The purpose of this paper is to analyze the indoor thermal environment and ventilation efficiencycreated by various heating and ventilation systems using CFD. In the case of one room, the value ofmean local air exchange efficiency????*1 of breathing zone*2 becomes about 1.0, because fresh airspreads completely in the room when air-conditioners are operated. In contrast, when air-conditionersare not operated, the mean ?? becomes smaller than 1.0, and the area of poor ventilation efficiencybecomes large. Air exchange efficiency is influenced by the layout of both the supply outlet and theexhaust inlet. In the case when the distance of the supply outlet and exhaust inlet is long, ventilationefficiency may be good. In the case that the whole house is analyzed, the air exchange rate whileheating becomes more than the mechanical ventilation air exchange rate (0.5?1/h?) due to thebuoyancy effect. And those cases are much in order of the ventilation system of mechanical supply andnatural exhaust, natural supply and mechanical exhaust, mechanical supply and mechanical exhaust.There are no differences in the amount of distribution of ??between the cases of heating byair-conditioner and floor heating.