This paper introduces the modeling of single-split coil room air-conditioning systems governed by modulating control action for use in building energy simulation. The model calculates energy consumption, sensible and latent cooling capacities of the split coil system at part-load operation, matching the sensible and latent cooling zone loads. As a result, the zone air states can be exactly determined. The model of the split system under two-position control has previously been developed and verified (Neymark and Judkoff 1998, 2000; Knabe and Le 2000a). Results of the simulation show a significant impact of the controller type on both room comfort (temperature and humidity) and energy consumption.