Occupant behaviour analysis

Many studies have proved that energy for operating process represents by far the largest share in the building life cycle (Sartori and Hestnes 2007, p.250). Adalberth published her research report in 1999 and proved that the energy use during the operational period equals 80-85 per cent of the total use during the life cycle with the consumption 5,000- 7,500 kWh/m2 usable floor area given a 50-years lifespan of occupancy (Adalberth 1999).

IPCC has also proved that the greatest part of greenhouse gas emissions in buildings (in- cluding commercial and residential buildings) take place during the building operation phase to meet various energy demands (Junnila 2004, Suzuki and Oka 1998, Adalberth et al. 2001). Meanwhile, the process of building operation and maintenance is also the main process, which allows occupants to participate in and play their role through the occupancy rate and their behaviours, thus to negotiate their indoor environment require- ments and outdoor environmental conditions. An overview of occupant behaviours by residential energy consuming is conducted as Fig. 4.5 (van Raaij et al. 1983).

Figure 4.5 Impact factors of occupant behaviour and the interrelation

The residential energy consumption refers to three behavioural phases: purchase, use and maintain:

- The purchase-related decision and behaviour are primarily influenced by the so- cio-demographic factors. The living tradition determines the household lifestyle to a great degree, however, the household income determines the affordability to purchase energy-efficient products at higher prices. Besides, the educational level influences directly whether the households are willing to purchase those products and use them frequently and correctly.

- The maintenance-related behaviours mean mainly some simple repair or improve- ment of household energy facilities without or with small additional cost. In a

Socio- demographic background (e.g., income, educational level) Building & Facilities requirement Climate conditions Household life style Building energy policies Energy-related attitude and awareness; social norm • Acceptance of efficient products and sence; • Perception

• Engagement & optimization • Cost-benefit tradeoff

Behavior change in: • Purchase-related

• Use-related

• Maintenance-related

Residential energy consumption

Consumption Billing CO2 emission

Prices & characteristics of household appliance Direct impact Indirect impact Mutual direct impact Mutual indirect impact

sense, the occupant awareness about environmental protection and their afforda- bility have impacts on the maintenance activities.

- The use-related behaviour is the key point that refers to the main energy-consum- ing activities of occupants at home. Occupant behaviours aim to meet the house- hold requirements on heating, cooling, lighting and others, which are affected by factors pertaining to from individual characteristics to social dimension. The en- ergy-related occupant awareness and behaviours can be well interpreted based on Driver-Needs-Actions-System Ontology, as Fig. 4.6 illustrates. Drivers represent the internal and external factors (e.g., the location of occupants, and the individual metabolic rate (Turner and Hong 2013, pp.6-7)) that simulate occupants to sprout an energy-related thought or idea, which evoke the Needs of occupant to optimize the indoor environmental quality. In the framework of residential building energy consumption, these needs refer to the household requirements on thermal comfort (Fanger 1970, Singh et al. 2014, Yang et al. 2014), visual comfort (Dilaura et al. 2011, Santos 2008), indoor air quality (Szokolay 2008), acoustic comfort (Ginn 1978, Guyer 2009), and privacy (Foster and Oreszczyn 2001), as well as other social satisfaction, e.g., enough view to outdoor environment (Reinhart and Voss 2003). Actions are the results of stimulation of those needs and the interaction between occupants and building energy Systems, which refer to all energy-related equipment or mechanism inside residential unit and affect the building energy performance through a series of interaction with occupants. The common systems in residential unit include doors and windows, window shutters/Venetian blinds, radiators, lights, water tap, water heater, and plug loads. The impact of the inter- action between occupants and systems is affected on the one hand by the occupant actions driven by their living requirements at home, on the other hand by the per- formance of building energy facilities themselves (e.g., insulation of façade, of window and window frame, COP-value of boilers and water heaters, and air con- ditioners, etc.). In addition, the occupant attitude and awareness toward energy use would govern how they interact with energy-related building systems.

Figure 4.6 Key components of DNAS ontology and the interaction framework

Energy use is invisible to the users, and most occupants have very vague idea about the influence of their daily behaviour on energy consumption (Darby 2006, p.3). Gu has also expressed in his research that energy consumption is the external reflection of human activities. (Gu 2007, p.11). A correct understanding of the human dimensions (e.g., their needs, awareness, abilities and motivations, opportunities and constraints) of energy con- sumption can catalyse and amplify technology-based energy conservation. This refers to social, cultural and traditional, physiological and psychological factors that shape and impact patterns of human behaviour associated with technology choice, adoption, use and maintenance (IEA 2014, p.21).

With regard to the concrete occupant interaction with building energy system especially, it refers to generally two main aspects: occupancy and energy-related behaviour. Occu- pancy determines that residents are able or willing to behave or interact with household appliances and energy equipment, so as to meet their requirements on indoor air quality and living comfort. Occupancy plays a very important role in building energy simulation, in particular HVAC utilization, lighting, plug load, natural ventilation or fans utilization, which influence the energy consumption in quantity and the energy balance due to the internal heat gain or loss. It varies among households with different schedules. The vari- ants determining or affecting household occupancy refer mainly to,

- Size of household, i.e. number of family members who reside in the same residen- tial unit.

- Employment status of family members, e.g., full- or part-time employees, retirees, and with/without school-age children, which determine the vacancy of residential units.

Energy-related behaviours are often influenced on the one hand by the availability of the energy-related technological structures at home, and the climate zones where residential units are located, on the other hand by the individual preferred indoor temperature and lifestyle that appear the variation between different types of household structure and so- cial backgrounds. In addition, the accessibility of energy-conservation information and affordability of energy-efficient products have also impacts on occupant consciousness and behaviour. “Energy information knowledgeable” and “Energy-efficient products af- fordable” for occupants are equally critical to optimizing energy-conservation awareness and behaviour. Gram-Hanssen indicated that residential energy consumption must take into account the impact of information and communication technology (ICT) in the future to a higher degree (Gram-Hanssen 2011, p.998).

It is worthy to note that occupant behaviour is particularly critical for reducing energy consumption in low-energy residential buildings, which have been well equipped with energy-conserving technologies, therefore further energy-saving potential could be ex- plored only with the help of the energy-saving behaviour of occupants. Adjusting the occupant attitudes and behaviours to the surrounding environment (e.g., clothing selec- tion instead of a higher thermal set point or lower cooling set point, rather shower than bath) is crucial for taking full advantage of energy efficiency technologies and thus re- ducing rebound effect as far as possible. Besides, changing social norms and expectation following from the improvement of technologies (Gram-Hanssen 2011, p.997), as well as building a rational and stable energy prices system should not be overlooked too. The general approaches for optimise the energy-related behaviours of occupants aim to deliver energy-saving information and consumption feedback to households continually, as well to bridge the effective connection between households and building/energy pro- viders. These approaches refer to, for example, survey, historical data analysis, indoor measuring or monitoring with occupancy sensors or loggers. The process of data collec- tion is conducted not only for the behavioural attributes (indoor area: individual behaviour and schedule) but also for the environmental and social situation (indoor & outdoor area: temperature, relative humidity, CO2 concentration and luminance). The collected data

shall be thorough as far as possible, so as to offset the passive impact of behavioural stochasticity.

Different approaches have their advantages and limits respectively. For instance analysis of historical energy consumption data, which represents the past situation under certain conditions and normally could only as a baseline figure for pre- and post-intervention comparison, when assessing the effectiveness of energy-saving investment, meanwhile relevant economic and political factors shall not be ignored. Measuring or monitoring with information-seeking techniques can detect the occupancy rate and behaviour with a relatively high accuracy, however the issue of privacy has to be considered and solved before installing them. A survey involving questionnaires and interviews is the most com- mon way to inquire such information. In particular, when planning a survey of occupants

in residential units, two issues need be clear, i.e. 1) which type of survey is appropriate? 2) and how to motivate occupants to participate in a survey? (Renz 2012).

1) For a pre-post comparison of energy consumption, a longitudinal survey with at least two periods is necessary, which is function with time (T, month) as x-coor- dinate and energy consumption (E, kWh) as y-coordinate, therefore the change of energy consumption before and after implementing energy-saving measures is compared as the (x,y) function depicts. If a comparison between different occu- pants groups who have considerable difference in energy-consuming behaviour and attitudes is the main target, a cross-sectional survey that focuses on one meas- uring point or period would be appropriate.

2) The response rate of occupants is crucial for the survey results and influences the validity or ultimate value of survey. A high participation or response rate is con- siderably important for a longitudinal survey process. Except for different survey time or instruments (e.g., questionnaires, face-to-face interview, telephone or online survey), appropriate monetary or non-monetary incentives (voucher, gift) are also suggested for attracting more participants. In addition, frequent infor- mation exchange and introduction about household energy saving would contrib- ute to motivate occupants to a certain extent.

Overall, the aim of increasing energy efficiency in residential building and the investi- gated measures in term of social perspective is to optimize the indoor comfort for resi- dents. Without “comfort” all efforts on residential energy efficiency lost their meaning completely, particular thermal comfort that has defined in ASHRAE Standard 55: thermal comfort is the condition of mind, which expresses satisfaction with the thermal environ- ment and is assessed by subjective evaluation.