# A Sustainability Analysis Based on the LCA-Energy-Carbon Emission Approach in the Building System
## 2 Material and Methods
### LCA-Carbon Emission Calculation Model  
The calculation formula of the carbon emission calculation model for the whole life cycle of buildings is as follows [73]:  
\[E_{W}=E_{\sigma}+E_{t}+E_{c}+E_{o}+E_{d} \tag{9}\]  
where \(E_{W}\) is the total carbon emission in the building system; \(E_{\sigma}\) is the carbon emission in the building material production stage; \(E_{t}\) is the carbon emission in the construction material transport stage; \(E_{c}\) is the carbon emission in the construction phase; \(E_{o}\) is the carbon emission in the operational use and maintenance phase; \(E_{d}\) is the carbon emission in the abandoned and dismantled stage. (1) Carbon emission calculation of building material production stage  
The building materials production stage includes the carbon emissions generated by mining, production and processing. The calculation equation is as follows:  
\[E_{\sigma}=\sum_{i=1}^{n}Q_{i}\times F_{i}+\mu_{i}\times[F_{i}\times(1-\varphi _{i})+F_{i}^{\prime}\times\varphi_{i}] \tag{10}\]  
where \(E_{\sigma}\) is the carbon emission calculation of the building material production stage; n is the quantity of building materials; \(Q_{i}\) is the consumption of building material \(i\); \(F_{i}\) is the carbon emission factor in the initial state; \(\varphi_{i}\) is the carbon emission factor in the recycling state; \(\mu_{i}\) is the rate of attrition; \(F_{i}^{\prime}\) is the recovery utilization rate. (2) Carbon emission calculation of construction transport stage  
The construction process needs a large number of vehicles, resulting in a mass of carbon emissions, which need to be counted and calculated. The transportation process includes two parts, one is the carbon emission calculation of building materials and mechanical equipment transported to the construction site; the other is the carbon emissions from construction waste and earthmoving. The specific calculation formula is as follows:  
\[E_{t}=\sum_{i,j}^{m,n}\frac{Q_{i}}{100}\times V_{i,j}\times D_{i}\times F_{j} \tag{11}\]  
where \(E_{t}\) is the carbon emission calculation of the construction transport stage; \(n\) is the quantity of building materials; \(Q_{i}\) is the consumption of building material \(i\); \(V_{i,j}\) is the amount of energy used to transport materials (\(t/100\) t\(\cdot\)km); \(D_{i}\) is the transportation distance of materials or equipment (km); \(F_{j}\) is the carbon emission factor. (3) Carbon emission calculation of building construction and renewal stage  
The carbon emissions of the construction phase is mainly the use of machinery and the electricity in the factory, which can be calculated by gasoline, diesel and electricity usage. The specific calculation equation is as follows:  
\[E_{c}=\sum_{i,j}^{m,n}Q_{\partial}\times L_{i,j}\times F_{j} \tag{12}\]  
where \(E_{c}\) is the carbon emission calculation of the building construction stage; \(n\) is the quantity of equipment; \(m\) is the number of energy types; \(Q_{\partial}\) is the total number of machines; \(L_{i,j}\) is the energy consumed by machinery; \(F_{j}\) is the carbon emission factor. (4) Carbon emission calculation of operational use stage  
There are two aspects of carbon emissions in this stage. On the one hand, it is the carbon emissions generated by the lighting load, air conditioning system load, refrigeration equipment, water supply and drainage load in the operation stage. On the other hand, the carbon emissions are generated by the upgrading and maintenance of building materials and facilities.