Using the theory of planned behaviour to predict intentions to purchase sustainable housing

Journal of Cleaner Production 215 (2019) 259e267

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Using the theory of planned behaviour to predict intentions to purchase sustainable housing Madeline Judge a, *, Georgia Warren-Myers b, Angela Paladino a a b

Faculty of Business and Economics, The University of Melbourne, Australia Faculty of Architecture, Building and Planning, The University of Melbourne, Australia

a r t i c l e i n f o

a b s t r a c t

Article history: Received 12 June 2018 Received in revised form 2 January 2019 Accepted 4 January 2019 Available online 7 January 2019

Homebuyers today are faced with a spectrum of choices when deciding to build a new home. However, encouraging more sustainable choices in housing and construction decisions has been challenging. In this paper, we apply the theory of planned behaviour (TPB) to investigate the factors predicting homebuyers’ intentions to purchase a dwelling with a sustainability certification. Three hundred and thirty Australian residents who had recently purchased property were recruited via an online panel provider. Attitudes, subjective norms, perceived behavioural control and green consumer identity each independently predicted higher intentions to purchase a sustainability-certified dwelling, and in combination accounted for 65% of the variance in intentions. Green consumer identity also significantly moderated the effect of subjective norms on intentions. In a separate analysis, the two strongest predictors of willingness to pay for a sustainability certification were familiarity with current sustainability certifications and subjective norms. Implications for theory and practice are discussed. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Theory of planned behaviour Sustainability certifications Green consumer identity Housing purchase intentions

1. Introduction Electricity and heat production from the burning of fossil fuels is one of the most significant contributors to greenhouse gas emissions globally (Environmental Protection Authority, 2018). In the building sector, both the energy consumed in the construction of new homes and ongoing household energy usage are significant contributors to emissions, and consequently have implications for climate change and environmental degradation. In Australia, the residential sector alone accounts for 7.7% of annual energy consumption and contributes significantly to water usage and solid waste sent to landfill (Department of Industry, Innovation and Science, 2016; Pitt & Sherry, 2014). Accordingly, it is imperative to develop a better understanding of how to promote the adoption of sustainability initiatives at a local level, regarding consumer decision-making in residential contexts. At present, approaches to promoting more sustainable housing in Australia have been limited to establishing a mandatory energy rating for new homes and providing a selection of voluntary sustainability tools, both of

* Corresponding author. The University of Melbourne, Level 10, 198 Berkeley St, Vic, 3010, Australia. E-mail addresses: [email protected] (M. Judge), g.warrenmyers@ unimelb.edu.au (G. Warren-Myers), [email protected] (A. Paladino). https://doi.org/10.1016/j.jclepro.2019.01.029 0959-6526/© 2019 Elsevier Ltd. All rights reserved.

which have been poorly implemented and communicated to consumers (Pitt & Sherry, 2014; Warren-Myers, 2017). Evidence suggests that most homebuyers value energy efficiency in a home (see, for example, Brounen and Kok, 2011; Deng et al., 2012; Fuerst et al., 2015; Fuerst and Shimizu, 2016; Kahn and Kok, 2014; Noiseux and Hostetler, 2010). In the Australian context, Fuerst and Warren-Myers (2018) found premiums associated with energy efficiency ratings and the presence of certain sustainability features in the home. However, this has not translated to an increased consumer demand for or awareness of sustainability certifications for new dwellings across Australia, due in part to poor communication and offerings by builders (Bryant and Eves, 2012; Hurst, 2012; Pitt & Sherry, 2014; Warren-Myers, 2017). A recent Commonwealth Scientific and Industrial Research Organisation (CSIRO) survey of 456 Australian residents found that participants expressed positive attitudes towards homes that were more energy efficient and reported that rating tools would be one of the key information sources they would seek (Romanach et al., 2015). This study identified that participants had a desire for more energy efficient homes, yet it did not specifically examine their views on current sustainability rating tools and certifications. Additionally, the range of competing motivations when purchasing a home can include the relationship between an increased substantial cost and capital outlay, borrowing capacity, and ‘dream

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home’ ideals, all of which contend for attention and play a unique role in decision-making, which differs from other lowerinvestment purchasing contexts. Given the need to encourage more sustainable housing choices by consumers, more research is needed to understand prospective homebuyers' attitudes toward sustainability certifications for dwellings, and the psychological factors that motivate or inhibit intentions to purchase a dwelling with a sustainability certification. The current research applies a psychological model of decisionmaking processes, the theory of planned behaviour (TPB; Ajzen, 1991), to investigate the subjective attitudes and beliefs contributing to intentions to purchase a dwelling with a sustainability certification. At present, most research on the psychological factors contributing to pro-environmental behaviours has focused on relatively low-investment behaviours, such as reducing one's overall consumption, increasing recycling, or choosing ‘green’ alternatives in the context of organic food, energy-efficient appliances, green mobile phones green hotels, electric cars, or energy providers (e.g. Carfora et al., 2017; Nigbur et al., 2010; Paladino and Ng, 2013; Smith and Paladino, 2010; Verma and Chandra, 2018; Whitmarsh and O'Neill, 2010; Yadav and Pathak, 2016; Yazdanpanah and Forouzani, 2015). Relatively little research has examined the role of sustainability concerns in consumer decisionmaking regarding one of the most significant investments that an individual may make in their lifetime; the purchase of a dwelling. Therefore, the present research makes a unique contribution to the literature by being one of the first to apply the TPB to intentions to purchase sustainable housing. The research also aims to provide clear directives for the housing sector stakeholders and government organizations who are trying to promote sustainability in housing, regarding what approaches will be more effective in enhancing sustainability uptake in housing. 1.1. Sustainability certifications and rating systems for dwellings in Australia In countries such as Australia, sustainability certifications for dwellings come in both voluntary and mandatory forms. Due to the National Construction Code, all newly constructed dwellings (and to an extent, dwellings that are being extended), are subject to comply with a 6-star Nationwide House Energy Rating System (NatHERS) rating. This is a thermal assessment design-based tool to assess potential thermal comfort, taking into account local weather extremes. The NatHERS tool has a relatively long history (being developed in 1993) and has had some form of mandatory inclusion since 1998. Subsequent rating tools that have been developed at the dwelling level include the Building Sustainability Index (BASIX), which only applies as a mandatory requirement in New South Wales and extends to include energy and water requirements; whilst the recent addition, the National Australian Built Environment Rating System (NABERS), is a voluntary tool that examines the current energy usage and assesses the performance of the dwelling. Additional voluntary tools have been applied in new housing estates at the development level, and consumers may be exposed to these certifications when purchasing homes within those housing estates. The development-based tools in the residential estate sector are primarily Green Star (either multi-unit or communities), Envirodevelopment and Built Environment Sustainability Scorecard (BESS, in Victoria only). The Green Star and Envirodevelopment tools are voluntary tools with a series of categories that developers can target, and as long as they fulfil enough criteria within the categories, they will receive a rating. The categories in the Green Star Communities tool comprise Governance, Liveability, Economic Prosperity, Environment and Innovation (Green Building Council of Australia, 2018), whilst the Green Star Multi-unit tool

(recently removed from the market) comprised traditional Green Star categories of Management, Indoor Environment Quality, Energy, Transport, Water, Materials, Land Use and Ecology, Emissions and Innovation (Green Building Council of Australia, 2008). The EnviroDevelopment tool is assessed using six categories known as ‘leaves’. Unlike the Green Star system, certain ‘leaves’ can be targeted and not all have to be attempted; consequently, the rating is issued with logos associated with the particular categories that have been achieved. The different categories include: Ecosystems, Waste, Energy, Materials, Water and Community (EnviroDevelopment, 2018). The BESS tool is a recent addition from 2015 and is being implemented through the Victorian planning scheme. BESS has elements similar to the two voluntary tools and will comprise a more mandatory approach for developers going forward in the Victorian planning scheme, once passed into legislation. Similar to the Green Star tool that includes criteria within the categories in a scoring type system, the different categories within the BESS tool comprise Management, Water, Energy, Stormwater, Indoor Environment Quality, Transport, Waste, Urban Ecology and Innovation (Municipal Association of Victoria, 2018). Given the increasing diversity and varying degrees of visibility of sustainability certifications in the building sector, it is important to investigate whether these sustainability certifications play a role in consumer decision-making regarding the purchasing of a dwelling. In other purchase contexts, eco-labels and star rating systems that inform consumers of the relative energy-efficiency of different products have been found to increase willingness-to-pay (e.g. Ward et al., 2011) and can even shape consumers’ experience of the product (although these effects can be moderated by level of €rqvist, environmental concern and the product involved; e.g, So et al., 2015). There are potential opportunities for builders and developers to market the sustainability certifications and attributes of their developments as a way to add value, given the positive connotations of these attributes for consumers. Yet at present, there is a lack of sustainability information available to consumers (Warren-Myers and McRae, 2017) and low rates of visibility of the NatHERS rating (the mandatory rating) in standard inclusions provided to new homebuyers (Warren-Myers et al., 2017). Preliminary research has identified various other barriers to increasing energy-efficiency in households for consumers, such as perceived initial costs, a lack of knowledge and education, poor communication with building professionals, and their inferior position to enforce or request more sustainable options (Bond, 2011; Crabtree, 2006; Crabtree and Hes, 2009; Warren-Myers et al., 2012; Williams and Dair, 2007). A recent news article also highlighted areas of inconsistency and potential confusion in meanings of star-rating tools across different dwelling sustainability certifications (Fifth Estate, 2017). 1.2. Theoretical framework In the present study, we apply the theory of planned behaviour (TPB), to investigate the subjective beliefs that predict intentions to purchase a dwelling with a sustainability certification. The TPB is a theoretical framework for predicting behaviour, which has been supported by a substantial amount of research across multiple behavioural domains (Ajzen, 1991; Armitage and Conner, 2001). In the model, intentions to perform the behaviour are conceptualised as the closest antecedent of actual behaviour, and intentions are predicted by an additive combination of attitudes towards the behaviour, subjective norms (beliefs about how important others view the behaviour, or whether others engage in the behaviour themselves) and perceived behavioural control over performing the behaviour. Perceived behavioural control is also sometimes included in the model as a direct predictor of actual behaviour. The

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TPB has been successfully applied to many domains of proenvironmental behaviour, including sustainable food consumption (Vermeir and Verbeke, 2008), fuel-efficient cars (Nayum and € ckner, 2014), willingness to pay for an urban park (Lo  pezKlo Mosquera et al., 2014) and the pro-environmental behaviours of high school students (De Leeuw, Valois, Ajzen & Schmidt, 2015). The model has been used to assist with developing educational interventions tailored to specific populations (De Leeuw et al., 2015). 1.3. The role of green consumer identity In the context of investigating pro-environmental behaviour, the TPB has often been extended by the inclusion of relevant selfidentity measures; specifically, pro-environmental identity or green consumer self-identity (e.g., Brick et al., 2017; Fielding et al., 2008; Sparks and Shepherd, 1992; Whitmarsh and O'Neill, 2010). Self-identity has been defined as “the salient part of an actor's self which relates to a particular behaviour” (Conner and Armitage, 1998, p. 1444). Although an individual may carry an identity related to a specific pro-environmental behaviour (e.g. a ‘recycler’ identity), a green consumer identity can be conceptualised as a global construct that impacts behaviour across multiple consumption domains. A recent study examining the role of identity across multiple pro-environmental behaviours found that proenvironmental self-identity significantly moderated the relationships between perceived behavioural control and intentions, and past behaviour and intentions (Carfora et al., 2017). In addition, identity was found to influence actual behaviour. In the current study, we investigated whether green consumer identity moderated the relationships between the three TPB predictors and intentions to purchase a dwelling with a sustainability certification. Although green consumer identity is usually applied to relatively low-investment behaviours, such as reducing food waste or recycling (Carfora et al., 2017), it is likely that green consumer identity is also relevant to the context of purchasing property (especially because housing purchases involve a high level public visibility). We predicted that sustainability certifications for dwellings would engage identity motivations and influence intentions to purchase a certified dwelling, depending on the extent to which one selfidentifies as a green consumer. In a related study, Tan (2013) applied an extended TPB model including self-identity to the context of purchasing a sustainable home in Malaysia. This study found that the strongest predictors of purchase intentions were attitudes and self-identity, whereas perceived behaviour control was a weaker predictor, and subjective norms were not a significant predictor of purchase intentions (Tan, 2013). A potential limitation to this study was that they did not target a sample of existing homebuyers, therefore some of their participants potentially did not have the ability to make housing purchases. In the current study, we restricted the sample to individuals who reported recently purchasing property, in order to collect data from participants for whom the behaviour of interest may be more possible and salient. We also extended previous research (e.g. Tan, 2013) by examining intentions to purchase sustainability-certified housing in an Australian context. 1.4. The role of past behaviour and familiarity with current certifications Extant research has found that past behaviour is one of the strongest predictors of future behaviours (Ajzen, 2011). Past behaviour is often conceptualised as habitual engagement in the behaviour. In the context of purchasing property, past behaviour is less likely to be an important factor, given that there are far fewer

261

opportunities to purchase a house (in comparison to the kinds of behaviours that have been examined in past research, such as purchasing food and beverages; e.g., Vermeir and Verbeke, 2008). Although past behaviour is not expected to have a significant relationship with future intentions, we controlled for this variable in the current study. Additionally, because we were investigating attitudes toward sustainability certifications in a general sense, rather than attitudes towards specific certifications, we also controlled for familiarity with existing sustainability certifications. We expected that attitudes, subjective norms and perceived behavioural control would be more proximal indicators of purchase intentions, compared to past behaviour or familiarity with specific certifications. 1.5. Hypotheses It is important to examine the psychological antecedents of homebuyers’ decision-making, in order to identify potential existing barriers to sustainability uptake as well as opportunities for educational interventions. An understanding of these variables is critical to gauge how to best structure messaging appeals to consumers to attract their attention and educate them of the role of sustainable certifications. The TPB provides a useful framework for examining the antecedents of intentions to purchase housing with a sustainability certification. Based on prior research examining the TPB in the context of sustainable consumer behaviours (e.g. Carfora et al., 2017), we predicted that the three standard TPB variables would predict intentions to purchase a dwelling with a sustainability certification, and that green consumer identity would moderate the relationships between the antecedents and intentions. More specifically, we proposed the following hypotheses. First, a positive attitude towards purchasing a sustainable dwelling is likely to be a strong positive predictor of intentions (H1); individuals are more likely to plan to make such a purchase if they view this behaviour as having positive consequences (in this context, positive consequences may include reducing one's impact on the environment or lowering household energy costs). Second, subjective norms (i.e. injunctive norms regarding the perception that important others would support the purchase, or descriptive norms regarding whether important others have engaged in the behaviour themselves) is also likely to be a positive predictor of intentions (H2). Housing purchases are often made with consideration of the needs and desires of one's spouse or family members; therefore, perceived social pressure may be a highly salient factor in this context. However, it is also possible that descriptive norms regarding the frequency of others' purchases of sustainable housing will not be a strong predictor, given that a certification is not a visible aspect of most houses. Third, perceived behavioural control is likely to be a strong positive predictor of intentions (H3), given that there are many external factors that may be perceived to inhibit one's control over such a purchase (e.g. the cost of purchasing a dwelling, or confidence in evaluating sustainability ratings). Even though all new buildings are now required to have a six-star energy rating by the government, there are no requirements for builders to display this information to homebuyers. Additionally, even when the six-star rating is communicated to consumers, it is considered the basic minimum standard and may be misinterpreted by consumers as a relatively high achievement (Fifth Estate, 2017). Therefore, it is possible that low perceived behavioural control may stem from a perception that there are not many certified dwellings available, or a perception that one has insufficient knowledge or confidence in the sustainability certifications for housing in Australia, and this is likely to lead to lower intentions to purchase. Fourth, self-identification as a green consumer is predicted to

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negatively moderate the relationships between the three TPB predictors and intentions (H4). It is expected that the desire to maintain consistency as a green consumer is likely to motivate intentions to purchase sustainable housing (as a form of proenvironmental behaviour), even when attitudes, subjective norms, or perceived behavioural control are relatively low (e.g. Carfora et al., 2017). Fig. 1 summarises the relationships under examination. As a secondary exploratory analysis, we explored the role of the same variables in predicting willingness to pay. We did not make any directional hypotheses for this analysis. We also included a free association task in order to orient participants towards the topic and to explore participant's unrestricted associations with the concept of ‘sustainable housing’. 2. Method 2.1. Participants The initial sample comprised 500 Australian residents recruited through an online panel recruitment agency (the screening criteria restricted the sample to individuals who reported recently purchasing property). After removing participants who failed an attention check item, the sample size was reduced to 330. There were 174 men and 156 women, who ranged in age from 19 to 83 (M ¼ 44.38, SD ¼ 13.90). The median income bracket was between $78,000 and $103,999, and the median level of education was a Bachelor's degree. Of the 330 participants, 67.6% had purchased a dwelling (house, apartment, unit or townhouse) and 21.8% had purchased a section of land for residential purposes (10.6% did not answer this question). Of the participants who had recently purchased a dwelling, 44% stated that their recent purchase was the first home they had purchased. Additionally, when asked if they were aware that the dwelling they had purchased had a sustainability certification, 20.6% were aware of a sustainability certification, 29.1% were not aware and 42.6% were unsure (7.2% responded ‘not applicable’). 2.2. Measures Participants took part in the survey online, first completing a

free association item, and then completing the TPB, green consumer identity, and demographic measures. 2.2.1. Free association qualitative item We included a single qualitative item to measure free associations with sustainable housing. The item read, “What first comes to mind when you think of sustainable housing?“. Following this item, participants were provided with enough space to write a few words or a sentence. 2.2.2. Attitudes, norms, perceived behavioural control and intentions We adapted the TPB measures to the context of purchasing a dwelling with a sustainability certification, following the suggestions of Ajzen (1991). Firstly, we adapted the general attitudes items to address the behaviour of purchasing a dwelling with a sustainability certification. These four items were constructed as semantic differentials, with seven points between each end-point. Then we developed items to measure subjective injunctive norms (4 items), subjective descriptive norms (3 items), perceived behavioural control (four items) and intentions (3 items). These items were measured on a scale from 1(Strongly disagree) to 7 (Strongly agree). A full list of items in these scales is provided in the Supplementary Materials file. 2.2.3. Willingness to pay We included a single item to measure the additional percentage of the original cost that participants would be willing to pay for a dwelling with a sustainability certification. The item was “I would be willing to pay this much more for a dwelling that has been certified as sustainable” and the scale ranged from 1 (0% more) to 8 (More than 30%), increasing in 5% points. 2.2.4. Familiarity with current sustainability certifications Participants were presented with the logos for five sustainability rating tools (Envirodevelopment, Greenstar, NABERS, NatHERs and BESS), and asked to rate their agreement with the item, “I am familiar with this logo” for each of the logos, on a scale from 1 (Strongly disagree) to 7 (Strongly agree). 2.2.5. Past behaviour We measured past behaviour with a single item that asked participants to indicate whether they had purchased a dwelling with a sustainability certification. Participants who selected “I have recently purchased a dwelling (house, unit, townhouse, apartment) with a sustainability certification” were coded as 1, and all other participants were coded as 0. 2.2.6. Green consumer identity We included two items from Whitmarsh and O'Neill (2010) to measure green consumer identity. A sample item is “I think of myself as an environmentally-friendly consumer”. Items were rated on a scale from 1 (Strongly disagree) to 7 (Strongly agree). 3. Results 3.1. Free associations with “sustainable housing”

Fig. 1. The Theory of Planned Behaviour including green consumer identity as a moderator.

The first item in the questionnaire was a qualitative free association task. Each participant provided a word, sentence or short paragraph describing the first thoughts that came to their mind when asked to think about sustainable housing. The length of responses ranged from no response to 36 words, with participants providing an average of three words. The first author performed minor corrections of the qualitative data and then categorised

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Table 1 Frequencies of categories in participants’ free associations with “sustainable housing”. Category General associations Environmentally friendly Energy efficient Affordability Long lasting Liveable Other positive associations (e.g. good, nice, everything included, a dream in Australia, proper way to do things, no brainer must do, in a growing area, relevant, needs of tomorrow, nice-looking) Other negative associations (e.g. unattractive, expensive, cramped) Specific features Solar (e.g. solar panels) Materials (e.g. renewable materials) Water (e.g. rainwater tanks) Spatial (e.g. compact home) Other features (e.g. double-glazing, insulation, green spaces, compost bin, shade, orientation, ventilation, off grid, carbon neutral, less waste, good neighbours, good location, public transport, modern features) Uncategorised Total

synonyms together in order to run a basic count analysis of the features that participants most frequently associated with sustainable housing (this included creating an ‘Uncategorised’ category for content that was not relevant, such as “na”). Table 1 displays the counts and proportion of coverage for each category. In general, participants' free associations with sustainable housing focused on energy efficiency, the environment, financial considerations and the social and liveable aspects of housing. However, when examining more specific categories, it was clear that there were specific housing features that were particularly salient to participants, such as solar power and rainwater tanks, suggesting that for many individuals, sustainable housing is closely associated with tangible features that connote sustainability. 3.2. Descriptive statistics Given that we had adapted the TPB scale items to a new behavioural domain, we first conducted a preliminary Confirmatory Factor Analysis (CFA) of the TPB items (attitudes, injunctive norms, descriptive norms, perceived behavioural control and intentions) to check the reliability and validity of the items in the measurement model. Model fit was examined following recommendations regarding goodness-of-fit indices. According to Byrne (2010), GFI and CFI indices higher than 0.95, and RMSEA values between 0.05 and 0.08, are considered good. This model was an adequate fit to the data, c2 ¼ 578.91, df ¼ 125, p < .001, c2/df ¼ 4.63, CFI ¼ 0.94, NFI ¼ 0.92, RMSEA ¼ 0.08 (the CFA also indicated that removing a reverse-scored perceived behavioural control item significantly improved the model fit, therefore this item was removed before calculating the composite measure). All items loaded >0.82 on their respective latent variables, with the exception of the first perceived behavioural control item (the loading for this item was still in the acceptable range, at 0.64). The correlation between injunctive and descriptive norms was 0.91; therefore, these items were merged to form a single composite measure of ‘subjective norms’ for subsequent analyses. Although several items exhibited high skewness and kurtosis (>1), all values were between the recommended threshold of 2 and þ2; therefore, these items were retained in the analyses. Means, standard deviations, reliabilities and correlations between the variables can be found in Table 2. On average, participants expressed high levels of positive attitudes, perceived behavioural control, intentions and green consumer identity. Perceived subjective norms were relatively lower, and participants also expressed

Count

%

90 60 53 37 24 16

14.8 9.9 8.7 6.1 4.0 2.6

8

1.3

44 32 31 13 43

7.2 5.3 5.1 2.1 7.1

156 607

25.7 100

low familiarity with current certifications. On average, participants were willing to pay between 10% and 15% more for a dwelling with a sustainability certification. All correlations between variables were significant and in the expected directions. 3.3. Predicting purchase intentions and willingness to pay We ran two hierarchical multiple regressions to examine the role of attitudes, subjective norms, perceived behavioural control and green consumer identity, in the prediction of future intentions to purchase and willingness to pay for a dwelling with a sustainability certification (see Table 3). All variables were mean-centred prior to analysis. Past behaviour and familiarity with current sustainability certifications were included in the first step of the regression, in order to control for these variables. In the second step, the three standard TPB predictors and green consumer identity were entered into the model, and were all highly significant predictors of intentions. When these variables were included in the model, past behaviour and familiarity were no longer significant predictors of intentions. In total, the predictors explained a significant amount of the variance in both purchase intentions (65%) and willingness to pay (45%). In the third step, we examined whether green identity moderated the effects of the TPB predictors on purchase intentions and willingness to pay. There was a significant interaction between green identity and subjective norms in the prediction of purchase intentions, suggesting moderation.1 However, there were no significant interactions found for willingness to pay; the only significant predictors of this single-item measure were familiarity with existing certifications, and subjective norms. 3.4. Moderation analyses To further investigate the interaction between subjective norms and green consumer identity, we ran a simple slopes analysis in PROCESS (Hayes, 2017) controlling for the other variables in the model (see Fig. 2). This analysis indicated that the effect of

1 We also ran a series of separate exploratory regression analyses including each interaction term individually (Jose, 2013). The significant interaction between perceived behavioural control and green consumer identity (see Table 3) became non-significant when it was examined by itself. Therefore, for subsequent analyses we focused on the interaction between subjective norms and green consumer identity, which was the only interaction term that was significant in both the omnibus analysis and when examined individually.

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Table 2 Means, standard deviations, reliabilities and correlations between variables. Variable

M

SD

a

1

2

3

4

5

6

7

1. 2. 3. 4. 5. 6. 7. 8.

5.77 4.39 5.09 5.00 3.40 2.91 .28 4.94

1.20 1.65 1.35 1.54 2.27 1.73 .45 1.26

.93 .94 .84 .93 e .93 e .84

.51** .38** .58** .38** .32** .32** .53**

.54** .74** .60** .66** .38** .36**

.57** .42** .52** .32** .39**

.51** .53** .36** .48**

.56** .33** .24**

.42** .29**

.24**

Attitudes Subjective norms Perceived behavioural control Intentions Willingness to pay Familiarity with certifications Past behaviour (0 ¼ no, 1 ¼ yes) Green consumer identity

*p < 01; **p < .001. a ¼ Cronbach's alpha.

Table 3 Hierarchical multiple regression predicting purchase intentions and willingness to pay. Purchase Intentions Step

Willingness to Pay

Predictor

B

SE B

b

Past behaviour Familiarity with certifications

0.57 0.40

0.19 0.05

0.17** 0.46***

Past behaviour Familiarity with certifications Attitudes Subjective norm Perceived behavioural control Green consumer identity

0.07 0.02 0.22 0.49 0.18 0.16

0.14 0.05 0.06 0.05 0.05 0.06

0.02 0.02 0.18*** 0.53*** 0.15** 0.13**

Past behaviour Familiarity with certifications Attitudes Subjective norms Perceived behavioural control Green consumer identity Attitude  Green identity Subjective norm  Green identity Perceived behavioural control  Green identity

0.14 0.02 0.16 0.49 0.20 0.15 0.04 0.11 0.07

0.14 0.05 0.06 0.05 0.05 0.05 0.04 0.04 0.04

0.05 0.02 0.13* 0.52*** 0.17*** 0.12** 0.06 0.16** 0.10*

1.

2.

R2

DR2

.31***

.31***

.65***

3.

.67***

B

SE B

b

0.53 0.68

0.27 0.07

0.11* 0.53***

0.31 0.36 0.13 0.52 0.09 0.07

0.26 0.09 0.12 0.10 0.10 0.11

0.06 0.28*** 0.07 0.38*** 0.05 0.04

0.31 0.35 0.14 0.52 0.10 0.08 0.01 0.06 0.07

0.27 0.09 0.12 0.10 0.10 0.11 0.08 0.07 0.07

0.07 0.28*** 0.07 0.38*** 0.06 0.04 0.01 0.06 0.06

.34***

.02**

R2

DR2

.34***

.34***

.42***

.08***

.42***

.003

Note. N ¼ 273. *p < 05; **p < 01; ***p < .001.

4. Discussion

Fig. 2. Simple slopes for the effect of subjective norms on purchase intentions by green consumer identity, controlling for attitudes and perceived behavioural control.

subjective norms on intentions to purchase was stronger when green consumer identification was low, b ¼ 0.61, 95% CI [0.48, 0.74 ], t ¼ 9.04, p ¼ <.001, compared to when green consumer identification was high, b ¼ 0.37, 95% CI [0.22, 0.52], t ¼ , p ¼ <.001. This suggests that subjective norms are less important to purchase intentions when green consumer identity is high.

In this study, we explored attitudes towards sustainable housing and applied an established psychological model, the TPB, to examine the antecedents of homebuyers' intentions to purchase housing with a sustainability certification. Overall, the findings suggest that most homebuyers in Australia have positive attitudes towards the notion of sustainable housing, although they were relatively unfamiliar with specific sustainability certifications. The responses to the free association item demonstrated that sustainable housing has many positive associations beyond the perceived benefits for the environment, such as being more affordable, better quality, built to last, and liveable. These positive associations with sustainable housing are consistent with previous literature (e.g., Crabtree and Hes, 2009; Noiseux and Hostetler, 2010; WarrenMyers, 2017). Although there were also a few negative terms associated with sustainable housing, such as ‘cramped’, ‘expensive’ and ‘unattractive’, negatively-valenced words comprised a very small proportion of the total number of free associations. Furthermore, the specific housing features associated with sustainable housing were consistent with the findings of previous studies; for example, Fuerst and Warren-Myers (2018) identified value premiums associated with solar based technologies, and WarrenMyers et al. (2012) also identified a desire for solar features, although these were perceived as cost prohibitive. The extended TPB model including green consumer identity explained 65% of the variance in intentions, with attitudes,

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subjective norms, perceived behavioural control and green consumer identity all significantly predicting intentions to purchase. The strongest predictor of purchase intentions for sustainable housing was subjective norms, which supports our hypothesis that subjective norms would be a strong predictor because purchasing a house often involves taking other people's views into consideration, and housing carries a high degree of identity symbolism. Attitudes, perceived behavioural control and green consumer identity were also significant predictors of purchase intentions. Subsequent analyses demonstrated that the effect of subjective norms on intentions was moderated by green consumer identity. When green consumer identity was high, subjective norms had a weaker relationship with intentions. This suggests that, for individuals who considered themselves to be green consumers, perceiving low subjective norms did not reduce their intentions to purchase a dwelling with a sustainability certification to the same extent as for individuals who did not see themselves as green consumers. The current findings are consistent with the inferences of Romanach et al. (2015); that, when provided with the option, consumers would find energy-efficient homes more attractive, and that self-identified green consumers were more likely to be interested in energy-efficient homes. This present study also extends other recent research that has investigated the moderating role of green consumer identity in the context of low-investment proenvironmental behaviours (Carfora et al., 2017). However, it should be noted that in the study by Carfora et al. (2017), green consumer identity moderated the relationship between perceived behavioural control and intentions, rather than between subjective norms and intentions e as in the present study. Therefore, although we have argued that purchasing a sustainable dwelling may be viewed as another form of pro-environmental behaviour that would be influenced by an overarching green consumer identity; there may be some unique features of the current context that differentiate it from relatively lower-investment pro-environmental behaviours. Unlike much previous research, past behaviour was not a strong predictor of future intentions. We propose that because purchasing a house is such a significant investment, most of the participants had likely only purchased property once in their lifetime and may not have had the opportunity to purchase a house with a sustainability certification. Indeed, 44% of participants stated that their recent purchase was their first home. Therefore, it is not surprising that past behaviour did not play a large role in future intentions in this context. Familiarity with current sustainability certifications was also not a significant predictor of intentions when the TPB predictors were included in the model, indicating that subjective beliefs about sustainable housing outweighed the importance of familiarity with specific sustainability certifications in predicting purchase intentions. In a secondary analysis, the variables included in the hierarchical regression also explained 45% of the variance in willingness to pay for a sustainability certification. In comparison to broad purchase intentions, familiarity with existing sustainability certifications appeared to play a larger role in willingness to pay. This could indicate that, although consumers are generally positive towards sustainability certifications and may choose a certified dwelling if all else was equal, willingness to pay more for a certification predominantly depends on one's familiarity with (and perhaps trust in) current certifications. This finding would need to be replicated in future research but has potentially important implications regarding the need for educational interventions to increase consumer awareness and confidence in their ability to evaluate sustainability certifications. The only TPB predictor that significantly predicted willingness to pay was subjective norms,

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further emphasising the importance of subjective norms in this context. 4.1. Limitations One of the main limitations of this study is that the TPB was designed to predict proximate and relatively low-investment behaviours that are expected to happen in the very near future (e.g. smoking or exercising), whereas for the current participants who had recently purchased property, their purchase intentions were likely focused on the distant future and comprised a long-term perspective. This means that it would be difficult to demonstrate a causal association between intentions and actual behaviour, as many other factors could intervene in the ensuing time-period. It is also possible that the experience of recently purchasing a house may have influenced participant responses. In future research, it would be useful to recruit participants who are in the process of searching for property, rather than those who had recently purchased property, as it is likely there would be a closer relation between intentions and action for this group and they may also hold different attitudes and beliefs. Additionally, there are many contextual constraints on performing this particular behaviour and since we did not measure actual behaviour in this study, it is not possible to test whether intentions predicted actual behaviour. The TPB model has received criticism in the past for omitting the crucial roles of actual behavioural control and habit (Ajzen, 2011). Although habit is unlikely to play a role in the purchase of a dwelling with a sustainability certification, actual behavioural control is likely to contribute significantly to whether people can carry out their intentions; firstly, because owning a house is increasingly out of reach for many people in Australia, and secondly, because sustainability certifications are not necessarily included in the marketing communications for dwellings. An additional limitation is the recruitment strategy for the current sample; panel members of online recruitment agencies may not be representative of all demographics (for example, it is possible that higher income homebuyers, or homebuyers who are infrequent internet users, would be less likely to be included). Future research may benefit from a different recruitment strategy, such as mailouts to targeted areas. 4.2. Applications and future research The current findings suggest that homebuyers have generally positive attitudes toward sustainable housing and high intentions to purchase a dwelling with a sustainability certification in the future. However, as noted in the introduction, this has not yet resulted in an increased demand for sustainable housing. A possible inference, therefore, is that there are broader contextual factors preventing these positive attitudes and intentions from translating into higher demand for current rating tools. This could be explained by the limited visibility and communication of the rating systems by builders and developers, as noted by Warren-Myers and McRae (2017) who identified a lack of disclosure across the Top 100 builders’ websites. Furthermore, Warren-Myers (2017) found that homebuyers reported that there was limited discussion about environmental certifications during the home-building process. Additionally, another relevant factor might be confusion about the meanings of the certifications. The growing number of rating systems that use star-based ratings, be it in regard to food, health, or environmentally-friendly consumer products, may be contributing to confusion for consumers in this context. This possibility was highlighted recently in an article in the Fifth Estate (2017), in which the author commented on the disparity between the current building rating tools. The author also noted that the NatHERs star

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rating could be misleading when compared to other 6-star ratings: “6 Star Green Star? Brilliant. 6 Star NABERS? Industry-leading. 6 Star NatHERS? Bare minimum” (Fifth Estate, 2017). It would not be surprising if there was a level of confusion about housing rating systems among consumers, when across three different systems, the meaning of a ‘6-star’ badge ranges from world-leading to a minimum standard. The widespread lack of information and confusing disparity in the meanings of the rating systems, means that housing consumers may have difficulty justifying the benefits associated with different systems, which would then affect their willingness to pay (as also noted by Romanach et al., 2015). Given the present findings, there are several potential interventions that could be employed to increase consumers' interest and awareness of sustainability certifications for dwellings. Firstly, interventions could include educating consumers about the features and benefits of sustainability certifications; for example, by including more information about sustainability certifications in the marketing materials for new dwellings in order to increase levels of perceived behavioural control. Secondly, it could be useful to consider designing ways of increasing the visibility of sustainability certifications for houses, so that descriptive subjective norms are more apparent to other people. Increasing the visibility of certifications may also strengthen the association between green consumer identity and intentions to purchase sustainable housing (e.g., Brick et al., 2017). Along similar lines, other researchers have also highlighted the need to increase the visibility of ‘green’ building features and the use of signage to draw attention to lessvisible sustainability initiatives (e.g., Cranz et al., 2014). Marketing communications could also better convey social norms by highlighting the proportions of consumers in the relevant location who have purchased sustainable housing (e.g. Goldstein et al., 2008). Thirdly, green consumer identities could be made more salient in contexts where consumers are considering purchasing a dwelling, to strengthen the perceived consistency between purchasing sustainability-certified housing and other pro-environmental consumer behaviours. The findings of the current study further suggest that although green consumers are likely to be relatively more engaged with sustainability ratings, potential educational interventions to increase perceived subjective norms may actually be more effective for those who are low in self-identification as a green consumer. Consequently, targeted effects to engage consumers with sustainability ratings through better information provision, drawing attention to social norms, and clear demonstration of the costs and benefits, will potentially have a greater impact on this group. Future research is required to test the effectiveness of these type of interventions. 5. Conclusions Our research expands on prior work by examining the TPB in the underexplored context of purchasing a dwelling with a sustainability certification. It also builds on previous work that has examined the moderating role of green consumer identity in intentions to engage pro-environmental consumer behaviours, by examining this relationship for a relatively high-investment consumer purchase. Accordingly, we provide two novel contributions to the literature. Firstly, we demonstrate that an expanded TPB model predicts intentions to purchase a dwelling with a sustainability certification; a high investment purchase decision with a substantial degree of financial risk. Secondly, we find that green consumer identity moderates the effect of subjective norms on intentions. Thus, it is in developers’ best interests to investigate if they are appealing to environmentally-conscious consumers. Those with a high green consumer identity will be less susceptible to normative influences on purchase, so appeals targeting their values

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