# Characteristics of Urban Heat Island in China and Its Influences on Building Energy Consumption
## 2 Methods
### Heating/Cooling Load-Related Electricity or Coal Consumption  
DesignBuilder (DesignBuilder V3, DesignBuilder Software Ltd., Stroud, UK), which was used in this study, has been widely used in building cooling/heating load simulation with reasonable accuracy and efficiency [47]). The residential building model with a typical layout was adopted to simulate the building energy consumption. The building envelope performance-related parameters (Table 1) were set abiding by the building design standards [48; 49; 50; 51]. The weather file for building energy simulation was formed based on the weather data recorded for 2019, which is the same dataset that was used for analyzing UHI in Section 2.2. Based on the actual heating/cooling demand and according to published standards [52], we defined the heating season and cooling season. In the regions of HSCWR, HSWWR, and MR, the heating and cooling season is December-February and March-November, respectively. The indoor temperature setting in different building climate zones are shown in Table 1. The power density is the electricity consumption of electric appliances including lighting. In addition to the heating/cooling load, the coefficient of performance (_COP_) of the energy conversion system also affects the final electricity or coal consumption. In the SCR and CR regions, a central heating system was applied and the central heating demand was mostly provided by heating boilers with coal consumption [49]. In the other building climate zones (HSCWR, HSWWR, and MR), heating and cooling are mainly provided by split air conditioners in residential buildings. The split air conditioner usually has a larger _COP_ during cooling compared to heating, in which case, the same value of heating or cooling load results in different electricity consumption. Therefore, we calculated three values to understand how the UHII affects energy consumption, as follows: (1) the load (cooling load and heating load), (2) the electricity consumption (converted from the load), and (3) the coal consumption (converted from electricity consumption and heating load in SCR and CR). In the calculation of electricity consumption, a split air conditioner was assumed to be used in SCR and CR as those in the other three-building climate zones (HSCWR, HSWWR, and MR) for the sake of the comparison. For the coal consumption calculation, central heating with coal combustion boilers was applied in SCR and CR during the heating season, while the split air conditioner was adopted during the cooling season \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Building Envelope** & **SCR** & **CR** & **HSCWR** & **HSWWR** & **MR** \\ \hline External wall (W/m\({}^{2}\) K) & 0.35 & 0.35 & 0.8 & 0.35 & 1.8 \\ \hline Roof (W/m\({}^{2}\) K) & 0.15 & 0.15 & 0.6 & 0.65 & 0.8 \\ \hline External window (W/m\({}^{2}\) K) & 2 & 2 & 3 & 6 & 3.5 \\ \hline Window–wall ratio & & & 0.25 & & \\ \hline Air tightness (ACH) & 0.5 & 0.5 & 1 & 1 & 0.5 \\ \hline Power density (W/m\({}^{2}\)) & & & 5 & & \\ \hline Heating/cooling temperature (\({}^{\circ}\)C) & 18/26 & 18/26 & 18/26 & 16/26 & 18/26 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of the building envelope in different building climate zones. in all five building climate zones and during the heating season in HSCWR, HSWWR, and MR. The typical required _COP_ values in national standards [50] are listed in Table 2. The electricity consumption (_EC_, KWh) can be obtained with Equation (4):  
\[EC\ =\ HL/COP_{h}\ +\ CL/COP_{c} \tag{4}\]  
where _HL_ (KWh) and _CL_ (KWh) are heating load and cooling load, and _COP\({}_{h}\)_ and _COP\({}_{c}\)_ are the _COP_ during heating and cooling, respectively.