Putting consumers first in design for sustainable behaviour: a case study of reducing environmental impacts of cold appliance use

Abstract

To slow down the increasing environmental degradation, design for sustainable behaviour (DfSB) has emerged in sustainable design aiming to promote behavioural change through design innovations to reduce environmental and social impacts from the demand side or consumer side. This paper presents a practice-based journey to investigate the process and results of the application of social-psychological theories into sustainable design. Focusing on the behaviour-related impacts of products and services during the use stage, a Design Behaviour Intervention Model (DBIM) is developed through the analysis and synthesis of the social-psychological theories and behaviour-changing strategies. The DBIM indicates that an in-depth study of consumer behaviour is the preliminary step in DfSB, which determines the application of design strategies and potentially the effectiveness of design interventions. A case study is presented to demonstrate the application of the model. The results show that consumer behaviour insights offer rich resources to assist designers in sustainable design innovation. Product-based design suggestions and a proposed solution highlight that the application of DBIM coupled with consumer involvement throughout the design process could produce desirable and sustainable patterns of household fridge use. Finally, the structured consideration of behavioural change and their possible application in DfSB are discussed.

Keywords:

• managing use and consumption
• environmental product design
• sustainable innovation
• consumer behaviour
• design strategy
• ethnographic research

1. Introduction

To overcome the energy use impacts of products and services most efforts have been made from two aspects: technological solutions to reduce the amount of energy they require to function and information-intensive campaigns to influence consumer purchase and use behaviours through energy labelling and guidelines. These efforts have offset the potential increase in the UK's domestic energy use, but have not achieved sustained energy reductions (House of Commons – Public Accounts Committee 2009). At a national level, the efficiency of UK households (including the buildings, heating systems and household appliances) has improved steadily by around 2% per year since 1970. However, the energy use of household appliances has increased by 70% over this time (Environmental Change Institute 2005). This means that the technical improvements of product efficiency are not necessarily turned into energy savings during the use stage. Consumer behaviours and practices have a significant impact on energy use and account for a variation by a factor of 2–3 in the technically identical houses with different occupants (Gill et al. 2010). There is growing agreement that the solutions to environmental challenges such as climate change must involve behavioural change for lasting effect (Stern 2007). The challenge does not only include helping people understand what they need to do, but more importantly, to help them to do it (House of Commons – Public Accounts Committee 2009). This means more effective measures are needed to invoke individual engagement and to secure a radical long-term change in the use patterns of products and services beyond the point of sale.

One way of addressing sustainable behaviour change is through the design of products, services and systems. Using design innovations to reduce negative social and environmental impacts of consumption (Jelsma and Knot 2002, Lockton et al. 2008, Pettersen and Boks 2008, Lilley 2009, Bhamra et al. 2011) is an emerging field in sustainable design. A dominant theme of this field is the complexity associated with understanding consumers and their daily life interactions with the products, services and environments so as to make radical changes in consumption. In response, several attempts have been made to explore theories and models rooted in the social sciences for sustainable design, two of which are starting to be used in the design community. One is ‘design for sustainable behaviour’ (DfSB) that aims to reduce the behaviour-related negative environmental, economic or social consequences resulting from consumer interaction with specific products, services and systems during the use stage. The foci include mismatching functionalities, where the delivered functions fail to match with the user's desired functionality (Jelsma and Knot 2002, Wever et al. 2008) and the unintended use of the product, service or system, where consumers use features in a manner unexpected by the designers (Pettersen and Boks 2008, Lilley 2009). Drawing on social-psychological theories, a range of design strategies are developed to evoke and steer the cognitive, behavioural or unconscious reaction to sustainability in the individuals (Tang and Bhamra 2008, Zachrisson and Boks 2010, Bhamra et al. 2011). The other approach, social practice theory, directs the research attention towards the social and systemic nature of consumption and the accomplishment of everyday practices. Built on this theory, practice-oriented design focuses on practices, routine consumption and the roles of conventions and conceptions of normality in shaping behaviours towards more sustainable practices (Ingram et al. 2007, Munnecke 2007, Hielscher et al. 2009, Kuijer and de Jong 2011, Scott et al. 2011). However, this exploration of social science theories for sustainability should be considered preliminary. To date, limited work has been undertaken with real world consumers to address the applications in sustainable design, although de Borja et al. (2010) have recently applied Shove et al.'s (2007) ‘stuff-image-skill model’ to the case of household food practices. Distilling useful insights from the complexities of consumers' values and daily behaviours and translating these into design interventions raise challenges for designers.

This paper presents a practice-based journey to investigate the process and results of the application of social-psychological theories into sustainable design, with the purpose of setting up the fundamentals of DfSB theory (Tang 2010). Focusing on the impacts of products and services during the use stage, a Design Behaviour Interventions Model (DBIM; Tang and Bhamra 2008, Bhamra et al. 2011) provides a framework for understanding the consumer behaviours and outlines the potential strategies and effects of DfSB interventions in changing behaviours and habits. A case study explores the relationship between consumer behaviours and product design in the context of household cold appliance use and illustrates how the structured consideration of behavioural change would help in the identification of the breakthrough points for DfSB. Product-based design suggestions and a solution proposed highlight that the application of DBIM coupled with consumer involvement throughout the design process could produce desirable and sustainable patterns of household fridge use.

2. Applying social-psychological theories in DfSB

Social-psychological theories have been widely applied in identifying the determinants of behavioural change in order to direct behaviours to a pro-environmental or sustainable level (Jackson 2005). Few attempts have been made to link the social-psychological theories to the domain of sustainable design. With this background, a comprehensive literature review in diverse disciplinary fields of enquiry was undertaken to uncover the social-psychological factors influencing use and their relevance for design.

2.1 Social-psychological theories and behaviour models

The literature reveals two perspectives to distinguish these social-psychological theories and behaviour models, referred as ‘internalist’ and ‘externalist’ (Jackson 2005). ‘Internalist’ posits that individual's intentions (affected by attitudes and subjective norms), perceived behavioural control (Ajzen 2006), affective (Triandis 1977, Steg and Vlek 2009) and habits (Triandis 1977, Jager 2003 cited Jackson 2005, Verplanken and Wood 2006) precede consumer behaviour. ‘Externalist’ recognises that the behaviour can be modified or constrained by various contextual factors, including social norms, incentives, cultural, institutional contexts and situational attributes (Stern 2000).

Triandis' (1977) Theory of Interpersonal Behaviour has recently drawn attention in the pro-environmental literature (e.g. Jackson 2005, Steg and Vlek 2009) for its reconciliation of two perspectives, viewing behaviours as a result of interactions between individual cognitive and contextual factors in shaping such processes. It gives equal attentions to the role of individual's attitudes, social factors and emotions in forming intentions and the role of habits in determining whether that intention turns into action or not. Importantly, it acknowledges the individual's cognitive limitations (Jackson 2005) and proposes that the facilitating conditions – similar to the contextual factors discussed in Stern's attitude–behaviour–context theory (2000) – may have negative or positive influences on the behaviour change.

2.2 Design Behaviour Intervention Model

By introducing concepts from social-psychological theories into DfSB, the DBIM (Figure 1) categorises interventions according to three antecedents of behavioural change: to inform, to maintain and to force the sustainable use of products, services or systems. Seven design strategies are located on the axis of influence (Lilley 2009) starting from user-agentive end, where the power in decision making lies completely with the user, to the other extreme, technological agentive end, where the power in decision making is with the product, service or system. In DfSB, the way the product, service or system is designed and the environment around it, working as contextual factors, could affect consumer behaviours through influencing their intention and habits, but also could directly determine the use experiences of products and services.

Figure 1 DBIM: linking antecedents of behavioural and habitual change with varying levels of design strategies.

As illustrated in Figure 1, intention is affected by attitudinal, social and affective factors that relate to beliefs, knowledge and skills, social norms, personal roles, self-concepts and emotional responses (Triandis 1977). The intention can direct behaviour in the declarative stage in Anderson's theory of development of cognitive skills (1982), when consumers are entering a new context or developing a new behaviour. Eco-information, eco-choice and eco-feedback strategies construct the conservation goals through showing the energy/resources existence, alternative options and feedback for the one to reflect upon and determine the ‘best’ course of action. When knowledge is converted into a procedural operation in the knowledge completion stage (Anderson 1982), the consumer only seeks input on its accomplishment, more forceful strategies, eco-spur and eco-steer are required to redirect the action. Finally, the procedural stage (Anderson 1982), when the behaviour becomes fully automatic and unconscious, needs a distinct cognitive effort or significant contextual change (Verplanken and Aarts 1999), such as eco-rechnology or clever design to impose the environmental beneficial manner of use.

The DBIM indicates that the in-depth study of the consumer's behaviour is the preliminary step in DfSB, which determines the application of design strategies and potentially, the effectiveness of design interventions.

3. Environmental impacts of the household fridge and freezer

A practice-based design project (Scrivener 2000), sustainable use of the fridge (SUF), was conducted as a case with two intentions: first, to explore the role of consumers and their interactions in DfSB and second, to show how behaviour could be studied and shaped by design, providing a reference for DfSB.

Since 1980, the technology efficiency of household fridges has improved by more than 67% (Rüdenauer et al. 2007), but the average size of cold appliances on the market increased by 15% between 1995 and 2001 (Environmental Change Institute 2005). This means that manufacturers are not selling appliances with lower overall energy consumption.

On the demand side, every household owns at least one cold appliance often with two or more (Environmental Change Institute 2005). In 2007, sales in this sector grew by 8% compared with 2005 (Mintel 2007). Recently, consumers are enthusing about larger and more energy hungry appliances, such as American style fridge freezers containing integrated LCDs or ice makes, and using small drink chillers and coolers in the bedroom and living room. Furthermore, consumer behaviours significantly influence the energy efficiency of cold appliances, for example through door opening practices. The current energy label test is criticised by consumer bodies and experts for not reflecting actual energy consumption of home use. For example, during the test doors are not opened, the test load is unrealistic and also temperature recovery from insertion of warmer food and response to ingress of humidity is not examined (VHK 2005, Market Transformation Programme 2007). Japanese surveys on actual energy consumption (Tsurusaki et al. 2006) monitored over 100 household fridges for 1 year concluded that the average annual actual electricity consumption was 65% larger than the JIS test value (Japan Industrial Standards test in 1999). Energy impact behaviours of cold appliance use and consumer surveys on energy wasted for each of the four behaviours are categorised in Table 1.

Table 1 Energy impact behaviours of cold appliance use and consumer surveys on energy wasted for each of the four behaviours.

Energy impact behaviours	Research community/reference
Door openings
Door openings were responsible for between 1% and 3% of the total electricity use	Market Transformation Programme (2007), Böhmer et al. (1998) cited EuP report (Stamminger et al. 2007)
A 12-s door opening caused the energy impact of 9–12.4 Wh	Saidur et al. (2002)
The effect of 20 door openings of a 200-l fridge with a 5-s opening time was 8% (2.2 W)	Mennink and Berchowitz (1994)
20 door openings a day increased electricity use between 1% and 6%	Lepthien (2000) cited EuP report (Stamminger et al. 2007)
40 door openings per day added between 50 and 120 kWh to its yearly energy use	Peart (1993)
In a young family with a single child, the door opening frequency increased the stated energy usage of a refrigerator by 49.82 kWh a year, an increase of 20% on the average energy use of a standard sized refrigerator which is approximately 250 kWh for a unit of this size	Elias (2011)
Inserting and storing hot or cold items
The influence of putting warm food in the fridge was 4–10%	FRPERC report cited MTP (2007)
The insertion of food into the fridge was responsible for 10% of its yearly energy consumption and cooling food with a temperature of 50°C used three times more energy than cooling food with a temperature of 20°C	Böhmer et al. (1998)
Thawing frozen food in the fridge could reduce the energy consumption up to 26%	Lepthien (2000) cited EuP report (Stamminger et al. 2007)
Operating temperature
1°C difference in operating temperature caused a 4% difference in energy consumption	VHK (2005)
1°C difference in operating temperature results in a 7.8% difference in energy consumption	Saidur et al. (2002)
On average, freezers were operating at 3.1°C colder than the recommended temperature ( − 18°C), leading to 17.6% more energy use	ECUEL project SAVE (1999) in France metered appliances in 98 households for a month
Surrounding temperature
Keeping a cold appliance in a non-heated storeroom rather than a kitchen gave an average energy saving of 36%	ECUEL project SAVE 1999 cited Market Transformation Programme (2007)
Fridges used 16% less energy in a room with temperature of 21–23°C instead of 25°C; 32% less with a room temperature of 17–21°C; 52% less with a room temperature of 13–17°C; a higher temperature of 32°C instead of 25°C increased the energy use by 55%	Studies cited EuP report (Stamminger et al. 2007)

Although prior research from different countries has provided interesting data on the real life of cold appliances, they are generally concerned with the end result, not the use process. Fridges and freezers are essential appliances in the household and widely used by a vari0ety of consumer groups associated with a range of household routines and energy practices. A consumer study of fridge and freeze use was, therefore, designed to reveal more detailed factors behind the energy figures, looking into ‘why’ and ‘how’ these energy impact behaviours occurred. The further task was to translate these findings into design opportunities to reduce the impacts through changing the consumer behaviours.

4. Methodology

Qualitative research methods were adopted for this study (Figure 2) to gain a real-life picture of cold appliances use. Using a combination of data collection methods, including ethnographic observations, self-completion questionnaires and semi-structured interviews allowed for a thorough investigation of consumer behaviours. This includes consumer attitudes, expectations, reasons for these attitudes and the gap between their thoughts and actual actions, which could not be probed in as much depth with a quantitative research approach. To minimise the unnatural factors affecting behavioural responses, participants were not informed of the study's detailed objectives, instead they were briefed on a ‘kitchen appliances’ study.

Figure 2 Consumer study design.

The consumer study comprised four elements:

•	Consumer profile questionnaires: to gather the information about the household and their kitchen appliances, food shopping patterns and cooking routines;
•	Ethnographic observations: to capture the actual use practices – considering household cold appliances and their central relationship to food preparation and consumption, the activities were arranged into three sections and correspondingly, three observations were conducted, including food unpacking, context of product in use and 24-h fridge use recording;
•	A post-intervention questionnaire: to capture participant's self-reported attitudes in relation to climate change and household energy consumption and their perceptions of the cold appliance usage patterns;
•	A semi-structured interview: scheduled as closed as possible after the observations and questionnaires had been completed, to assess the environmental consequences of three stages of the product life cycle – before use (selection and purchase), mid-use (operation and maintenance) and after use (disposal or recycle).

Eighteen British families, with adults aged between 25 and 65, were involved in this study. They had owned their fridge or freezer for between 4 months and 16 years. All the activities were recorded by written notes, photographs and video recordings. These materials assisted the discussions with participants in the interview and the subsequent in-depth analysis to extract, compare and collate similarities and differences between and with data-sets through coding, matrix and mapping and clustering (Miles and Huberman 1994).

5. Results

Four themes that are relevant to DfSB and correspond to the three elements of behavioural change in DBIM (Figure 1) are given below:

•	Links between the fridge and freezer use and environmental awareness, intention and other daily actions (intention);
•	Use scenarios of the household fridge and freezer (habits);
•	Fridge and freezer in use and design (habits and contextual factors) and
•	Kitchen plans (contextual factors).

5.1 Environmental intentions and fridge and freezer use

The results of the questionnaires and interviews disclosed the recurring issues influencing the decision-making process and the barriers to sustainable use of fridges and freezers.

‘End of life of the product’ and ‘using electricity all the time’ were cited as the two main environmental impacts of using household cold appliances. Many participants reported that it was important to keep the fridge not too full or too empty. Participants were shown a list of nine items (Figure 3) and asked about their self-assessments of fridge and freezer use behaviour. The majority of householders stated that they always checked the content of the fridge and/or freezer and decided what they needed to buy before the main shop. Sometimes they left the door open while transferring items; they forgot what they wanted to remove after opening it and when they felt hungry, opened the fridge and/or freezer to decide what to eat. It was also common that people found the fridge/freezer door left open, found food at back that was out of date and that they forgot to replace the packaging on items before putting them into the fridge.

Figure 3 Self-assessment questions relating to nine fridge and freezer use behaviours in the post-intervention questionnaire.

When asked about their attitudes towards positive behavioural change in fridge and freezer use patterns, all participants expressed that they would like to do the right things to reduce energy use, to help the environment and to save money. Most of them disagreed that ‘it was not worth doing the right things’, since they have minor impacts on the environment or they ‘couldn't save lots of money’. However, most preferred to choose a fridge and freezer with a high energy efficiency rating, even if it cost more, rather than changing their use habits. The reasons for preventing them doing more are summarised below:

•	Householders assumed that the 24/7 working fridge and freezer were the most efficient appliance in the home; therefore, energy used by the fridge and freezer was not an environmental concern in the same way as the tumble dryer for example;
•	Householders were unaware of the link: they considered that individual actions would not make a big difference;
•	Householders considered that they were doing enough: they considered that nothing could be improved;
•	Householders find it hard to change established habits and considered that it takes too much effort;
•	Many householders have locked-in lifestyle, e.g. the organised way of shopping, storing and cooking food did not fit in with an often busy and rushed lifestyle;
•	Householders have concerns about food safety and hygiene: although participants understood that the freezer should be operated at − 18°C and the lower temperature settings consumed more energy, running the freezer at 2–3°C lower than recommended made them feel more secure;
•	Households with children: e.g. the frequent use by children is a key cause of operating cold appliances at the lower temperature;
•	Householders lacked information on the sustainable use of cold appliances;
•	Householders lacked motivation: although financial incentives, such as saving money, were not citied as a major reason for behavioural change, a small group still favoured a system that ‘rewarded’ them to encourage the ‘good’ practice.

5.2 Use scenarios of the household fridge and freezer

The video footage demonstrated that the use impacts with the fridge were closely tied to the temporal routines of food preparation and consumption. Bouts of intensive activities that took place around the unpacking grocery shopping and meals characterised the typical scenarios for the fridge use. The analysis was focused on three areas of intensive work with the fridge and freezer: ‘morning’, ‘evening meal’ and ‘unpacking grocery shopping’ to identify the sequence of routinising use. The morning activities are discussed in this paper.

5.2.1 Morning

Energy intensive use patterns of 15 fridges in the households where members were out at work or school during the weekday were selected as samples. Two most damaging behaviours of the fridge use in the morning were unearthed: ‘high frequency of door opening’ and ‘door left open’. Reducing the environmental impact of the fridge use is not consciously habitual in many households, when it conflicted with other obligations such as preparing meals as quickly as possible for hungry children, for breakfast or for work and school. Combined with the demographic information from consumer profile questionnaires, factors influencing the intensive use of fridges in the morning included:

•	Number of family members: the more family members, the more door openings;
•	Age of children;
•	Time of breakfast preparation: in some of the households, the husband was the first one to appear in the video and often organised and ate his own breakfast in the early weekday morning; therefore, the same food for breakfast, such as, milk, was taken out repeatedly;
•	Different types of drinks: the variety of drinks for breakfast increased the frequency of door openings;
•	Food variety: compared with all childless and in full-time employment, families with children at home consumed more vegetables, fruit and yoghurts, had more proper breakfasts and used the fridge more;
•	The preparation of fruit bags and lunch boxes for work and school.

People often intended to get ‘quick tasks’ done with the door open, such as checking ‘use by’ dates, pouring drinks, searching for vegetables in the bottom drawers, making sandwiches for lunch boxes and fruit bags as well as transferring items between the worktop and fridge one by one. For example, one householder spent 68 s transferring food for breakfast between the worktop and fridge (MUS-F04). Morning chaos made householders ill-disciplined during breakfast preparation. First, they were not planning in advance. Another householder opened the fridge five times for her and her husband's breakfast, but four times within 1 min (MUS-F16). Second, they opened the fridge for making breakfast without thinking about all family members. Milk was taken out four times by four different family members during breakfast time (MUS-F15), and twice in a two-person household within 5 min (MUS-F02).

5.3 Fridge and freezer in use and design

The gap between product design and people's real requirements is evident as one of the reasons for their patterns of energy intensive use of cold appliances.

5.3.1 Use content

In terms of what is needed to be stored in the fridge and what did not, the divergences in their opinions lay with egg storage and individual preference for cold fruit and drinks. In some households, there was a second fridge particularly for keeping wine cool.

The combination of the results from interviews and observations showed that participants located items according to certain procedures and rules, including the ‘use by’ and ‘best before’ dates; types of food; weight of the items; user of food and drinks; temperature distribution in the fridge; frequency of the use – for easy access; routinising practice, habitual place; where there is space and the fridge design. Load conditions may contribute to the energy waste when fridges and freezers were overfilled, too empty and when the items were placed in a mess so that consumers lost sight of items. The factors influencing food stock in the fridge and freezer included:

•	Having parties or visitors;
•	Product promotions (e.g. special offers; ‘multi-packs’);
•	frequency of shopping affected by work patterns and the distance between the shops/supermarket and home;
•	Entering different life stages affected by having children and having a healthier diet;
•	Growing vegetables in the garden;
•	Living in a friendly community, e.g. receiving food from friends and neighbours;
•	Ordering online food deliveries resulted an overcrowded fridge and/or freezer to get the money worth;
•	Going on holiday that is the main reason for using up or throwing away the food so that the fridge could be as empty as possible.

The presence of children was particularly influential in fridge and freezer practices. Having children, grown-up children at home and leaving home were the three key stages for the change in loads in fridge and freezer. The food in the fridge needed particular sorting for the younger children, e.g. locating those food together that were convenient for adults to prepare meals for them, placing drinks in the lowest door bin where they could easily grab them. As the children grew, they became one of the key reasons for inefficient product use. The high-energy intensity and high level of children's interaction with the fridge and freezer were witnessed in the observation. Table 2 provides the examples of how the young generation behaved in a less environmentally responsible manner.

Table 2 A selection of energy-intensive behaviour of younger generations.

Code	Household size (person/household)	Age group	Time	Duration of opening (s)	Action
MUS-F04	Four	12–18	07:25:43–07:26:53	70	Son left the door open while making sandwiches
		12–18	07:36:07–07:36:53	46	Son took a container out and spent 46 s deciding and selecting fruit for his lunch
MUS-F07	Four	12–18	18:28:08–18:28:23	15	Daughter searched inside but took nothing out
MUS-F12	Five	5–11	15:56:43–15:57:09	26	Daughter spent 26 s pouring juice with door widely open
MUS-F14	Four	5–11	18:23:09–18:23:26	17	Daughter spent 17 s trying but failed to reach yoghurts on the top shelf
			18:23:36–18:24:06	30	Daughter moved a stool to the fridge, opened the fridge and stood on the stool to transfer yoghurts to the third shelf, which was easy for her to see until her father came to help
MUS-F17	Five	12–18	15:48:12–15:48:37	25	Son left the door open while pouring juice and drinking and kicked the door to close
			16:05:47–16:06:08	21	Son opened the fridge three times within 5 min to make his quick meal after school
			16:07:37–16:07:59	22
			16:10:12–16:10:20	8
MUS-F18	Five	12–18	08:11:09–08:12:02	53	Daughter searched, decided and discussed with her brother what need to be taken out
		Three children aged 12–18	08:26:19–08:27:07	48	Children forgot to put items back to the fridge and it took parents 48 s to return them back to the fridge

5.3.2 Fridge and freezer design and use behaviour

Behaviour recordings exposed how the use of fridges and freezers was linked to the product design and people's capability of adaptation to the design. Many of the practices relating to the product design were energy intensive:

Figure 4 Use condition of the accessories of the fridge and/or freezer.

•	Under counter fridges and freezers resulted in a relatively energy intensive nexus of practises: people had to always bend, squat or kneel down to reach the back and the bottom of the fridges/freezers to search for desired items and sort out the contents.
•	Interior design: there was time wasted, when the door was open, for people to search for the desired item and to shuffle food around to make them fit when restocking between the shelves, in doors and drawers. The observation demonstrated how the participants designed and rearranged their fridge to meet their individualised needs so that the tasks could be achieved effortlessly. These included rearranging narrow shelves as storage according to the size of the food packaging, storing things that were not taken out often on the top shelf.
•	Accessories of the fridge and freezer: observations showed the failures of accessory design in meeting customer needs and the ways they adapted products to better suit their needs. Linking the findings of the observations and interviews, the gaps between the consumers' ‘actual’ versus ‘assumed’ needs were identified. Some examples are given in Figure 4.

5.4 Modern kitchen plan and fridge and freezer use

Increased indoor temperature and limited space in the modern kitchen were considered by the participants to be directly responsible for putting more items in the fridge and occasionally locating the fridge and/or freezer in another room. At busy times such as parties and Christmas, food was kept in places, such as the garage, a porch, an unheated dining room and even a toilet.

The design of modern kitchens contributed to the ownership of the built-in style and the second under counter fridges and freezers. It also caused the placement of the fridge and/or freezer near heat sources, such as besides the oven, the cooker (MUS-F06) or facing the sun. What is more, the kitchen plan is responsible for increased opening of the door for transferring items between the fridge and/or freezer and the unpacking place or the dinner table in batches. Figure 5 demonstrates the need to offer facilitators that could help consumers hold items while transferring them between the fridge and unpacking places or dining tables.

Figure 5 Facilitators were needed when transferring items.

6. Discussion

The consumer study illustrated that different usage patterns of household cold appliances resulted in unnecessary energy consumption and underlined the opportunities to regulate consumer behaviour through design.

6.1 Household cold appliance use behaviour and its relevance to the elements of behavioural change

On reflection, these examples strongly supported the argument for three determinants of behavioural change (intention, habits, contextual factors) in the DBIM (Figure 1). When householders interacted with the fridges and freezers, they swung between:

1.	An intended course of action: participants execute with intentions and on the basis of a conscious assessment of existing practices or knowledge learnt from the past experience and others, such as their family home, friends and media including magazines, TV and radio;
2.	A habitual and routine process for the most participants: a habit that is ‘highly automated’ (Jackson 2005) as immediate responses to specific cues, operating outside awareness with a minimum of deliberation or little cognitive effort. It was observed that participants maintained a certain degree of routine to operate the fridge (e.g. procedures and principles of putting items in the fridge in Section 5.3.1); however, they could not explain why they do so in the interviews;
3.	A framed behaviour regulated by the artefact and its surrounding environment: it is evident that the design of cold appliances (e.g. the physical manipulation or the combined technology) and kitchen infrastructures direct and influence users to behave in a specific way, such as: • Leading to redundant functions or unexpected interactions; • Developing the adaptation to overcome the failures of design; • Informing consumer behaviours: ‘We know that those will fit into the door, so I do not buy three 4 pints of skimmed milk. I do not buy what would not fit in the door’ (MUS-F07) and • Restricting use patterns: ‘The fridge in the garage only works when the weather is quite warm; when the weather is cold it does not work. We bought that fridge and freezer without knowing that. Wanting to use it all the time, but then it does not work half the time in the garage’ (MUS-F04).

Element (1) corresponding to ‘intention’ implied that the consumers' real actions were consistent with their intentions and desires for ‘being green people’. Element (2), habitual and ill-disciplined fridge practices fitted in with an often busy and rushed lifestyle were confirmed by the observed: e.g. the principles of locating ‘where there is space’, packing lunch with the door open in the morning. Element (3) corresponding to ‘contextual factors’ meant that the design of the product, service, system or environment and/or combined with advanced technology affected not only the consumers' actual use patterns, but their perceived ability to use them and their motives for use.

The results showed the large gap between the environmental intention and real use of the cold appliances. Consumer behaviours were ‘out of control’ or ‘locked-into the daily practice’. Although all of the participants expressed that they would like to do the right things to reduce the energy use, to help the environment or to save money, it was a challenge for people to integrate the energy conscious awareness and behaviour into their daily routines of the fridge use. To address the habitual nature of the fridge use behaviours, the corresponding design strategies, eco-spur and eco-steer, were a key consideration in the design concept generation. These strategies would simplify the process of rationalising and the immediate, effortless and often unconscious choices. Thus, a more promising change in behaviours with more moral concerns was embedded in the design, instead of solely adopting the strategies at a passive level (e.g. eco-feedback) to build energy conversation or at an aggressive level (e.g. clever design) to cause the consumer to feel controlled or restricted by the product, service or system in DIBM.

6.2 Design suggestions

Drawing on the results of consumer studies, several product-based design solutions are suggested below. They illustrate that the design can potentially minimise the environmental impacts (e.g. behavioural energy waste and food waste) resulting from the use of cold appliances by allowing flexibility in use to different consumers.

6.2.1 Improving the design of the product

A few design features can limit behavioural energy wastage when using the fridge and/or freezer. For example, the fridge and freezer cools and freezes a large area regardless of whether it is going to be used or not. Splitting chilling and freezing spaces into smaller sections (e.g. divisible cooling or freezing sections) would allow more flexibility in using what was needed and switching off what is not.

Making good use of space inside the fridge is also identified. ‘The design means you must be careful to leave about 4 inches unfilled at the front of each shelf’ (MUS-F09). Reducing the spaces between the shelves and pulling out the shelves like drawers would improve the accessibility of the items at the back and make a good use of the space in the fridge.

Additionally, rather than being dictated by the fridge manufacturer, the fridge could be modular. A more adaptable interior and a kit of compartments would enable individuals to decide the food location and create the optimum arrangement in the fridge. To reduce door opening times, internal structures or facilitators could be provided for consumers to organise food for children at different ages or for the temporal routines of food preparation and consumption. Milk and butter/margarine storage solutions for making quick meals and drinks may reduce the time that the door is open for tasks such as pouring milk into tea. The frequency of this particular task is potentially one of the most energy consuming behaviours observed. Interestingly, this shows that the fridge interaction can be highly culture-dependent and culture-specific interaction can result in different energy requirements, and consequently design requirements. What is more, increasing the visibility of the contents could reduce the opening time for finding items inside, e.g. using shallow drawers, see-through doors or software to keep a shopping record can provide a clear view of the food inside for future uses.

Results from the main study underlined the necessity to regulate the product use behaviour. How the fridge can be operated in an environmentally responsible manner was a rather nebulous concept, largely dependent on the view and habit of the consumers. Rather than providing information through consumer guidelines and eco-operation tips, making desirable use patterns visible or aesthetically and emotionally rewarding through the product design can be more effective in promoting sustainable behaviours. To improve the temperature control, integrating with smart temperature and humidity responsive technologies, indicators should be provided, for example, graphically within the fridge, to show where the coldest part is likely to be and which temperature sensitive foods should be stored there; numerically on the dial or display, to indicate which direction produces a cooler or warmer temperature and what is the optimal temperature and humidity level for the fridge and freezer. To standardise the operations, for example, visual indicators could make consumers aware of the right amount of items (e.g. at least three quarters full) (Peterson 2009) in the fridge and freezer.

6.2.2 Improving the design of the context

Considering the food storage, preparation, fridge and freezer design and kitchen design as a whole, greater eco-efficiencies can be achieved by fulfilling consumer needs within an optimised system, such as designing a food system in the kitchen to reduce the energy losses of transferring items between the worktop and fridge with the door open and the food waste resulting from the increased indoor temperature. The ambient surrounding temperature and location of the cold appliances could have the effect on their energy use. This requires a careful consideration by kitchen designers so that locating cold appliances next to heat resources, e.g. the cooker and oven, can be avoided. An easy access to electronic appliances could be delivered by kitchen design to achieve the sustainable use. Mounting the fridge at a suitable height (e.g. at eye level) would make the items inside easily accessible for consumers to reduce the time wasted for body movements. Considering the life cycle of the product, after point of sale services would bring tangible benefits, such as upgrading the mode, offering the accessories kit (e.g. the compartments, shelves and drawers) and guidance on DIY maintenance. These measures would avoid unnecessary replacement and the use of a second cold appliance. They also allow more flexibility in use so that to maximise the use of total system resources as needed, instead of being confined by the product physical boundaries.

7. Design solutions

Drawing on the findings of the consumer study, 25 design concepts were proposed for SUF (Tang 2010). The following offers an example of how more sustainable and responsible consumer behaviour could be afforded or constrained (Tang and Bhamra 2008) by a single product solution.

7.1 BreakFAST BOX – design for organising food preparation

The video footage exposed that in the households where members were out at work or school during the weekday, ‘morning’ was the most energy-intensive time of fridge use. People were often not organised during breakfast preparation: they were not planning in advance; they opened the fridge for making breakfast without thinking about all family members; they were unaware of all the door openings, as all the tasks were achieved with the largest amount of convenience and the least amount of effort. To organise the ‘morning rush’, the ‘BreakFAST box’ (Figure 6) was created as a compact unit offering easy access to the most common items, which consists of:

Figure 6 BreakFAST BOX.

Figure 7 Behaviour constraints – the big container.

Figure 8 Bottle drawer.

Figure 9 Displaying the content.

Figure 10 A removable condiment tray.

Figure 11 Taking the tray out to the table.

•	A drawer container to keep salad vegetables, soft fruit, yoghurt and cooked sliced meat for preparing breakfast and making a lunchbox: instead of a shelf, the form of the container (Figure 7) deliberately encourages consumers to adopt a specific arrangement, removing all the items for their breakfast and/or lunchbox in one go rather than sorting through the items on the shelves;
•	A bottle drawer (Figure 8) for accommodating the opened bottles: sections of the shelves can be moved independently to accommodate bottles of various sizes.
•	Hooks on the door and a shallow drawer to display the contents (Figure 9): the sliced cooked meat could be hung up on the door and the whole shallow drawer could be pulled out and provides a clear view of the content inside even at the back of the fridge;
•	A removable tray (Figure 10) as an affordance makes it possible to remove all the most commonly used small items for preparing and having breakfast (Figure 11) as well as making tidying up the table easier so that there are reductions in the number of door openings.

8. Conclusions

This paper demonstrates the feasibility of product-based solutions to reduce environmental impacts by modifying consumer behaviours. Consumer behaviour studies offer rich resources in innovative sustainable design. By linking behavioural antecedents with different design intervention strategies, DBIM has been shown to be a useful and inspirational tool for gaining deeper understanding of consumers and making informed decisions about which strategies to apply.

The qualitative data uncover the way in which the product is used and its impacts on the energy consumption, the gap between environmental awareness and real action and the reasons for such a gap. As the case study showed, consumers are not sensitised to various details of their daily routines. They have not ever consciously thought about and deliberately remembered. The ethnographical observations not only successfully expose environmentally significant behaviours, but also evoke design solutions to real problems rather than assuming consumer needs. The critical role of product and context design plays in daily routines is identified. Limitations with current designs and the effects they have on consumer behaviour can be transformed into design opportunities to create more desirable and sustainable use patterns of the product, service or system. In summary, studying behaviours and interactions in context will inform sustainable design in the following ways:

•	Ensuring that functionality matches the consumers' articulated and latent requirements within an eco-efficient system;
•	Fulfilling the sustainability goals perceived by consumers;
•	Eliminating the unintended usage (Beale 2007) and rebound effects (Dimitropoulos and Sorrell 2006).

Additionally, incorporating behavioural elements into a DfSB project has optimised the design process in the following ways:

•	Designing a more structured and purposive consumer study to achieve a more sustainable result: the dynamics between the intention, habits and context characteristics provides a possibility for deeper understanding of the behaviour and identifying design opportunities for behavioural change. Especially, when greater sustainable goals surpassing consumers' needs, theirs beliefs, attitudes and intentions are not in line with the intended behaviour. Gaining insights into behavioural antecedents can help designers to determine and intervene the interactions at three behavioural levels: ○ Consumers' willingness to take control over the interaction by themselves or delegate control to technology; ○ Potentials of emotional attachment, aesthetic elements and physical functionality attached to interventions as trade-offs to secure consumers' cooperation and compliance; ○ The scope of behaviours afforded to the consumer: weighing up the severity of the consequence derived from the interactions and righteousness of the intent behind design interventions.
•	Collecting natural and realistic data from multiple sources: an appropriate order and arrangement of the behaviour/interaction activities minimises the unnatural behavioural response tendencies; and a comparison of data from multiple sources reveals the disparity between consumers' thoughts and actions and the reasons behind them. It was partially due to the connection between the seemingly trivial and habitual nature of product use and the other related household activities;
•	Analysing the behaviour in its context: to offer systematic thinking and analysis to appreciate the interconnectivity of the issues that lie within the consumer and interactions of products, services and systems;
•	Responding to problems: following the conclusion of the behaviour study, to select the most effective and efficient behaviour-changing strategies.

Shifting behavioural change through product design is not easy to realise. DBIM provides a good starting point to deal with DfSB tasks. To facilitate this transition in real life, a detailed design process to translate the qualitative research data into design solutions needs to be developed. Furthermore, indicators and criteria are required to evaluate the success of interventions. The acceptability of consumers to buy and use the behaviour-changing interventions would be also very interesting to explore further, which indeed is the primary factor to the outcome of the DfSB project.

Notes

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