The building bioclimatic charts of Givoni are used to test whether passive downdraught evaporative cooling, in conjunction with night ventilation, might yield thermal comfort in an office building in Southern Europe. Dynamic thermal simulation indicated that the direct evaporative cooling boundary, proposed by Givoni, was an unreliable indicator of the climatic conditions for which comfort could be provided. New boundaries, defining the climatic limit of thermal comfort for direct evaporative cooling in offices, with differing levels of internal heat gain, are proposed. For each one, a band of climatic conditions, within which comfort is sometimes achieved and sometimes not, is also indicated.