The experiment was conducted in order to clarify airflow characteristics in rooms heated by heat pump and floor heating systems and effects of supply air and cold draft. The following results were obtained: (1) The airflow in rooms heated by a heat pump system circulated gradually and included the high values of power spectrum ratio in the high frequency range. (2) The airflow in rooms heated by floor heating system showed the high values of power spectrum ratio in the low frequency range and low air velocity. (3) The air volume of supply air and shapes of ventilation hole have small effects on airflow characteristics.