An integrated passive and active retrofitting approach toward minimum whole-life carbon footprint.

[Display omitted] • Transform office buildings towards whole-life minimum carbon. • Integrated optimisation of retrofitting plan and operating schedules. • 44%, 74% and 68% decline in whole-life costs, carbon and energy after retrofitting. • 4–51% saving in whole-life carbon emission compared to design optimisation strategy. • 10% saving in whole-life carbon emission compared to operating optimisation strategy. The state-of-the-art retrofitting strategies generally use either passive or active measures to reduce carbon emissions during its operating stage. The coordination among a range of passive and active energy devices is not considered while the concept of whole-life carbon emission minimisation is not introduced. To overcome these three research gaps and to transform existing office buildings toward minimum whole-life carbon emissions, an integrated passive and active retrofitting approach is proposed. Through two inter-related design optimisation and operating optimisation processes, the set of retrofitting options can be identified to achieve overall optimal economic, energy, and environmental performance. The first research gap, lack of simultaneous consideration of various active and passive retrofitting measures, is solved by the whole system simulation of a range of active and passive refurbishment measures. The second research gap, lack of coordination among a range of active energy devices, is solved by iteratively determining the optimal operating schedules of active energy devices with overall retrofitting plan at the design stage. The third research gap, lack of whole-life carbon emission minimisation, is solved by simultaneously minimising both embodied and operating carbon emissions. A real three-floor office building acquiring retrofitting is used to test the effectiveness of this integrated passive and active retrofitting approach. Compared to the building at its current status, there could be 44%, 74% and 68% reduction in lifelong costs, carbon emissions and energy usages if the proposed retrofitting strategy is adopted. Compared to retrofitting the building using the state-of-the-art "design optimisation only" strategy, the proposed retrofitting approach can reduce 5.36%-34.37% whole-life energy consumption and 4.31%-51.10% carbon emissions. Compared to retrofitting the building using the state-of-the-art "operating carbon emission only" strategy, there is 11.92%, 10.55%, and 10.48% reduction in whole-life cost, energy usage and carbon emissions, respectively. Therefore, this paper is innovative in an aspect that minimum whole-life carbon emissions can be reached through integrated design of passive and active retrofitting measures. It can provide building owners, energy engineers and decision-makers with insightful building retrofitting solutions to tackle the energy crisis and climate change problems. This proposed retrofitting approach can also be modified to provide guidance in designing new low-carbon buildings. [ABSTRACT FROM AUTHOR]