This study examines isothermal dehumidification systems using hollow fiber membranes and vacuum pumps, focusing on their integration with conventional air conditioning systems. Since membrane dehumidification technology is still under development, replacing traditional systems entirely is not yet feasible. Therefore, this research explores how membrane dehumidification can supplement conventional air conditioning to enhance dehumidification capacity and improve energy efficiency. The study confirms that membrane dehumidification effectively supports conventional systems, maintaining thermal comfort by preventing excessive room temperature increases. However, it also reveals that the additional energy consumption from increased fan and vacuum pump power leads to higher overall energy use. To address this issue, a control strategy is proposed, in which membrane operation is stopped during intermediate periods to minimize unnecessary energy consumption. It is expected that this approach helps keep energy use at a relatively low level while still achieving significant energy-saving effects. The findings highlight the potential of membrane dehumidification systems as a complementary technology, offering a feasible pathway toward more efficient and comfortable air conditioning solutions.