| Author: | Weerasinghe, Lichini Nikesha Kumari |
| Title: | Development of a model for sustainable decision-making in net zero carbon retrofitting of existing residential buildings |
| Advisors: | Chan, P. C. Albert (BRE) Darko, Amos (BRE) |
| Degree: | Ph.D. |
| Year: | 2026 |
| Department: | Department of Building and Real Estate |
| Pages: | xxi, 273 pages : color illustrations, maps |
| Language: | English |
| Abstract: | Net zero carbon (NZC) retrofitting of existing residential buildings contributes to improving occupants' wellbeing and addressing carbon footprint directly and is key to solving the global climate crisis. However, residential building NZC retrofitting is influenced by numerous challenges, and it is difficult to decide the optimal retrofit strategies that maximize social, environmental, and economic sustainability. To effectively retrofit the existing residential buildings to NZC, it is critical to identify the issues and understand the optimal retrofit strategies to enhance social, environmental, and economic sustainability. Therefore, this study aims to develop a model to select the optimal retrofit strategy for maximizing social, environmental, and economic sustainability in residential building NZC retrofitting. To achieve this aim, four objectives were pursued: (1) to analyze and model the challenges and benefits of retrofitting existing residential buildings for NZC, (2) to identify and model the available retrofitting measures to reduce carbon emissions in existing residential buildings, (3) to evaluate the social, environmental, and economic sustainability changes due to retrofitting, and (4) to develop a model to select optimal retrofit strategies for NZC retrofitting of existing residential buildings. This study focused on residential buildings in Hong Kong, since 81% of the existing building stock is residential, representing approximately 27% of energy usage and associated carbon emissions. Consequently, the outcomes of this study contribute to the attainment of NZC from the existing residential buildings in Hong Kong as well as other developed regions. It is worth mentioning that while various studies have investigated the issues addressed in this study, there is a scarcity of research focused on social, environmental, and economic sustainability in achieving NZC residential buildings from the existing buildings in developed regions, particularly in Hong Kong. A comprehensive literature review was conducted to identify benefits, challenges, and measures for building NZC retrofitting, to identify the focus on social, environmental, and economic sustainability in building NZC retrofitting, and to identify the approaches followed to make optimal decisions on residential building NZC retrofitting. First, questionnaire surveys were conducted with building occupants and experts in Hong Kong to achieve objectives 1 and 2, and the data were analyzed using the mean score ranking method, the Friedman test, and partial least squares structural equation modeling (PLS-SEM). Objectives 3 and 4 were achieved through a case study that was conducted based on a two-person residential unit. Accordingly, multi-objective optimization analysis was conducted using the data collected through simulations, market surveys, and embodied carbon calculations. Finally, a multi-objective optimization model was deployed in the Streamlit framework to automate the multi-objective optimization. Based on the questionnaire surveys, the study systematically identified key benefits, challenges, and measures for residential building NZC retrofitting in Hong Kong. On the 17 benefits of residential building NZC retrofitting, "lower building maintenance costs", "reduce energy costs", and "attractive return on investments" were identified as the foremost benefits driving residential building NZC retrofitting. In addition, PLS-SEM results demonstrated the significant influence of economic and environmental benefits on residential building NZC retrofitting. On the 28 challenges for residential building NZC retrofitting, "obstacles to domestic renewable energy (i.e., technical limitations and regulatory issues)", "difficulties due to high-rise, high-density urban environments", and "lack of knowledge and awareness on retrofitting" were identified as the first three critical challenges. PLS-SEM results demonstrated that "social challenges" and "technical challenges" had a significant impact on residential building NZC retrofitting. On the measures of residential building NZC retrofitting, Friedman test analysis represented occupant's higher preference towards the implementation of renewable energy sources rather than measures on building envelope and energy system upgrades. Furthermore, PLS-SEM analysis results indicated that wall and window retrofitting, HVAC and hot water system retrofitting, and the use of solar energy sources are most suitable for building envelopes, energy system, and renewable energy upgrades in residential building NZC retrofitting. Based on the findings from the sustainability analysis, the different retrofit strategies showed the highest carbon savings, economic profitability, and occupant satisfaction. Therefore, multi-objective optimization was performed to decide optimal retrofit strategies that maximize carbon saving, economic profitability, and occupant satisfaction. The results indicated that optimal retrofit strategies including 75mm and 100mm wall insulation thickness, 400mm width of wall shading, triple glazed windows with 6mm thick glazing, and 14 number of PV panel installation showed a positive economic profitability percentage range from 129.36% to 133.47%, carbon saving percentage range from 186.90% to 188.58%, and lower values for the predicted percentage of dissatisfaction (PPD) compared to the base case, indicating higher occupant satisfaction. Finally, an automated model was developed by incorporating the multi-objective optimization model into the Streamlit framework to deploy the NZC retrofit decision-making model developed by this study. The two datasets derived from the case study were implemented into the automated model to validate the application's efficacy and responsiveness across a spectrum of different counts of retrofit measures. Accordingly, the findings of this study contribute significantly to the literature on residential building NZC retrofitting. Further, the models developed to represent the relationship among challenges, benefits, and measures with residential building NZC retrofitting would assists academics, policymakers, decision-makers, advocates, and other stakeholders, particularly in developed regions, in promoting residential building NZC retrofitting to create a zero-emission sustainable built environment. In addition, the web application developed to make optimal decisions on building NZC retrofitting would contribute to achieving NZC in the building sector. Overall, this study would be advantageous in achieving a zero-emission, sustainable built environment. |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/14429