## 2 Methodology to Achieve the Results  
This study adopted a mixed method approach, combining quantitative and qualitative research methodologies to elucidate the intricate relationship between traditional HVAC systems and green building design principles. An exhaustive literature review was conducted to understand the current state of research in the domain. Scholarly articles, conference proceedings, and industry reports were reviewed. This helped in the understanding of existing HVAC technologies, their energy consumption patterns, the evolution of green building principles, and the perceived gaps between them [22]. A quantitative analysis was performed on the energy consumption of traditional HVAC systems. Data were collected from various buildings, both residential and commercial, over one year. The data were then benchmarked against buildings incorporating green building principles and newer HVAC technologies [27]. Surveys were administered to occupants of buildings with traditional HVAC systems to gauge their comfort levels. Simultaneously, structured interviews were conducted with architects, HVAC engineers, and green building consultants. This qualitative approach provided more profound insights into the perceived challenges and opportunities in integrating HVAC systems with green building designs [18]. Several green buildings that have successfully integrated innovative HVAC systems were chosen as case studies. These provided practical insights into real-world applications and challenges. Each case study was analysed regarding energy efficiency, occupant comfort, retrofitting complexities, and the use of eco-friendly refrigerants [15]. The collected data were analysed using statistical tools and software packages. Quantitative data from energy consumption analysis and surveys were subjected to regression analysis, ANOVA, and \(t\)-tests to determine significant differences and patterns. Qualitative data from interviews were analysed using thematic analysis, allowing for the emergence of designs and themes related to challenges and solutions [14]. The mixed method approach provided a holistic perspective on the challenges and opportunities in integrating traditional HVAC systems with green building principles. While conventional systems posed significant challenges regarding energy inefficiency and incongruence with sustainability, innovative alternatives showed promise in bridging the gap. This study emphasises the urgency of transitioning to newer HVAC technologies that align with green building principles, ensuring energy efficiency, ecological sustainability, and occupant comfort.  
The graphic in Figure 3 represents data from keywords searched on Scopus with the keywords \"thermal AND comfort; AND green AND buildings\". This visualisation, a 3D bubble chart, suggests a trend analysis over time, possibly evaluating the relationship between thermal comfort and green building practices from 2000 to 2030. Each bubble likely represents a dataset or a collection of studies published on the topic in a given year. As time progresses, the increasing size of the bubbles could indicate a growing number of studies or an increase in a particular metric related to thermal comfort in green buildings. The numbers within the bubbles could signify the number of research papers or the scoring of a specific index linked to the research intensity or impact in that year. For example, the jump from 82 in 2015 to 100 in 2020 could indicate a significant increase in research activities or findings on thermal comfort in green buildings.