The present paper deals with heat transfer inside a ventilated enclosure. The enclosure is heated by a horizontal downward-facing constant-temperature hot plate. In order to provide a comprehensive picture of the problem. three main approaches are used in parallel: temperature measurement, flow visualization, and numerical simulation. The measurements are done by thermocouples distributed uniformly at the vertical mid-plane of the enclosure. The visualization is performed using the smoke of incense sticks, with video recording and consequent image processing. The computer simulations of the flow and temperature fields are performed both for steady and transient ventilation and compared with the results of the measurements and visualization. Applicability to ventilation is discussed.