In recent years, with actualization of a global warming issue, the need for simultaneous pursuit of progress of comfort in living space at residential house and energy saving is now becoming greater and greater. In this study, we investigated the indoor thermal environment and air distribution by natural ventilation at earth sweet home in summer, middle and winter seasons in Japan. This house is designed so that the effect of natural ventilation may become high. We report the results with focus on the effects of indoor thermal and air environment by opening window in middle season. By using a skylight, it is showed that the cross-ventilated air volume is increased and the effect of SET* fall is high at the second floor room in this house. Also, this house is planed that the bathroom and the changing room protrude on the north side. Since this bulge has achieved the window catcher's effect, it has succeeded in passing indoor the wind is blown from the east side which is a predominant wind direction in this region. As a result, in indoor habitation space, it turned out that the air distribution environment of suitable wind velocity is formed in the wide range. Moreover, it is shown by here that the effect of the SET* fall by a cross-ventilated air is high similarly. In addition, we report that effects of heating insulation of whole in house, double sliding screen and thermal storage floor in summer and winter season too. As a result, through every year, to outside-air-temperature change, change of room temperature is small and has proved insulative effect, and also indoor thermal environment is improved by using double sliding screen in both seasons. And, the improvement effect of the thermal environment is acquired by gaining solar radiation heat from thermal storage floor in this measured house. From here onwards, it is thought that the energy saving effect of winter is fully expectable by gaining solar radiation heat from thermal storage floor.