depletion. This comprehensive assessment is often referred to as a Life-Cycle Assessment (LCA) or a cradle-to-grave analysis [35,36]. For example, in Gao et al. [37]’s study, life-cycle assessments and project management were combined, and the idea of green management was put forward. From the initial planning to the demolition of the construction project, through appropriate management means, the rational use of natural resources to reduce energy emissions, and the sustainable advancement of the project itself could be achieved. Green management mainly consists of three stages: (1) Green planning of project, (2) implementation of green management measures during operation, and (3) verification of green management results. Through the operation of the green management system, the building can not only maintain sustainable development throughout its life-cycle, but also provide a good living environment for occupants, improving their quality of life.

Life-cycle cost (LCC) calculation, on the other hand, focuses on evaluating the costs associated with a building throughout its life-cycle, including initial costs, operating and maintenance costs, end-of-life disposal costs, etc. LCA and LCC are interconnected because environmental impacts can have financial implications and vice versa. For example, a decision to use more energy-efficient materials and technologies in a building (LCA consideration) can reduce energy consumption and, consequently, operational costs (LCC consideration). The integration of LCA and LCC in green buildings management could first of all provide support for a multi-stage decision-making process: LCA holds significant value for decision-making at various stages of planning, structural design, and material selection. It not only assists in setting goals but also allows for the assimilation of insights from past cases at the conclusion of the process [38]. Secondly, this integration can also help with optimal solution identification and implementation, thereby reducing costs and emissions throughout the entire life-cycle of the building. Thirdly, the approach enhances the design solutions. Finally, both LCA and LCC can be employed to enhance and optimize construction projects and streamline the selection and development of product categories [39]. In summary, integrating the two complementary tools can lead to more sustainable and cost-effective decision-making, helping organizations and individuals make informed choices factoring in both environmental impact and financial considerations.

Besides the stated advantages, LCA studies have disadvantages as well. They generally require a significant amount of time, making it challenging to provide timely information for decision-making. The extended time frame can increase costs as well, potentially diminishing the appeal of these methods for the cost-conscious building sector [38]. However, by combining Building Information Modeling (BIM) and LCA, it is possible to reduce the amount of work required to obtain data at each stage of the building design, thereby mitigating the shortcomings of the time-consuming LCA evaluation process, and achieving a dynamic synergy between design and evaluation through the generation of models [40]. In addition, BIM-LCA research can assist designers in optimizing the design of sustainable building solutions, which take into account the environmental impact of building materials and operations [41].

3.2.3. Green Buildings Rating System

Notably, the green buildings rating system has garnered widespread attention from researchers [42,43,44,45]. Currently, one of the most authoritative green building certification systems is the BRE Environmental Assessment Method (BREEAM) in the United Kingdom, launched by the Building Research Establishment (BRE) in 1990. It is the oldest green building certification system in the world. BREEAM aims to provide sustainable solutions in the construction industry by improving energy consumption and reducing harmful emissions throughout the entire life-cycle of a building in a scientifically regulated manner. It has six levels of evaluation and assesses performance in nine areas: management, health and wellbeing, energy, transport, water, materials, waste, land use and ecology, and pollution. Another widely used certification system is the Leadership in Energy and Environmental Design (LEED) in the United States, developed by the U.S. Green Building Council (USGBC) in 1998. Additional evaluation systems include the Comprehensive Assessment System for Built Environment Efficiency (CASBEE) established in Japan in 2001, the Green Mark Certification Scheme launched by the Building and Construction Authority (BCA) in Singapore in 2005, and the Three-Star Green Building Evaluation Label (GBEL) released in China in 2006. Since there are already many articles providing details about these green building evaluation systems [46,47,48], they will not be discussed in detail here.

3.2.4. Energy Performance and Greenhouse Gas Emissions

With the signing of the Paris Agreement in 2015, the world is striving to achieve the goal of limiting global warming to well below 2 degrees Celsius above pre-industrial levels. Green buildings assume a pivotal role in confronting the challenges posed by climate change; they emphasize the reduction of energy consumption and greenhouse gas (GHG) emissions as essential strategies. As the world transitions toward a sustainable future, understanding the intricacies of energy performance in green buildings becomes paramount.

“Embodied energy”, as a keyword with high citation bursts related to energy performance in green buildings, refers to the energy consumed during the entire life-cycle of a building, from material extraction and manufacturing to construction and demolition [49]. Green buildings aim to minimize embodied energy by using sustainable materials, reducing transportation distances, and optimizing the energy required for construction processes [50]. Life-cycle assessment (LCA) methodologies help assess and mitigate embodied energy impacts. For example, Guan et al. [51] described an input–output based LCA model that, through sensitivity analysis, could identify the energy embedded in a building and discover important energy pathways. The amount of energy embodied in a building can also be quantified so that measures can be proposed to mitigate its impact. Alwan et al. [52] also suggested that combining LCA and BIM methods could expedite the identification of energy-critical regions, ultimately allowing for the analysis of embodied energy.

The concept of net-zero energy buildings (NZEBs) takes energy performance in green buildings to the next level. NZEBs are designed to generate an equivalent amount of energy to what they consume throughout the year, achieving a balance between energy production and consumption [53,54]. Key aspects of NZEBs [53] include: (1) Energy efficiency: NZEBs prioritize energy efficiency through passive design, high-performance insulation, and energy-efficient systems. (2) On-site renewable energy: These buildings often feature on-site renewable energy sources, such as solar panels or wind turbines, to generate electricity. (3) Energy storage: To manage energy fluctuations, NZEBs may incorporate energy storage solutions like batteries. (4) Monitoring and management: Real-time energy monitoring and management systems optimize energy use and production. While the significance of nearly zero energy buildings (NZEBs) are being recognized globally, their implementation is only progressing at a gradual pace. For instance, a study by Cielo and Subiantoro [54] examined the determinants impacting the adoption of NZEBs in New Zealand. The findings indicated that New Zealand’s climate is conducive to NZEBs, and the necessary technological and economic resources are accessible. Nonetheless, there is a need for targeted and purposeful legislation and policies to effectively promote and incentivize the broader acceptance of the NZEB concept within the country.

Energy performance in green buildings plays a critical role in reducing energy consumption and greenhouse gas emissions. Through energy-efficient designs, materials, and systems, green buildings minimize their environmental footprint. The integration of renewable energy sources, adherence to the Paris Agreement, and the concept of net-zero energy buildings further demonstrate the industry’s commitment to sustainable practices. Green buildings are instrumental in achieving global sustainability goals, contributing to a more environmentally friendly and energy-efficient built environment.

3.2.5. Indoor Environmental Quality (IEQ)

As quality of life continues to improve, indoor environmental quality (IEQ) and occupant satisfaction have gained increasing importance and have become key criteria in the evaluation of green buildings [3]. The quality of indoor environments and occupant satisfaction can be broadly divided into physical and non-physical factors. Physical factors encompass measurable parameters such as thermal comfort, indoor air quality, lighting, and acoustic environment. Conversely, non-physical factors encompass indoor qualities that are challenging to quantify using instruments, including spatial layout, privacy, furnishings, cleanliness, amenities, landscaping, and more [55].

In the past, physical parameters need to be measured through carts equipped with numerous sensors stationed on-site for a certain period of time [56,57], which proved to be time-consuming and labor-intensive for field professionals. In recent years, with the continuous advancement of science and technology, the construction industry has deepened its integration with big data and the Internet of Things (IoT), leading to smarter buildings and more convenient data collection methods for IEQ. For example, physical parameters can be collected through a single integrated sensor wirelessly connected to a cloud server for data reception and analysis [3]. These sensors not only provide remote access to required data but are also simpler to deploy and less labor-intensive to operate than their predecessors. SAMBA, a low-cost desktop device developed by Parkinson et al. [58] is one example. Other similar devices include the IEQ computer developed by Geng, Ji, Wang, Lin, and Zhu [3], which is integrated with sensors capable of detecting five fundamental parameters: temperature, humidity, irradiance, carbon dioxide levels, and sound pressure, for the goal of objectively analyzing indoor environmental quality.

Optimizing the IEQ can lead to increasing happiness and satisfaction among occupants, as numerous studies have demonstrated. For example, Lin et al. [59] conducted an investigation into IEQ and building serviceability satisfaction using SPSS statistical software. This involved the amalgamation of diverse environmental thermal conditions and work performance within the room. IEQ was analyzed by creating box plots representing occupant satisfaction from different distributions, and a comparison was made between occupant satisfaction in normal and green buildings using the median values from the box plots. The study’s results revealed that the median satisfaction levels for all IEQ aspects were higher in green buildings compared to normal ones. Similarly, Liang et al. [60] did a comparative analysis of three buildings certified under Taiwan’s Ecological Energy, Waste, and Health (EEWH) system and two non-certified buildings. It was concluded that satisfaction with IEQ was notably higher in the certified buildings compared to the non-certified ones. These findings underscored the close relationship between indoor environmental quality and green buildings.

3.2.6. Green Roof/Wall

The combination of buildings with green plants, for example, green roofs, green walls, green facades, etc., has received significant attention from researchers, designers, and constructors in recent years, reflecting the innate need and desire to have living nature in our surroundings.

A green roof, also known as an eco-roof or rooftop garden, is a vegetative layer grown on top of a building roof [61]. It typically contains several parts [62]: First is the vegetation itself, then the growth substrate. The substrate is not only pivotal for vegetation growth, but also affects water quality, peak flow rates, thermal efficiency, and acoustic insulation [63,64]. The choosing of proper substrate should consider its load on buildings, as well as local conditions and weather [65]. The third component is the filter fabric. The filter layer plays a crucial role in preventing the growth substrate from entering the drainage layer and blocking any plant fragments or small soil particles from obstructing the underlying drainage system. Geotextile fabrics are commonly employed as filtration layers in green roofs [66]. Drainage materials are important as well. The drainage layer is fundamental in green roof construction and can significantly influence its success. It helps maintain a balance between air and water. The type of drainage layer chosen can impact construction costs, vegetation selection, and the scale of the roof project [65]. The last critical piece is the root barrier; green roofs have a waterproofing layer which directly affects whether occupants experience leaks. Roof leaks are generally considered green roof failures, and if a leak occurs on an established green roof, all layers must be removed to locate the source of the leak. The choice of waterproofing material depends on the type of green roof, cost, availability, and expected lifespan. Root barriers safeguard the roof structure from damage caused by plant root systems [63].

Building green roofs can yield various benefits, including reducing energy consumption levels, mitigating urban heat islands, addressing air pollution, enhancing urban air quality, improving the quality of water runoff and stormwater management, mitigating noise pollution, and promoting biodiversity [61]. For example, in a comparative analysis of exposed roofs and green roofs conducted by Theodosiou et al. [67] under a typical Mediterranean climate, green roofs exhibited different thermal behaviors in different seasons. During the winter season, the average temperature values between exposed roofs and green roofs did not differ significantly. However, during summer seasons, green roofs show substantial thermal benefits. Green roofs can also reduce the risk of flooding by retaining water on the roof or decreasing peak flow rates [68]. As rainwater passes through a green roof, some of it is captured and absorbed by the substrate or the pores between the substrates. Most of this water is taken up by the vegetation; some is stored in the plant tissues, or released back into the atmosphere through plant respiration. The remaining water enters the filtration layer and eventually flows away through the drainage layer. In simulation experiments involving rainfall carrying heavy metal ions, the growth substrate demonstrates an ability to absorb these ions such as Cu, Cr, Cd, Ni, Pb, Zn, etc., thereby improving the quality of runoff [65]. Green roofs can also act as barriers between indoor and outdoor spaces, mitigating urban noise pollution stemming from road, rail, and air traffic [64,69,70]. A comparison between green roofs and bare roofs revealed that green roofs were more aesthetically pleasing and provide a sense of comfort. Additionally, green roofs can help mitigate the loss of biodiversity resulting from urban development [65].

With the advantages of green roofs, some emerging technologies have been developed to further enhance their benefits. For example, Mousavi et al. [71] described a methodology for integrating green roofs with intelligent systems at the design stage. This involves integrating software, such as machine learning and design generators, for collecting and analyzing parameters for optimal energy savings and improved thermal comfort [71]. Mazzeo et al. [72] employed artificial intelligence to analyze different parameters of green roofs to generate simulations. The green roof parameters were analyzed through AI, resulting in a simulation database that serves as a valuable tool for assessing the thermal impact of green roofs and reducing the heat island effect. Alonso-Marroquin and Qadir [73] conducted research on the double-roof system consisting of photovoltaic panels and green roofs with the goal of saving energy and reducing emissions. It was concluded that this system offered superior benefits compared to ordinary green roofs in multiple aspects, making it a worthy candidate for future construction projects.

In addition to green roofs, there are other similar applications such as green walls, green facades, etc. Green walls, also known by several other names including living walls or vertical gardens, are constructions with soil or growing medium covering their surface or volume, typically penetrated by plant roots. In contrast, green facades consist of vertical trellises or framework structures that support plants with their branches rooted in the ground, containers at the base of the framework, or floating containers attached at regular intervals to the facade frame. With ongoing urbanization, the availability of green space and vegetation in cities is rapidly declining. However, green wall design can replace the reduced green space and alleviate the impact of the heat island effect. Additionally, green walls have a certain thermal effect which can result in decreased energy usage and provide sound insulation for residents, improving their overall living experience. Currently, green walls have been extensively constructed. Korol and Shushunova [74] carried out a comparative analysis of technologies and options for implementing green walls. The life-cycle approach emerged as the most feasible option for the development of such systems. This study would aid future researchers in the field of green construction, whilst also providing a point of reference for the green building industry, leading to an environment that can be more energy efficient. Wilkinson et al. [75] scrutinized the issues associated with green walls and investigated the potential of combining Wallbot and green walls, complemented by smart technologies, to tackle the challenges posed by fire risk detection and perception. This innovative approach is expected to gain popularity and drive development in the field in the foreseeable future.

3.3. Directions for Further Research

Currently, green buildings development is experiencing rapid growth. As can be seen from Figure 6, 21 keywords with strong citation bursts were analyzed by CiteSpace, which is a direct reflection of how much attention a particular area is receiving during a period of time [8,14,15]. For example, in most recent years, keywords of “policy”, “energy conservation”, “renewable energy”, “plant”, “industry”, etc. have high popularity. Combining these analysis results with the literature review, four research directions were proposed. Multiple factors were considered in formulating our proposal, including the potential social/commercial impact, the possibility of making novel discoveries, and finally practicality of the potential research outcome. Although Artificial Intelligence (AI) did not appear as a keyword with strong citation burst, it has been receiving attention in all walks of life, and impacting products and services in many domains; thus, it was also proposed as a further research direction.

3.3.1. Introducing Government Promotion Measures

In the future development of green buildings, government agencies will play a pivotal role in promoting the industry. Adequate and consistent government regulations and legislation can effectively mitigate the negative impacts on companies in the green buildings sector due to legal changes [76,77]. Li et al. [78] emphasized that official regulation and supervision are the most effective methods in driving the construction industry toward green buildings practices. Passive attitudes of buyers towards green buildings and insufficient subsidies hinder their active selection. Consequently, in order to sustain the development of such buildings, governmental interventions are deemed necessary [28]. It can also be seen from Figure 6 that the keyword “policy” started appearing in the literature from the year 2013, and persisted until the present day, with a very strong burst between 2017 and 2019. In contrast with other keywords with strong bursts recently, it stands out as one that is not directly linked to technology and engineering practices. However, it has a universal ramification on the adoption of technology as pointed out by several articles [24,25,26,27,28]. Governmental promotion is therefore believed to be an important aspect worthy of more attention from the research community.

3.3.2. Use of Renewable Energy

Incorporating renewable energy sources in green buildings directly supports the Paris Agreement’s aim to transition to a low-carbon economy. These sources include: (1) Solar Panels: Photovoltaic (PV) solar panels produce electricity from sunlight, which can be used on-site or fed back into the grid, like NZEBs [79]. (2) Wind Turbines: In areas with sufficient wind resources, wind turbines can generate clean, renewable energy [80]. (3) Geothermal Systems: Ground-source heat pumps utilize the Earth’s consistent temperature to provide efficient heating and cooling [81]. (4) Biomass: Biomass systems convert organic waste into energy, reducing reliance on fossil fuels [82]. This is a technological field which is currently undergoing a lot of development, as can be seen from Figure 6, where the citation burst for the keyword “renewable energy” is still not over. Renewable energy research can also lead to numerous commercial opportunities as advancements in this fields can directly lead to real cost savings and efficiency improvements, especially when complementary governmental incentives are in place. Based on the existing research hotspot, as revealed by the scientometric analysis, and the application potential, renewable energy was seen as one of the most promising research directions in the near future.

3.3.3. Better Integration with Plants

Nowadays, many cities recognize the significance of combining architecture with vegetation, and there is a possibility of incorporating green plants in both horizontal and vertical positions in buildings. With the safety aspect of greenery in buildings studied extensively, it has been recommended that the construction of green vegetation necessitates additional safety systems and their related maintenance. However, self-growing connections offer an innovative and safe alternative to cages for falling plants. As such, this concept can develop stronger connections between plants and buildings, making ways for more green buildings in the future [83]. For example, Lewandowski, et al. [84] investigated building materials’ physio-chemical properties which can enhance compatibility with vegetation. It is worth noting that the concept of integration with plants is one with a relatively short history. In Figure 6, the keyword “plant” only started appearing in 2020, and there is still a lot of room for exploration and many discoveries to be made. It is therefore one of those fields where it is easier for researchers to demonstrate a higher level of novelty and make potentially high-impact contributions.

3.3.4. Application of Artificial Intelligence (AI)

As technology continues to advance, big data methods and intelligent algorithms (AI) are gaining popularity. There is a clear trend towards combining AI with green buildings practices. AI-powered buildings aim to optimize their operation throughout their life-cycles. These smart buildings are equipped with various instruments and sensors that collect extensive data, including indoor air quality, energy consumption, and water usage. By analyzing these data, it becomes possible to optimize building operations and enhance indoor environmental quality [85]. Wu [86] applied AI technology to a green hospital in a sustainable city, resulting in an improved hospital environment as well as operation efficiency. Although AI-related keywords have not seen any citation bursts yet, various forms of building automation can already be found in many studies [3]. Additionally, combining AI with building management has been receiving attention in the business world [87]. It can be expected that if progress with real-world implications can be made, there would be feasible pathways for research results to quickly find applications in various practical use cases.

4. Conclusions

In this study, a total of 1986 articles about green buildings was obtained from the WoS core collection database and imported into CiteSpace 6.2.R4 Advanced for co-citation reference and keyword citation burst analysis. Using this method, the latest research trends, hotspots, future directions of the field, as well as core journals, key countries, and institutions in the area were thoroughly discussed. In particular, the findings in this study demonstrated that green buildings research has grown swiftly in recent years and has emerged as a focal point of global interest. In terms of the main contributors in the field, China and the US have published the highest number of papers, with Malaysia also making notable contributions, having the fourth highest number of publications. Moreover, China’s active collaboration with other countries in this domain is also signified by its highest intermediate centrality. The identification of research hotspots in the field was conducted using co-citation analysis, where several large clusters were recognized and discussed in detail, including the adoption of green buildings, project management, green building evaluation systems, energy performance, greenhouse gas emissions, indoor environment quality, and green roof/wall. It can be observed that each hotspot is trending towards lower energy consumption and improved indoor environments, thereby facilitating a better living experience for occupants.

Looking into the future, the incorporation of artificial intelligence into the development of green buildings is expected to increase, resulting in the creation of smarter buildings. Furthermore, novel construction materials will enhance the indoor environment’s quality, improve compatibility with greenery, and ultimately promote healthier living conditions. Additionally, robust government backing is crucial for the proliferation of green building technologies.

This study also has several limitations. In terms of the data source, although the authors’ institution has subscribed to most of the indexes in the WoS core collection, Book Citation Index-Science (BKCI-S) and Book Citation Index-Social Sciences and Humanities (BKCI-SSH) are not included [88]. Furthermore, the information provided by the WoS core collection in general may not be exhaustive and the most up-to-date, despite it being acknowledged as the world’s leading citation database with extensive coverage, consistent and high-quality data. In Liu’s [89] research for instance, it is recognized that Scopus, a newer database launched in 2004, has been gaining traction and is becoming an alternative source of information for analysis. WoS also suffers from the lack of coverage for non-English publications in certain research domains [90]. Therefore, there might be small biases in the obtained results in our study, which solely rely on WoS. However, due to the large timespan and number of publications this study covers, the identified trends and prospects should not be skewed. When compared to other studies targeting related fields [21,91,92], this work has provided the most up-to-date analysis of the general field of green buildings, where all aspects of the research fields are being included. It is also worth noting that the development prospects put forth in this work reflect the authors’ understanding of the current technological and policy trends.

In conclusion, our study highlighted the dynamic evolution of green buildings and identified the potential area for continued advancement, which would ultimately lead to more sustainable and comfortable living spaces.