# Integration of Building Services in Modular Construction: A PRISMA Approach
## 3 Results  
### Quantitative Analysis of Publications in Modular Construction Building Services  
The distribution of the publications and their evolution per frequency is first discussed. Figure 3(a) shows the distribution of modular construction and building services research articles across academic journals, whereas Figure 3(b) shows the annual frequency of publications. Figure 3(a) shows a focused output in a few journals, with _Automation in Construction_ leading with ten articles. _Journal of Building Engineering_ and _Engineering Structures_ have eight and six publications, respectively. Other notable contributions come from _Buildings_ and _Construction and Architectural Management_, each with five publications. Figure 3(b) shows a rising publishing trend, indicating a growing awareness of modular construction services. Few publications were made in the early years. However, the subsequent years have seen a rise, peaking at 17 publications in 2023. Figure 5 shows a modular construction building services literature keyword co-occurrence network. The network is divided into color-coded topical research groupings. The \"Integration\" cluster is the only one containing many building services keywords. This cluster includes \"building information modeling,\" \"digital twin,\" and \"integration\" itself, showing a strong research focus on information management and technology intersecting with modular building processes. The timeline gradient at the bottom of Figure 5 shows research themes from 2010 to 2025. The \"Integration\" cluster emerged later in the timeline,  
highlighting its expanding prominence in the discipline. This suggests that incorporating building services into modular construction has gained research impetus due to technical advances and a focus on efficiency and coordination. Figure 6 also shows the Scopus citation frequency for modular construction research articles as of December 2023. The collection's most referenced article, \"Life Cycle Design and Prefabrication in Buildings: A Review and Case Studies in Hong Kong,\" has over 200 citations, demonstrating its influence. Both \"Design issues of using prefabrication in Hong Kong building construction\" and \"Steel concrete composite systems for modular construction using BIM-based buildings,\" with 181 and 128 citations, also significantly influence the research corpus. Figure 4: (**a**) Distribution of publications by top ten _journals_; (**b**) Evolution of publication frequency over _time_. Figure 5: Keyword co-occurrence and cluster analysis. As seen in Figure 6, the article with the highest citation counts focuses on life cycle analysis, design, and prefabrication techniques, and integrating building information modeling (BIM) within modular construction processes. The prevalence of citations in these topics suggests they are critical areas of interest and research. A rough estimate of keywords on building services was selected from data from the keyword co-occurrence network (see Figure 5) to preview the ratio of these keywords to the total publications used in this study. Two intriguing trends were discovered. First, the overall link strength for selected keywords is 200, reflecting the degree of linkage between these keywords in the literature. 'All Keywords', on the other hand, has a significantly greater link strength of 2740, indicating a more prominent, integrated research topic. Figure 7 depicts a similar gap in the occurrences of these terms, with the selected keywords appearing 41 times and 'All terms' appearing 542 times. While modular construction has become a well-researched issue, the subset of selected keywords related to building services integration occurs less frequently, indicating a more narrow or emerging study area within the broader field. Figure 7 depicts the frequency of keywords appearing in the study literature. With seven linkages, the most commonly recurring term is 'industrialized building system', followed by 'heating, ventilation, and air conditioning (HVAC)' with three.