# A Sustainability Analysis Based on the LCA-Energy-Carbon Emission Approach in the Building System
## 1 Introduction  
Increasingly affected by environmental degradation, the building system's sustainability, as a gathering place for humans, is under scrutiny [1; 2]. From the ecological field, ecological architecture is a professional term that defines that a building system is sustainable and can achieve long-term development, in a sustainable way [3; 4]. However, in order to maintain the ecologically sustainable state of a building system, it needs the continuous support of continuous resources, energy and a service system, which objectively leads to the increase in carbon emissions. At the same time, global warming is caused by excess carbon emissions, and it is also a growing threat to the world's living environment [5; 6]. One obvious fact reveals the level of carbon emissions in the building system, which accounts for more than a third of total carbon emissions [7; 8]. Therefore, an ecological sustainability study and the carbon emissions of building systems should be focused on simultaneously by scholars. From the field of ecological economics, the energy concept is a new viewpoint for the sustainability evaluation of several systems, including agriculture [9; 10], urban systems [11; 12; 13; 14], water treatment processes [15; 16], industrial products [17; 18; 19], material production systems [20; 21], health systems [22], plant ecology [23], regional analysis [24; 25], building systems analysis [26; 27], economic subsystem [28], etc. Therein, the building system is an important focus based on energy analysis. Simultaneously, a series of scholars conducted energy calculations and assessments to explore the sustainability of building systems. For instance, [PERSON] et al. (2021) integrated the energymethod and BIM to realize their union [29]. So as to confirm the environmental building design change, the energy approach has been used to define a net zero energy building system [30]. By replacing disparate energy sources in green buildings, their sustainable evaluations have been revealed on the basis of an energy view [31]. Taking the net-zero energy building system as an example, a sustainable assessment has been executed from the view of energy considerations [32]. Because it involves a lot of data analysis, the sensitivity analysis of building systems has been investigated [33]. Through the integration of the energy method and sensing system analysis, the effectiveness of smart building has been of concern [34]. Since a building system consists of multiple devices, to verify the utility, energy analysis has been adopted to confirm the effect of the heating and cooling subsystem integrated with the air source heat pump subsystem [35]. At the same time, the evaluation and selection of construction equipment systems can also be confirmed using the energy method [36]. Building material systems are also a key field of energy analysis [37]. The energy method can also be applied to the updating of the building system to guide the updating design [38]. In addition to the above studies, it is a very popular idea to study the whole life cycle of a building system. Many scholars have studied the building system by leveraging the LCA method [39; 40; 41; 42; 43; 44; 45]. However, there are few comprehensive studies integrating the LCA method and the energy method. As an unusual combination, LCA-Emergy can conduct a sustainable exploration of building systems. After reviewing the literature in the last five years, several articles were discussed using the LCA-Emergy framework. For example, a residential building was selected for sustainability investigation in view of energy analysis [46]. As a necessary part of the building system, the building cement material system was of concern and was analyzed using an energy view [47]. As a special form of architecture, highway engineering has also been surveyed through energy evaluation [48]. By relying on an LCA-Emergy approach, different renewal strategies for building systems are demonstrated, so as to select a better renewal strategy [49].