1. Introduction
The construction industry plays an important role in the impact of various industries on the natural environment. It is a typical industry with high energy and resource consumption and high pollution [
1]. Studies show that the energy consumption of existing buildings is approximately 30% of the cumulative energy consumption, and the use of energy may lead to nearly 30% of carbon emissions [
2]. In the entire life cycle of a building, 80% of building energy consumption occurs in the actual use stage rather than the construction stage [
3]. Therefore, a reasonable solution to reduce global greenhouse gas emissions and total energy consumption is the green retrofitting of existing buildings. As an inevitable requirement of the deep development of green buildings, green retrofitting has undergone minimal development in China. As of 2017, China’s existing construction area has exceeded 60 billion square metres, and it continues to expand by 1.6 billion to 2 billion square metres every year [
4]. However, the green building area only measures 460 million square meters, which is less than 1% of the total construction area; moreover, the existing building area open to green retrofitting is only approximately 3.07 million square metres [
5]. Therefore, retrofitting in this context is suitable. At present, most existing buildings suffer from issues such as functional degradation, high energy consumption, high emissions and large negative environmental impact. Reducing the impact of existing buildings on the environment through green retrofitting is urgent [
6,
7]. The service life of most existing buildings is 50–100 years [
7]. On the one hand, the demolition of existing nongreen buildings not only involves a huge waste of resources and energy but also causes secondary pollution and damage to the ecological environment [
8]. On the other hand, if nongreen buildings continue to be used, their negative impact on the environment will continue [
9]. Therefore, the green retrofitting of existing buildings is more resource efficient and sustainable than developing new green buildings [
10]. Through retrofitting, demolition and reconstruction can be avoided [
11], thereby reducing the generation of construction waste [
12] and the consumption of materials and other resources to promote the sustainable development of the society.
Sustainable development entered the world stage after the United Nations published a report titled ‘World Commission on Environment and Development’ (WCED). The Sustainable Development Goals (SDGs), otherwise known as the global goals, are a universal call to action to end poverty, protect the planet, and ensure that all people enjoy peace and prosperity. SDGs need to satisfy economic development while taking care not to impair the benefits of the next generation. SDGs include three dimensions, namely, economic, environmental and social [
13,
14]. The green retrofitting of existing residential buildings echoes the principles of sustainable development defined in the WCED. Retrofitting is the modification or alteration of an existing process, facility or structure and is thus contrary to a complete replacement [
15]. For example, it may involve the addition, deletion, rearrangement, or replacement of one or more parts of a facility [
16]. Scholars agree that green retrofitting should stick to the three bottom lines of the economy, the environment, and social harmony [
17]. Furthermore, the green retrofitting of existing housing is a type of building retrofitting mode which accords with the core concept of sustainable development. It is based on original building data that cover the aspects of energy saving, water saving, and indoor and outdoor environment and structural safety and were obtained to satisfy the standard of green building, save resources and energy, protect the environment to the greatest extent, and provide a healthy, safe, and comfortable living environment for occupants. The green retrofitting of existing buildings is different from that of ordinary green buildings. It is carried out on the basis of the original buildings. It generally includes the improvement of the performance of air-conditioning systems [
18], upgrade of lighting systems [
19], implementation of lighting control [
20], thermal insulation of roof systems [
21,
22], and retrofitting of wall and mechanical ventilation systems [
23]. The green retrofitting of existing buildings significantly reduces the energy consumption and cost of existing buildings and provides a healthy, suitable, and efficient space for occupants. These features are important in prolonging the life cycle of buildings [
24], saving resources, protecting the environment, and resolving the bottleneck of energy resource constraints [
25]. Moreover, green retrofitting is a crucial way to quicken the implementation of strategies for green city development and the construction of energy-saving and environmentally friendly cities. Green retrofitting is beneficial to sustainable development and urban renewal.
With the release and implementation of GB/T51141-2015, the assessment standard for the green retrofitting of existing buildings, marks the official shift from ‘new construction’ to ‘retrofit’ in the development of green buildings in China. Existing buildings are retrofitted and upgraded from ‘energy-saving retrofitting’ to ‘green retrofitting’. However, the green retrofitting of existing buildings is still in the awkward situation of ‘pushing but not moving’. This condition is due to the fundamental determining power of micro subjects. As the main body of the green retrofitting of existing buildings, residents directly impact the promotion of the green retrofitting of existing buildings. Only if residents have subjective will and participate in the upgrading can the green retrofitting of existing buildings be effectively promoted. However, the determinants that significantly affect residents’ intention toward green retrofitting and the relationship between these determinants and residents’ intention toward green retrofitting remain unclear. In addition, previous studies on the green retrofitting of existing residential buildings mainly focused on technical retrofitting, evaluation methods [
26,
27,
28], energy efficiency improvement [
29,
30,
31], cost and benefit calculation of retrofitting [
32,
33], and retrofitting risks [
34,
35]. They generally ignored the intention of the subject to participate at the micro level, thereby leading to the poor effectiveness of the intervention of macro policies. Lorraine Murphy pointed out that countries should formulate green retrofitting strategies in accordance with their own national conditions and regional characteristics [
36]. China has a large number and a wide range of existing residential buildings. Different regions have their own unique building systems, living habits, building types and regional cultural characteristics. However, at present, no scholar has explored the differences in the intention toward green retrofitting between the eastern and western regions of China and different groups (educational level, income level, age, and occupation). The differences in the intention toward green retrofitting amongst these groups should be studied to properly select and cultivate market segmentation and accurately identify the target market. Therefore, exploring a set of research models that are suitable for Chinese residents is important in the study of residents’ intention toward the green retrofitting of existing residential buildings in the unique context of China. The investigation using such models should help resolve the problem of the green retrofitting of many existing buildings and old ‘stock’ buildings that have been generated over time in China. This study focuses on urban residential buildings because residential buildings account for the vast majority of existing buildings.
To fill the research gap, this study explores the main factors that affect the intention of Chinese residents toward the green retrofitting of existing residential buildings. This work also evaluates whether significant differences exist between these main factors and the intention toward green retrofitting of residents in eastern and western China, as well as amongst different groups. The three reasons for China’s status as an effective research laboratory are as follows. Firstly, China is the largest construction market in the world. With a large stock of existing buildings, the green retrofitting of existing buildings should significantly reduce the country’s total energy consumption and greenhouse gas emissions. In this way, China may contribute to world sustainable development. Therefore, the results of the study can satisfy the urgent needs of the Chinese government to vigorously promote the green retrofitting of existing buildings. Second, China is the largest developing country in the world. The results of this study can be used as a reference for other developing countries to carry out the green retrofitting of existing housing. Third, most previous studies focused on green retrofitting technology without considering the subjective intention of residents toward retrofitting. Moreover, no scholar has studied the significant differences in the intention toward green retrofitting amongst residents in the eastern and western regions of China, as well as amongst different groups. In this work, these differences are analysed with multigroup structural equation modelling (SEM).
The remainder of this paper is organised as follows.
Section 2 outlines the literature review and hypothesis development.
Section 3 presents the methodology, data collection, and data processing.
Section 4 provides the results, including model testing, effect analysis, and multigroup analysis.
Section 5 discusses the critical factors and corresponding strategies.
Section 6 presents the summary.
5. Discussion
PFs (0.645) had the greatest impact on green RI for existing residential buildings, followed by GRC (0.354), behavioural attitude (0.350), and SNs (0.230). PBC (0.160) had the smallest impact, but GRC was confirmed to have no direct and significant impact on green RI.
5.1. Effects of Behavioural Attitude, Subjective Norms and Perceived Behavioural Control on Green Retrofitting Intention
Behavioural attitude, SNs, and PBC in relation to green retrofitting showed direct and significant effects on green RI. The results validate the importance of behavioural attitude, SNs, and PBC in predicting residents’ green RI. This conclusion is consistent with most research results, such as those on street food supply [
76], food safety [
77], green product purchase [
66], and green consumption [
49]. Only a few studies have reached inconsistent conclusions. For example, Zhang’s research showed that PBC exerts no significant effect on purchase intention toward green building [
51]. We consider two reasons behind the difference in results. On the one hand, consumers have the autonomy to decide whether or not to purchase products or services. Zhang’s research used young Chinese consumers as the research samples. Whether this group is able to purchase green buildings is largely determined by their parents and not by the young consumers themselves. By contrast, the sample in the current study can decide whether or not to carry out the green retrofitting of existing residential buildings. On the other hand, a large gap exists in the cost between purchase and retrofitting. Purchasing new green buildings requires large funding, whereas the green retrofitting of existing residential buildings entails a relatively low cost [
78]. Residents who lack large consumption funds can decide whether or not to carry out green retrofitting. These factors contribute to the differences in the results of the current work and those of other studies.
5.2. Impact of Policy Factors on Green Retrofitting Intention
PFs showed the greatest impact on green RI. The promotion and application of the green retrofitting of existing residential buildings in society cannot be separated from the vigorous guidance and policy encouragement of the government. The green retrofitting of existing residential buildings is still in its infancy in China. Through the government’s incentive policy, most residents can obtain additional economic income to compensate for the cost of green retrofitting. Hence, such policy greatly improves the enthusiasm of residents toward green retrofitting. This result accords with the findings of Mickaityte [
79], Baek [
80], and other scholars. The government’s financial support, loan preferential policies, and tax preferential policies are important driving forces for the green retrofitting of buildings. Therefore, to achieve and promote the large-scale retrofitting of existing residential buildings, the Chinese government should formulate a combination of economic incentive policies and actively guide residents in carrying out the green retrofitting of existing residential buildings. In this study, PFs were mainly measured by five variables: economic subsidies, tax preferences, loan interest rate discount, technical program support for green retrofitting, and direct reward for retrofitting behaviour. The results of the model operation suggest that the top three influencing factors of government policy are as follows: economic subsidies, whose standard factor load and average value were 0.91 and 5.88, respectively; loan interest rate discount, whose standard factor load and average value were 0.87 and 4.79, respectively; and direct reward for retrofitting behaviour, whose standard factor load and average value were 0.72 and 5.03, respectively. Most residents attach great importance to direct government subsidies, loan interest rate discount, and direct rewards, probably because the green retrofitting of residential buildings in China is still in the initial stage of exploration and only a few incentives, such as subsidies for green retrofitting at the government level, are available. These incentives are insignificant relative to the cost of green retrofitting. Government financial subsidies seem to be the most attractive to the majority of residents. For example, the local government of Hong Kong has subsidised residents to implement green residential retrofitting, thereby proving the suitability of government-led green retrofitting of existing residential buildings [
80]. This incentive has significantly increased the intention of residents toward green retrofitting. This conclusion echoes similar findings by Bon–Gang Hwang [
81]. However, because of China’s large number of existing residential buildings, all types of subsidies inevitably bring serious financial burden to the government. The government alone cannot make up for the large financial gap related to green retrofitting. Therefore, using a market mechanism to promote green retrofitting whilst reducing financial burden is necessary. This requirement may be met with a tripartite cooperation model based on government, social capital and residents. Moreover, integrating tripartite objectives and social, economic and environmental benefits is a sensible option. Property management and heating companies are the best partners. Property management companies provide economic subsidies for potential residents who are inclined to carry out green retrofitting. In the operation stage after green retrofitting, these subsidies can be obtained by reducing the maintenance costs of daily equipment and facilities in the community. In summary, financing via public–private partnership can realise the effective combination of social and government capital and thereby make enterprises the main body of retrofitting investment. By realising the cost sharing and benefit sharing of financial funds by enterprises and residents involved in green retrofitting projects, the market-oriented operation of green retrofitting may be promoted.
5.3. Impact of Green Retrofit Cognition on Green Retrofitting Intention
Beyond the expectation of this study, GRC had no direct and significant impact on green RI. This study did not confirm the view of Bartels [
82] and Tan [
83]. We speculate that the reason is mainly due to the different properties of the research objects. The aforementioned authors studied conventional household products with low purchase cost and repeatability. However, green retrofitting entails substantial costs and is disposable. For the purchase of expensive products, we believe that consumers are rational. Thus, they will not have the intention to carry out green retrofitting because they have a certain degree of awareness. They will also consider whether or not they have the corresponding economic strength and other factors. Although the perception of green retrofitting had no direct significant impact on green RI, it had an indirect impact on green RI through behavioural attitude and SNs, which are only second to government PFs. Hence, GRC plays a crucial role in promoting residents’ intention to carry out green retrofitting. GRC was mainly measured by seven variables, namely, conformity to sustainable development, rental and sale value, retrofitting technology, retrofitting cost, residential performance after retrofitting, retrofitting convenience, and operating cost. The top three cognitive effects on green retrofitting were as follows: retrofitting cost, whose standardised factor load was 0.94; operating cost, whose standardised factor load was 0.85; and improvement of rental and sale value, whose standardised factor load was 0.79.
The results suggest that most residents attach great importance to the cost of green retrofitting, the improvement of housing value, and the subsequent operating cost. In essence, economic considerations remain the primary concern of residents. This research also confirms the view of Mark Dowson [
84] and Jagarajan [
85]. The average value of GRC in the current work was 4.32, which indicated that most of the residents had a low level of GRC, similar to previous research conclusions [
86]. Therefore, if the Chinese government aims to succeed in the green retrofitting of large and extensive stock housing, then it must publicise relevant information on green retrofitting through necessary measures to make residents agree with green retrofitting. With an improved awareness of green retrofitting of existing buildings, residents can directly and effectively understand the connotation and advantages of green retrofitting. Residents may also realise that existing residential buildings not only have high energy consumption and high cost but also cause serious pollution, which adversely affects the environment and people’s physical and mental health.
After retrofitting, existing residential buildings may be recognised as green, environmentally friendly, and energy saving. The effect is strengthened through intuitive data comparison. For example, pilot projects involving small-scale green retrofitting may be conducted, and typical demonstration projects involving the green retrofitting of residential buildings may be developed. In addition, the living experience of residents after green retrofitting, the comparison of building energy consumption before and after the retrofitting, and the reduction degree of water and electricity bills may be highlighted. The positive impact on people who increasingly pursue a healthy and comfortable environment at the present stage should be strengthened to enhance their awareness and improve their intention toward green retrofitting. The residents may then be guided to improve their green RI for existing residential buildings.
5.4. Multigroup Analysis
The results of the multigroup analysis showed no significant difference in gender, except for H4 and H7. In terms of age, only H6 and H7 showed a difference, probably because the low age groups easily accept new things and are relatively emotional. Although high age groups focus on environmental protection, their inherent ideas hinder their acceptance of new things. Thus, low age groups are particularly willing to participate in green retrofitting. The findings are consistent with those of Magnusson MK [
87].
From the perspective of occupational categories, only enterprise personnel and government personnel did not have significant differences, whereas the other groups showed differences. We speculate that the main reason is that the income of enterprise personnel and government personnel is stable; they have easy access to national green retrofitting policies and a high degree of cognition of green retrofitting policies relative to other groups. In terms of the per capita monthly family income, significant differences were observed in other paths, except for H4 and H5. We speculate that the main reason is that low income groups do not have additional income to allow their families to undergo green retrofitting. Therefore, the intention of low-income groups to carry out green retrofitting greatly depends on the strength of government policy support. On the contrary, groups with high family income are likely to accept green retrofitting because they expect improved life experience through green retrofitting. This conclusion further validates the viewpoint of Doling, John [
88]. Therefore, to enable low income groups to participate in green retrofitting, the Chinese government should launch a green retrofitting incentive plan for low income groups, which may include providing high subsidies and low loan interest rates to allow all income groups to enjoy equal opportunities for green retrofitting.
In terms of education level, differences were noted between H1, H6, H7, and H8. We assume that the main reason is that the income of the group with a high educational level, as well its awareness of green retrofitting, is higher to some extent than that of the group with a lower educational level. To reflect the social status brought about by a high level of education and obtain a sense of satisfaction, the group with a high level of education is likely to accept green retrofitting. This conclusion is consistent with that of Ritter, Agata M [
89].
From the perspective of region, no differences were found in H1, H4, and H5, but the remaining paths were different. We speculate that the result may be due to the eastern region being economically developed; hence, people’s income level and overall quality of life here are relatively high. The pilot of ‘resource-saving and environmentally friendly society’ is mainly concentrated in the eastern region. Therefore, residents in the eastern region have high GRC and are likely to accept green retrofitting. By contrast, the economy in the western region is relatively weak, and the income level of the local people is not generally high. As a result, residents in the western region have no additional economic income to subsidise the high cost of green retrofitting. To enable the residents in western regions to participate in green retrofitting, the government can provide substantial economic subsidies to families with low incomes in western regions. In addition, the effects of retrofitting can be vigorously publicised in the community, and the operating cost before and after retrofitting can be compared using a direct diagram to increase residents’ awareness of green retrofitting costs and clarify that the operating cost after retrofitting can completely make up for the cost of retrofitting.
5.5. Research Limitations
The study has several limitations that need to be addressed in future research. The expanded TPB model seems to be the appropriate framework for predicting the intention of residents to retrofit existing residential buildings. However, future research will need to inspect whether this extended TPB model can be used to predict other green consumption behaviours. Furthermore, the variable of behaviour was not considered in this study because the measurement of residents’ green retrofitting behaviour is complicated and selecting the survey data is difficult. Moreover, shifting from residents’ intention toward green retrofitting to actual retrofitting behaviour requires a substantial amount of time. Future research can extend the variables to improve the predictability of actual retrofitting behaviour by investigating actual behaviour. At the same time, the research on the relationship between intention and behaviour is achieved through field visits and household surveys. The data in this study were all collected in the Chinese context. As a result of differences in national environment and policies, whether the conclusions of this work are applicable to other countries has yet to be confirmed. Thus, green retrofitting cases in other countries or regions should be considered in follow-up studies.
6. Conclusions and Implications
The green retrofitting of existing residential buildings has become an important breakthrough for the construction industry to achieve sustainable development and has been upgraded to the national strategic level. The greening of existing houses improves the performance of existing houses and extends the life of buildings. The strategy is equally important in urban renewal. Therefore, green transformation is advantageous in promoting economic and social sustainable development.
The purpose of this study is to explore the intention of residents toward the green retrofitting of existing residential buildings in the context of China. On the basis of theoretical modelling construction, data were obtained through questionnaire survey in eastern (Shandong, Jiangsu, and Fujian) and western (Sichuan, Guizhou, and Guangxi Zhuang Autonomous Region) regions. On the basis of the survey data obtained, the influencing factors and mechanism of residents’ green retrofitting of existing residential buildings were analysed. The study concluded that the extension of PFs and GRC into the TPB can effectively predict the green RI of residents. Green RI can be predicted directly or indirectly by behavioural attitude, SNs, PBC, GRC, and PFs. PFs had the greatest impact on the intention toward green retrofitting, followed by GRC, behavioural attitude, SNs, and PBC. Demographic characteristics (gender, age, monthly family income, education level and occupation) and regional variables (eastern, western) showed significant differences in terms of the impact of different hypothetical paths. Furthermore, the research methods and ideas of this study can be further expanded. In the future research, the value–belief norm theory and theory of planned behaviour can be integrated to study the public environment participation behaviour, and the differences in the path of the statistical variables in the model can be compared by SEM and multi-group analysis, such as marital status and the number of family members.
This study provides three main contributions. First, the TPB is applied to residents’ intention toward the green retrofitting of existing residential buildings. The study not only enriches the application scope of the TPB but also provides a new approach to the study of residents’ green retrofitting behaviour. Second, a multigroup analysis method is used to test and discuss different groups and regions; this method is conducive to the segmentation of the green retrofitting market and the selection and cultivation of a precise target market. Finally, a model of Chinese residents’ intention toward the green retrofitting of existing residential buildings is constructed. This model identifies the key factors affecting the intention toward green retrofitting to deepen residents’ understanding and support for the green retrofitting of existing residential buildings. At the government level, relevant policies can be formulated in accordance with the conclusions of this study to promote green retrofitting and social sustainable development.
Several policy implications are put forward according to the empirical analysis. First, the government should increase financial subsidies for residents to encourage the retrofitting of existing residential buildings. Second, the green retrofitting consciousness of social masses should be improved to expand the green retrofitting of existing residential buildings. Finally, the green retrofitting of existing residential buildings is beneficial to urban renewal and social sustainable development. Therefore, the government should vigorously promote the green retrofitting of existing residential buildings.