Building orientation is a significant design consideration, mainly with regard to solar radiation and wind. In predominantly hot humid regions like Malaysia which receives sunlight all year around, buildings should be oriented to minimize solar gain and maximize natural ventilation. This paper describes an investigation into the effect of building orientation in view of solar radiation absorptance of exterior wall, varied area ratio of glazed window to wall and the effect of natural ventilation on the thermal performance for residential building in tropical region. The FAJAR BAKTI building (postgraduate student residential building) which is oriented in the east west directions, and a located in USM Campus, Penang. The selected case study are two rooms, the first one is facing east direction while the other faced west. The differences in in/out door air temperature and air velocity of both rooms have been measured from the field directly using the comprehensive datalogger BABUC/M, this data have been analyzed and investigated. The results shows that east windows have more obvious effect on increasing indoor air temperature than west windows, that is applicable for ventilated or unventilated rooms.