Atria have become popular additions to many building types in recent years. There is a common misconception that they will automatically result in lower energy consumption, but this is not necessarily the case. Only when designed and used in an appropriate way will atria contribute to energy conservation. In this paper the performance of two school buildings, one incorporating a heated atrium, the other an unheated atrium, was studied. Comparisons between their performance were made with respect to thermal comfort, heating costs, overheating and daylighting. While heating the atrium incurred a cost penalty, it resulted in comfortable conditions in the space for a greater proportion of the time in winter, and consequently created a more useful space. In summer months overheating was likely unless an area of opening vents the equivalent of 10% or more of the floor area is provided in the atrium roof.