Throughout the night．The outdoor air temperature often drops below the comfort temperature． Cvcn during sumnler．And is considered as a cooling SOUICe This low outside tcmpcrature can be used to reduce the energy consumption of cooling processes in commercial buildings．They arc venntilated with large、olumes utilizing I 00％outdoor air either at night or during the off-hours．This study first in、‘oh’ed the CX’aluation of an integrated multi-room airflOW model．CONTAM．With the multi-roonl thcmlal model Type 56 from TRNSYS．The results from the thermal and airflow studies show’that a coupled airflow／ thermal model must bc considered．Additionally．A simulation study was undertaken to investigate the feasibilit)’of Offohour accelerated、‘entilation in a real 9 floor commercial office building in reducing the air conditioning energy consumption while maintaining acceptable indoor environmeutal conditions．The mechanical system is designed to bc emplo)’cd in either normal or accelerated ventilation(flee-cooling) mode．