The first Romanian passive office building has been constructed by the AMVIC Company in Bragadiru, 10 km south of Bucharest. The overheating rate and the cooling load are higher for a passive building than for a standard building. The internal heat sources and the maximum allowed indoor temperature do markedly affect the cooling load. A time-dependent model shows that cooling is necessary during April-September. The ground heat exchanger is an effective system for cooling-down the fresh air inlet temperature. Also, the Venetian blinds prove to be efficient in diminishing the building heat input. However, these two systems are not able to ensure a controlled thermal comfort during summer. This suggests that an active cooling system should be used when passive buildings are implemented in the Romanian climate. The standard configuration of the passive buildings ventilation system (which is usually designed for heating purposes), must be changed in case cooling becomes necessary during the warm season. The results are of interest for other countries in Southeastern Europe. (C) 2010 Elsevier Ltd. All rights reserved.