## 3 Results
\begin{tabular}{l c c c c c c c} \hline  & **(1)** & **(2)** & **(3)** & **(4)** & **(5)** & **(6)** & **(7)** & **(8)** \\ \hline HVAC system & & & & & & & \\ (1) Temperature & 1 & & & & & & \\ (2) RH & \(-0.624\) ** & 1 & & & & & & \\ (3) CO\({}_{2}\) & \(-0.468\) ** & \(-0.769\) ** & 1 & & & & \\ (4) PM\({}_{0.85}\) & \(-0.036\) & \(0.232\) & \(-0.123\) & 1 & & & \\ (5) PM\({}_{10}\) & \(0.030\) & \(0.165\) & \(-0.093\) & \(0.965\) ** & 1 & & \\ (6) PM\({}_{4.5}\) & \(0.002\) & \(0.197\) & \(-0.145\) & \(0.981\) ** & \(0.974\) ** & 1 & \\ (7) PM\({}_{1}\) & \(0.002\) & \(0.182\) & \(-0.236\) & \(0.862\) ** & \(0.793\) ** & \(0.888\) ** & 1 \\ (8) Airborne bacteria & \(-0.219\) & \(0.467\) & \(-0.685\) * & \(0.576\) & \(0.321\) & \(0.523\) & \(0.571\) & 1 \\ \hline LDAC system & & & & & & \\ (1) Temperature & 1 & & & & & \\ (2) RH & \(-0.732\) ** & 1 & & & & \\ (3) CO\({}_{2}\) & \(-0.521\) ** & \(0.335\) * & 1 & & & \\ (4) PM\({}_{0.05}\) & \(-0.005\) & \(0.263\) & \(0.152\) & 1 & & & \\ (5) PM\({}_{10}\) & \(-0.117\) & \(0.216\) & \(0.219\) & \(0.895\) ** & 1 & & \\ (6) PM\({}_{2.5}\) & \(-0.133\) & \(0.321\) * & \(0.282\) & \(0.953\) ** & \(0.924\) ** & 1 & \\ (7) PM\({}_{1}\) & \(-0.215\) & \(0.464\) ** & \(0.349\) * & \(0.851\) ** & \(0.678\) ** & \(0.843\) ** & 1 \\ (8) Airborne bacteria & \(-0.006\) & \(0.358\) & \(0.164\) & \(0.127\) & \(0.321\) & \(0.200\) & 0.201 & 1 \\ \hline \multicolumn{8}{l}{ROAC system} & & & & \\ (1) Temperature & 1 & & & & & \\ (2) RH & \(-0.629\) ** & 1 & & & & \\ (3) CO\({}_{2}\) & \(-0.228\) & \(-0.077\) & 1 & & & & \\ (4) PM\({}_{0.85}\) & \(-0.407\) ** & \(0.393\) * & \(0.422\) ** & 1 & & \\ (5) PM\({}_{10}\) & \(-0.366\) * & \(0.380\) * & \(0.321\) * & \(0.930\) ** & 1 & & \\ (6) PM\({}_{2.5}\) & \(-0.392\) * & \(0.383\) * & \(0.395\) * & \(0.954\) ** & \(0.967\) ** & 1 & \\ (7) PM\({}_{1}\) & \(-0.418\) ** & \(0.362\) * & \(0.345\) * & \(0.816\) ** & \(0.694\) ** & \(0.786\) ** & 1 & \\ (8) Airborne bacteria & \(-0.333\) & \(0.370\) & \(-0.139\) & \(0.564\) & \(0.779\) ** & \(0.681\) * & \(0.374\) & 1 \\ \hline \end{tabular}   
* *As shown in Figure 3, the daily ambient temperature had moderate to strong associations with the daily total energy consumption of the conventional HVAC system (\(\rm{r_{s}}=0.648,\,p<0.001\), Figure 3A), LDAC system (\(\rm{r_{s}}=0.742,\,p<0.001\), Figure 3B), and RDAC system (\(\rm{r_{s}}=0.815,\,p<0.001\), Figure 3C). Furthermore, the daily total energy consumption of the conventional HVAC system (\(\rm{r_{s}}=0.108,\,p=0.039\), Figure 3A) and the LDAC system (\(\rm{r_{s}}=0.162,\,p=0.002\), Figure 3B) had a very weak association with the daily ambient RH level. The regression analysis showed that the increase in ambient temperature led to a significant increase in the log-transformed daily total energy consumption in the ORs (HVAC system: regression coefficient [\(\beta_{1}\)] = 0.044, \(p<0.001\); LDAC system: \(\beta_{1}=0.017,\,p<0.001\); RDAC system: \(\beta_{1}=0.029,\,p<0.001\)). Additionally, an increased ambient RH caused an increased log-transformed daily total energy consumption in the OR that was using the LDAC system (\(\beta_{1}=0.004,\,p=0.002\)). Figure 3: Association between daily ambient temperature/RH and daily total energy consumptions of HVAC (**A**), LDAC (**B**), and RDAC (**C**) systems.