2.2.1. Life Cycle Inventory

The framework selected in this study is in the light of the standards of ISO [20] and the Society of Environmental Toxicology and Chemistry (SETAC) [21]. The functional unit is considered as floor area (m2). The cut-off principle of this study is in reference to previous research [22]: sorting all the building materials according to their mass, with the cumulative quality accounting for more than 80% of the building materials being taken into consideration.

As the two case studies are located in China, a local LCI database, Chinese Life Cycle Database (CLCD), is preferred. Although the life cycle inventory (LCI) has achieved remarkable process since last decade, the local LCI database is not able to cover all the material. Therefore, the Europe Life Cycle Database (ELCD) [23] is used to complete the case studies (see Table 2).


**Table 2.** Data sources of the study.
