The atrium is an open interior space that may be linked to the external environment; it is becoming more and more popular and a key element in the architectural design of many buildings, due to its attractive and symbolic aesthetic characteristics for the public. It is a filter against unwanted external environmental phenomena such as rain, snow and wind. A well-designed atrium can contribute towards having a significant effect on the indoor environment, affecting the comfort of the occupants. However, in certain hot and arid regions such as the city of Laghouat in the south of Algeria characterized by a scalding and dry summer, and cold winter, these fully enclosed atrium spaces with their untouched typological and architectural diversity, and due to lack of a good renewal of the indoor air, can cause considerable thermal discomfort to the occupants of space, and thermal stratification inside, especially in summer. The present work studies the impact of the atrium configuration on the inside thermal environment, for summers and winter periods, and to provide a sufficient air renewal within the atrium to ensure good air quality. As a result, a rectangular, fully enclosed, unventilated central atrium building was examined with its adjacent spaces, by a series of field measurements to study two geometric factors that have a considerable impact on the interior thermal comfort, the height width ratio (SAR Index) and the glazed coverage ratio. The impact of SAR index and glazed area ratio on thermal comfort and stratification of the air in summer and winter period were also examined.