An Atrium is a great glassed volume on a building that allows the light to enter within it. Its border location between indoor and outdoor, implies that the environmental conditions like solar radiation, ventilation and heat energy, appear intensified, turning them on spaces with a great environmental potential. However, in Santiago these spaces have been designed imitating the aesthetic of buildings suited for colder climates. This fact has produced that atrium buildings are often known by its low comfort standards and excessive cooling demands. The aim of this paper is to answer in which way some design considerations on atrium buildings can maximise its energy saving potential on the Mediterranean climate of Santiago Chile. This is carried out with software Tas, which allows to simulate the effect on thermal demand over a theoretical atrium building when changing: 3 glazing types, 3 ventilation regimes and 3 solar protections forms; resulting on 27 iterations which reveal the more environmentally efficient combinations.