Occupant behavior and its impact on energy consumption of urban residential buildings

Abstract

Improving the energy efficiency of buildings cannot be circumvented to address two big challenges confronting us today - energy security and climate change. Operation of buildings alone accounted for 30% of global final energy consumption and 28% of global greenhouse gas emissions in 2018 (IEA, 2019). With rapid urbanization and growth in household income, especially among developing countries, energy demand from buildings may double or even triple by mid-century if we go with business as usual (IPCC, 2014). Energy reduction and decarbonization of buildings is hence critical for both ensuring energy security and mitigating climate change, where technology alone is not sufficient and the behaviors of building occupants have a role to play. This thesis explores human-building interactions and examines the impact of occupant behavior on energy consumption of residential buildings with empirical evidence from a large-scale survey in Beijing, China. The findings of this work can help us better understand various energy-related behaviors and how they influence building energy use at the city scale, adding to existing technology and policy solutions for improving building energy efficiency and contributing with empirical evidence to both building energy research and effective energy policy-making.

To begin with, by a systematic review of research on occupant behavior and building energy performance, the energy-saving potential of occupant behavior is estimated to be in the range of 10-25% for residential buildings and 5-30% for commercial buildings. Four existing research gaps in the field have also been identified, namely the needs for understanding occupant behavior in a systematic framework; for stronger empirical evidence beyond individual buildings and at a larger city scale; for linking occupant behavior to socio-economic and policy variables; and for evaluating the role of occupant behavior in the effectiveness of building energy efficiency policy.

Following the literature review, the thesis goes on to explore occupants' energy-related behavior in residential buildings. An in-depth and comprehensive picture of occupant behavior in Beijing households are presented: Purchase behavior is overall energy-efficient; air conditioning (AC), for both purchase and usage behaviors, plays a critical role as the residents usually have less energy efficient AC in their homes and use it more often and for a longer period of time than other devices; habitual behavior are consistent across all habitual categories. Furthermore, there is no single, straightforward and coherent pattern of behavior that can be explained by any single socio-economic factor.

With a better understanding occupant behavior in buildings on the basis of the empirical data from Beijing, the thesis further examines the effect of occupant behavior on energy consumption of urban residential buildings. Several key findings emerge - i.e. occupant behavior overall explains about 25% of the variability in residential energy consumption, 28% in space heating energy and 12% in non-space-heating energy; purchase behavior explains the most variability; space heating option and fuel type of the primary kitchen stove are the two most influential purchase behaviors in residential energy use.

The relationship between attitude and behavior relating to residential energy use is also investigated. The results show a mixed picture: An attitude-behavior gap exists for purchase behavior as the occupants generally don't behave consistently with their reported willingness to pay more for energy efficient products, but when it comes to the energy efficiency of household products, there is a consistency between attitude and behavior; likewise, for habitual behavior, the occupants display an attitude-behavior gap in terms of behavior relating to thermal comfort and lighting, whereas their habitual action towards unused appliances/equipment is consistent with their reported attitude.