A solar combisystem consists of a solar collector, a storage tank along with an auxiliary heater for backup and short term storage facility. Solar combisystem can be a feasible alternative for space heating as well as for Domestic hot water services. Two house types and three system concepts have been simulated in this study. The model includes collector, collector loop, auxiliary heater, bivalent shunt, pumps, heat exchangers, buffer storage tank, control valves and control system. The goal of this study was to improve the system by maximising solar gain and minimizing the auxiliary power and to investigate if there is any possibility for improvements in system with varying different parameters and connecting the collector circuit directly to the floor via an external heat exchanger. An assumption was made that by utilizing the storage capacity of the floor will make it possible to store more solar heat and therefore increase the solar gains and decrease auxiliary energy. Simulations were done with two different houses type A and type B, Type A was a low energy house i.e., a well insulated house and type B was a high energy house or con-ventional house. Both the houses type A and type B were divided into three zones: zone1, zone2, zone3. In this study three system concepts were simulated for comparison purpose, namely the base case sys-tem, the advance control system and the direct solar floor concept. Three parametric variations have been performed in this study for comparison purpose, with two different Buffer storage tanks, with two different collector slopes and with two different comfort criteria’s. The comparative study of these three systems has shown significant improvements in energy savings i.e. increased solar energy utilization and decreased auxiliary energy consumption with the improvements in the control systems. It can be con-cluded from these results that the concrete floor can be utilized to store energy and that with more im-proved control strategies and parametric variations, more and more solar energy can be utilized and more and more auxiliary power can be saved.