Abstract For residential buildings located in the subtropics, it is more challenging and difficult to deal with space latent cooling load than space sensible load, using a room air conditioner (RAC), partly due to hot and humid climates. This paper reports a simulation study on the characteristics of space cooling load and indoor humidity control for residences in the subtropics, using a building energy simulation program. Both the weather conditions and the typical arrangements of high-rise residential blocks in subtropical Hong Kong were used in the simulation study. The simulation results on both the space cooling load characteristics and the hourly application sensible heat ratio (SHR) in the living/dining room and the master bedroom in a selected west-facing apartment under different operating modes of RACs in the summer design day are presented. The problem of indoor humidity control due to the mismatching between an application SHR and an equipment SHR in the two rooms both in the summer design day and during part load operations and the influences of indoor furnishings acting as moisture capacitors on indoor RH level are discussed.