## 3 Literature Review
### National Life Cycle Inventory (LCI) Database  
The LCI databases are used as basic data for conducting LCAs of products. Such data include the quantities of inputs and outputs into a product system during the collection of raw materials needed for production, transportation and distribution, use, and disposal per functional unit of the product [19; 36].  
Countries and research institutes have conducted studies comparing the environmental performance of buildings using each nation's LCI (Life Cycle Inventory) database. However, these studies face limitations due to insufficient databases for construction materials and difficulties in comparing evaluation results at the project level. In particular, the absence of integrated data combining material input quantities with environmental impact data has hindered the ability to quantitatively present CR potential and overall carbon neutrality performance. Table 2 highlights the key distinctions between previous studies and this present study [37; 38; 39; 40; 41]. Table 2 shows the differences between this study and previous studies in the LCI database.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Year** & **Authors** & **Main Contents** & **Differences in This Study** \\ \hline
2015 & [PERSON] et al. [37] & \
\begin{tabular}{c} Compared and analyzed data \\ developed in France with data \\ from Europe. \\ \end{tabular} &
\begin{tabular}{c} Previous studies had limitations in \\ the number of materials analyzed \\ and lacked a methodology for \\ deriving comparative results across \\ actual buildings. \\ \end{tabular} \\ \hline
2016 & [PERSON] & \
\begin{tabular}{c} Established criteria for selecting \\ LCA databases when \\ inconsistencies exist between the \\ database and building conditions. \\ \end{tabular} &
\begin{tabular}{c} Although selection criteria have been \\ suggested, no study has proposed \\ constructing a database that satisfies \\ those criteria and allows for \\ application to real building cases. \\ \end{tabular} \\ \hline
2021 & [PERSON] et al. [39] & \
\begin{tabular}{c} Proposed carbon input \\ calculation criteria within the \\ UK context. \\ \end{tabular} &
\begin{tabular}{c} While UK data are available, they \\ lack comprehensive coverage of \\ materials used throughout the full \\ construction process. \\ \end{tabular} \\ \hline \end{tabular}
\end{table}
Table 2: Review of the existing literature.  
Figure 3: System boundary of building life cycle assessment.  
In the case of Korea, energy and resources, basic materials, building materials, industrial products, transportation and logistics, waste treatment, etc., have 747 LCI databases, of which 61 are construction materials. This database is managed by the Korea Environmental Industry and Technology Institute (KEITI), a governmental organization, and is publicly accessible through its official website [19]. In January 2025, KEITI plans to develop new national guidelines for LCI database development, aiming to update and expand the existing LCI database, which is currently outdated or insufficient [42]. Table 3 presents the CE data from the Korean LCI database for major construction materials.